Comparative Characterization of InGaN/GaN Multiple Quantum Wells by Transmission Electron Microscopy, X-Ray Diffraction and Rutherford Backscattering

The composition, elastic strain and structural defects of InCaN/CaN multiple quantum wells （MQWs） are comparatively investigated by using x-ray diffraction （XRD）, transmission electron microscopy and Rutherford backscattering/channelling. The InGaN well layers are fully strained on CaN, i.e. the degree of relaxation is zero. The multilayered structure has a clear defined periodic thickness and abrupt interfaces. The In composition is deduced by XRD simulation. We show how the periodic structure, the In composition, the strain status and the crystalline quality of the InGaN/GaN MQ, Ws can be determined and cross-checked by various techniques.     

离子注入掺铒硅发光中心的光致发光研究

本文详细地分析了离子注入掺铒硅的光致发光谱，有５个发光峰分别位于１．５３６μｍ、１．５５４μｍ、１．５７０μｍ、１．５９８μｍ和１．６４０μｍ，其中１．５３６μｍ发光峰最强．结合背散射谱，认为其有效的发光中心为处于Ｔｄ对称中心的填隙铒Ｅｒ３＋离子．在Ｅｒ与Ｏ、Ｎ、Ｃ共掺样品应分别存在Ｅｒ－Ｏ、Ｅｒ－Ｎ和Ｅｒ－Ｃ发光中心，其对应的ＰＬ发光峰分别为１．５７０μｍ、１．５３６μｍ和１．６０８μｍ．     

Determination of Al Composition in Strained AlGaN Layers

AlxGa1-xN/GaN heterostructures are grown on c-sapphire with the Al composition x from 0.2 to 0.4 and thicknesses from 20nm to 30nm. The lattice parameters a and c are determined from 2θ/ω scan. The AIGaN layers are found to be under tensile strain by using x-ray diffraction. Vegard＇s law induces a large deviation in Al composition determination by only considering the linear relationship between one lattice parameter （α or c） and Al composition. The accurate determination of Al composition is only possible with consideration of both the lattice parameters α and c, by assuming the tetragonal distortion in the AlGaN layer. Additionally, the results obtained from x-ray diffraction are verified by Rutherford backscattering.     

A Practical Guide for X-Ray Diffraction Characterization of Ga（A1, In）N Alloys

Ca(In, Al)N alloys are used as an active layer or cladding layer in light emitting diodes and laser diodes, x-ray diffraction is extensively used to evaluate the crystalline quality, the chemical composition and the residual strain in Ca(Al,In)N thin films, which directly determine the emission wavelength and the device performance. Due to the minor mismatch in lattice parameters between Ca(Al, In)N alloy and a CaN virtual substrate, x-ray diffraction comes to a problem to separate the signal from Ca(Al,In)N alloy and CaN. We give a detailed comparison on different diffraction planes. In order to balance the intensity and peak separation between Ca(Al,In)N alloy and CaN, (0004) and (1015) planes make the best choice for symmetric scan and asymmetric scan, respectively.     

Structural, Morphology and Optical Properties of Epitaxial ZnO Films Grown on Al2O3 by MOCVD

Epitaxial ZnO films are grown on Al2O3 （0001） by the MOCVD method. These films are high quality wurtzite crystals with （0001） orientation. Big hexagonal crystallites （diameter from several decades to 100 μm） are found on the surface. Inside these crystallites, a stronger luminescence is observed compared with the plain area. Transmission electronic microscopy reveals that the film is thicker inside the hexagonal crystallites than the plain area, and some crystallites are not connected with each other and are slightly rotated with respect to their neighbours.     

Unidirectional expansion of lattice parameters in GaN induced by ion implantation

This paper reports that the 150-keV Mn ions are implanted into GaN thin film grown on Al2O3 by metal-organic chemical vapour deposition.The X-ray diffraction reciprocal spacing mapping is applied to study the lattice parameter variation upon implantation and post-annealing.After implantation,a significant expansion is observed in the perpendicular direction.The lattice strain in perpendicular direction strongly depends on ion fluence and implantation geometry and can be partially relaxed by post-annealing.While in the parallel direction,the lattice parameter approximately keeps the same as the unimplanted GaN,which is independent of ion fluence,implantation geometry and post-annealing temperature.     

异质外延GaN及其三元合金薄膜的RBS/channeling研究

本文阐述了用ＲＢＳ／ｃｈａｎｎｅｌｉｎｇ技术研究异质外延ＧａＮ及其三元合金薄膜的重要性和必要性,报道了实验测量出的ＧａＮ及其三元合金ＡｌＧａＮ、ＩｎＧａＮ膜的结构,给出了较为准确的元素种类、成分配比、薄膜厚度、合金元素的浓度随深度的分布、结晶品质、晶轴取向等信息,测出了几种薄膜的背散射沟道谱与随机谱之比χｍｉｎ值（Ａｌ０．１５Ｇａ０．８５Ｎ的χｍｉｎ值可低至１．１７％）和沟道坑的半角宽Ψ１／２（ＧａＮ的半角宽为０．７４°）,对于其他测试方法无法给定的中间层的情况及不同衬底对成膜的影响,本文亦有明确的说明．