Dark current mechanism of unpassivated mid wavelength type II InAs/GaSb superlattice infrared photodetector

We investigate the dark current mechanism for an unpassivated mid wavelength (MW) type II InAs/GaSb superlattice infrared photodetector by doing the variable-area diode tests. The bulk resistance-area product and the resistivity due to the surface current are determined to be 17.72 Ω cm2 and 704.23 Ω cm at 77 K, respectively. It is found that for all the mesa sizes used, the dark current is dominated or predominated by the surface component, and with scaling back the mesa size, the surface current increases while the bulk component decreases. The activation energy is determined to be 145 meV for the temperature range around 140–280 K, while it is 6 meV when temperature is below 100 K. It is also found that the dark current is dominated by the generation-recombination current for the MW device when temperature is between 140 and 280 K.