Al₂O₃-Induced Sub-Gap Doping on the IGZO Channel for the Detection of Infrared Light

Abstract

Wide band gap oxide materials with additional infrared (IR) photosensing have rarely been reported because of the lack of the IR-associated sub band gap absorption. In this work, we report that the insertion of a thin aluminum oxide (Al2O3) layer between the Al electrode and indium gallium zinc oxide (IGZO) channel, deposited by atomic layer deposition, enables the material to absorb 850 nm IR light as well as light at visible wavelengths (400 and 530 nm). UV–visible absorption and photoluminescence measurements showed that the Al2O3/IGZO-stacked channel layers could induce additional IR absorption and, consequently, IR-excited charge carriers owing to sub-gap doping within the IGZO band gap. Notably, this approach provides the synergetic effect of enabling IR detection as well as improving the contact properties in the IGZO transistor. Furthermore, the clear dynamic photoswitching behavior was observed only for the Al2O3/IGZO transistor device, revealing a photocurrent 50 times higher than the device containing only IGZO. Thus, the simple approach of engineering the interface of wide band gap oxide materials made it possible to introduce unexpected dual-band gap photosensing characteristics, thereby extending the range of photonic applications of these materials.