GaN/Surface-modified graphitic carbon nitride heterojunction: Promising photocatalytic hydrogen evolution materials

The coupling of two-dimensional (2D) layered materials is an effective way to realize photocatalytic hydrogen production. Herein, using first-principles calculations, the photocatalytic properties of GaN/CNs heterojunctions formed by two different graphite-like carbon nitride materials and GaN monolayer are discussed in detail. The results show that the GaN/C₂N heterojunction can promote the effective separation of photogenerated electron and hole pairs, which is attributed to its type-II band orientation and high carrier mobility. However, the low overpotential of GaN/C₂N for photocatalytic hydrogen production limits the photocatalytic performance. On this basis, we adjust the CBM position of the GaN/C₂N heterojunction by applying an electric field to enhance its hydrogen evolution capability. In addition, the GaN/g-C₃N₄ is a type-I heterojunction, which is suitable for the field of optoelectronic devices. This work broadens the field of vision for the preparation of highly efficient photocatalysts.     

GaN中质子辐照损伤的分子动力学模拟研究

本文利用分子动力学方法研究了GaN在质子辐照下的损伤。对不同能量（1~10 keV）初级离位原子（PKA）引起的级联碰撞进行了研究，分析了点缺陷与PKA能量的关系、点缺陷随时间的演化规律、点缺陷的空间分布及点缺陷团簇的尺寸特征。研究结果表明，点缺陷的产生与PKA能量呈线性关系，不同类型的点缺陷随时间演化规律相似，点缺陷多产生在PKA径迹旁，点缺陷团簇多为孤立的点缺陷和小团簇。     

Improving performance of high-power indium gallium nitride/gallium nitride-based vertical light-emitting diodes by employing simple n-type electrode pattern

In this work, simple n-type electrode structures were used to enhance the electrical and optical performances of fully packaged commercially mass-produced vertical-geometry light-emitting diodes (VLEDs). The forward bias voltage of the VLED with a Y-pattern electrode increased less rapidly than that of VLEDs with a reference electrode. The VLEDs with the reference and Y-pattern electrodes exhibited forward voltages of 2.93±0.015 and 2.89±0.015 V at 350 mA and 3.77±0.015 and 3.53±0.015 V at 2000 mA, respectively. The VLEDs with the Y-pattern electrode resulted in a higher light output than the VLEDs with the reference electrode with increase in the drive current to 2000 mA. The emission images showed that the VLEDs with the Y-pattern electrode exhibited better current spreading behavior and lower junction temperatures than the VLEDs with the reference electrode. With increase in the current from 350 to 2000 mA, the VLEDs with the Y-pattern electrode experienced a 39.4% reduction in the wall plug efficiency, whereas the VLEDs with the reference electrode suffered from a 43.3% reduction.     

Recent progress of physical failure analysis of GaN HEMTs

Gallium nitride (GaN)-based high-electron mobility transistors (HEMTs) are widely used in high power and high frequency application fields,due to the outstanding physical and chemical properties of the GaN material.However,GaN HEMTs suffer from degradations and even failures during practical applications,making physical analyses of post-failure devices extremely significant for reliability improvements and further device optimizations.In this paper,common physical characterization techniques for post failure analyses are introduced,several failure mechanisms and corresponding failure phenomena are reviewed and summarized,and finally device optimization methods are discussed.     

Dislocation luminescence in GaN single crystals under nanoindentation

This work presents an experimental study on the dislocation luminescence in GaN by nanoindentation, cathodoluminescence, and Raman. The dislocation luminescence peaking at 3.12 eV exhibits a series of special properties in the cathodoluminescence measurements, and it completely disappears after annealing at 500°C. Raman spectroscopy shows evidence for existence of vacancies in the indented region. A comprehensive investigation encompassing cathodoluminescence, Raman, and annealing experiments allow the assignment of dislocation luminescence to conduction-band-acceptor transition involving Ga vacancies. The nanoscale plasticity of GaN can be better understood by considering the dislocation luminescence mechanism.     

