Structural Optimization And Properties Of In_0.82Ga_0.18As/InP Heterostructures

In_x Ga_1-x As material can produce the detector with high sensitivity and detect ion rate,the cutoff wavelength changes linearly with the In component content.In recent years,there is more and more demands on the long wavelength In_0.82Ga_0.18As semiconductor materials.If the In_0.82Ga_0.18As epitaxial layers grown directly on InP substrates,the lattice mismatch between In_0.82Ga_0.18As and InP materials is up to 2% that will lead to the existence of a large number of misfit dislocations or defects in In_0.82Ga_0.18As layer,and the quality of the epitaxial material becomes worse.So how to solve the problem of dislocation or defect caused by lattice mismatch between In_0.82Ga_0.18As and InP and improve the crystal quality of In_0.82Ga_0.18As epitaxial layer has an important significance to improve the properties of the materials.This paper is mainly to achieve dislocation inhibition and blocking effect and reduce the mismatch stress by adding a certain thickness of the buffer layer between the substrate and the epitaxial layer and increasing the thickness of the epitaxial layer to optimize the structure.Metal organic chemical vapor deposition is used to prepare In_0.82Ga_0.18As/InP/InP heteroepitaxial materials with different thickness of the buffer layer and epitaxial layer.The internal structure of the material,especially the dislocation,was studied by transmission electron microscopy;Scanning electron microscopy and atomic force microscopy were used to test the surface morphology of In_0.82Ga_0.18As materials;Crystal quality of materials were studied by XRD and Raman scattering spectra;And the stress of the epitaxial was calculated using Raman scattering spectra;Finally,the carrier concentration and mobility of In_0.82Ga_0.18As heterojunction materials were analyzed by Holzer tester.The results show that the In_0.82Ga_0.18As epitaxial layer grows directly on substrate of InP.The surface of the material is formed with a lot of deep holes and overlapping curve,which makes the surface of the sample very rough.The dislocations or defects in the interface extend directly into the epitaxial layer without buffer layer,which affects the crystalline quality of epitaxial layer.The introduction of a certain thickness of the buffer layer between the substrate and the epitaxial layer can effectively release the mismatch stress and reduce the extension of the dislocation to the surface.Thereby improving the surface morphology and crystal quality of the sample,the performance of the sample will be improved;However,too thick buffer layer makes the surface morphology and performance worse,so we must add t he appropriate thickness of the buffer layer to optimize the surface topography and performance of the sample.Increasing the thickness of epitaxial layer of the sample can also make the surface morphology of the samples become better.The stress of epitaxial layer is reduced and the performance is better.