非故意掺杂GaN薄膜方块电阻与载气中N2比例关系研究

利用金属有机气相外延方法研究了非故意掺杂GaN薄膜的方块电阻与高温GaN体材料生长时载气中N₂比例的关系.研究发现,随着载气中N₂比例的增加,GaN薄膜方块电阻急剧增加.当载气中N₂比例为50%时,GaN薄膜方块电阻达1.1×10⁸Ω/□,且GaN表面平整,均方根粗糙度为0.233nm.二次离子质谱分析发现,载气中N₂比例不同的样品中碳、氧杂质含量无明显差别.随着载气中N₂比 关键词： 半绝缘GaN薄膜 载气 金属有机气相外延 位错     

基于X射线衍射的GaN薄膜厚度的精确测量

结合Williamson-Hall plot方法和线型分析方法的优点,提出了一种有效分离有限晶粒尺寸和非均匀应力等X射线衍射展宽效应的方法,可以用于GaN外延层厚度等参数的快速精确测量.用该方法对一系列在蓝宝石衬底上生长的厚度在0.7—4.2μm的GaN外延膜进行了测量,并与椭圆偏振光谱法测量结果进行了比较,结果表明其差别<4%,反应了这种方法的准确性. 关键词： GaN薄膜 厚度测量 X射线衍射     

Effects of SiNx on two-dimensional electron gas and current collapse of AlGaN/GaN high electron mobility transistors

SiN_x is commonly used as a passivation material for AlGaN/GaN high electron mobility transistors (HEMTs). In this paper, the effects of SiN_x passivation film on both two-dimensional electron gas characteristics and current collapse of AlGaN/GaN HEMTs are investigated. The SiN_x films are deposited by high- and low-frequency plasma-enhanced chemical vapour deposition, and they display different strains on the AlGaN/GaN heterostructure, which can explain the experiment results.     

Effects of SiNx on two-dimensional electron gas and current collapse of A1GaN/GaN high electron mobility transistors

SiNx is commonly used as a passivation material for AlGaN/GaN high electron mobility transistors (HEMTs). In this paper, the effects of SiN x passivation film on both two-dimensional electron gas characteristics and current collapse of AlGaN/GaN HEMTs are investigated. The SiNx films are deposited by high- and low-frequency plasma-enhanced chemical vapour deposition, and they display different strains on the AlGaN/GaN heterostructure, which can explain the experiment results.     

GaN基三维结构生长与器件应用

目前,c面氮化镓(GaN)基发光二极管的制备技术已经十分成熟并取得了商业化成功,但仍面临极化电场导致的大电流密度下效率下降(Droop效应)和黄绿光波段效率低的问题。为消除极化电场的影响,人们开始关注半极性和非极性面GaN。其中,基于传统极性面衬底通过三维结构生长来获得半极性和非极性GaN的方法,由于其低成本和生长的灵活性,受到了广泛研究。本文首先总结了三种GaN三维结构的制备方法并分析其生长机理。接着,在此基础上介绍了不同晶面InGaN量子阱的外延生长和发光特性。最后,列举了GaN基三维结构在半极性面LED、颜色可调LED和无荧光粉白光发光二极管方面的应用。     

Improved Surface Characteristics and Contact Performance of Epitaxial p-AlGaN by a Chemical Treatment Process

The comparative study of epitaxial 380-run-thick p-Al0.091 Ga0.909 N materials without and with special surface chemical treatment is systematically carried out. After the treatment process, the deep level luminous peak in the 10 K photoluminescence spectrum is eliminated due to the decrease of surface nitrogen vacancy VN related defective sites, while the surface root-mean-square roughness in atomic force microscopy measurement is decreased from 0.395nm to 0.229nm by such a surface preparation method. Furthermore, the performance of surface contact with Ni/Au bilayer metal fihns is obviously improved with the reduction of the Schottky barrier height of 55meV. The x-ray photoelectron spectroscopy （XPS） results show a notable surface element content change after the treatment which is considered to be the cause of the above-mentioned surface characteristics improvement.     

分子束外延生长InGaN/AlN量子点的组分研究

报道了分子束外延生长的绿光波段InGaN/AlN量子点材料,并综合考虑InGaN量子点的应变弛豫,以及应力和量子限制斯塔克效应对量子点发光波长的影响,提出了一种结合反射式高能电子衍射原位测量与光致荧光测量确定InGaN量子点组分的方法.     

Luminescence properties of InxGa1-xN（x～0.04） films grown by metal organic vapour phase epitaxy

In x Ga 1-x N (x ～ 0.04) films are grown by metal organic vapour phase epitaxy.For the samples grown on GaN directly,the relaxation of InGaN happens when its thickness is beyond a critical value.A broad band is observed in the luminescence spectrum,and its intensity increases with the increasing degree of relaxation.Secondary ion mass spectrometry measurement rules out the possibility of the broad band originating from impurities in InGaN.The combination of the energy-dispersive X-ray spectra and the cathodeluminescence measurements shows that the origin of the broad band is attributed to the indium composition inhomogeneity caused by the phase separation effect.The measurement results of the tensile-strained sample further demonstrate the conclusions.     

AlGaN插入层对6H-SiC上金属有机物气相外延生长的GaN薄膜残余应力及表面形貌的影响

研究了具有不同台阶数目的AlGaN插入层对在6H-SiC衬底上利用金属有机物气相外延（MOVPE）生长的GaN体材料残余应力和表面形貌的影响.高分辨率X射线衍射测试表明样品的c轴晶格常数随台阶数目的增多而增大;低温光荧光谱中GaN发光峰也随着台阶数目增多而发生蓝移,这些变化都反映出GaN中残余张应力的减小.此外,原子力显微镜测试表明样品表面起伏和粗糙度也都随着插入层的引入和台阶数目的增多得到了明显的改善. 关键词： 残余应力 表面形貌 SiC衬底 AlGaN插入层     

Studies on the nucleation of MBE grown III-nitride nanowires on Si

GaN and AlN nanowires (NWs) have attracted great interests for the fabrication of novel nano-sized devices. In this paper, the nucleation processes of GaN and AlN NWs grown on Si substrates by molecular beam epitaxy (MBE) are investigated. It is found that GaN NWs nucleated on in-situ formed Si₃N₄ fully release the stress upon the interface between GaN NW and amorphous Si₃N₄ layer, while AlN NWs nucleated by aluminization process gradually release the stress during growth. Depending on the strain status as well as the migration ability of III group adatoms, the different growth kinetics of GaN and AlN NWs result in different NW morphologies, i.e., GaN NWs with uniform radii and AlN NWs with tapered bases.