Pulsed CO/sub 2/-laser induced melting and nonlinear optical studies of GaAs

The authors report new optical and structural properties of p-type GaAs that result from the absorption of high-intensity 10.6 μm radiation. Prior to the onset of surface melting, the authors find that the absorption coefficient decreases with increasing intensity in a manner predicted by an inhomogeneously broadened two-level model. As the energy density of the CO/sub 2/ laser radiation is increased further, the surface topography shows signs of melting, formation of ripple patterns, and vaporization. Auger spectroscopy and electron-induced x-ray emission show that there is loss of As, compared to Ga, caused by the melting of the surface. Using plain-view TEM they find that Ga-rich islands are formed near the surface during the rapid solidification of the molten layer. Auger and SIMS measurements are used to study the incorporation of oxygen in the near-surface region, and the results show that oxygen incorporation can occur for GaAs samples that have been irradiated in air