Dark-Current-Blocking Mechanism in BIB Far-Infrared Detectors by Interfacial Barriers

We fabricate Ge:B-blocked impurity band (BIB) far-infrared detectors using near-surface processing techniques. The current-voltage ( ${I}$ - ${V}$ ) characteristics and the energy band structure are investigated. It is found that there are three interfacial barriers in Ge:B BIB detectors due to the bandgap narrowing effect. The barrier height can be adjusted by changing the doping concentration in the contact region of BIB detectors. A new dark-current-blocking mechanism is proposed that the interfacial barriers can block the transport of carriers at low temperatures. Moreover, the greater the barrier height, the stronger the blocking effect. Utilizing this new blocking mechanism, the ${I}$ - ${V}$ characteristics of Ge:B BIB detectors can be better explained. By increasing the barrier heights, the dark current is reduced significantly, almost six orders of magnitude within a certain voltage range, and the working temperature is increased from the usual 4.2-10 K, which is of great significance for extending the service life of BIB detectors on outer space observation platforms. Our findings will help to better design BIB detectors and improve their performance.