A band-to-band tunneling injection mechanism for charge carriers in composite wide bandgap field emission sources

Recently there has been much activity in developing composite thin film diamond devices for use as high current, low power field emission electron sources. Prototypes of such devices have been fabricated by Gels et al. (GTL, 1996), Okano et al. (Okano, 1996), and Weiss et al. (1997). Although these are all composite thin film structures, the compositional and structural properties of the diamond samples differ somewhat in each and this must be considered in any theory of operation of these devices. In the Weiss et al. device, the diamond film is composed of amorphous tetrahedrally bonded carbon, which leads to a more complicated band structure than for crystalline diamond. The operation of this device has not yet been studied in detail by the authors. Therefore, we shall only discuss the first two by GTL and Okano.