Mn-doped GaN epitaxial films were grown by metal organic chemical vapour deposition （MOCVD）. Microstructural properties of films are investigated using Raman scattering. It is found that with increasing Mn-dopants l...Mn-doped GaN epitaxial films were grown by metal organic chemical vapour deposition （MOCVD）. Microstructural properties of films are investigated using Raman scattering. It is found that with increasing Mn-dopants levels, longitudinal optical phonon mode A1 （LO） of films is broadened and shifted towards lower frequency. This phenomenon possibly derives from the difference in bonding strength between Ga-N pairs and Mn-N pairs in host lattice. In addition, optical properties of films are investigated using cathodoluminescence and absorption spectroscopy. Mn-related both emission band around 3.0eV and absorption bands around 1.5 and 2.95eV are observed. By studies on structural and optical properties of Mn-doped GaN, we find that Mn ions substitute for Ga sites in host lattice. However, carrier-mediated ferromagnetic exchange seems unlikely due to deep levels of Mn acceptors.展开更多
Fe-doped GaN thin films are grown on c-sapphires by metal organic chemical vapour deposition method （MOCVD） Crystalline quality and phase purity are characterized by x-ray diffraction and Raman scattering measuremen...Fe-doped GaN thin films are grown on c-sapphires by metal organic chemical vapour deposition method （MOCVD） Crystalline quality and phase purity are characterized by x-ray diffraction and Raman scattering measurements. There are no detectable second phases formed during growth and no significant degradation in crystalline quality as Fe ions are doped. Fe-related optical transitions are observed in photoluminescence spectra. Magnetic measurements reveal that the films show room-temperature ferromagnetic behaviour. The ferromagnetism may originate from carrier-mediated Fe-doped GaN diluted magnetic semiconductors or nanoscale iron clusters and FeN compounds which we have not detected.展开更多
Due to the bandwidth limitation of the ultraviolet-C(UV-C) optical communication system and strong channel attenuation, it is difficult to transmit high-frequency signals. In this paper, the temporal ghost imaging(TGI...Due to the bandwidth limitation of the ultraviolet-C(UV-C) optical communication system and strong channel attenuation, it is difficult to transmit high-frequency signals. In this paper, the temporal ghost imaging(TGI) algorithm was first applied to the UV-C communication experimentally, and we realized the transmission of a 4 GHz signal through 95.34 MHz system bandwidth. The study indicates that the TGI algorithm can significantly improve the signal-to-noise ratio(SNR) compared with the on–off keying method. Our research provides a new approach for alleviating transmission frequency limitation due to poor SNR and insufficient hardware bandwidth.展开更多
We have grown transition metal （Fe, Mn） doped GaN thin films on c-oriented sapphire by metal-organic chemical vapor deposition. By varying the flow of the metal precursor, a series of samples with different ion con-...We have grown transition metal （Fe, Mn） doped GaN thin films on c-oriented sapphire by metal-organic chemical vapor deposition. By varying the flow of the metal precursor, a series of samples with different ion con- centrations are synthesized. Microstructural properties are characterized by using a high-resolution transmission electron microscope. For Fe over-doped GaN samples, hexagonal Fe3N clusters are observed with Fe3N （0002） parallel to GaN （0002） while for Mn over-doped GaN, hexagonal Mn6N2.58 phases are observed with Mn6N2.58（0002） parallel to GaN （0002）. In addition, with higher concentration ions doping into the lattice matrix, the partial lattice orientation is distorted, leading to the tilt orGaN （0002） planes. The magnetization of the Fe over-doped GaN sam- ple is increased, which is ascribed to the participation of ferromagnetic iron and Fe3N. The Mn over-doped sample displays very weak ferromagnetic behavior, which probably originates from the Mn6N2.58.展开更多
基金Supported by the National Basic Research Programme of China under Grant Nos 2006CB604905 and 2006CB604907, the National Hi-Tech Research Programme of China under Grant No 2006AA03Z411, the National Natural Science Foundation of China under Grant Nos 60721063, 60731160628 and 60820106003.
