Properties of thin strained layers of GaAs grown on InP

Single strained layers of GaAs grown on InP have been studied by a variety of optical experiments. Raman spectroscopy shows the strain-shifted ${\mathrm{LO}}^{\mathrm{\Gamma }}$ phonon, thus proving that the layers are strained. The photoluminescence is strong, allowing photoluminescence excitation spectroscopy to be performed in a diamond-anvil cell. The absorption is found to increase slowly close to the threshold. A theory of absorption in type-II quantum wells is used in order to compare with experiment. Photoconductivity and modulated-reflectance experiments have been carried out on the samples and indications of the presence of heavy-hole states are seen. The strain Hamiltonian of the valence band has been transformed into a 6×6 matrix, which is parametrized by the strain-tensor elements, allowing easy calculation of the strain shift of the band edges even in unusual strain situations. The experimental results are consistent with a marginally type-II structure in which the holes are confined to the GaAs layer but the electrons reside in the InP layers.