The effect of V:III ratio on the growth of InN nanostructures by molecular beam epitaxy

We have investigated the growth of thin layers of indium nitride (InN) on gallium nitride (GaN) by molecular beam epitaxy (MBE) using two different nitrogen sources. Using thermally cracked ammonia as the nitrogen source, we explored the effect of the V:III ratio by varying the ammonia pressure. With a low V:III ratio, we did not detect InN growth, and instead observed the formation of irregularly shaped indium islands on the GaN surface. With higher V:III ratios, nanostructure growth was observed for thin (≈2 ML) layers. Further deposition resulted in the growth of polycrystalline material. The differences between the two pressure regimes may be explained in terms of the interplay between equilibrium thermodynamics and growth kinetics. We performed similar experiments at higher V:III ratios using a modified nitrogen plasma source. Stranski–Krastanov growth occurred, and we were able to obtain high-temperature in vacuo STM images of the as-grown nanostructures.