Numerical analysis of the short-circuit current density in GaInAsSb thermophotovoltaic diodes

In this paper, a simulation and analysis on the short-circuit current density (Jsc) of the P-GaSb window/P-GaxIn1−xAs1−ySby emitter/N-GaxIn1−xAs1−ySby base/N-GaSb substrate structure is performed. The simulations are carried out with a fixed spectral control filter at a radiator temperature (Trad) of 950 °C, diode temperature (Tdio) of 27 °C and diode bandgap (Eg) of 0.5 eV. The radiation photons are injected from the front P-side. Expressions for minority carrier mobility and absorption coefficient of GaxIn1−xAs1−ySby semiconductors are derived from Caughey–Thomas and Adachi’s model, respectively. The P-GaxIn1−xAs1−ySby emitter with a much longer diffusion length is adopted as the main optical absorption region and the N-GaxIn1−xAs1−ySby base region contribute little to Jsc. The effect of P-GaSb window and P-GaxIn1−xAs1−ySby emitter region parameters on Jsc is mainly analyzed. Dependence of Jsc on thickness and carrier concentration of the window are analyzed; these two parameters need to be properly selected to improve Jsc. Contributions from the main carrier recombination mechanisms in the emitter region are considered; Jsc can be improved by suppressing the carrier recombination rate. Dependence of Jsc on the carrier concentration and layer thickness of the emitter P-region are also analyzed; these two parameters have strong effect on Jsc. Moreover, adding a back surface reflector (BSR) to the diode can improve Jsc. The simulated results are compared with the available experimental data and are found to be in good agreement. These theoretical simulations help us to better understand the electro-optical behavior of GaxIn1−xAs1−ySby TPV diode and can be utilized for performance enhancement through optimization of the device structure.