Crystallization of Isolated Amorphous Zones in Semiconductor Materials

Abstract

Crystallization of spatially isolated amorphous zones in Si, Ge, GaP, InP and GaAs was stimulated thermally and by irradiation with electrons and photons. The amorphous zones were created by a 50 keV Xe⁺ implantation. Significant thermal crystallization occurred at temperatures greater than 425 K, 375 K and 200 K in Si, Ge and GaAs, respectively. Electrons with energies between 25 and 300 keV stimulated crystallization in all materials at temperatures between 90 K and room temperature. For electron energies above the displacement threshold, the crystallization rate decreased as the electron energy decreased. As the electron energy was decreased below approximately 100 keV, the crystallization rate unexpectedly increased. The crystallization rate was independent of temperature for all electron irradiations. Irradiation with a 532 nm green laser (hv= 2.33 eV) caused crystallization in Si (E_g = 1.11 eV) and Ge (E_g = 0.67 eV) at a rate comparable to a thermal anneal at 425 K and 375 K, respectively, and caused minimal crystallization in GaP (E_g = 2.26 eV). The electron and photon irradiation results are consistent with the model that crystallization is controlled by defects (dangling bonds and kinks) created by electronic excitation at the amorphous-crystalline interface.