The effect of rapid thermal annealing (RTA) on Ni/Au contacts on P-type GaN
was investigated in terms of surface morphology and diffusion depth of met
allic species. Ni/Au contacts were evaporated on the P-type 0.5 mu m thick
top layer of a GaN P/N homojunction. Optical micrographs revealed that the
contact morphology degrades when annealed above 800 degrees C for 1 min. At
the same time, both Ni and Au atoms strongly diffuse in the P-type layer a
nd even can reach the junction for a I min long annealing at 900 degrees C,
therefore making the junction structure unoperable. This behavior was evid
enced using the Auger voltage contrast (AVC) technique.