Enhanced efficiency in 808 nm GaAs laser power converters via gradient doping

Two batches of GaAs laser power converters (LPCs) with or without a localized gradient doping layer were fabricated via metalorganic chemical vapor deposition for converting the power of 808 nm lasers. The gradient doping layer was introduced into the base layer above the back surface field layer with a doping concentration that varied exponentially from 1×1018/cm3 to 5×1018/cm3. The two batches of LPCs were tested under various 808 nm laser light intensities ranging from 100 to 2500 mW. The LPC structures with and without the gradient doping layer both displayed their highest conversion efficiency of 55.1% and 53.4%, respectively, at a laser power of 1200 mW. The addition of the gradient doping layer improved the separation efficiency of the photogenerated carriers and reduced the recombination rate in the base region of the GaAs LPCs, which increased the open-circuit voltage of the LPCs by 13.3 mV and the short-circuit current density by 3.6 mA. Furthermore, the absolute value of the fill factor increased by 1.2% at an incident light intensity of 1200 mW, resulting in a 1.7% improvement in the photoelectric conversion efficiency of the GaAs LPCs.