A study of strain-related effects in the molecular-beam epitaxy growth of InxGa1−xAs on GaAs using reflection high-energy electron diffraction

Abstract

In this paper we examine the role of strain in the molecular‐beam epitaxy (MBE) growth process by studying growth in In_xGa_1−xAs on GaAs with x varying from 0 to 0.5. This range covers the critical thickness regime for dislocation formation from ∞ to 12 monolayers. We have studied MBE growth for both on‐axis (100) and misoriented substrates. The first issue we address in this paper is the role of strain in controlling the atomic‐surface migration. We find from reflection high‐energy electron diffraction (RHEED) studies during growth of In_xGa_1−xAs that as x is increased, the surface migration decreases rapidly. The growth front of the growing structure roughens due to this decreased migration and we have studied the recovery time for the growth front to smoothen. The surface recovery time increases rapidly as the strain in the system increases. Conversely, when GaAs growth is resumed, there is a recovery of the RHEED average intensity and oscillations (peak to peak). At higher growth temperatures, layer‐by‐layer growth is again restored. Dynamic changes in the RHEED pattern were video recorded, and the data indicate that in the three‐dimensional island growth mode observed, the lattice constant in the strained overlayer changes monotonically and attains an equilibrium value before the conventionally calculated critical thickness h_c is reached. Low‐temperature photoluminescence measurements on misoriented (0°–4°) InGaAs/InAlAs MQW grown directly on GaAs indicate that device‐quality material can be obtained for growth at high temperatures (∼570 °C).