Abstract
Sandwich metal–semiconductor (a-Si:H)-metal specimens with different front and back metal contacts have been characterized by measurement of current against voltage for different temperatures. Under suitable conditions a flat-band voltage, V FR, at the forward-biased contact can be identified by a rapid rise in the hole current. The theory is developed to relate V FB to the front- and back-contact band bending so that the contact potential barriers can be evaluated. A figure for the density of states at the Fermi level is also obtained. It is shown that the lower surface contact is dominated by the initial layers of deposition and the top contact by surface oxide.