缓冲层对InSb/GaAs薄膜质量的影响

InSb是制作3~5μm红外探测器的重要材料。在GaAs衬底上外延生长InSb,存在的主要问题在于两种材料间14.6%的晶格失配度,会引入较大的表面粗糙度以及位错密度,使外延材料的结构和电学性能均会受到不同程度的影响。通过系列实验,研究了在生长过程中缓冲层对薄膜质量的影响。利用高能电子衍射仪(RHHEED)得到了合适的生长速率和Ⅴ/Ⅲ比,研究了异质外延InSb薄膜生长中低温InSb缓冲层对材料生长质量以及不同外延厚度对材料电学性质的影响。采用原子力显微镜(AFM)、透射电子显微镜(TEM)、X射线双晶衍射(DCXRD)等方法研究了InSb/GaAs薄膜的表面形貌、界面特性以及结晶质量。通过生长合适厚度的缓冲层,获得了室温下DCXRD半高峰宽为172″,77 K下迁移率为64300 cm²·V^-1·s^-1的InSb外延层。

Studying of Buffer Effect on Quality of InSb on GaAs Substrate

There has been sustained interesting in the area of band-gap III-V compound semiconductors for 3~5 μm infrared device applications.InSb is an attractive material because of its potential use for large area detector arrays,high frequency devices and magnetoresistive sonsors for position sensing.Unfortunately,InSb itself cannot be used as a substrate due to its very large parallel conduction.Semi-insulating GaAs has been widely employed as the substrate for InSb growth,because of its electrical isolation,low-cost and mechanical strength.The main obstacle to acquiring high quality InSb comes from the large lattice mismatch of 14.6%,between InSb and GaAs,which is particularly detrimental to thin films.In the experiments,obtaining high quality InSb by two-step growth process had been reported in the high mismatch systems.In this study,all the InSb epitaxial thin films were grown on SI-GaAs by VG solid source MBE.Reflection high-energy electron diffraction(RHEED) was used for in-situ monitoring InSb surface morphology,the effect of the buffer on quality of heteroepitaxial InSb films was systematically studied.Including a serious of samples,a GaAs buffer was not required,as it shows no apparent improvement for the quality of InSb.Optimized of the low-temperature(LT) layer was performed at maintaining binary growth,which in the cases was 350℃,and the folllowing high-temperature(HT) growth at 450℃.The epitaxial thin films characterization was presented and analyzed,including surface morphology,interface inspection and crystalline quality by atomic force microscopy(AFM),transmission electron microscopy(TEM) and X-ray diffraction(XRD) etc.We also described the problem between the different thickness InSb epilayer and Hall-mobility.In conclusion,high quality InSb epilayers strongly depends on LT InSb buffer layer.The InSb films were grown directly onto semi-insulating GaAs substrate,for our typical InSb samples with optimized buffer layer,room temperature DCXRD FWHM of 172″ and mobility of 64300 cm²·V^-1·s^-1 at 77 K,were obtained.