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Growth of Highly Conductive n-Type Al0.7Ga0.3N Film by Using AlN Buffer with Periodical Variation of Ⅴ/Ⅲ Ratio

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Chinese Physics Letters 2008年第12期25卷 4449-4452页

作者：张洁郭丽伟邢志刚葛炳辉丁国建彭铭曾贾海强周均铭陈弘 Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190

High quality and highly conductive n-type Al0.7Ga0.3N films are obtained by using AlN multi-step layers （MSL） with periodical variation of Ⅴ/Ⅲ ratios by low-pressure metalorganic chemical vapour deposition （LP-MOCVD）. The full-width at half-maximum （FWHM） of （0002） and （1015） rocking curves of the Si-doped Al0.7Ga0.3N layer are 519 and 625 arcsec, respectively, Room temperature （RT） Hall measurement shows a free electron concentration of 2.9 × 10^19 cm^-3, and mobility of 17.8cm^2V^-1s^-1, corresponding to a resistivity of 0.0121 Ω cm. High conductivity of the Si-doped AlGaN film with such high Al mole fraction is mainly contributed by a remarkable reduction of threading dislocations （TDs） in AlGaN layer. The TD reducing mechanism in AlN MSL growth with periodical variation of Ⅴ/Ⅲ ratio is discussed in detail.

关键词： ELECTRIC conductivity METAL organic chemical vapor deposition gallium nitride ALUMINUM nitride LOW pressure (Science) HALL effect SEMICONDUCTORS DISLOCATIONS in crystals

Variation of Optical Quenching of Photoconductivity with Resistivity in Unintentional Doped GaN

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Chinese Physics Letters 2010年第5期27卷 208-211页

作者：侯奇峰王晓亮肖红领王翠梅杨翠柏李晋闽 Materials Science Center Institute of Semiconductors Chinese Academy of Sciences P. O. Box 912 Beijing 100083 Key Laboratory of Semiconductor Materials Science Chinese Academy of Sciences P. O. Box 912 Beijing 100083

The optical quenching of photoconduetivity under dual illumination in GaN samples with different resistivity is investigated to reveal the variation of deep levels. The samples are grown by metal organic chemical vapour deposition without intentional doping. Quenching bands centered at 1.35 eV, 1.55 eV, 1.98eV, and 2.60 eV are observed. It is found that the 1.98eV quenching band is dominated in all the samples and the 2.60eV band is observed only in the high-resistivity samples. The possible defect levels responsible for the quenching bands and the origin of different quenching behaviour at 2.60eV are discussed. It is suggested that the defect level responsible for quenching at 2.60 eV plays an important role for the enhancement of resistivity.

关键词： METALS -- Quenching PHOTOCONDUCTIVITY ELECTRIC resistance gallium nitride METAL organic chemical vapor deposition CRYSTAL growth

Effect of Annealing on the Optical Properties of GaN Films Grown by Pulsed Laser Deposition

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Journal of Materials Science & Technology 2013年第8期29卷 752-756页

作者： M.Baseer Haider M.F.Al-Kuhaili S.M.A.Durrani Imran Bakhtiari Department of Physics King Fahd University of Petroleum & MineralsDhahran 31261Saudi Arabia

In the present study, gallium nitride thin films were grown by using pulsed laser deposition. After the growth samples were annealed at 400 and 600 ℃ in the nitrogen atmosphere. Surface morphology of the as-grown and annealed samples was observed by atomic force microscopy. Post-growth annealing results in an improved surface roughness of the films. Chemical analysis of the samples was performed by X-ray photoelectron spectroscopy. Stoichiometric gallium nitride thin films were obtained for the samples annealed at 600 ℃. Optical measurements of the samples were performed to measure the band gap and optical constants of the films. Effect of annealing on the band gap and optical constants of the films was studied.

