LASER-INDUCED RECRYSTALLIZATION AND DAMAGE IN GAAS

We have investigated the recrystallization of ion-implanted amorphous GaAs using a frequency-doubled 10-8-s pulsed Nd: YAG laser. The best results were obtained by spatially overlapping laser pulses at 20 MW/cm 2. At power densities above 20 MW/cm2, not only does the GaAs surface begin to show uneven solidification, but also an increasing degree of disorder is revealed in Raman scattering and by a broad hump in the spectrum of channeled He-ion backscattering. This laser-induced damage is similar for single-crystal and ion-implanted GaAs samples. We attribute the damage at high power densities to the loss of arsenic and subsequent rapid cooling of a gallium-rich liquid.