Observation of gain operation mode in Ge:B BIB THz detector

Blocked impurity band (BIB) detectors play an important role in astronomical detection from the mid-infrared to THz region. We demonstrated the field dependence of the photoresponse in BIB detectors using both experimental results and theoretical calculations. It was found that there is a gain operation region between the saturation voltage of the photocurrent and the breakdown voltage of the dark current. The photoconduction gain in the gain operation region is several orders of magnitude larger than that in the other voltage range. Considering the field-assisted thermal ionization process and the photon-assisted impact ionization process, the gain operation mode can be well explained. Utilizing the gain operation mode, Ge:B BIB detectors can even detect the objects with a temperature as low as 10 K. We provide a theoretical basis to optimize BIB detectors and further improve their detection performance.