Abstract
One of the most important semiconductors, AlGaAs, is always fabricated using one of several different growth techniques. This thesis reports the successful synthesis of AlGaAs by ion implantation. A detailed study of the quality of the material using Rutherford Backscattering (RBS), Photoluminescence (PL), Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectroscopy (SIMS), Scanning Electron Microscopy (SEM) and X-Ray Microprobe analysis is presented. The values of the implantation energy chosen were 400keV and 135keV for the As+ and A1+ respectively so that their maximum concentration is at the same depth. The implantation doses were 1x1015- 1 x 10 17/cm2. After implantation the samples were rapid thermal annealed (RTA) at a temperature of 650°C-1000°C for 25 seconds. Before annealing the samples were capped with Si3N4/AlN encapsulants and where appropriate their quality was checked with SEM. Implantations were made both at room temperature and at 230°C. The AlGaAs layer was identified by its clear PL signal and by the RBS spectra, which fitted computer simulation. TEM diffraction patterns from these layers were that of a single crystal and SIMS chemical analysis showed the aluminium profile extended to a depth of 0.3mum in agreement with the theoretical projected range. The observed reduction in the implantation damage with increasing annealing temperature was investigated using RBS and TEM. The RBS channelling spectra showed a decrease in the damage and that regrowth was taking place. TEM showed the disappearance of all the precipitates at increased temperatures. The layer thickness was measured using SIMS, SEM, and RBS. X-Ray Microprobe together with RBS and SIMS was used to calculate the aluminium mole fraction value, x, to a good degree of accuracy. The ion beam mixing and damage enhanced methods for synthesis were also used to synthesize AlGaAs. Again successful synthesis of AlGaAs was shown by its PL signal and SIMS was used to show the aluminium profile obtained. The effect of annealing temperature was studied using TEM, which showed that a single crystal AlGaAs layer free of precipitates had been produced. SIMS results of the damage enhanced synthesis showed the A1 buried to a depth of 0.4mum and the PL signal indicated that the material was of reasonable quality.