Quantum well intermixing of a quantum well structure grown on an InAsP metamorphic pseudosubstrate on InP

InGaAsP quantum well (QW) structures, with ∼1% compressive strain, have been grown on an InAs0.21P0.79 metamorphic substrate layer (MSL) deposited on an InP substrate. For comparison, a similar QW structure is grown directly on InP. A consequence of growth on the MSL is to move the QW and barrier compositions outside the spinodal isotherm resulting in a significant reduction in phase separation. This is shown to increase the photoluminescence wavelength and improve its quality in terms of linewidth and intensity. Thermally induced QW intermixing (QWI) has also been carried out on these structures both with and without a low-temperature InP capping layer. The defects present in the underlying metamorphic buffer layers are shown to have no effect on the QWI process. However, the samples with the MSL are shown to exhibit more intermixing either due to a higher diffusion or greater P–As exchange probability in the different composition QW and barrier layers compared to the QW structure grown without the MSL, and possibly influenced by the large reduction in phase separation.