Impurity-Free Vacancy Diffusion of InGaAsP/InGaAsP Multiple Quantum Well Structures Using SiH_4-Dependent Dielectric Cappings

摘要

We report the impurity-free vacancy diffusion (IFVD) behaviors of In_(0.86)Ga_(0.14)As_(0.64)P_(0.36)/In_(0.88)Ga_(0.12)As_(0.25)P_(0.75) multiple quantum well (MQW) structures using dielectric films as a capping layer. The effects of SiO_x and SiNr films deposited using different SiH_4 flow rates on the IFVD are investigated by photoluminescence measurements and ellipsometry analysis. The properties of dielectric capping layer play a key role in the intermixing of this MQW structure, indicating that the increased porosity of SiO_x and SiN_x layers enhances the bandgap energy shift of MQWs. A significant blue shift of 173nm (i.e., 106meV) for the sample capped with a relatively more porous SiN_x, which was deposited using 20 seem SiH_4, was obtained after a thermal annealing of 850 ℃ for 30 s for 30 s. The mechanism was analyzed by using transmission electron microscopy and energy dispersive X-ray spectroscopy. It is believed that the enhanced blue shift is ascribed to the dominant interdiffusion of group V atoms because the compositions of group III atoms are kept almost identical in the wells/barriers.