p-n Junction Photocurrent Modelling Evaluation under Optical and Electrical Excitation

Abstract: Based upon the quasi-equilibrium approximation, the validity of p-n junction modelling, has been experimentally investigated under synchronous electrical and optical excitation of silicon photo-diodes. The devices had areas of 8.2 mm² and reverse bias saturation currents of the order of 10^-10 A. Their current-voltage (I-V) response was exploited experimentally both in the dark and under various illumination levels. The quoted values for the saturation current, the ideality factor, the series resistance and the reverse-bias photocurrent are investigated for the simulation of the I-V curves via the quasi-equilibrium model. In addition, the measured I-V data have been further analysed to estimate the produced photocurrent as a function of the applied bias (forward or reverse) under given illumination levels. Comparisons between the simulated curves and the experimental data allowed a detailed photocurrent modelling validation. The proposed approach could be useful towards studying other parameters of optically activated p-n junctions such as: the bias dependence of the minority carrier diffusion lengths and/or the generated rates of electron-hole pairs (EHP).