Study of impurity free quantum well intermixing and its application to photonic integrated circuit

Abstract

This thesis covers several aspects of impurity free vacancy enhanced quantum well (QW) intermixing in GaAs/AlGaAs and InGaAs/GaAs quantum well structures. Spin-on silica film and thermal oxidation of GaAs were shown to be effective in enhancing the QW intermixing. Control of bandgap tuning was realized by varying the thickness of a buried Al or Ge thin interlayer. Interdiffusion coefficient is obtained by comparing the measured photoluminescence peak energy with the calculated transition energy levels. Monolithically integrated multi-wavelength lasers and a two-wavelength laser incorporating a Y junction coupler and an isolator were successfully fabricated using the QW intermixing technology. Improved carrier transport was observed in the intermixed QW laser structure having multi-quantum-well cladding layers. Blueshift of the bandgap in In0.2Ga0.8N/GaN single quantum well was observed at thermal annealing temperatures below 1000 Celsius degrees and is explained by the spatial redistribution of atomic In and Ga in the QW.