Single-crystal zincblende GaN growth on GaP substrate in molecular beam epitaxy
ABSTRACT Zincblende GaN (β-GaN) has recently attracted much attention because of its significant advantages over wurtzite GaN (α-GaN), such as higher doping efficiencies, higher carrier mobilities, and the possibility of optoelectronic integration with GaAs or Si devices. Due to its metastability, however, it is difficult to obtain single-crystalline β-GaN. Several groups reported that As or P overpressure was beneficial to enhance the growth of β-GaN without phase mixture. We report the growth of single-crystalline β-GaN epilayers achieved by varying the V/III ratio of a GaN nucleation layer (NL) grown on a GaP substrate. Adjustment of the V/III ratio in an NL stage resulted in phase transition from wurzite to zincblende GaN. GaP was employed as a substrate because of its smaller difference in lattice constants and thermal expansion coefficients with those of GaN, compared to GaAs, and, especially because of the possibility of growing,β-GaN on GaP/Si.