关键词： gallium nitride Pulsed laser deposition (PLD) nitride semiconductors X-ray photoelectron spectroscopy (XPS) Transmittance spectra Optical constants

Measurement of GaN/Ge（001） Heterojunction Valence Band Offset by X-Ray Photoelectron Spectroscopy

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Chinese Physics Letters 2010年第6期27卷 183-186页

作者： GUO Yan LIU Xiang-Lin SONG Hua-Ping YANG An-Li ZHENG Gao-Lin WEI Hong-Yuan YANG Shao-Yan ZHU Qin-Sheng WANG Zhan-Guo Key Laboratory of Semiconductor Materials Science Institute of Semiconductors Chinese Academy of Sciences PO Box 912 Beijing 100083

X-ray photoelectron spectroscopy has been used to measure the valence band offset （VBO） at the GaN/Ge heterostructure interface. The VBO is directly determined to be 1.13 ±0.19 eV, according to the relationship between the conduction band offset AEc and the valence band offset △Ev：△Ec =EgGaN -EgGe - △Ev, and taking the room-temperature band-gaps as 3.4 and 0.67eV for GaN and Ge, respectively. The conduction band offset is deduced to be 1.6±0.19 eV, which indicates a type-I band alignment for GaN/Ge. Accurate determination of the valence and conduction band offsets is important for the use of GaN/Ge based devices.

关键词： gallium nitride HETEROJUNCTIONS X-ray photoelectron spectroscopy SEMICONDUCTOR junctions CONDUCTION band TEMPERATURE effect ENERGY gaps (Physics)

Study on nitridation processes of β-Ga_2O_3 single crystal

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Chinese Optics Letters 2008年第4期6卷 282-285页

作者：李星夏长泰何肖丽裴广庆张俊刚徐军 Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai 201800 Key Laboratory of Materials Physics and Anhui Key Laboratory of Nanomaterials and Nanostructures Institute of Solid State PhysicsChinese Academy of SciencesHefei 230031 GE(China)Research and Development Center Company Limited Shanghai 201203

Nitridated β-Ga2O3 （100） substrate was investigated as the substrate for GaN epitaxial growth. The effects of nitridation temperature and surface roughness of β-Ga2O3 wafers on the formation of GaN were studied. It was found that the most optimized nitridation temperature was 900 ℃, and hexagonal GaN with preferred orientation was produced on the well-polished wafer. The nitridation mechanism was also discussed.

关键词： Epitaxial growth gallium compounds gallium nitride Nitridation Single crystals Surface roughness

The optimal thickness of a transmission-mode GaN photocathode

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Chinese Physics B 2012年第8期21卷 517-521页

作者：王晓晖石峰郭晖胡仓陆程宏昌常本康任玲杜玉杰张俊举 Science and Technology on Low-Light-Level Night Vision Laboratory Institute of Electronic Engineering and Optoelectronic Technology Nanjing University of Science and Technology Department of Physics Institute of Binzhou

A 150-nm-thick CaN photocathode with a Mg doping concentration of 1.6 × 1017 cm-3 is activated by Cs/O in an ultrahigh vacuum chamber, and a quantum efficiency （QE） curve of the negative electron affinity transmission-mode （t-mode） of the GaN photocathode is obtained. The maximum QE reaches 13.0% at 290 nm. According to the t-mode QE equation solved from the diffusion equation, the QE curve is fitted. From the fitting results, the electron escape probability is 0.32, the back-interface recombination velocity is 5 ×104 cm. s^-1, and the electron diffusion length is 116 nm. Based on these parameters, the influence of CaN thickness on t-mode QE is simulated. The simulation shows that the optimal thickness of GaN is 90 nm, which is better than the 150-nm GaN.

