Ballistic electron emission microscopy study of transport in GaN thin films

Ballistic electron emission microscopy (BEEM) measurements on GaN grown on sapphire substrates reveal a second conduction band minimum -340 meV above the absolute band minimum at the zone center (G point). A significant lateral variation of the energy difference between the two band minima, ± 50 meV, was observed which may result from nonuniform strain in the material. The existence of two conduction bands in close proximity may affect device applications, i.e., GaN based lasers and electronic devices