We propose a periodic structure as an extra absorption layer（i.e., absorber） based on surface plasmon resonance effects, enhancing dual-band absorption in both middle wavelength infrared（MWIR） and long wavelength ...We propose a periodic structure as an extra absorption layer（i.e., absorber） based on surface plasmon resonance effects, enhancing dual-band absorption in both middle wavelength infrared（MWIR） and long wavelength infrared（LWIR）regions. Periodic gold disks are selectively patterned onto the top layer of suspended SiN/VO_2/SiN sandwich-structure.We employ the finite element method to model this structure in COMSOL Multiphysics including a proposed method of modulating the absorption peak. Simulation results show that the absorber has two absorption peaks at wavelengths λ =4.8 μm and λ = 9 μm with the absorption magnitudes more than 0.98 and 0.94 in MWIR and LWIR regions, respectively. In addition, the absorber achieves broad spectrum absorption in LWIR region, in the meanwhile, tunable dual-band absorption peaks can be achieved by variable heights of cavity as well as diameters and periodicity of disk. Thus, this designed absorber can be a good candidate for enhancing the performance of dual band uncooled infrared detector, furthermore, the manufacturing process of cavity can be easily simplified so that the reliability of such devices can be improved.展开更多
We fabricated a set of symmetric gate-recess devices with gate length of 70 nm.We kept the source-to-drain spacing(L_(SD))unchanged,and obtained a group of devices with gate-recess length(L_(recess))from 0.4µm to...We fabricated a set of symmetric gate-recess devices with gate length of 70 nm.We kept the source-to-drain spacing(L_(SD))unchanged,and obtained a group of devices with gate-recess length(L_(recess))from 0.4µm to 0.8µm through process improvement.In order to suppress the influence of the kink effect,we have done SiN_(X) passivation treatment.The maximum saturation current density(ID_(max))and maximum transconductance(g_(m,max))increase as L_(recess) decreases to 0.4µm.At this time,the device shows ID_(max)=749.6 mA/mm at V_(GS)=0.2 V,V_(DS)=1.5 V,and g_(m,max)=1111 mS/mm at V_(GS)=−0.35 V,V_(DS)=1.5 V.Meanwhile,as L_(recess) increases,it causes parasitic capacitance C_(gd) and g_(d) to decrease,making f_(max) drastically increases.When L_(recess)=0.8µm,the device shows f_(T)=188 GHz and f_(max)=1112 GHz.展开更多
Heterogeneous integrated InP high electron mobility transistors(HEMTs)on quartz wafers are fabricated successfully by using a reverse-grown InP epitaxial structure and benzocyclobutene(BCB)bonding technology.The chann...Heterogeneous integrated InP high electron mobility transistors(HEMTs)on quartz wafers are fabricated successfully by using a reverse-grown InP epitaxial structure and benzocyclobutene(BCB)bonding technology.The channel of the new device is In_(0.7)Ga_(0.3)As,and the gate length is 100 nm.A maximum extrinsic transconductance gm,max of 855.5 mS/mm and a maximum drain current of 536.5 mA/mm are obtained.The current gain cutoff frequency is as high as 262 GHz and the maximum oscillation frequency reaches 288 GHz.In addition,a small signal equivalent circuit model of heterogeneous integration of InP HEMTs on quartz wafer is built to characterize device performance.展开更多
A set of 100-nm gate-length In P-based high electron mobility transistors(HEMTs)were designed and fabricated with different gate offsets in gate recess.A novel technology was proposed for independent definition of gat...A set of 100-nm gate-length In P-based high electron mobility transistors(HEMTs)were designed and fabricated with different gate offsets in gate recess.A novel technology was proposed for independent definition of gate recess and T-shaped gate by electron beam lithography.DC and RF measurement was conducted.With the gate offset varying from drain side to source side,the maximum drain current(I_(ds,max))and transconductance(g_(m,max))increased.In the meantime,fTdecreased while f;increased,and the highest fmax of 1096 GHz was obtained.It can be explained by the increase of gate-source capacitance and the decrease of gate-drain capacitance and source resistance.Output conductance was also suppressed by gate offset toward source side.This provides simple and flexible device parameter selection for HEMTs of different usages.展开更多
Ferroelectric(FE)HfZrO/Al_(2)O_(3) gate stack AlGaN/GaN metal-FE-semiconductor heterostructure high-electron mo-bility transistors(MFSHEMTs)with varying Al_(x)Ga_(1-x)N barrier thickness and Al composition are investi...Ferroelectric(FE)HfZrO/Al_(2)O_(3) gate stack AlGaN/GaN metal-FE-semiconductor heterostructure high-electron mo-bility transistors(MFSHEMTs)with varying Al_(x)Ga_(1-x)N barrier thickness and Al composition are investigated and com-pared by TCAD simulation with non-FE HfO_(2)/Al_(2)O_(3) gate stack metal-insulator-semiconductor heterostructure high-electron mobility transistors(MISHEMTs).Results show that the decrease of the two-dimensional electron gas(2DEG)density with decreasing AlGaN barrier thickness is more effectively suppressed in MFSHEMTs than that in MISHEMTs due to the enhanced FE polarization switching efficiency.The electrical characteristics of MFSHEMTs,including transcon-ductance,subthreshold swing,and on-state current,effectively improve with decreasing AlGaN thickness in MFSHEMTs.High Al composition in AlGaN barrier layers that are under 3-nm thickness plays a great role in enhancing the 2DEG den-sity and FE polarization in MFSHEMTs,improving the transconductance and the on-state current.The subthreshold swing and threshold voltage can be reduced by decreasing the AlGaN thickness and Al composition in MFSHEMTs,affording favorable conditions for further enhancing the device.展开更多