关键词： gallium nitride transmission-mode quantum efficiency optimal thickness

Fabrication and Characterization of High Power InGaN Blue-Violet Lasers with an Array Structure

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Chinese Physics Letters 2010年第5期27卷 109-112页

作者：季莲张书明江德生刘宗顺张立群朱建军赵德刚段俐宏杨辉 State Key Laboratory on Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Sciences PO BOX 912 Beijing 100083 Suzhou Institute of Nano-tech and Nano-bionics Chinese Academy of Sciences Suzhou 215123

InGaN/GaN multi-quantum-well-structure laser diodes with an array structure are successfully fabricated on sapphire substrates. The laser diode consists of four emitter stripes which share common electrodes on one laser chip. An 800-μm-long cavity is formed by cleaving the substrate along the （1100） orientation using laser scriber. The threshold current and voltage of the laser array diode are 2A and 10.5 V, respectively. A light output peak power of 12 W under pulsed current injection at room temperature is achieved. We simulate the electric properties of GaN based laser diode in a co-planar structure and the results show that minimizing the difference of distances between the different ridges and the n-electrode and increasing the electrical conductivity of the n-type GaN are two effective ways to improve the uniformity of carrier distribution in emitter stripes. Two pairs of emitters on a chip are arranged to be located near the two n-electrode pads on the left and right sides, and the four stripe emitters can laser together. The laser diode shows two sharp peaks of light output at 408 and 409 nm above the threshold current. The full widths at half maximum for the parallel and perpendicular far field patterns are 8° and 32°, respectively.

关键词： MICROFABRICATION LASER beams QUANTUM wells gallium nitride OPTICAL detectors SAPPHIRES ELECTRODES TEMPERATURE effect SIMULATION methods & models

Simulation and Experimentation for Low Density Drain AlGaN/GaN HEMT

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Chinese Physics Letters 2014年第3期31卷 177-180页

作者： WANG Chong HE Yun-Long DING Ning ZHENG Xue-Feng ZHANG Peng MA Xiao-Hua ZHANG Jin-Cheng HAO Yue Key Lab of Wide Band Gap Semiconductor Materials and Devices and Institute of Microelectronics Xidian University Xi'an 710071

In order to improve the breakdown voltage of AlGaN/GaN high electron mobility transistors （HEMTs）, we report a feasible method of low density drain （LDD） HEMT. The fluoride-based plasma treatment using CF4 gas is performed on the drain-side of the gate edge. The channel two-dimensional electron gas （2DEG） concentrations are modulated by fluoride plasma treatment, and the peak electric field at the gate edge is effectively reduced, so the breakdown voltage is improved. The electric field distributions of the LDD-HEMTs are simulated using the Silvaco software, and the peak of the electric field on the gate edge is effectively reduced. Experimental results show that, compared with the conventional HEMT, LDD-HEMTs have a lower reverse leakage current of the gate, and the breakdown voltage is increased by 36%. The current collapse characteristics of the LDD-HEMTs are confirmed by dual-pulse measurement, and an obvious pulse current reduction is due to the surface states by implanting F ions between the gate and the drain.

关键词： HIGH electron mobility transistors RESEARCH gallium nitride PLASMA (Ionized gases) -- Research CHEMICAL vapor deposition PHYSICS research

Effect of annealing on performance of PEDOT:PSS/n-GaN Schottky solar cells

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Chinese Physics B 2014年第7期23卷 673-676页

作者：冯倩杜锴李宇坤时鹏冯庆 School of Microelectronics Xidian University Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices Xidian University

We develop a heterojunction-based Schottky solar cell consisting of n-type GaN and PEDOT：PSS and also investigate the effect of annealing on the performance of the solar cell. The results show that the open circuit voltage （Voc） increases from 0.54 V to 0.56 V, 0.71 V and 0.82 eV while decreases to 0.69 eV after annealing at 100 ℃, 130 ℃, 160 ℃, and 200 ℃, respectively, which can be ascribed to the change of barrier height of PEDOT：PSS/GaN Schottky contact induced by variation of the work function of the PEDOT：PSS. Furthermore, the conductivity and surface roughness measurements of the PEDOT：PSS indicate that annealing can increase the grain size and improve the connectivity between PEDOT and PSS particles, and cause thermal degradation at the same time, which leads to the rise in short-circuit current density （ISC） up to 160 ℃ and the dropoff in ISC after annealing at 200 ℃.

关键词： gallium nitride PEDOT:PSS Schottky solar cell post-annealing