Molecular Beam Epitaxy of GaN under N-rich Conditions using NH₃

Abstract

Ammonia has been used to grow GaN layers by molecular beam epitaxy on c-plane sapphire substrates. The ratio of nitrogen to Ga active species, i.e., the actual V/III ratio, has been varied from 1 to 4. It is found that increasing the V/III ratio improves the material properties both in terms of optoelectronic and structural quality. This is demonstrated by photoluminescence (PL) experiments, Hall measurements, secondary ion mass spectroscopy (SIMS), and atomic force microscopy. The origin of the residual n-type doping of undoped GaN layers is also discussed on the basis of SIMS and PL results.

Mechanisms of ammonia—MBE growth of GaN on SiC for transport devices

“…Under those conditions, even smaller RMS roughness of 1 nm was observed [5]. The same trend of improved surface smoothness at high V/III ratios was also observed in a previous study of ammonia MBE growth on sapphire substrates with ammonia BEP varied between 3.1 Â10 À5 and 1.3 Â 10 À4 Torr [11].…”

Origins of GaN(0001) surface reconstructions

“…2. At 800 C under normal N-rich growth conditions [19] the RHEED pattern observed during growth is mainly (11) with a faint diffuse trace of (22). We call this surface phase (11)-N because of the N-rich growth conditions (see the lower panel of Fig.…”

Recent developments in surface studies of GaN and AlN

“…In this case growth is performed under N-rich conditions and a 2×2 structure is observed on the surface. 18,19,20 Theoretically a variety of 2×2 structures involving H, NH 2 or NH 3 termination of the surface have been predicted under similar conditions of temperature and H pressure, 21 and thus the 2×2 structure seen in RMBE likely is associated with one of these structures. It is notable that relatively smooth growth morphology can be obtained during RMBE growth, at temperatures similar to that used for PA-MBE i.e.…”