MOCVD growth of a-plane InN films on r-Al2O3 with different buffer layers

InN films have been grown on (1 –1 0 2) r-plane Al2O3 substrates by metalorganic chemical vapor deposition with GaN buffer, with GaN and low-temperature (LT) InN buffers, and without any buffer layer. It is found that all of the samples are in the non-polar (1 1 –2 0) a-plane and an increase in the growth temperature of GaN buffer to about 800 °C can improve the crystal quality of the InN films as compared to the film grown on GaN buffer at 550 °C, while 550 °C is the usual GaN buffer growth temperature in c-plane InN growth. Surface morphologies of the films show a stripe-like pattern. Introducing GaN buffer can reduce the anisotropy of the full-width at half-maximum of X-ray (1 1 –2 0) rocking curves along different directions in plane. The added LT-InN layer cannot improve the morphology and the crystallography of a-plane InN, but it can increase the intensity of photoluminescence (PL) spectrum remarkably and make about 10 meV blueshift as to the sample with only GaN buffer. The PL measurements reveal that the InN films have a fundamental band gap of about 0.75 eV.