EFFECT OF FACETING ON THE BAND-GAP OF ORDERED GAINP

It has been shown that under certain growth conditions the pseudobinar y semiconductor alloy GaInP shows cation site ordering into the Cu-Pt structure, and that this ordering results in a lowering of the band ga p E(g) from that of the disordered alloy. The E(g) lowering is known t o depend on growth conditions, including the orientation of the substr ate. We study the dependence of E(g) on epilayer thickness for GaInP g rown by metal-organic vapor-phase epitaxy. For epilayers grown on sing ular (100) substrates under growth conditions conventionally used to p roduce ordered material, E(g) decreases dramatically with increasing e pilayer thickness: E(g) for a 10-mum-thick epilayer is approximately 4 0 meV lower than for a 1-mum-thick epilayer. This dependence of E(g) o n thickness can be understood in terms of the recently observed faceti ng of the GaInP growth surface.