An ultra-fast WSe2 homojunction photodiode with a large linear dynamic range towards in-sensor image processing†

Abstract

The versatile photoresponse tunability of two-dimensional (2D) semiconductors achieved by tuning the gate voltage has opened promising pathways for in-sensor visual processing. However, the current limited dynamic range and slow response speed of the gate-tunable 2D photodetectors inhibit their implementation under challenging lighting conditions. Here, using a facile, efficient, and universal localized electrostatic screening strategy, we demonstrate an electrostatic screening enabled single-gate-tunable in-plane homojunction photodiode based on WSe₂ with bipolar high dynamic ranges (HDRs) and ultrafast photoresponse. The demonstrated WSe₂/PdSe₂ van der Waals (vdW) stacking in-plane homojunction photodiode leveraging the efficient band alignment and less interface recombination inherited from its vdW nature exhibits a large physical linear dynamic range (LDR) of up to 142 dB and an ultrafast response time down to 8 ns. These superior properties ensure that the device captures high-precision HDR images and performs in-sensor image processing with low latency. Our results provide an effective strategy for constructing 2D photodetectors with tunable positive/negative responses and high LDRs, which are promising for in-sensor visual processing of scenes with HDRs.