AlGaN/GaN异质结构的X射线衍射研究

X-ray diffraction studies on AlGaN/GaN heterostructures

在(0001)取向的蓝宝石(α-Al2O3)基片上用金属有机物化学气相沉积(MOCVD)方法生长了势垒层厚度为1000?的Al0.22Ga0.78N/GaN异质结构;;利用高分辨X射线衍射(HRXRD)技术测量了样品的对称反射(0002)和非对称反射(1014)的倒易空间Mapping(RSM)。结果表明;;样品势垒层的内部微结构与应变状态和下层i-GaN的微结构与应变状态互相关联。样品势垒层的微应变已经发生弛豫;;而且具有一种“非常规”应变弛豫状态;;这种弛豫状态的来源可能与n-AlGaN的内部缺陷以及i-GaN/α-Al2O3界面应变弛豫状态有关。掠入射X射线衍射研究表明样品内部的应变是不均匀的;;由表层的横向压应变状态过渡到下层的张应变状态;;与根据倒易空间Mapping分析得到的结果一致。

A modulation-doped AlxGa1-xN/GaN heterostructure with 1000? Si-doped n-Al0.22Ga0.78N barrier ( n-AlGaN ) was deposited on ( 0001 ) -oriented sapphire( α-Al2O3 ) by metal-organic chemical vapor deposition ( MOCVD ) . The reciprocal space mappings ( RSMs ) of symmetric reflection ( 0002 ) and asymmetric reflection ( 1014 ) were measured with the method of high resolution X-ray diffraction ( HRXRD ) . The results indicate that the microstructure and strain status of the barrier correlate to those of the i-GaN layer. The barrier holds an “abnormal” strain-relaxation status, which probably results from the internal defects of n-AlGaN and the strain relaxation status at the i-GaN/α-Al2O3 interfaces. The results from grazing incidence X-ray diffraction show that the strain in barrier is nonuniform, which is consistent with the results from the reciprocal space mappings.