Growth mechanism and structural characterization of hexagonal GaN films grown on cubic GaN (1 1 1)/GaAs (1 1 1)B substrates by MOVPE

Abstract

Hexagonal phase GaN layers were grown by metalorganic vapor phase epitaxy (MOVPE) on GaAs (1 1 1)B substrates using the cubic phase GaN (c-GaN) as an intermediate layer. High-resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM) measurements showed fairly good crystalline qualities of the h-GaN layers. Dislocation densities estimated from cross-sectional TEM micrographs were found to be as low as 10 7–10 8 cm −2. Flat growth of the c-GaN intermediate layer on GaAs (1 1 1)B substrate was achieved at a low-growth temperature (600 °C). The interface between the GaN layer and the GaAs (1 1 1)B substrate is very smooth without any voids, in spite of the high-growth temperatures of 880–960 °C. It is interesting that the lattice-matched h-GaN layer to the c-GaN intermediate layer can be obtained by controlling the cubic-to-hexagonal structural transition during the MOVPE growth process at appropriate growth temperatures. The growth mechanism and characteristics of the grown h-GaN layers are discussed.