The effects of arsenic pressure on the properties of In 1− x− yGa xAl yAs layers grown by molecular beam epitaxy

Abstract

In this paper, we report the effects of arsenic pressure (V/III ratio) on the properties of undoped In 1− x− y Ga x Al y As layers grown by molecular beam epitaxy (MBE) on InP(1 0 0) substrates. X-ray diffraction (XRD) analysis 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 significant effect on the XRD full-width at half-maximum (FWHM), XRD intensity, 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 reported was achieved at V/III ratio=33. The PL and XRD FWHM broadened 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 flux ratio. Within the range of V/III flux ratio investigated, the optimum flux ratio for the growth of InGaAlAs layers was found to be within 21–50. The effect of the V/III ratio on the change in the optical and crystalline properties was explained in terms of clustering which was characterised by analysing the difference between the PL peak energy and the band gap energy calculated from XRD compositional measurement.