文摘Mn-doped GaN epitaxial films were grown by metal organic chemical vapour deposition （MOCVD）. Microstructural properties of films are investigated using Raman scattering. It is found that with increasing Mn-dopants levels, longitudinal optical phonon mode A1 （LO） of films is broadened and shifted towards lower frequency. This phenomenon possibly derives from the difference in bonding strength between Ga-N pairs and Mn-N pairs in host lattice. In addition, optical properties of films are investigated using cathodoluminescence and absorption spectroscopy. Mn-related both emission band around 3.0eV and absorption bands around 1.5 and 2.95eV are observed. By studies on structural and optical properties of Mn-doped GaN, we find that Mn ions substitute for Ga sites in host lattice. However, carrier-mediated ferromagnetic exchange seems unlikely due to deep levels of Mn acceptors.
基金Supported by the National Basic Research Programme of China under Grant Nos 2006CB604905 and 2006CB604907, the National Hi-Tech Research and Development Programme of China under Grant Nos 2006AA03A142 and 2006AA03Z411, the National Natural Science Foundation of China under Grant Nos 60731160628, 60776001 and 60421003, the Fund of Ministry of Education of China （10416）, and the Natural Science Foundation of Jiangsu Province （BK2005210）.
文摘Fe-doped GaN thin films are grown on c-sapphires by metal organic chemical vapour deposition method （MOCVD） Crystalline quality and phase purity are characterized by x-ray diffraction and Raman scattering measurements. There are no detectable second phases formed during growth and no significant degradation in crystalline quality as Fe ions are doped. Fe-related optical transitions are observed in photoluminescence spectra. Magnetic measurements reveal that the films show room-temperature ferromagnetic behaviour. The ferromagnetism may originate from carrier-mediated Fe-doped GaN diluted magnetic semiconductors or nanoscale iron clusters and FeN compounds which we have not detected.
基金This work was supported by the National Natural Science Foundation of China(NSFC)(Nos.61974031 and 61705041)Hehai University-CIOMP Joint Fund(No.FC2020-001)Shanghai Technical Standard Program(No.18DZ2206000).
文摘Due to the bandwidth limitation of the ultraviolet-C(UV-C) optical communication system and strong channel attenuation, it is difficult to transmit high-frequency signals. In this paper, the temporal ghost imaging(TGI) algorithm was first applied to the UV-C communication experimentally, and we realized the transmission of a 4 GHz signal through 95.34 MHz system bandwidth. The study indicates that the TGI algorithm can significantly improve the signal-to-noise ratio(SNR) compared with the on–off keying method. Our research provides a new approach for alleviating transmission frequency limitation due to poor SNR and insufficient hardware bandwidth.
基金supported by the Special Funds for Major State Basic Research Project,China(No.2011CB301900)the Hi-Tech Research Project,China(No.2009AA03A198)+2 种基金the National Natural Science Foundation of China(Nos.60990311,60820106003,608201060,60906025,60936004,61106009)the Natural Science Foundation of Jiangsu Province,China(Nos.BK2008019,K2009255,BK2010178, BK2010385)the Research Funds from NJU-Yangzhou Institute of Opto-Electronics
文摘We have grown transition metal （Fe, Mn） doped GaN thin films on c-oriented sapphire by metal-organic chemical vapor deposition. By varying the flow of the metal precursor, a series of samples with different ion con- centrations are synthesized. Microstructural properties are characterized by using a high-resolution transmission electron microscope. For Fe over-doped GaN samples, hexagonal Fe3N clusters are observed with Fe3N （0002） parallel to GaN （0002） while for Mn over-doped GaN, hexagonal Mn6N2.58 phases are observed with Mn6N2.58（0002） parallel to GaN （0002）. In addition, with higher concentration ions doping into the lattice matrix, the partial lattice orientation is distorted, leading to the tilt orGaN （0002） planes. The magnetization of the Fe over-doped GaN sam- ple is increased, which is ascribed to the participation of ferromagnetic iron and Fe3N. The Mn over-doped sample displays very weak ferromagnetic behavior, which probably originates from the Mn6N2.58.
