In situ monitoring of reflection high-energy electron diffraction oscillation during the growth of gallium nitride films by gas-source molecular beam epitaxy

Abstract

Reflection high-energy electron diffraction (RHEED) specular intensity oscillations have been observed during the growth of gallium nitride (GaN) films by gas-source molecular beam epitaxy (GS-MBE) for the first time. The GaN films were grown on sapphire substrates using metal gallium and ammonia as source materials, following the deposition of a GaN buffer layer at lower temperature. The incident electron beam was parallel to the GaN [1 1 00] azimuth direction and the signal intensity was measured with a photo-multiplier via an optical fiber fixed on the specular spot. The total thickness of the film was 1700 Å which includes the 180 Å buffer layer. RHEED oscillations during growth were observed on the sapphire (0001) substrate. Comparing the period of the RHEED intensity oscillations with those calculated from the growth rate, we found that a single period of the RHEED intensity oscillation corresponds to a monolayer growth of GaN.