SELECTIVE QUANTUM-WELL INTERMIXING IN GAAS-ALGAAS STRUCTURES USING IMPURITY-FREE VACANCY DIFFUSION

Impurity-free vacancy disordering (IFVD) using SiO2 and SrF2 dielectri c caps to induce selective quantum-well (QW) intermixing in the GaAs-A lGaAs system is studied, The intermixing rate of IFVD was found to be higher in n-i-p and intrinsic than in p-i-n structures, which suggests that the diffusion of the Group III vacancy is not supported in p-typ e material, Single-mode waveguides have been fabricated from both as-g rown and bandgap-tuned double-quantum-well (DQW) laser samples, Propag ation losses as low as 8.5 dB cm(-1) were measured from the bandgap-tu ned waveguides at the lasing wavelength of the undisordered material, i.e., 860 nm. Simulation was also carried out to study the contributio n of free-carrier absorption from the cladding layers, and the leakage loss induced by tile heavily p-doped GaAs contact layer, It was found that the leakage loss contributed by the GaAs cap layer is significan t and increases with wavelength. Based on IFVD, we also demonstrate th e fabrication of multiple-wavelength lasers and multichannel wavelengt h division multiplexers using the one-step ''selective intermixing in selected area'' technique, This technique enables one to control the d egree of intermixing across a wafer, Lasers with bandgaps tuned to fiv e different positions have been fabricated on a single chip. These las ers showed only small changes in transparency current, internal quantu m efficiency, or internal propagation loss, which indicates that the q uality of the material remains high after being intermixed, Four-chann el wavelength demultiplexers based on a waveguide photodetector design have also been fabricated, Photocurrent and spontaneous emission spec tra from individual diodes showed that the absorption edge was shifted by different degrees due to the selective degree of QW intermixing, T he results obtained also imply that the technique can be used in the f abrication of broad-wavelength emission superluminenscent diodes.