Dependence of band gap energy shift of In0.2Ga0.8As/GaAs multiple quantum well structures by impurity-free vacancy disordering on stoichiometry of SiOx and SiNx capping layers

Abstract

Effects of In 0.53 Ga 0.47 As cap layer and stoichiometry of dielectric capping layers on impurity-free vacancy disordering of In 0.53 Ga 0.47 As /InP multiquantum well structuresWe have investigated the effects of the stoichiometry of SiO x and SiN x capping layers on the band gap energy shift induced by impurity-free vacancy disordering of the In 0.2 Ga 0.8 As/GaAs multiple quantum well structures. The stoichiometry of the SiO x and SiN x capping layers was changed by varying the flow rate of silane (SiH 4 ) gas, and argon gas was employed as the carrier gas of the diluted SiH 4 gas to eliminate any possible incorporation of nitrogen into the deposited film when nitrogen gas is employed as the carrier gas. A blueshift of photoluminescence peak of up to 112 meV is observed after rapid thermal annealing at 950°C for 50 s from the sample capped with SiO x ͑provided with a SiH 4 flow rate of 20 sccm͒. It is observed that the magnitude of the blueshift increases with the decrease of SiH 4 flow rate for the SiO x and SiN x capping layer because of the increased porosity of dielectric capping layers. The insertion of intermediate GaAs cap layer reduces the band gap energy shift irrespective of the SiO x or SiN x capping layer.