Carrier transport in highly generated carrier concentration

We have investigated photo-generated carrier transport (photocurrent) in the p–n junction experimentally and theoretically. The photocurrent was measured with various laser-pulse intensities under different reverse bias conditions applied at the p–n junction. For a low laser intensity, the measured photocurrent maintains the same shape as the irradiated laser pulse with diminished time delay. Increasing the laser intensity, however, transport delay of the measured photocurrent is observed with broadened pulse shapes, especially under weak bias conditions. This broadened photocurrent shape could not be reproduced by conventional two-dimensional (2D) device simulations, which solve the basic device equations. Under highly generated carrier concentration, it is demonstrated here that the carrier transport is mostly governed by non-equilibrium carrier dynamics, which is not included in the conventional device equations.