PHOTOLUMINESCENCE AND X-RAY-DIFFRACTION ANALYSIS OF IN1-X-YGAXALYAS INP STRUCTURES GROWN 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 quaternary samples were analysed using double axis X-ra y diffraction (XRD), low temperature photoluminescence (PL) and energy dispersive X-ray spectroscopy (EDX). The crystalline quality and opti cal properties were found to be sensitive to the substrate temperature within the range investigated. The optimum substrate temperature rang e for the lowest XRD and PL full width ar half maximum (FWHM) was foun d to be from 510 to 530 degrees C. The PL FWHMs were lower than 20 meV for samples grown at 510 degrees C, with the lowest value of 11.6 meV being recorded from the sample grown at 530 degrees C. These values a re comparable to the best values reported for this material system. Fr om the PL spectra, the changeover from type I to type II transition wa s found to occur at an Al content exceeding 18%. The relationship betw een the normalised indium flux and lattice mismatch is presented. (C) 1998 Elsevier Science Ltd. All rights reserved.