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

Abstract

Spontaneous ${\mathrm{CuPt}}_{\mathit{B}}$-type ordering along 〈111〉 can reduce the crystal symmetry in ${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$P, splitting the valence-band maximum and introducing optical anisotropy in the interband transition-matrix elements. The growth of lattice-mismatched layers also reduces the symmetry. We present a simple model to describe the combined influence of strain and ordering on the valence-band maximum. We calculate that the valence-subband dispersion and optical-matrix elements are strongly anisotropic over a significant energy range in ${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$P quantum wells with coexistent epitaxial strain and [1\ifmmode\bar\else\textasciimacron\fi{}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 ${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$P layers.