Influence of V/III Flow Ratio on Growth of InN on GaN by PA-MOMBE

Abstract

InN epilayers were prepared on c-GaN/sapphire substrates by plasma-assisted metal-organic molecular beam epitaxy using N-2 and trimethylindium precursor as the V/III sources. We studied the influence of the V/III flow ratio on the film structure, surface morphology, film compositions, and optical and electrical properties using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction, X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), photoluminescence (PL) measurement and Hall effect. The results show that epitaxial InN films can be obtained with the V/III ratio in the range between 1.81 and 4 at 500 degrees C. The InN growth rate decreases from 1.9 to 1.4 mu m/h when the ratio increases from 1.81 to 4. The surfaces of the InN films are not smooth in the V/III range used. Cross-sectional TEM revealed that the planar defect density in InN is as high as similar to 1.5 x 10(6) cm(-1) at a V/III ratio of similar to 1.81. XPS and SIMS results show that the film surface contains oxygen, which is found to affect the measured carrier mobility and concentration. (C) 2013 The Electrochemical Society. All rights reserved.