We show the structural and optical properties of non-polar a-plane GaN epitaxial films modified by Si ion implantation.Upon gradually raising Si fluences from 5×10^(13)cm^(-2)to 5×10^(15)cm^(-2),the n-type d...We show the structural and optical properties of non-polar a-plane GaN epitaxial films modified by Si ion implantation.Upon gradually raising Si fluences from 5×10^(13)cm^(-2)to 5×10^(15)cm^(-2),the n-type dopant concentration gradually increases from 4.6×10^(18)cm^(-2)to 4.5×10^(20)cm^(-2),while the generated vacancy density accordingly raises from 3.7×10^(13)cm^(-2)to 3.8×10^(15)cm^(-2).Moreover,despite that the implantation enhances structural disorder,the epitaxial structure of the implanted region is still well preserved which is confirmed by Rutherford backscattering channeling spectrometry measurements.The monotonical uniaxial lattice expansion along the a direction(out-of-plane direction)is observed as a function of fluences till 1×10^(15)cm^(-2),which ceases at the overdose of 5×10^(15)cm^(-2)due to the partial amorphization in the surface region.Upon raising irradiation dose,a yellow emission in the as-grown sample is gradually quenched,probably due to the irradiation-induced generation of non-radiative recombination centers.展开更多
In order to solve the problem of ambiguous acquisition of BOC signals caused by its property of multiple peaks,an unambiguous acquisition algorithm named reconstruction of sub cross-correlation cancellation technique(...In order to solve the problem of ambiguous acquisition of BOC signals caused by its property of multiple peaks,an unambiguous acquisition algorithm named reconstruction of sub cross-correlation cancellation technique(RSCCT)for BOC(kn,n)signals is proposed.In this paper,the principle of signal decomposition is combined with the traditional acquisition algorithm structure,and then based on the method of reconstructing the correlation function.The method firstly gets the sub-pseudorandom noise(PRN)code by decomposing the local PRN code,then uses BOC(kn,n)and the sub-PRN code cross-correlation to get the sub cross-correlation function.Finally,the correlation peak with a single peak is obtained by reconstructing the sub cross-correlation function so that the ambiguities of BOC acquisition are removed.The simulation shows that RSCCT can completely eliminate the side peaks of BOC(kn,n)group signals while maintaining the narrow correlation of BOC,and its computational complexity is equivalent to sub carrier phase cancellation(SCPC)and autocorrelation side-peak cancellation technique(ASPeCT),and it reduces the computational complexity relative to BPSK-like.For BOC(n,n),the acquisition sensitivity of RSCCT is 3.25 dB,0.81 dB and 0.25 dB higher than binary phase shift keying(BPSK)-like,SCPC and ASPeCT at the acquisition probability of 90%,respectively.The peak to average power ratio is 1.91,3.0 and 3.7 times higher than ASPeCT,SCPC and BPSK-like at SNR=–20 dB,respectively.For BOC(2n,n),the acquisition sensitivity of RSCCT is 5.5 dB,1.25 dB and 2.69 dB higher than BPSK-like,SCPC and ASPeCT at the acquisition probability of 90%,respectively.The peak to average power ratio is 1.02,1.68 and 2.12 times higher than ASPeCT,SCPC and BPSK-like at SNR=–20 dB,respectively.展开更多
In order to overcome the limitations of a unitary reference station in mobile communication positioning network differential barometric altimetry(DBA)and broaden the action scope of the reference station and improve p...In order to overcome the limitations of a unitary reference station in mobile communication positioning network differential barometric altimetry(DBA)and broaden the action scope of the reference station and improve positioning accuracy of elevation,an integrated interpolation algorithm model based on generalized extended approximation(GEA)algorithm and Kriging interpolation in time-space domain of reference station is proposed.In the time domain,barometric measured data is considered the maximum value estimated by bilateral extension to avoid wrong direction of estimation,which is approaching true value.In the spatial domain,barometric relevance among multiple reference stations is utilized,the weighted coefficients of multiple reference stations is calculated by the integrated algorithm model based on the GEA algorithm and Kriging interpolation.The impact of each reference station to the measured station is quantified,so that a virtual reference station is constructed,which can overcome the limitation of barometric correction by a unitary reference station.In addition,the measurement error due to irregular change in atmospheric pressure will be eliminated.展开更多
We proposed a sandwich structure to realize broadband asymmetric transmission(AT) for both linearly and circularly polarized waves in the near infrared spectral region. The structure composes of a silica substrate and...We proposed a sandwich structure to realize broadband asymmetric transmission(AT) for both linearly and circularly polarized waves in the near infrared spectral region. The structure composes of a silica substrate and two sand-clock-like gold layers on the opposite sides of the substrate. Due to the surface plasmons of gold, the structure shows that the AT parameters of linearly and circularly polarized waves can reach 0.436 and 0.403, respectively. Meanwhile, a broadband property is presented for the AT parameter is over 0.3 between 320 THz and 340 THz. The structure realizes a diode-like AT for linearly wave in forward and circularly wave in backward, respectively. The magnetic dipoles excited by current in the two gold layers contribute to the broadband AT. The current density in top and bottom metallic layers illustrates the mechanism of the polarization conversion for broadband AT in detail.展开更多
A novel silicon-on-insulator（SOI） high breakdown voltage（BV） power device with interlaced dielectric trenches（IDT） and N/P pillars is proposed. In the studied structure, the drift region is folded by IDT embedde...A novel silicon-on-insulator（SOI） high breakdown voltage（BV） power device with interlaced dielectric trenches（IDT） and N/P pillars is proposed. In the studied structure, the drift region is folded by IDT embedded in the active layer,which results in an increase of length of ionization integral remarkably. The crowding phenomenon of electric field in the corner of IDT is relieved by the N/P pillars. Both traits improve two key factors of BV, the ionization integral length and electric field magnitude, and thus BV is significantly enhanced. The electric field in the dielectric layer is enhanced and a major portion of bias is borne by the oxide layer due to the accumulation of inverse charges（holes） at the corner of IDT.The average value of the lateral electric field of the proposed device reaches 60 V/μm with a 10 μm drift length, which increases by 200% in comparison to the conventional SOI LDMOS, resulting in a breakdown voltage of 607 V.展开更多
