Visible–infrared dual-band detection with a polarization sensitivity based on GeSe/Ge heterojunction field effect transistor

Electronic and optoelectronic devices based on two-dimensional (2D)/three-dimensional (3D) semiconductor heterostructures, combining their respective advantages, have attracted wide attention. In this work, we fabricate a mixed-dimensional GeSe/Ge heterojunction field effect transistor (HJFET), which combines high carrier mobility of 2D GeSe and near-infrared detection of 3D bulk Ge. A significant on/off ratio of 5 × 102 and a transconductance of 0.23 μS are obtained, indicating a convincing gate control ability. Under 532 nm illumination, the HJFET exhibits an excellent photoresponse with high responsivity, detectivity, and external quantum efficiency (88.4 A/W, 2.25 × 1012 Jones, and 3280%), and it also can detect the infrared light of 1550 nm due to the absorption of Ge gate. The photogenerated electrons at 532 nm flow to Ge back gate when HJFET works at the reverse voltage bias, which prolongs the lifetime of photogenerated holes in the GeSe channel, thus increasing photocurrent and obtaining better the detection properties. Additionally, the transistor also exhibits polarization-sensitive behavior with a dichroic ratio of 2.37, which can be attributed to the strong anisotropic absorption property of GeSe in armchair and zigzag directions. These results indicate that the device has promising potential as a multifunctional optoelectronic unit, including on/off characteristic, broadband photodetection, and polarization sensitivity.