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.
- quantum wells