THE ORIGIN OF QUANTUM EFFICIENCIES GREATER-THAN UNITY IN A-SI-H SCHOTTKY BARRIERS

A photogating effect, recently predicted with computer simulations and subsequently observed in a-Si:H p-i-n structures, is shown to be also present in a-Si:H Schottky barrier devices, it is experimentally demo nstrated that this photogating effect can be so significant that it ca n lead to quantum efficiency values greater than unity in Schottky bar rier a-Si:H devices even in the annealed state. This photogating effec t is found to be present under blue bias light and, for the annealed s tate, at low forward biasing conditions. Using our computer simulation s, we show that, as in p-i-n devices, this photogating effect is cause d by modulation of the field with blue bias light present near the fro nt contact. We show also that this photogating effect is dependent on material and device parameters.