Power- and Spectral-Dependent Photon-Recycling Effects in a Double-Junction Gallium Arsenide Photodiode

Photon-recycling effects improve radiative efficiencies of semiconductor materials and play important roles in the design of high-performance optoelectronic devices. Conventional research mostly studies the impact of photon-recycling on the voltage of photodiodes. Here we systematically analyze the photon response of a microscale gallium-arsenide (GaAs)-based double-junction photodiode. In such a device, the current-matching condition between two subcells is determined by their photon coupling. Photodynamics in the device is examined and reveals the material's internal quantum efficiencies. By leveraging photon distributions inside the device, we discover that its photocurrent and spectral responses are highly dependent on the illumination intensity. Consistent with theoretical analyses, the device's photocurrents exhibit linear and superlinear power-dependent characteristics under near-infrared and violet-blue illuminations, respectively. Because of the strongly enhanced photon-recycling effects under strong illumination, broadband photon responses (external quantum efficiency close to 50% from 400 to 800 nm) could be achieved in such a strongly current mismatched GaAs dual-junction device. The understanding of photon processes in such devices would offer routes to the design of high-performance photodetectors and solar cells.