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

Abstract

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 photo-generated 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 $\mu \text{m}$ , a blackbody responsivity of 1.01 A/W, a dark-current density of 5 $\times \,\,10^{-4}$ A/cm2 and a dark-current limited specific detectivity over 1 $\times \,\,10^{11}$ cm $\cdot \sqrt {\textrm {Hz}}$ /W.