Interplay of strain and superlattice ordering on GaInP2 quantum-well valence-subband structure

Spontaneous CuPt_B-type ordering along <111> can reduce the crystal symmetry in Ga_1-xIn_xP, splitting the valence-band maximum and introducing optical anisotropy in the interband transition-matrix elements. The growth of lattice-mismatched layers also reduces the symmetry. We present a simple model to describe the combined influence of strain and ordering on the valence-band maximum. We calculate that the valence-subband dispersion and optical-matrix elements are strongly anisotropic over a significant energy range in Ga_1-xIn_xP quantum wells with coexistent epitaxial strain and [1¯11] chemical ordering, using the simple model to explain the observed results. Comparison with disordered, unstrained quantum wells indicates that a combination of chemical ordering and strain may lead to significantly improved gain characteristics in high-quality Ga_1-xIn_xP layers.