Thermal annealing effect on 1.3-μm GaInNAs/GaAs quantum well structures capped with dielectric films

Two kinds of dielectric films, Si₃N₄ and SiO₂, deposited onto the surface of 1.3-μm GaInNAs/GaAs quantum well (QW) structures were studied upon post-growth thermal annealing. The blue-shift in photoluminescence (PL) as a function of annealing time showed distinct dependence on the selection of the dielectric films. It was found that a Si₃N₄ cap layer inhibits the blue-shift under specific annealing conditions and the blue-shift inhibition effect increases with the thickness of the Si₃N₄ cap; while a SiO₂ cap layer enhances the PL blue-shift. X-ray diffraction (XRD) and secondary-ion-mass-spectrometry (SIMS) indicated that the enhanced blue-shift in PL from the SiO₂-capped sample was caused by two factors: interdiffusion of Ga and In atoms across the QW interfaces and the decrease of N-Ga ion density (and hence N) in the QW material. Compared with the SiO₂ caps, Si₃N₄ cap layers can inhibit both of these factors. Time-resolved PL decay measurements at room temperature were performed to study the optical properties of the uncovered and Si₃N₄-capped samples.