Intimate morphology of Au-nGaN contacts for the configuration of near ideal Schottky diodes

摘要

The intimate configuration of gold Schottky contacts formed in-situ on n-type GaN grown by MOVPE on A1_2O_3 (0001) substrates as a function of the semiconductor surface treatment prior to metallisation, has been investigated by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Two approaches are described: (ⅰ) the deposition of several monolayers of elemental Ga, followed by annealing at 900°C, and (ⅱ) annealing at 600°C. Samples metallised following method (ⅰ) exhibit an intermixed morphology leading to poor ideality factors and lower barrier heights of Schottky contacts. Conversely, for the 600°C annealed samples, the interface is abrupt and non-reacted. Current-voltage (I-V) measurements also indicate the highest barriers yet reported (1.2-1.3 eV), with very low ideality factors (n=1.03).