SUBSTRATE-TEMPERATURE EFFECTS ON THE GROWTH OF IN1-X-YGAXALYAS ON INPSUBSTRATES BY MOLECULAR-BEAM EPITAXY

We have investigated the effect of substrate temperature (T-s varied f rom 410 to 560 degrees C) on the crystalline and optical properties of In1-x-yGaxAlyAs layers grown on InP substrates by molecular beam epit axy (MBE). The quarternary samples were analysed using double axis X-r ay diffraction (XRD), low temperature photoluminescence (PL) and energ y dispersive X-ray spectroscopy (EDX). The crystalline quality and opt ical properties were found to be sensitive to the substrate temperatur e within the range investigated. The optimum substrate temperature ran ge for the lowest XRD and PL full width at half maximum (FWHM) was fou nd to be from 510 to 530 degrees C. The PL FWHMs were lower than 20 me V for samples grown at 510 degrees C, with the lowest value of 11.6 me V being recorded from the sample grown at 530 degrees C. These values are comparable to the best values reported for this material system. F rom the PL spectra, the changeover from type I to type II transition w as found to occur at Al content exceeding 18%. The relationship betwee n the normalised indium flux and lattice mismatch is presented. (C) 19 98 Elsevier Science B.V. All rights reserved.