REPLACEMENT OF GROUP-III ATOMS ON THE GROWING SURFACE DURING MIGRATION-ENHANCED EPITAXY

An InAs monolayer is grown between GaAs layers using migration-enhanced epitaxy. The surface chemical characteristics during growth are investigated by reflection high-energy electron diffraction. With low As4 pressure and with a substrate temperature of 500 °C, the oscillation amplitude of the reflected electron beam after growth of one monolayer of InAs vanishes during the growth of GaAs over more than 20 atomic layers. High-resolution secondary-ion-mass spectroscopic analysis and photoluminescence characteristics of fabricated structures indicate an anomalous distribution of In atoms with a gradual slope toward the growth direction only when the substrate temperature is 500 °C. Numerical calculation shows that the experimental results are explained by the In atoms in the InAs monolayer being replaced by subsequently deposited Ga atoms. The comparison between experimental results and calculated ones indicates that replacement occurs with a probability of 98% at 500 °C. An InGaAs layer was also grown on an InP substrate using migration-enhanced epitaxy with the deposition of two monolayer metallic atoms per one cycle. X-ray diffraction analysis shows that the composition is modulated with a period of two monolayers in the grown InGaAs layer. This phenomenon is also explained in terms of metallic atom replacement.