Very-long wave ternary antimonide superlattice photodiode with 21 μm cutoff

We describe a ternary antimonide superlattice photodiode with a 21 μm cutoff wavelength. The active region consists of 150 periods of 10 monolayers (MLs) of In0.07Ga0.93Sb and 19 MLs of InAs with InSb-like interfacial bonds. The device has a detectivity of 3×109 cm√Hz/W, dynamic impedance-area product of 0.18 Ω cm2, and peak external quantum efficiency of 3% at 40 K. X-ray diffraction and cross-sectional scanning tunneling microscopy show the structure to have a high degree of order with abrupt interfaces. A simulation of the absorption spectrum effectively reproduces the observed spectrum.