A double-recessed offset gate process technology for In P-based high electron mobility transistors(HEMTs)has been developed in this paper.Single-recessed and double-recessed HEMTs with different gate offsets have been...A double-recessed offset gate process technology for In P-based high electron mobility transistors(HEMTs)has been developed in this paper.Single-recessed and double-recessed HEMTs with different gate offsets have been fabricated and characterized.Compared with single-recessed devices,the maximum drain-source current(I_(D,max))and maximum extrinsic transconductance(g_(m,max))of double-recessed devices decreased due to the increase in series resistances.However,in terms of RF performance,double-recessed HEMTs achieved higher maximum oscillation frequency(f_(MAX))by reducing drain output conductance(g_(m,max))and drain to gate capacitance(C_gd).In addition,further improvement of fMAXwas observed by adjusting the gate offset of double-recessed devices.This can be explained by suppressing the ratio of C_(gd)to source to gate capacitance(C_gd)by extending drain-side recess length(Lrd).Compared with the single-recessed HEMTs,the f;of double-recessed offset gate HEMTs was increased by about 20%.展开更多
C70 nanotubes with a fcc lattice structure are polymerized through being irradiated by lasers with a wavelength of 514.5 nm at various power values. Raman spectra and photoluminescence (PL) spectra are employed to cha...C70 nanotubes with a fcc lattice structure are polymerized through being irradiated by lasers with a wavelength of 514.5 nm at various power values. Raman spectra and photoluminescence (PL) spectra are employed to characterize the polymeric phases of the laser treated samples, showing that the disordered C70 oligomers are formed in the C70 nanotubes irradiated by such strong green lasers. Comparative studies further indicate that intermolecular bonds are formed between C70 molecules on the surface of nanotubes, which are similar to those formed under high pressure and high temperature (HPHT) conditions. And the content of intermolecular bonds increases obviously with the laser power increasing.展开更多
P-type Mg_(3)Sb_(2)-based Zintls have attracted considerable interest in the thermoelectric(TE)field due to their environmental friendliness and low cost.However,compared to their n-type counterparts,they show relativ...P-type Mg_(3)Sb_(2)-based Zintls have attracted considerable interest in the thermoelectric(TE)field due to their environmental friendliness and low cost.However,compared to their n-type counterparts,they show relatively low TE performance,limiting their application in TE devices.In this work,we simultaneously introduce Bi alloying at Sb sites and Ag doping at Mg sites into the Mg_(3)Sb_(2)to coopera-tively optimize the electrical and thermal properties for the first time,acquiring the highest ZT value of∼0.85 at 723 K and a high average ZT of 0.39 in the temperature range of 323-723 K in sample Mg_(2.94)Ag_(0.06)Sb_(1.9)Bi_(0.1).The first-principle calculations show that the codoping of Ag and Bi can shift the Fermi level into the valence band and narrow the band gap,resulting in the increased carrier concentration from 3.50×10^(17)cm^(-3)in the reference Mg 3 Sb 0.9 Bi 0.1 to∼7.88×10^(19)cm^(-3)in sample Mg 2.94 Ag 0.06 Sb 0.9 Bi 0.1.As a result,a remarkable power factor of∼778.9μW m^(-1)K^(-2)at 723 K is achieved in sample Mg 2.94 Ag 0.06 Sb 0.9 Bi 0.1.Meanwhile,a low lattice thermal conductivity of∼0.48 W m^(-1)K^(-1)at 723 K is also obtained with the help of phonon scattering at the distorted lattice,point defects,and nano-precipitates in sample Mg 2.94 Ag 0.06 Sb 0.9 Bi 0.1.The synergistic effect of using the multi-element co-doping/-alloying to optimize electrical properties in Mg_(3)Sb_(2)holds promise for further improving the TE performance of Zintl phase materials or even others.展开更多
Si-based thermoelectric(TE)materials are exhibiting remarkable perspectives in self-energized applications with their special advantages.However,the relatively high total thermal conductivity(κ)prevents their TE enha...Si-based thermoelectric(TE)materials are exhibiting remarkable perspectives in self-energized applications with their special advantages.However,the relatively high total thermal conductivity(κ)prevents their TE enhancement.Here,a strategy of co-compositing dual oxides was implemented for enhancing the TE properties of p-type Si_(80)Ge_(20) bulks.Composited Ga2O_(3) was demonstrated to enhance the power factor(PF)due to the crystallization-induced effect of produced Ga by decomposition on SiGe matrix.Associating with compositing SiO_(2) aerogel(a-SiO_(2))powder,not only introduced the fine amorphous inclusions and decreased the grain size of host matrix,but also various nano morphologies were formed,i.e.,nano inclusions,precipitations,twin boundaries(TBs),and faults.Combining with the eutectic Ge,hierarchical scattering centers impeded the phonon transport comprehensively(decreasing the phonon group velocity(a v)and relaxation time)for reducing the lattice-induced thermal conductivity(lκ).As a result,a minimumκof 2.38 W·m^(−1)·K^(−1) was achieved,which is significantly dropped by 32.6%in contrast with that of the pristine counterpart.Ultimately,a maximal dimensionless figure of merit(ZT)of 0.9 was achieved at 600℃,which is better than those of most corresponding oxide-composited Si-based bulks.展开更多
A stacked lateral double-diffused metal–oxide–semiconductor field-effect transistor(LDMOS) with enhanced depletion effect by surface substrate is proposed(ST-LDMOS), which is compatible with the traditional CMOS pro...A stacked lateral double-diffused metal–oxide–semiconductor field-effect transistor(LDMOS) with enhanced depletion effect by surface substrate is proposed(ST-LDMOS), which is compatible with the traditional CMOS processes. The new stacked structure is characterized by double substrates and surface dielectric trenches(SDT). The drift region is separated by the P-buried layer to form two vertically parallel devices. The doping concentration of the drift region is increased benefiting from the enhanced auxiliary depletion effect of the double substrates, leading to a lower specific on-resistance(Ron,sp). Multiple electric field peaks appear at the corners of the SDT, which improves the lateral electric field distribution and the breakdown voltage(BV). Compared to a conventional LDMOS(C-LDMOS), the BV in the ST-LDMOS increases from 259 V to 459 V, an improvement of 77.22%. The Ron,sp decreases from 39.62 m?·cm^2 to 23.24 m?·cm^2 and the Baliga's figure of merit(FOM) of is 9.07 MW/cm^2.展开更多
