Electroluminescence and forward bias currents in amorphous silicon p-i-n diodes: the effect of steady state bias and large i-layer thickness

Abstract

The transport and recombination in amorphous silicon p-i-n diodes is studied experimentally and by computer modelling. It is found that the rise time of the transient double injection current is strongly affected by applying a steady state bias voltage. Calculations reveal changes of the barrier height for hole injection as the major effect. The rise time exhibits a power law dependence on the magnitude of the applied forward bias voltage both experimentally and as a result of the calculation. The recombination is strongest at the p-i interface at all double injection conditions. In diodes with large i-layer thickness (> 1 μm), the rise of the double injection current is no longer continuous but shows a hump on top of the expected current which is also observed in the electroluminescence signal. It is interpreted as due to a transient reduction of the electrical field in the i-layer when at the same time the barrier for hole injection is low.