Growth process from amorphous GaN to polycrystalline GaN on Si (111) substrates

摘要

Amorphous GaN (a-GaN) films on Si (111) substrates have been deposited by RF magnetron Sputtering with GaN powder target. The growth process from amorphous GaN to polycrystalline GaN is studied by XRD, SEM, PL and Raman. XRD data mean that annealing under flowing ammonia at 850-950 degrees C for 10 min converts a-GaN into polycrystalline GaN (p-GaN). The growth mechanism can be mostly reaction process through N3- in amorphous GaN replaced by N3- of NH3. Annealing at 1000 degrees C, the appearance of GaN nanowires can be understood based on the vapor-liquid-solid (VLS) mechanism. In addition, XRD, PL and Raman measurement results indicate that the quality of GaN films increases with increasing temperature. The tensile stress in the films obtained at 1000 degrees C is attributable to the expansion mismatch between GaN and Si, with the gallium in tile film playing a negligible role.