We propose a Fano switch arising from the superlattice array of a plasma-filled quartz tube,which can be tuned and reconfigured by the plasma density in the tube.The generation of the switch depends on a Fano band that ...We propose a Fano switch arising from the superlattice array of a plasma-filled quartz tube,which can be tuned and reconfigured by the plasma density in the tube.The generation of the switch depends on a Fano band that is induced by the interference between the Mie resonance in an isolated cylinder and Bragg scattering in a periodic array.The underlying dispersion characteristics reveal that a localized tunableflat band corresponding to the Mie resonance plays an important role in the appearance of the Fano resonance.This active tunable switch can be potentially applied to microwave communications as a single-pole multi-throw switch and to monitor environmental variables that impact the plasma density.展开更多
A fifth order operational transconductance amplifier-C （OTA-C） Butterworth type low-pass filter with highly linear range and less passband attenuation is presented for wearable bio-telemetry monitoring applications ...A fifth order operational transconductance amplifier-C （OTA-C） Butterworth type low-pass filter with highly linear range and less passband attenuation is presented for wearable bio-telemetry monitoring applications in a UWB wireless body area network. The source degeneration structure applied in typical small transconduc- tance circuit is improved to provide a highly linear range for the OTA-C filter. Moreover, to reduce the passband attenuation of the filter, a cascode structure is employed as the output stage of the OTA. The OTA-based circuit is operated in weak inversion due to strict power limitation in the biomedical chip. The filter is fabricated in a SMIC 0.18-μm CMOS process. The measured results for the filter have shown a passband gain of -6.2 dB, while the -3-dB frequency is around 276 Hz. For the 0.8 Vpp sinusoidal input at 100 Hz, a total harmonic distortion （THD） of-56.8 dB is obtained. An electrocardiogram signal with noise interference is fed into this chip to validate the function of the designed filter.展开更多
A finite-difference-time-domain(FDTD)approach is undertaken to investigate the extraordinary optical transmission(EOT)phenomenon of Au circular aperture arrays deposited on a Bragg fiber facet for refractive index(RI)...A finite-difference-time-domain(FDTD)approach is undertaken to investigate the extraordinary optical transmission(EOT)phenomenon of Au circular aperture arrays deposited on a Bragg fiber facet for refractive index(RI)sensing.Investigation shows that the choice of effective indices and modal loss of the Bragg fiber core modes will affect the sensitivity enhancement by using a mode analysis approach.The critical parameters of Bragg fiber including the middle dielectric RI,as well as its gap between dielectric layers,which affect the EOT and RI sensitivity for the sensor,are discussed and optimized.It is demonstrated that a better sensitivity of 156±5 nm per refractive index unit(RIU)and an averaged figure of merit exceeding 3.5 RIU‒1 are achieved when RI is 1.5 and gap is 0.02μm in this structure.展开更多
Multicomponent oxide(Ga_(x)In_(1−x))_(2)O_(3)films are prepared on(0001)sapphire substrates to realize a tunable band-gap by magnetron sputtering technology followed by thermal annealing.The optical properties and ban...Multicomponent oxide(Ga_(x)In_(1−x))_(2)O_(3)films are prepared on(0001)sapphire substrates to realize a tunable band-gap by magnetron sputtering technology followed by thermal annealing.The optical properties and band structure evolution over the whole range of compositions in ternary compounds(Ga_(x)In_(1−x))_(2)O_(3)are investigated in detail.The X-ray diffraction spectra clearly indicate that(Ga_(x)In_(1−x))_(2)O_(3)films with Ga content varying from 0.11 to 0.55 have both cubic and monoclinic structures,and that for films with Ga content higher than 0.74,only the monoclinic structure appears.The transmittance of all films is greater than 86%in the visible range with sharp absorption edges and clear fringes.In addition,a blue shift of ultraviolet absorption edges from 380 to 250 nm is noted with increasing Ga content,indicating increasing band-gap energy from 3.61 to 4.64 eV.The experimental results lay a foundation for the application of transparent conductive compound(Ga_(x)In_(1−x))_(2)O_(3)thin films in photoelectric and photovoltaic industry,especially in display,light-emitting diode,and solar cell applications.展开更多
基金supported by the One Hundred Talents Program of the Chinese Academy of Sciencesthe National Natural Science Foundation of China(Grant Nos.61376083 and 61307077)+1 种基金the China Postdoctoral Science Foundation(Grant Nos.2013M530613 and 2015T80080)the Guangxi Key Laboratory of Precision Navigation Technology and Application(Grant Nos.DH201505,DH201510,and DH201511)
文摘We propose a periodic structure as an extra absorption layer（i.e., absorber） based on surface plasmon resonance effects, enhancing dual-band absorption in both middle wavelength infrared（MWIR） and long wavelength infrared（LWIR）regions. Periodic gold disks are selectively patterned onto the top layer of suspended SiN/VO_2/SiN sandwich-structure.We employ the finite element method to model this structure in COMSOL Multiphysics including a proposed method of modulating the absorption peak. Simulation results show that the absorber has two absorption peaks at wavelengths λ =4.8 μm and λ = 9 μm with the absorption magnitudes more than 0.98 and 0.94 in MWIR and LWIR regions, respectively. In addition, the absorber achieves broad spectrum absorption in LWIR region, in the meanwhile, tunable dual-band absorption peaks can be achieved by variable heights of cavity as well as diameters and periodicity of disk. Thus, this designed absorber can be a good candidate for enhancing the performance of dual band uncooled infrared detector, furthermore, the manufacturing process of cavity can be easily simplified so that the reliability of such devices can be improved.
