Bias-Selectable Si Nanowires/PbS Nanocrystalline Film n-n Heterojunction for NIR/SWIR Dual-Band Photodetection

In this study, a solution method derived dual-band photodetector (PD) based on silicon nanowires /PbS nanocrystalline film n-n heterojunction, which exhibits typical bias-selectable spectral response in both near-infrared (NIR) and short-wave infrared (SWIR) bands, is presented. It is found that by adjusting the polarity of the bias voltage, the photoresponse of the device can be switched between three operation modes. The device exhibits high responsivities of 2100 mA W-1 at -0.15 V and 31 mA W-1 at 0 V, respectively, in the NIR region. Remarkably, the maximum responsivity and detectivity under 2000 nm illumination are determined as 290 mA W-1 and 2.4 x 10(10) Jones, comparable to or even better than some PbS commercial PDs. The enhanced performance comes from the improved optical absorption and higher efficiency of charge separation and collection owing to the heterojunction geometry. It's also revealed that the bias-controllable spectral response is attributed to the selectively transportation of photocarriers across the junction barrier. The study demonstrates the capability of detecting two distinct IR regions with the same pixel, which has great potential in future optoelectronic systems for IR imaging applications.