ICPCVD-SiN_x对GaN/AlGaN基紫外探测器的钝化效果的研究

采用ICPCVD-SiNx薄膜对GaN/A1GaN基紫外探测器进行钝化,从薄膜绝缘特性、钝化效果两方面,对ICPCVD-SiNx、磁控溅射-SiOx、PECVD-SiOx和PECVD-SiNx四种钝化膜进行对比.制作了钝化膜/GaN MIS器件,通过测试MIS器件漏电流密度和薄膜击穿电场的大小表征薄膜绝缘性能,结果表明ICPCVD-SiNx对应的MIS器件的漏电特性最好,外加偏压为100 V时,其漏电流密度保持在1×10-7 A/cm2以下,薄膜击穿电场大于3.3 MV/cm.采用不同钝化方法制作了p-i-n型AlGaN基紫外探测器,通过计算钝化前后器件暗电流的变化,表征不同钝化方法的钝化效果.结果表明ICPCVD-SiNx钝化的器件,其暗电流比其他钝化方法的器件小近两个数量级,在-5V偏压下暗电流密度为7.52 A/cm2.     

日盲雪崩探测器滤波膜系的优化设计及器件性能的影响

利用传输矩阵法设计了空气与基本膜系之间具 有3个周期减反膜结构的日盲紫外探测器滤波膜系,并利用半导体 器件仿真软件Atlas分析集成了滤波膜系的GaN/AlGaN异质结雪崩光电探测器(APDs)的光 电性能。研究结果表明,相对 无减反射膜的滤波膜系,本文设计的膜系明显提高了光在日盲区的透过率及截止区的反射率 ,使GaN/AlGaN APDs有更 加平滑的光谱响应曲线、更大的响应度、更陡峭的响应截止边频及更好的滤波性能;同时, GaN/AlGaN APDs比传统AlGaN APDs 更有利于光生空穴的注入,使GaN/AlGaN APDs的最大光谱响应度及紫外/可见抑制比较传统的 APDs提高超过300%。     

面向高速应用的GaN基HEMT器件

工作在毫米波、亚毫米波频段的固态功率放大器可广泛应用于无线通信、汽车雷达等电子系统。氮化物材料具备禁带宽度大、电子速度高等特点,使得GaN 基HEM T 器件成为面向高频器件和高速数字电路等高速应用的理想候选器件。但是为实现更佳的器件指标,仍需要进行多层次的设计和优化。重点讨论了面向高速应用的GaN 基器件所面临的挑战,如载流子限域性、电子速度以及在等比例缩小规律下的导通电阻等问题。分析表明,这些问题的解决将使GaN 基器件在高速、高频等领域得到广泛应用。     

玻璃衬底上制备GaN薄膜的研究进展

近年来,GaN基发光二极管(LED)的发展异常迅速,以玻璃为衬底的LED具有成本低、可大面积化生产等优点而引起了国内外许多科研机构的广泛研究兴趣.但由于普通玻璃较低的软化温度(500～ 600℃)以及与GaN之间存在较大的晶格失配问题,一直阻碍其发展.重点综述了玻璃衬底上生长GaN薄膜的方法以及改善外延层晶体质量的技术.分别介绍了两种在普通玻璃上生长GaN的方法,即低温生长和局部加热生长,同时详述了采用缓冲层和横向外延过生长(ELO)技术对外延GaN晶体质量的影响.对局部加热、ELO等技术在玻璃衬底LED方面的应用进行了分析和预测,认为以玻璃为衬底的LED终会取得快速地发展.     

p型InGaN/GaN超晶格N面GaN基LED的光电特性

随着氮(N)面GaN材料生长技术的发展,基于N面GaN衬底的高亮度发光二极管(LED)的研究具有重要的科学意义.研究了具有高发光功率的N面GaN基蓝光LED的新型结构设计,通过在N面LED的电子阻挡层和多量子阱有源层之间插入p型InGaN/GaN超晶格来提高有源层中的载流子注入效率.为了对比N面GaN基LED优异的器件性能,同时设计了具有相同结构的Ga面LED.通过对两种LED结构的电致发光特性、有源层中能带图、电场和载流子浓度分布进行比较可以发现,N面LED在输出功率和载流子注入效率上比Ga面LED有明显的提升,从而表明N面GaN基LED具有潜在的应用前景.