Optimizing the Size of Vertical-Junction GaAs PV Cells With AlGaAs Gradient Waveguide

In GaAs-based side-input laser photovoltaic converters (LPVC) with an AlxGa1-x As gradient waveguide light comes into the semiconductor crystal perpendicular to the direction of growth. Even a slight deviation from the normal allows for the refraction of the rays. The light goes in the direction of the refractive index increasing to the region with low AlAs content and to the p-n junction. As a result, the light propagates not only along the growth direction of the crystal, but also in the lateral direction. In terms of minimizing material consumption as well as increasing current density, the optimal strategy would be to shorten the LPVC. However, optical losses are observed in too short samples. Some of the light introduced into the crystal leaves the structure through the opposite (to the photoreceiving) surface. Thus, two competing tendencies affect the efficiency of photoconversion: elongation and shortening. This letter is devoted to the theoretical and practical investigation of choosing the optimal size of the vertical p-n junction LPVC.