基金the National Natural Science Foundation of China(Grant No.61434006).
文摘We fabricated a set of symmetric gate-recess devices with gate length of 70 nm.We kept the source-to-drain spacing(L_(SD))unchanged,and obtained a group of devices with gate-recess length(L_(recess))from 0.4µm to 0.8µm through process improvement.In order to suppress the influence of the kink effect,we have done SiN_(X) passivation treatment.The maximum saturation current density(ID_(max))and maximum transconductance(g_(m,max))increase as L_(recess) decreases to 0.4µm.At this time,the device shows ID_(max)=749.6 mA/mm at V_(GS)=0.2 V,V_(DS)=1.5 V,and g_(m,max)=1111 mS/mm at V_(GS)=−0.35 V,V_(DS)=1.5 V.Meanwhile,as L_(recess) increases,it causes parasitic capacitance C_(gd) and g_(d) to decrease,making f_(max) drastically increases.When L_(recess)=0.8µm,the device shows f_(T)=188 GHz and f_(max)=1112 GHz.
基金the National Natural Science Foundation of China(Grant No.61434006).
文摘Heterogeneous integrated InP high electron mobility transistors(HEMTs)on quartz wafers are fabricated successfully by using a reverse-grown InP epitaxial structure and benzocyclobutene(BCB)bonding technology.The channel of the new device is In_(0.7)Ga_(0.3)As,and the gate length is 100 nm.A maximum extrinsic transconductance gm,max of 855.5 mS/mm and a maximum drain current of 536.5 mA/mm are obtained.The current gain cutoff frequency is as high as 262 GHz and the maximum oscillation frequency reaches 288 GHz.In addition,a small signal equivalent circuit model of heterogeneous integration of InP HEMTs on quartz wafer is built to characterize device performance.
基金supported by the National Natural Science Foundation of China (No. 61474081)Guangxi Key Laboratory of Precision Navigation Technology and Application, Guilin University of Electronic Technology (No. DH201513)
基金Project supported by the National Nature Science Foundation of China(Grant No.61434006)。
文摘A set of 100-nm gate-length In P-based high electron mobility transistors(HEMTs)were designed and fabricated with different gate offsets in gate recess.A novel technology was proposed for independent definition of gate recess and T-shaped gate by electron beam lithography.DC and RF measurement was conducted.With the gate offset varying from drain side to source side,the maximum drain current(I_(ds,max))and transconductance(g_(m,max))increased.In the meantime,fTdecreased while f;increased,and the highest fmax of 1096 GHz was obtained.It can be explained by the increase of gate-source capacitance and the decrease of gate-drain capacitance and source resistance.Output conductance was also suppressed by gate offset toward source side.This provides simple and flexible device parameter selection for HEMTs of different usages.
基金Project supported by Guangxi Science and Technology Planning Project (Grant Nos. AD19245066, AA19254015, AD21220150, and AD18281037)the National Nature Science Foundation of China (Grant Nos. 61874036, 62174041, and 62041403)+4 种基金China Postdoctoral Science Foundation (Grant No. 2020M683626XB)the Natural Science Foundation of Guangxi Zhuang Autonomous Region (Grant No. 2018GXNSFAA138025)Guangxi Innovation Research Team Project (Grant No. 2018GXNSFGA281004)GUET Excellent Graduate Thesis (Grant No. YXYJRX01)the Fund from the State Key Laboratory of ASIC & System (Grant No. KVH1233021)
文摘Ferroelectric(FE)HfZrO/Al_(2)O_(3) gate stack AlGaN/GaN metal-FE-semiconductor heterostructure high-electron mo-bility transistors(MFSHEMTs)with varying Al_(x)Ga_(1-x)N barrier thickness and Al composition are investigated and com-pared by TCAD simulation with non-FE HfO_(2)/Al_(2)O_(3) gate stack metal-insulator-semiconductor heterostructure high-electron mobility transistors(MISHEMTs).Results show that the decrease of the two-dimensional electron gas(2DEG)density with decreasing AlGaN barrier thickness is more effectively suppressed in MFSHEMTs than that in MISHEMTs due to the enhanced FE polarization switching efficiency.The electrical characteristics of MFSHEMTs,including transcon-ductance,subthreshold swing,and on-state current,effectively improve with decreasing AlGaN thickness in MFSHEMTs.High Al composition in AlGaN barrier layers that are under 3-nm thickness plays a great role in enhancing the 2DEG den-sity and FE polarization in MFSHEMTs,improving the transconductance and the on-state current.The subthreshold swing and threshold voltage can be reduced by decreasing the AlGaN thickness and Al composition in MFSHEMTs,affording favorable conditions for further enhancing the device.
基金the Key-Area Research and Development Program of Guangdong Province,China(Grant Nos.2019B010132001,2020B010174003,and 2019B121204004)the Basic and Application Basic Research Foundation of Guangdong Province,China(Grant Nos.2020A1515110891 and 2019A1515111053)the Fund from the Ion Beam Center(IBC)at HZDR.
文摘We show the structural and optical properties of non-polar a-plane GaN epitaxial films modified by Si ion implantation.Upon gradually raising Si fluences from 5×10^(13)cm^(-2)to 5×10^(15)cm^(-2),the n-type dopant concentration gradually increases from 4.6×10^(18)cm^(-2)to 4.5×10^(20)cm^(-2),while the generated vacancy density accordingly raises from 3.7×10^(13)cm^(-2)to 3.8×10^(15)cm^(-2).Moreover,despite that the implantation enhances structural disorder,the epitaxial structure of the implanted region is still well preserved which is confirmed by Rutherford backscattering channeling spectrometry measurements.The monotonical uniaxial lattice expansion along the a direction(out-of-plane direction)is observed as a function of fluences till 1×10^(15)cm^(-2),which ceases at the overdose of 5×10^(15)cm^(-2)due to the partial amorphization in the surface region.Upon raising irradiation dose,a yellow emission in the as-grown sample is gradually quenched,probably due to the irradiation-induced generation of non-radiative recombination centers.
