BALLISTIC-ELECTRON-EMISSION MICROSCOPY STUDY OF TRANSPORT IN GAN THIN-FILMS

Ballistic electron emission microscopy (BEEM) measurements on GaN grow n on sapphire substrates reveal a second conduction band minimum simil ar to 340 meV above the absolute band minimum at the zone center (Gamm a point). A significant lateral variation of the energy difference bet ween the two band minima, +/-50 meV, was observed which may result fro m nonuniform strain in the material. The existence of two conduction b ands in close proximity may affect device applications, i.e., GaN base d lasers and electronic devices. (C) 1997 American Institute of Physic s.