缓冲层对InSb/GaAs薄膜质量的影响

Studying of Buffer Effect on Quality of InSb on GaAs Substrate

InSb是制作3～5 μm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64 300 cm^2·V^-1·s^-1的InSb外延层.

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 hightemperature （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 64 300 cm^2·V^-1·s^-1at 77 K, were obtained.