Temperature dependence of photoemission characteristics from Al_xGa_1-xAs/GaAs photocathodes

In this work, photon-enhanced thermionic emission (PETE), which simultaneously harvests solar photonic and thermionic energies, is studied theoretically and experimentally with a transmission-mode Al_xGa_1-xAs/GaAs cathode within a compact photodiode. The effect of temperature on energy distribution and photoemission yield was experimentally studied in the wavelength range 450-850 nm. The variation of the energy distribution with increasing temperatures demonstrates that direct photoemission gradually declines, while PETE contribution increases with increased heat. Further quantitative proof of the PETE phenomenon can be observed at 850 nm, as temperature increases from 20°C to 90°C. The PETE model with the t-mode Al_xGa_1-xAs/GaAs cathode is deduced, and the temperature dependence of electron affinity can be achieved. The results show promising applications of the Al_xGa_1-xAs/GaAs cathode in combined solar/thermal energy conversion.