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

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 s olar cells. Four series of samples were prepared anti 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 minor ity carriers lifetime (tau (eff)) and the diodes ideality factors. The valu es of the tau (eff) were found to lie between 5.7 ps and 0.14 ns for i-regi on widths between 0 and 0.8 mum. These results were used to model the multi layer structure with the two-diode representation and explain the conductan ce mechanisms inside the diodes, This modeling showed that the recombinatio n/generation currents were dominating in forward biased diodes and the ohmi c loss current in reverse bias. (C) 2001 Elsevier Science B.V. All rights r eserved.