基金supported by the National Science Foundation of China(61561016 61861008+4 种基金 11603041)the Guangxi Natural Science Foundation Project(2018JJA170090)the Innovation Project of Guet Graduate Education(2018YJCX19 2018YJCX31)Guangxi Key Laboratory of Precision Navigation Technology and Application,Guilin University of Electronic Technology(DH201707)
文摘In order to solve the problem of ambiguous acquisition of BOC signals caused by its property of multiple peaks,an unambiguous acquisition algorithm named reconstruction of sub cross-correlation cancellation technique(RSCCT)for BOC(kn,n)signals is proposed.In this paper,the principle of signal decomposition is combined with the traditional acquisition algorithm structure,and then based on the method of reconstructing the correlation function.The method firstly gets the sub-pseudorandom noise(PRN)code by decomposing the local PRN code,then uses BOC(kn,n)and the sub-PRN code cross-correlation to get the sub cross-correlation function.Finally,the correlation peak with a single peak is obtained by reconstructing the sub cross-correlation function so that the ambiguities of BOC acquisition are removed.The simulation shows that RSCCT can completely eliminate the side peaks of BOC(kn,n)group signals while maintaining the narrow correlation of BOC,and its computational complexity is equivalent to sub carrier phase cancellation(SCPC)and autocorrelation side-peak cancellation technique(ASPeCT),and it reduces the computational complexity relative to BPSK-like.For BOC(n,n),the acquisition sensitivity of RSCCT is 3.25 dB,0.81 dB and 0.25 dB higher than binary phase shift keying(BPSK)-like,SCPC and ASPeCT at the acquisition probability of 90%,respectively.The peak to average power ratio is 1.91,3.0 and 3.7 times higher than ASPeCT,SCPC and BPSK-like at SNR=–20 dB,respectively.For BOC(2n,n),the acquisition sensitivity of RSCCT is 5.5 dB,1.25 dB and 2.69 dB higher than BPSK-like,SCPC and ASPeCT at the acquisition probability of 90%,respectively.The peak to average power ratio is 1.02,1.68 and 2.12 times higher than ASPeCT,SCPC and BPSK-like at SNR=–20 dB,respectively.
基金Supported by the National Key Research Program of China"Collaborative Precision Positioning Project"(2016YFB 0501900)the National Natural Science Foundation of China(11603041)+1 种基金Key Laboratory of Cognitive Radio and Information Processing,Ministry of Education(Guilin University of Electronic Technology)Guangxi Key Laboratory of Precision Navigation Technology and Application
文摘In order to overcome the limitations of a unitary reference station in mobile communication positioning network differential barometric altimetry(DBA)and broaden the action scope of the reference station and improve positioning accuracy of elevation,an integrated interpolation algorithm model based on generalized extended approximation(GEA)algorithm and Kriging interpolation in time-space domain of reference station is proposed.In the time domain,barometric measured data is considered the maximum value estimated by bilateral extension to avoid wrong direction of estimation,which is approaching true value.In the spatial domain,barometric relevance among multiple reference stations is utilized,the weighted coefficients of multiple reference stations is calculated by the integrated algorithm model based on the GEA algorithm and Kriging interpolation.The impact of each reference station to the measured station is quantified,so that a virtual reference station is constructed,which can overcome the limitation of barometric correction by a unitary reference station.In addition,the measurement error due to irregular change in atmospheric pressure will be eliminated.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11965009,61874036,61805053,and 61764001)the Natural Science Foundation of Guangxi Zhuang Autonomous Region,China(Grant Nos.2018JJA170010 and 2018GXNSFAA281193)the Innovation Project of GUET Graduate Education(Grant No.2020YCXS019)。
文摘We proposed a sandwich structure to realize broadband asymmetric transmission(AT) for both linearly and circularly polarized waves in the near infrared spectral region. The structure composes of a silica substrate and two sand-clock-like gold layers on the opposite sides of the substrate. Due to the surface plasmons of gold, the structure shows that the AT parameters of linearly and circularly polarized waves can reach 0.436 and 0.403, respectively. Meanwhile, a broadband property is presented for the AT parameter is over 0.3 between 320 THz and 340 THz. The structure realizes a diode-like AT for linearly wave in forward and circularly wave in backward, respectively. The magnetic dipoles excited by current in the two gold layers contribute to the broadband AT. The current density in top and bottom metallic layers illustrates the mechanism of the polarization conversion for broadband AT in detail.
基金Project supported by the Guangxi Natural Science Foundation of China(Grant Nos.2013GXNSFAA019335 and 2015GXNSFAA139300)Guangxi Experiment Center of Information Science of China(Grant No.YB1406)+2 种基金Guangxi Key Laboratory of Wireless Wideband Communication and Signal Processing of China,Key Laboratory of Cognitive Radio and Information Processing(Grant No.GXKL061505)Guangxi Key Laboratory of Automobile Components and Vehicle Technology of China(Grant No.2014KFMS04)the National Natural Science Foundation of China(Grant Nos.61361011,61274077,and 61464003)
文摘A novel silicon-on-insulator（SOI） high breakdown voltage（BV） power device with interlaced dielectric trenches（IDT） and N/P pillars is proposed. In the studied structure, the drift region is folded by IDT embedded in the active layer,which results in an increase of length of ionization integral remarkably. The crowding phenomenon of electric field in the corner of IDT is relieved by the N/P pillars. Both traits improve two key factors of BV, the ionization integral length and electric field magnitude, and thus BV is significantly enhanced. The electric field in the dielectric layer is enhanced and a major portion of bias is borne by the oxide layer due to the accumulation of inverse charges（holes） at the corner of IDT.The average value of the lateral electric field of the proposed device reaches 60 V/μm with a 10 μm drift length, which increases by 200% in comparison to the conventional SOI LDMOS, resulting in a breakdown voltage of 607 V.
