Photon recycling effect on electroluminescent refrigeration

We study electroluminescent refrigeration in an AlGaAs/GaAs double heterostructure by a self-consistent calculation with photon recycling considered. To gain insight, we investigate the influence of the recycling on the carrier density and the current components due to various recombination mechanisms in the device under different bias voltages. The photon recycling is a feedback process, which behaves as an internal source of generating electron-hole pairs in the active region and causes an effective feedback current to compensate the driving current from the external source. Consequently, it reduces the driving current, improves the external quantum efficiency, and loosens the requirement on the photon extraction efficiency for refrigeration. For the device with a 1 μm GaAs active layer operating at 300 K, the minimum required extraction efficiency is less than 20% if the trapped photons are completely recycled and remains a feasible value of 45% if the recycling efficiency is 90%, which is not difficult to achieve. In addition, photon recycling eases the problem of the drastic deterioration of the cooling power and the external efficiency as the extraction efficiency reduces. These results reveal a good possibility of realizing electroluminescent refrigeration in semiconductors.