THE EFFECTS OF ARSENIC PRESSURE ON THE PROPERTIES OF IN1-X-YGAXALYAS LAYERS GROWN BY MOLECULAR-BEAM EPITAXY

In this paper, we report the effects of arsenic pressure (V/III ratio) on the properties of undoped In1-x-yGaxAlyAs layers grown by molecula r beam epitaxy (MBE) on InP(100) substrates. X-ray diffraction (XRD) a nalysis showed that the lattice mismatch was relatively insensitive to flux ratio variations within the range investigated (V/III from 14 to 73). However, changes in the V/III flux ratio was found to have a sig nificant effect on the XPD full-width at half-maximum (FWHM), XRD inte nsity, photoluminescence (PL) FWHM and PL intensity (at 5 K). PL FWHM as low as 12.7 meV (at 5 K), a value which is comparable to the best r eported was achieved at V/III ratio = 33, The PL and XRD FWHM broadene d significantly as the V/III ratio was decreased below 21. Broadening of the PL and XRD FWHM was also observed in samples grown at high flux ratios exceeding 50, although this effect was not as drastic compared to that in samples grown at low Aux ratio. Within the range of V/III flux ratio investigated, the optimum flux ratio for the growth of InGa AlAs layers was found to be within 21-50. The effect of the V/III rati o on the change in the optical and crystalline properties was explaine d in terms of clustering which was characterised by analysing the diff erence between the PL peak energy and the band gap energy calculated f rom XRD compositional measurement. (C) 1998 Elsevier Science B.V. All rights reserved.