CORRELATION BETWEEN GAP DENSITY-OF-STATES AND RECOMBINATION PROCESSESIN HIGH ELECTRONIC QUALITY A-C-H

The investigation on electronic density of states (DOS) and photolumin escence processes in a-C:H films has attracted, in the last years, int erest, due to the foreseen technological application of carbon based m aterials. In this paper we present a new model for electronic DOS of a -C:H having sp(2) fraction less than a percolation threshold. This mod el is able to explain the optical absorption coefficient for photon en ergies in the range 0.7 to 3.5 eV. Moreover, with this model we correl ate, as it happens in a-Si:H, the photoluminescence quantum efficiency and the density of states close to the Fermi energy. Such states, how ever, can have either diamagnetic or paramagnetic nature so that some of them can be detected by electron spin resonance and others by optic al transitions. (C) 1998 Elsevier Science B.V. All rights reserved.