Gate controlled photocurrent generation mechanisms in high-gain In2Se3 phototransistors

摘要

Photocurrent in photodetectors incorporating van der Waals materials istypically produced by a combination of photocurrent generation mechanisms thatoccur simultaneously during operation. Because of this, response times in thesedevices often yield to slower, high gain processes which cannot be turned off.Here we report on photodetectors incorporating the layered material In2Se3,which allow complete modulation of a high gain, photogating mechanism in the ONstate in favor of fast photoconduction in the OFF state. While photoconductionis largely gate independent, photocurrent from the photogating effect isstrongly modulated through application of a back gate voltage. By varying theback gate, we demonstrate control over the dominant mechanism responsible forphotocurrent generation. Furthermore, due to the strong photogating effect,these direct-band gap, multi-layer phototransistors produce ultra-high gains of(9.8 +- 2.5) x 10^4 A/W and inferred detectivities of (3.3 +- 0.8) x 10^13Jones, putting In2Se3 amongst the most sensitive 2D materials forphotodetection studied to date.