<title>Quantum well structures with almost-degenerate valence bands</title>

A novel technique for bringing the light- and heavy-hole valence bands in a quantum well, (QW), into approximate degeneracy is described and demonstrated. It utilizes pseudomorphic tensile strain in the barriers generated by lattice mismatch between the barrier and the substrate material. An important consequence of this strain is that the splitting of the light- and heavy-hole valence band energies at the Brillouin zone center, due to the quantum confinement effect, is approximately cancelled. Unlike a similar result in systems with tensily strained wells, this degeneracy is not sensitive to the exact QW width (for QW widths greater than 5 nm) or the precise strain present in the layer. It is thus more amenable to the growth and fabrication of devices which should simultaneously exhibit the polarization isotropy of bulk structures and the enhanced performance of QWs. The technique is demonstrated by an optical investigation of GaAs/GaAs_{1 - y}P_y quantum wells grown on GaAs substrates by metalorganic chemical vapor deposition.