Modification of GaN Schottky barrier interfaces probed by ballistic-electron-emission microscopy and spectroscopy

Ballistic-electron-emission microscopy (BEEM) and spectroscopy have been us ed to investigate the properties of Au/GaN interfaces. The effects of in si tu and ex situ annealing on the starting GaN surface were examined, with th e aim of increasing the surprisingly low value of interface electron transm ission observed in previous BEEM measurements. BEEM imaging and spectroscop y have demonstrated that much higher, more uniform transmission across the Au/GaN interface can be achieved. However, while methods were identified th at increase transmission by more than an order of magnitude, BEEM spectrosc opy indicates that annealing can substantially alter the Schottky barrier h eight. These barrier height changes at moderate temperatures are attributed to vacancy diffusion. (C) 2000 American Institute of Physics. [S0003-6951( 00)03113-2].