Characterization of MOVPE-grown GaN layers on GaAs (111)B with a cubic-GaN (111) epitaxial intermediate layer

We have proposed the use of cubic-GaN (c-GaN) as an intermediate layer for the metalorganic vapor phase epitaxy (MOVPE) growth of hexagonal-GaN (h-GaN) on GaAs (111)B substrates. Insertion of the c-GaN layer at the h-GaN (0001)/GaAs (111) interface significantly improves the crystallinity of the h-GaN layer. Although, we have used [111]-oriented c-GaN layer so far, the lattice-mismatch between h-GaN (0001) and c-GaN (111) is expected to be less than 0.1%, which is much smaller than that for the other commonly used substrate materials. Furthermore, the c-GaN layer was grown at a relatively low growth temperature (T_g = 600 °C) to prevent the GaAs substrate from thermal decomposition and to provide a strain relief template layer. This technique enables us to succeed in obtaining nearly strain free h-GaN layers on GaAs (111)B substrates. In this report, the relationship between the nature of the c-GaN intermediate layer and the cubic-to-hexagonal structural transition machanisms are discussed.