Blocking layer of dark current for Si-based short-wave infrared photodetection

Abstract

Effective suppression of dark current is essential for improving the performance of bulk defect-mediated absorption (BDA) photodetectors. Blocked impurity band (BIB) infrared detectors have been developed and utilized from mid-infrared to far-infrared wavelength regions for low noise. In this work, a blocking layer of dark current was applied to a BDA short-wave infrared (SWIR) photodetector, emulating the concept of BIB detectors. ZnO was chosen as the blocking layer to impede the transport of electrons from the bulk defect levels due to its wide bandgap and to allow the photocurrent to remain nearly unaffected by proper positioning of the conduction band minimum. After introducing the ZnO blocking layer, the dark current density of the photodetector was reduced by two orders of magnitude, and the specific detectivity was enhanced by one order of magnitude. The effects of TiO2 and WO3 as blocking layers were also investigated and compared with ZnO. This work offers an effective method for enhancing detectivity in SWIR BDA photodetection by suppressing the dark current efficiently.