EFFECT OF FACETING ON THE BAND-GAP OF ORDERED GAINP

It has been shown that under certain growth conditions the pseudobinary semiconductor alloy GaInP shows cation site ordering into the Cu-Pt structure, and that this ordering results in a lowering of the band gap E(g) from that of the disordered alloy. The E(g) lowering is known to depend on growth conditions, including the orientation of the substrate. We study the dependence of E(g) on epilayer thickness for GaInP grown by metal-organic vapor-phase epitaxy. For epilayers grown on singular (100) substrates under growth conditions conventionally used to produce ordered material, E(g) decreases dramatically with increasing epilayer thickness: E(g) for a 10-mum-thick epilayer is approximately 40 meV lower than for a 1-mum-thick epilayer. This dependence of E(g) on thickness can be understood in terms of the recently observed faceting of the GaInP growth surface.