Uniformly Broadband Far-Infrared Response From the Photocarrier Tunneling of Mesa Si:P Blocked-Impurity-Band Detector

The silicon-based blocked-impurity-band (BIB) detectors play an irreplaceable role in long-wavelength and far-infrared detection applications from 2 to $40~\mu \text{m}$ , especially in astronomy. However, how to remove the anomalous sharp peaks in the spectral response of the planer structures is still unresolved. Here, we propose a tunneling current model to demonstrate the carrier transport mechanism in the planar structures. Specifically, the surface channel induced by dry etching on sidewalls of the mesa structures facilitates the photocarriers to bypass the interface barrier according to the model. Two structures with the same photosensitive area are fabricated and measured to characterize the role of the interface barrier. The disappearance of the sharp response peak at $31.8~\mu \text{m}$ in the measured photocurrent spectra of the mesa structure well confirms our model. Moreover, the manipulation of the localized energy level of the interface barrier is then utilized to optimize the mesa structure. A much lower dark current of the mesa structures is realized compared with that of the planar ones. Peak detectivity of $5.6\times 10^{12}$ Jones and uniformly broadband response among 2.5– $40~\mu \text{m}$ are also achieved. We believe the results will find potential applications in the BIB detectors design.