V/III Flux Ratio Dependence of InAs Epilayers Grown on GaAs Subsutrates by Molecular Beam Epitaxy

Abstract

InAs epilayers 2 µm thick were grown on (100) GaAs substrates. Under the As stabilized condition, the epilayer growth progresses in the mode of 2-dimensional (2D)-3D-2D growth. The lattice constant changes sharply from that of GaAs to the bulk value of InAs in the early stage of growth. A high density of small islands are formed in the initial stage and strain due to lattice mismatching is relaxed by the occurrence of island merging. As a result, the 2-µm-thick epilayers show smooth surface morphology and high electrical quality. On the other hand, when the epilayer growth is carried out under the In-stabilized condition, the lattice constant shows two-step saturation. The lattice constant saturates once in the initial stage, and after some time begins to increase toward the bulk value of InAs. In this case, the island density is low and each island grows laterally. Then, rather large strain is incorporated in the epilayers even after island merging and, as a result, dislocations are widely distributed in the latter half of epilayer growth. As a result, the 2-µm-thick epilayers show rather rough surface morphology, and the electrical properties also deteriorate.