The optical absorption edge in some amorphous semiconductors

The optical absorption coefficient ( alpha ) has been measured as a function of photon energy (h(cross) omega ) in binary vanadate glasses containing 50 mol.% of vanadium in different glass formers (P 2 O 5 , TeO 2 and GeO 2 ). Data on absorption in these glasses and in some other semiconductors have been analysed in the light of the theory developed by Davis and Mott ( alpha h(cross) omega varies as (h(cross) omega -E 0 ) n ). E 0 is the optical energy gap and n=2 or 3. It is found that a cubic relation gives the best fit to the data.