High performance type II superlattice photo diodes for long wavelength infrared applications

In this paper we report improved device performance for type II superlattice (SL) photo diodes by inserting a graded AlGaSb barrier layer inserted into the depletion region of the PIN diode to suppress dark current and employing SiO2 as a passivation layer. The I-V characteristics shows presence of AlGaSb barrier layer in the device structure increased R0A values by up to a factor of 40 times. Sidewall resistivity was increased by an order of magnitude with SiO2 passivation. The fabricated photo diode with λc=12.8-μm shows peak responsivity of 3.7 A/W at 10.6 μm and Johnson noise limited peak detectivity of 1×1011 cmHz1/2/W under zero bias at 83 K under 300 K background radiation with a 2π field-of-view.