Influence of dielectric deposition parameters on the In _0.2Ga _0.8As/GaAs quantum well intermixing by impurity-free vacancy disordering

We investigated the influence of the deposition parameters of SiO _x and SiN _x capping layers in the plasma-enhanced chemical vapor deposition on the band gap energy shift of the In _0.2Ga _0.8As/GaAs multiple quantum well (QW) structures induced by impurity-free vacancy disordering. The investigated deposition parameters were deposition pressure, deposition temperature, and rf power. A blueshift of photoluminescence (PL) peak energy up to 161 meV was observed after rapid thermal annealing at 950°C for 50 s in the samples capped with SiO _x deposited at 1.5 Torr. We observed that the blueshift of the PL peak energy increased greatly with the increase of deposition pressure and slightly with the decrease of deposition temperature. The influence of rf power was found to be negligible. All these dependences were related to the porosity in the dielectric capping layers in the QW intermixing.