Direct tunneling at the front contact of amorphous silicon p-i-n devices

The device physics behind hole direct tunneling currents at the front contact of a-Si:H p-i-n homojunction have been explored. In this paper, the dark I-V, the light I-V, and the QE characteristics of this structure with and without hole direct hole tunneling currents are evaluated and compared. The three differential equation systems of the Poisson´s equation, the continuity equation for free electrons, and the continuity equation for free holes have been solved with allowances for direct tunneling currents. Hole direct tunneling currents at the front contact of a-Si:H p-i-n homojunctions give rise to a significant increase in the dark current level at high forward voltages and to an increase in the open-circuit voltage of the light I-V characteristic when the front electron barrier is low. The hole thermionic emission current and the hole direct tunneling current have been carefully compared to the front contact. Hole tunneling currents introduce important modifications to the carrier transport physics not only to the front contact but also in the bulk of the a-Si:H p-i-n homojunction