V/III ratio effects on the growth of In 1− x− yGa xAl yAs on InP substrates 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 (100) substrates. The quaternary samples were analysed using double-axis X-ray diffraction (XRD) and low-temperature photoluminescence (PL). XRD analysis showed that the lattice mismatch was relatively insensitive to flux ratio variations within the range investigated (V/III from 14 to 73). PL full width at half-maximum (FWHM) as low as 12.7 meV (at 5 K), a value which is comparable to the best reported, was achieved at a V/III ratio = 33. The PL and XRD FWHMs broadened significantly as the V/III ratio was decreased below 21 or increased above 50. Within the range investigated, the optimum V/III ratio for the growth of InGaAlAss layers was found to be 21–50. The effect of the V/III ratio on the optical and crystalline properties was explained in terms of clustering, which was characterized by analysing the difference between the PL peak energy and the band-gap energy calculated from XRD compositional measurements.