Low temperature growth of gan nanowires by plasma-enhanced chemical vapor deposition

In this work, a novel plasma-assisted chemical vapor deposition method was developed to fabricate GaN nanowires by the Vapor-Liquid Solid Mechanism. Nitrogen plasma was used as a nitrogen source to grow GaN crystals. Compared to NH ₃ used in thermal CVD systems, nitrogen plasma is more active and its ability to produce active nitrogen radicals is insensitive to temperature, making it more suitable for low temperature growth of GaN crystals. The growth temperature of GaN nanowires varied from 900 to 550° C followed by transmission electron microscopy (TEM), photoluminescence (PL) and X-ray diffraction analysis to investigate the effect of growth temperature on the crystal structure and quality. High quality GaN nanowires were grown at 900° C, which was lower than the normal growth temperature of 1000° C in thermal CVD. According to TEM and PL analysis, the crystal quality was still high, even after lowering the growth temperature to 700° C. When the growth temperature was further reduced to 550° C, defects formed in the bulk and on the surface of nanowires due to the slow surface diffusion of Ga adatoms on the sidewall of nanowires resulting from the N-rich growth environment and low surface temperature.