Investigation of the Surface Leakage Current of the Nbn InGaAsSb Infrared Photodetector by Using Photoreflectance Spectroscopy

The surface leakage current of the nBn infrared detector based on InGaAsSb/AlGaSb heterostructure was studied by using photoreflectance spectroscopy (PR). The Franz-Keldysh oscillations (FKOs) in PR spectra showed that the minority carriers (electrons) mainly affect the surface electric field in the nbn structures. The results show that the electric field increases due to the photovoltaic effect as the temperature increases. However, the increased ratio of the electric field at low temperature is lower than that of high temperature. At low temperatures, when the temperature drops, the generation-recombination (G-R) associated with dark current is eliminated, and the surface electric field variation becomes lower. By increasing the temperature and dark current, the electric field changes more. In addition, the unipolar barrier photodiode exhibits no surface leakage current at low temperatures without blocking the bulk currents.