The effect of charge transport mechanisms on the efficiency of Al$_{x}$Ga$_{1-x}$As/GaAs photodiodes

Photovoltaic characteristics of heterostructure Al$_{x}$Ga$_{1-x}$As/GaAs $p$–$i$–$n$ photodiodes fabricated by molecular-beam epitaxy have been studied. Efficiencies of 50% were reached in conversion of monochromatic light in the photovoltaic mode at power density of up to 200 W/cm$^2$ at a wavelength $\lambda$ = 830 nm. A relationship was demonstrated between the “saturation currents” for the diffusion-related charge-transport mechanism (Shockley) in $p$–$i$–$n$ photodiodes, calculated from dark current–voltage characteristics, and the experimental values of efficiency. As the “saturation current” of the diffusion-related charge-transport mechanism increases by an order of magnitude, a relative decrease in the efficiency from the maximum value by more than 10% is observed under excitation by constant or pulsed monochromatic light.