A growth method to obtain flat and relaxed In0.2Ga0.8As on GaAs (001) developed through in situ monitoring of surface topography and stress evolution

In this paper we develop a growth process for obtaining Bat and relaxed In0 .2Ga0.8As layers on GaAs (0 0 1). The process designed is based on the resu lts obtained by in situ and real time characterization of surface morpholog y and layer relaxation. In particular, our results show that for growth tem peratures T-s less than or equal to 200 degreesC the relaxation of In0.2Ga0 .8As layers is inhibited and the morphology does not evolve to a crosshatch ed pattern. After growth thermal treatments of these low-temperature (LT) I n0.2Ga0.8As layers induce the development of a very faint (rms = 0.5 nm) cr osshatched-like morphology. The relaxation process during the thermal annea ling is strongly asymmetric and the layers present a high final strain stat e. By growing on top of the LT layer another In0.2Ga0.8As layer at higher t emperature, relaxation is increased up to R approximate to 70% and becomes symmetric. Depending on the growth process of the top layers morphology evo lution differs, resulting in better morphologies for top layers grow by ato mic layer molecular beam epitaxy (ALMBE) at T-s = 400 degreesC. We have obt ained 400 nm In0.2Ga0.8As layers with a final degree of relaxation R approx imate to 70% and very flat surfaces (rms = 0.9 nm). (C) 2001 Elsevier Scien ce B.V. All rights reserved.