We describe p-type gallium nitride (GaN) as a candidate for high brightness
photocathodes. Experiments utilizing photoemission spectroscopy and quantu
m yield measurements were performed on GaN films to characterize various ce
sium and oxygen activations. Quantum efficiencies of 0.1%-4% were obtained
in reflection for the cesiated p-type 0.5 mum thick GaN films and 25%-50% o
n the 0.1 mum thick GaN films. The corresponding emission currents are 142-
300 nA for 0.5 mum thick films and 0.7-1.3 muA for the 0.1 mum thick films.
This results in an increase of several orders of magnitude in the emission
current from the starting GaN films. Furthermore, an initial desorption me
asurement was performed in order to evaluate the Cs binding strength to GaN
relative to GaAs. We observe Cs was bound to the GaN surface (0001) at 700
degreesC and completely desorbed at 450 degreesC for a (100) GaAs surface.
Finally, an alternate barium activation on GaN is included for preliminary
comparison with the various cesium activations. (C) 2000 American Vacuum S
ociety. [S0734-211X(00)10806-6].