Electrical characterization and carrier transport mechanisms of GaAs p/i/n devices for photovoltaic applications

Abstract

GaAs p/i/n diodes made by Metal-Organic Vapour Phase Epitaxy were examined by electrical measurements for evaluating the optimum i-region for use as solar cells. Four series of samples were prepared and studied each one with a different i-region width. The performance of the devices was examined by means of Admittance spectroscopy as well as classical current–voltage and capacitance–voltage characterization, allowing the calculation of the minority carriers lifetime ( τ eff) and the diodes ideality factors. The values of the τ eff were found to lie between 8.7 ps and 0.14 ns for i-region widths between 0 and 0.8 μm. These results were used to model the multilayer structure with the two-diode representation and explain the conductance mechanisms inside the diodes. This modeling showed that the recombination/generation currents were dominating in forward biased diodes and the ohmic loss current in reverse bias.