Effect of Group V/III Flux Ratio on Lightly Si‐Doped AlxGa1 − xAs Grown by Molecular Beam Epitaxy

Abstract

Optical and electrical properties of lightly Si‐doped layers grown by molecular beam epitaxy under various V/III flux ratios (1 to 4) and at various substrate temperatures (720°–780°C) have been studied by low temperature (≈4 K) photoluminescence and Hall measurements. Bound exciton (BE) peak intensity and Hall mobility increase with decreasing flux ratio and increasing substrate temperature. An excess reduction in the flux ratio causes the condensation of group III metals on epilayers. An optimum flux ratio was found to be 2.3 for the highest substrate temperature investigated here, 780°C. The peak intensity of the defect complex has been shown to be correlated with the growth conditions. It is suggested that the defect complex includes defects dominant under excess arsenic population. Reflection electron diffraction patterns from the growing layers have been related to the growth conditions and the qualities of the epitaxial layers. A sample with the highest BE peak intensity and smooth surface has been grown with a metal‐rich structure present on the surface. A structure has reproducibly been observed at intermediate amounts of group V/III composition on the surface between those for the and the arsenic‐stabilized structures. Growth conditions which result in surfaces with a structure are found to cause surface roughening on the epilayers.