Comparison of Photoresponse of Si-Based BIB THz Detectors

We fabricate Si-based blocked impurity band (BIB) terahertz detectors using p-dopant through a standard silicon device fabrication technology. Comparison of photoresponse of the detectors under alternate operating mode and conventional operation mode (COM) is made. We demonstrate that the detectors can achieve high responsivity through positive bias on the active layer side, namely, alternate operating mode (AOM). The response of the detectors terminates at wavelength of 35 μm (8.57 THz) under AOM; on the contrary, the response is cutoff at 31 μm (9.68 THz) with a positive bias on the blocking layer, namely, COM. The relative responsivity at 0.6 V under AOM is 2.3 times of that under COM. By developing an energy band model, we find that the response difference under the two modes originates from the change of band offsets. The electric field in the blocking layer under AOM is much smaller than COM and most of the voltage drops in the active layer under AOM, which leads to the bigger multiplication of the photon-generated carriers than COM. By analyzing the origination of the dark current under the AOM, a method to improve the performance of BIB detectors under AOM is proposed.