Tunneling Spectroscopy of Amorphous Semiconductors

The tunneling transmission coefficient as calculated by the WKB and the multi-potential approximation (MPA) is compared for tunneling through an a-Si:H/a-SiNx:H double barrier structures. The MPA method leads to shifts in the location of the quantum well states, which complicates the interpretation of quantum size effects in amorphous silicon multilayers. Experimental studies of tunneling currents through a-Si:H/a-SiNx:H single barrier structures are presented. At low temperatures the conductance data resembles tunneling data for metal/insulator/metal structures with an asymmetric barrier, while at room temperature a pronounced peak is observed in the conductance-volatge characteristics.