Effects Of Annealing On The Optical Properties Of Proton Irradiated n-type Gallium Arsenide

The optical properties of proton irradiated n-type GaAs, implanted at room temperature and subsequently furnace annealed, are examined using infrared reflectance spectroscopy. Substantial changes in the reflectance spectra are observed with post-implantation annealing. Computer simulations , based on a Drude model free carrier contribution to the dielectric constant, are used to obtain best fit parameters to the measured spectra. The resulting free carrier profiles display a two layer characteristic. The top layer encompasses the implanted region and remains stable with thermal treatment up to 500 C. A lower layer appears with annealing at 200 C and diffuses deeply into the substrate material. Further annealing eliminates the lower layer but the top layer is present even after a 600 C anneal. An activation energy of 1.2 eV and a diffusion preexponential factor of 4.3 E-1 cm2/s are found for this process.