Dual-active-layer(DAL)amorphous InGaZnO(IGZO)thin-film transistors(TFTs)are fabricated at low temperature without post-annealing.A bottom low-resistance(low-R)IGZO layer and a top high-resistance(high-R)IGZO layer con...Dual-active-layer(DAL)amorphous InGaZnO(IGZO)thin-film transistors(TFTs)are fabricated at low temperature without post-annealing.A bottom low-resistance(low-R)IGZO layer and a top high-resistance(high-R)IGZO layer constitute the DAL homojunction with smooth and high-quality interface by in situ modulation of oxygen composition.The performance of the DAL TFT is significantly improved when compared to that of a single-active-layer TFT.A detailed investigation was carried out regarding the effects of the thickness of both layers on the electrical properties and gate bias stress stabilities.It is found that the low-R layer improves the mobility,ON/OFF ratio,threshold voltage and hysteresis voltage by passivating the defects and providing a smooth interface.The high-R IGZO layer has a great impact on the hysteresis,which changes from clockwise to counterclockwise.The best TFT shows a mobility of 5.41 cm^2/V·s,a subthreshold swing of 95.0 mV/dec,an ON/OFF ratio of 6.70×10^7,a threshold voltage of 0.24 V,and a hysteresis voltage of 0.13 V.The value of threshold voltage shifts under positive gate bias stress decreases when increasing the thickness of both layers.展开更多
Si-doped zinc oxide（SZO） thin films are deposited by using a co-sputtering method,and used as the channel active layers of ZnO-based TFTs with single and dual active layer structures.The effects of silicon content o...Si-doped zinc oxide（SZO） thin films are deposited by using a co-sputtering method,and used as the channel active layers of ZnO-based TFTs with single and dual active layer structures.The effects of silicon content on the optical transmittance of the SZO thin film and electrical properties of the SZO TFT are investigated.Moreover,the electrical performances and bias-stress stabilities of the single- and dual-active-layer TFTs are investigated and compared to reveal the effects of the Si doping and dual-active-layer structure.The average transmittances of all the SZO films are about 90% in the visible light region of 400 nm-800 nm,and the optical band gap of the SZO film gradually increases with increasing Si content.The Si-doping can effectively suppress the grain growth of ZnO,revealed by atomic force microscope analysis.Compared with that of the undoped ZnO TFT,the off-state current of the SZO TFT is reduced by more than two orders of magnitude and it is 1.5 × 10^-12 A,and thus the on/off current ratio is increased by more than two orders of magnitude.In summary,the SZO/ZnO TFT with dual-active-layer structure exhibits a high on/off current ratio of 4.0 × 10^6 and superior stability under gate-bias and drain-bias stress.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674405,61874139,and 11675280)
文摘Dual-active-layer(DAL)amorphous InGaZnO(IGZO)thin-film transistors(TFTs)are fabricated at low temperature without post-annealing.A bottom low-resistance(low-R)IGZO layer and a top high-resistance(high-R)IGZO layer constitute the DAL homojunction with smooth and high-quality interface by in situ modulation of oxygen composition.The performance of the DAL TFT is significantly improved when compared to that of a single-active-layer TFT.A detailed investigation was carried out regarding the effects of the thickness of both layers on the electrical properties and gate bias stress stabilities.It is found that the low-R layer improves the mobility,ON/OFF ratio,threshold voltage and hysteresis voltage by passivating the defects and providing a smooth interface.The high-R IGZO layer has a great impact on the hysteresis,which changes from clockwise to counterclockwise.The best TFT shows a mobility of 5.41 cm^2/V·s,a subthreshold swing of 95.0 mV/dec,an ON/OFF ratio of 6.70×10^7,a threshold voltage of 0.24 V,and a hysteresis voltage of 0.13 V.The value of threshold voltage shifts under positive gate bias stress decreases when increasing the thickness of both layers.
基金supported by the National Natural Science Foundation of China(Grant Nos.61076113 and 61274085)the Natural Science Foundation of Guangdong Province(Grant No.2016A030313474)the University Development Fund(Nanotechnology Research Institute,Grant No.00600009)of the University of Hong Kong,China
文摘Si-doped zinc oxide（SZO） thin films are deposited by using a co-sputtering method,and used as the channel active layers of ZnO-based TFTs with single and dual active layer structures.The effects of silicon content on the optical transmittance of the SZO thin film and electrical properties of the SZO TFT are investigated.Moreover,the electrical performances and bias-stress stabilities of the single- and dual-active-layer TFTs are investigated and compared to reveal the effects of the Si doping and dual-active-layer structure.The average transmittances of all the SZO films are about 90% in the visible light region of 400 nm-800 nm,and the optical band gap of the SZO film gradually increases with increasing Si content.The Si-doping can effectively suppress the grain growth of ZnO,revealed by atomic force microscope analysis.Compared with that of the undoped ZnO TFT,the off-state current of the SZO TFT is reduced by more than two orders of magnitude and it is 1.5 × 10^-12 A,and thus the on/off current ratio is increased by more than two orders of magnitude.In summary,the SZO/ZnO TFT with dual-active-layer structure exhibits a high on/off current ratio of 4.0 × 10^6 and superior stability under gate-bias and drain-bias stress.
