EFFECT OF FILM THICKNESS AND LASER ENERGY DENSITY ON THE STRUCTURAL CHARACTERISTICS OF LASER-ANNEALED POLYCRYSTALLINE GALLIUM ARSENIDE FILMS

摘要

Scanning electron microscopy and high-resolution electron backscatter diffraction (EBSD) have been used to study the texture and microstructure evolution during the crystallization of initially amorphous GaAs thin films. A KrF excimer laser with 30 ns pulse duration was used for crystallization of a-GaAs grown on SiO{sub}2 substrate using molecular beam epitaxy (MBE) technique. The effect of laser energy density and film thickness on grain morphology has been studied. The integrated information on grain size distribution, preferred orientation, and nature of grain boundaries provides useful information to postulate the mechanism of grain-growth and likely role of different contributing parameters in the evolution of final texture under the highly transient processing conditions prevailing during the short laser irradiation. The results show that for thick films the laser crystallization results in a weak <111> fiber texture. While for a thinner films the grains have a strong <001> texture that strengthens with a decrease in film thickness and increase in laser energy density.