基金supported by the National Natural Science Foundation of China(Grant Nos.61874036,62174041,and61434006)the Open Project of State Key Laboratory of ASIC and System(Grant No.KVH1233021)+3 种基金the Opening Foundation of the State Key Laboratory of Advanced Materials and Electronic Components(Grant No.FHR-JS-201909007)the Guangxi Innovation Research Team Project(Grant Nos.2018GXNSFGA281004 and 2018GXNSFBA281152)the Guangxi Innovation Driven Development Special Fund Project(Grant No.AA19254015)the Guangxi Key Laboratory of Precision Navigation Technology and Application Project(Grant Nos.DH201906,DH202020,and DH202001)。
文摘A double-recessed offset gate process technology for In P-based high electron mobility transistors(HEMTs)has been developed in this paper.Single-recessed and double-recessed HEMTs with different gate offsets have been fabricated and characterized.Compared with single-recessed devices,the maximum drain-source current(I_(D,max))and maximum extrinsic transconductance(g_(m,max))of double-recessed devices decreased due to the increase in series resistances.However,in terms of RF performance,double-recessed HEMTs achieved higher maximum oscillation frequency(f_(MAX))by reducing drain output conductance(g_(m,max))and drain to gate capacitance(C_gd).In addition,further improvement of fMAXwas observed by adjusting the gate offset of double-recessed devices.This can be explained by suppressing the ratio of C_(gd)to source to gate capacitance(C_gd)by extending drain-side recess length(Lrd).Compared with the single-recessed HEMTs,the f;of double-recessed offset gate HEMTs was increased by about 20%.
基金Project supported by the Natural Science Foundation of Liaoning Province, China (Grant Nos. 20180550100 and XLYC1807004)the National Natural Science Foundation of China (Grant No. 51772041)+1 种基金the Program for Dalian Excellent Talents, China (Grant No. 2017RQ148)the Open Project of the Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, China (Grant No. 20162016003).
文摘C70 nanotubes with a fcc lattice structure are polymerized through being irradiated by lasers with a wavelength of 514.5 nm at various power values. Raman spectra and photoluminescence (PL) spectra are employed to characterize the polymeric phases of the laser treated samples, showing that the disordered C70 oligomers are formed in the C70 nanotubes irradiated by such strong green lasers. Comparative studies further indicate that intermolecular bonds are formed between C70 molecules on the surface of nanotubes, which are similar to those formed under high pressure and high temperature (HPHT) conditions. And the content of intermolecular bonds increases obviously with the laser power increasing.
基金supported by the National Natural Science Foundation of China(Grant Nos.U21A2054,52273285,52061009,52262032)the National Key Research and Development Program of China(No.2022YFE0119100)the Guangxi Science and Technology Planning Project(Grant No.AD21220056).
文摘P-type Mg_(3)Sb_(2)-based Zintls have attracted considerable interest in the thermoelectric(TE)field due to their environmental friendliness and low cost.However,compared to their n-type counterparts,they show relatively low TE performance,limiting their application in TE devices.In this work,we simultaneously introduce Bi alloying at Sb sites and Ag doping at Mg sites into the Mg_(3)Sb_(2)to coopera-tively optimize the electrical and thermal properties for the first time,acquiring the highest ZT value of∼0.85 at 723 K and a high average ZT of 0.39 in the temperature range of 323-723 K in sample Mg_(2.94)Ag_(0.06)Sb_(1.9)Bi_(0.1).The first-principle calculations show that the codoping of Ag and Bi can shift the Fermi level into the valence band and narrow the band gap,resulting in the increased carrier concentration from 3.50×10^(17)cm^(-3)in the reference Mg 3 Sb 0.9 Bi 0.1 to∼7.88×10^(19)cm^(-3)in sample Mg 2.94 Ag 0.06 Sb 0.9 Bi 0.1.As a result,a remarkable power factor of∼778.9μW m^(-1)K^(-2)at 723 K is achieved in sample Mg 2.94 Ag 0.06 Sb 0.9 Bi 0.1.Meanwhile,a low lattice thermal conductivity of∼0.48 W m^(-1)K^(-1)at 723 K is also obtained with the help of phonon scattering at the distorted lattice,point defects,and nano-precipitates in sample Mg 2.94 Ag 0.06 Sb 0.9 Bi 0.1.The synergistic effect of using the multi-element co-doping/-alloying to optimize electrical properties in Mg_(3)Sb_(2)holds promise for further improving the TE performance of Zintl phase materials or even others.
基金funded by the National Natural Science Foundation of China (Grant Nos.U21A2054,52061009,52273285,and 52262032)Guangxi Natural Science Foundation of China (Grant No.2020GXNSFAA159111)+1 种基金Guangxi Science and Technology Project (Grant Nos.2021AC19206 and AD20159006)the National Key R&D Program of China (Grant No.2017YFE0198000).
文摘Si-based thermoelectric(TE)materials are exhibiting remarkable perspectives in self-energized applications with their special advantages.However,the relatively high total thermal conductivity(κ)prevents their TE enhancement.Here,a strategy of co-compositing dual oxides was implemented for enhancing the TE properties of p-type Si_(80)Ge_(20) bulks.Composited Ga2O_(3) was demonstrated to enhance the power factor(PF)due to the crystallization-induced effect of produced Ga by decomposition on SiGe matrix.Associating with compositing SiO_(2) aerogel(a-SiO_(2))powder,not only introduced the fine amorphous inclusions and decreased the grain size of host matrix,but also various nano morphologies were formed,i.e.,nano inclusions,precipitations,twin boundaries(TBs),and faults.Combining with the eutectic Ge,hierarchical scattering centers impeded the phonon transport comprehensively(decreasing the phonon group velocity(a v)and relaxation time)for reducing the lattice-induced thermal conductivity(lκ).As a result,a minimumκof 2.38 W·m^(−1)·K^(−1) was achieved,which is significantly dropped by 32.6%in contrast with that of the pristine counterpart.Ultimately,a maximal dimensionless figure of merit(ZT)of 0.9 was achieved at 600℃,which is better than those of most corresponding oxide-composited Si-based bulks.
