▎ 摘　　要

The Fowler-Nordheim tunneling (FNT) is an important tunneling mechanism and an efficient route to improve the photoresponse of a photodetector. Herein, we report the quantum mechanical FNT mechanism based on graphene 2D/GaN 3D ultra-shallow van der Waals heterojunctions ultraviolet (UV) photodetector via atomic layer deposition Al2O3 tunneling layer, and the conversion between direct tunneling (DT) and FNT has also been systematically studied. At reverse bias (< -0.253 V) with the high build-in field, the high-speed photogenerated carriers overcome the thin insulator layer through the FNT, occurring impact ionization during the process resulting in a multiplication of the photocurrent. Consequently, the photodetector demonstrates pronounced photoresponse performances working under a weak light of 5 mu W/cm2 at - 2 V, including remarkable responsivity (122.57 A/W), ultrahigh specific detectivity (5.63 x 10(14) Jones), and high sensitivity (1.29 x 10(7)%), which indicated that the device has excellent weak light detection ability. This work presents a novel route to fabricate high-performance optoelectronic devices by using the FNT tunneling mechanism.