Influence of the GaAs substrate orientation on the composition of Ga xIn 1 − xP ( x ≈ 0.5) grown by LPE and MOCVD

Abstract

It has been shown that the segregation coefficients in III–V ternary systems depend on substrate orientation. This effect was observed, in particular, in the system GaInP grown on GaAs substrates by LPE. All articles studying this effect were based on results obtained growing on substrates with different orientations. In these studies the liquid phase composition was changed in each experiment. Analyses of their growth methodology show that important parameters such as the initial supercooling and liquidus temperature can differ from one experiment to another. These uncontrolled growth parameters introduce, naturally, some uncertainty on the results. Moreover the evaporation of phosphorus from the liquid phase can change its composition and this could be a reason of another experimental error. All these errors can lead to different conclusions and even some authors do not observe any effect of the substrate orientation at all. In this work, to eliminate these uncertainties, we have grown simultaneously GaInP on GaAs substrates with different orientations but from the same liquid phase. In this way we are sure that the growth conditions are the same for different substrates even if the liquidus temperature and supercooling are not exactly known. The samples obtained were studied by HRXRD, photoluminescence and SIMS. It was found that the Ga concentration in the epitaxial layers depends on substrate orientation. Additionally, analogue experiments were done by MOCVD using as substrates GaAs (100), (111)A and (111)B growing the GaInP simultaneously during the same growth experiment. The results were very similar to those obtained by LPE.