基金supported by the National Natural Science Foundation of China(Grant No.61464003)the Guangxi Natural Science Foundation,China(Grant Nos.2015GXNSFAA139300 and 2018JJA170010)
文摘A stacked lateral double-diffused metal–oxide–semiconductor field-effect transistor(LDMOS) with enhanced depletion effect by surface substrate is proposed(ST-LDMOS), which is compatible with the traditional CMOS processes. The new stacked structure is characterized by double substrates and surface dielectric trenches(SDT). The drift region is separated by the P-buried layer to form two vertically parallel devices. The doping concentration of the drift region is increased benefiting from the enhanced auxiliary depletion effect of the double substrates, leading to a lower specific on-resistance(Ron,sp). Multiple electric field peaks appear at the corners of the SDT, which improves the lateral electric field distribution and the breakdown voltage(BV). Compared to a conventional LDMOS(C-LDMOS), the BV in the ST-LDMOS increases from 259 V to 459 V, an improvement of 77.22%. The Ron,sp decreases from 39.62 m?·cm^2 to 23.24 m?·cm^2 and the Baliga's figure of merit(FOM) of is 9.07 MW/cm^2.
基金supported by National Natural Science Foun-dation of China(Nos.11965009,61761010,61765004,61764001 and 62075084)Natural Science Foundation of Guangxi(Nos.2018JJA170010 and 2018GXNSFAA281193)by the Guangdong Basic and Applied Basic Research Foundation(No.2020A1515010615).
文摘We propose a Fano switch arising from the superlattice array of a plasma-filled quartz tube,which can be tuned and reconfigured by the plasma density in the tube.The generation of the switch depends on a Fano band that is induced by the interference between the Mie resonance in an isolated cylinder and Bragg scattering in a periodic array.The underlying dispersion characteristics reveal that a localized tunableflat band corresponding to the Mie resonance plays an important role in the appearance of the Fano resonance.This active tunable switch can be potentially applied to microwave communications as a single-pole multi-throw switch and to monitor environmental variables that impact the plasma density.
基金Project supported by the National Natural Science Foundation of China(Nos.61161003,61264001,61166004)the Guangxi Natural Science Foundation(No.2013GXNSFAA019333)
文摘A fifth order operational transconductance amplifier-C （OTA-C） Butterworth type low-pass filter with highly linear range and less passband attenuation is presented for wearable bio-telemetry monitoring applications in a UWB wireless body area network. The source degeneration structure applied in typical small transconduc- tance circuit is improved to provide a highly linear range for the OTA-C filter. Moreover, to reduce the passband attenuation of the filter, a cascode structure is employed as the output stage of the OTA. The OTA-based circuit is operated in weak inversion due to strict power limitation in the biomedical chip. The filter is fabricated in a SMIC 0.18-μm CMOS process. The measured results for the filter have shown a passband gain of -6.2 dB, while the -3-dB frequency is around 276 Hz. For the 0.8 Vpp sinusoidal input at 100 Hz, a total harmonic distortion （THD） of-56.8 dB is obtained. An electrocardiogram signal with noise interference is fed into this chip to validate the function of the designed filter.
基金This work is partially supported by the National Natural Science Foundation of China(Grant Nos.61465004 and 61765004)the Guangxi Natural Science Foundation(Grant Nos.2017GXNSFAA1981642016GXNSFAA380006)the Guangxi Key Laboratory of Precision Navigation Technology and Application,Guilin University of Electronic Technology Foundation(Grant No.DH201804).
文摘A finite-difference-time-domain(FDTD)approach is undertaken to investigate the extraordinary optical transmission(EOT)phenomenon of Au circular aperture arrays deposited on a Bragg fiber facet for refractive index(RI)sensing.Investigation shows that the choice of effective indices and modal loss of the Bragg fiber core modes will affect the sensitivity enhancement by using a mode analysis approach.The critical parameters of Bragg fiber including the middle dielectric RI,as well as its gap between dielectric layers,which affect the EOT and RI sensitivity for the sensor,are discussed and optimized.It is demonstrated that a better sensitivity of 156±5 nm per refractive index unit(RIU)and an averaged figure of merit exceeding 3.5 RIU‒1 are achieved when RI is 1.5 and gap is 0.02μm in this structure.
基金Project supported by the National Natural Science Foundation of China(Nos.61764001,61665001,51665009,11965009,61874036,and 61805053)the Guangxi Science and Technology Base and Talent Special Project,China(Nos.AD18281084,AD18281030,AD18281034,and AD18281037)+3 种基金the Guangxi Key Laboratory of Precision Navigation Technology and Application,China(No.DH201808)the One Hundred Person Project of Guangxi as well as the Thousands of Key Teacher Training Project of Guangxi Education Department,Chinathe Innovation Project of Guilin University of Electronic Technology Graduate Education,China(No.2019YCXS021)the Natural Science Foundation of Shanghai,China(No.19ZR1420100)。
文摘Multicomponent oxide(Ga_(x)In_(1−x))_(2)O_(3)films are prepared on(0001)sapphire substrates to realize a tunable band-gap by magnetron sputtering technology followed by thermal annealing.The optical properties and band structure evolution over the whole range of compositions in ternary compounds(Ga_(x)In_(1−x))_(2)O_(3)are investigated in detail.The X-ray diffraction spectra clearly indicate that(Ga_(x)In_(1−x))_(2)O_(3)films with Ga content varying from 0.11 to 0.55 have both cubic and monoclinic structures,and that for films with Ga content higher than 0.74,only the monoclinic structure appears.The transmittance of all films is greater than 86%in the visible range with sharp absorption edges and clear fringes.In addition,a blue shift of ultraviolet absorption edges from 380 to 250 nm is noted with increasing Ga content,indicating increasing band-gap energy from 3.61 to 4.64 eV.The experimental results lay a foundation for the application of transparent conductive compound(Ga_(x)In_(1−x))_(2)O_(3)thin films in photoelectric and photovoltaic industry,especially in display,light-emitting diode,and solar cell applications.
