Metal/GaN Schottky barriers characterized by ballistic-electron-emission microscopy and spectroscopy

Ballistic-electron-emission microscopy (BEEM) and spectroscopy have been used to characterize the Pd/GaN and Au/GaN interfaces. BEEM spectra yield a Schottky barrier height for Au/GaN of ∼1.05 eV that agrees well with the highest values measured by conventional methods. For both Pd and Au, a second threshold is observed in the spectra at about 0.2–0.3 V above the first threshold. Imaging of these metal/GaN interfaces reveals transmission in nearly all areas, although the magnitude is small and spatially varies. Attempts to perform BEEM measurements on other GaN material have resulted in no detectable transmission in any areas, even at voltages as high as 3.5 V.