Optimization of Long-Wavelength InAs/GaSb Superlattice Photodiodes With Al-Free Barriers

We demonstrate long-wavelength InAs/GaSb superlattice photodiodes grown on InAs substrates in a production-scale metal-organic chemical vapor deposition system. An aluminum-free heterojunction scheme was adopted where mid-wavelength superlattices served as electron barriers alongside an n-type long-wavelength absorber. Both electrical modeling and experimental characteristics suggest that suppressed dark current and unimpeded transport of photogenerated carriers can be both achieved with engineered barrier layers. Under 77 K and a reverse bias of -0.1 V, the optimized device has shown a cut-off wavelength around 12 μm, a blackbody responsivity of 1.01 A/W, a dark-current density of 5 × 10
^-4
A/cm
²
and a dark-current limited specific q' detectivity over 1 × 10
¹¹
cm· √Hz/W.