Formation process of sharp-pointed structures on GaN nanorods during RF-MBE growth and their field emission characteristics

We have investigated layer structures of an AlN/GaN superlattice (SL) in nanorods by cross-sectional transmission electron microscopy to clarify the formation process of sharp-pointed structures on GaN nanorods during plasma assisted molecular beam epitaxial (PA-MBE) growth. It is found that during 75-160 nm MBE growth, flat interfaces of the AIN/GaN SL in nanorods develop into chevron-shaped interfaces. Beyond a thickness of 165 nm, AIN/GaN SL nanorods continue to grow with nearly the same chevron-shaped interfaces, and finally these interfaces appear as the sharp-pointed structures on the top of nanorods. In contrast to GaN and AIN/GaN SL nanorods, no formation of the sharp-pointed structures is observed for AlN nanorods. This indicates that the formation of the sharp-pointed structures is ascribed to GaN growth. We will discuss thickness dependence of FE characteristics of GaN nanorods in relation with the formation of the sharp-pointed structures. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim