Self-biased wavelength selective photodetection in an n-IGZO/p-GeSe heterostructure by polarity flipping.

Transparent semiconductor oxides with two-dimensional (2D) heterostructures have been extensively studied as new materials for thin-film transistors and photosensors due to their remarkable photovoltaic characteristics, making them useful for newly developed optoelectronics. Here we demonstrate the fabrication and characterization of an ITO/n-IGZO/p-GeSe transparent selective wavelength photodetector. The wavelength-dependent photovoltaic behavior of the n-IGZO/p-GeSe heterostructure under UV-Visible laser light shifts the I - V curves down with positive V oc and negative I sc values of about 0.12 V and -49 nA and 0.09 V and -17 nA, respectively. Interestingly, when an NIR laser irradiated the device, the I - V curves shifted up with negative V oc and positive I sc values of about -0.11 V and 45 nA, respectively. This behavior is attributed to the free carrier concentration induced by photogenerated carriers across the device at different points that varied with the wavelength-dependent photon absorption. Consequently, the direction of the electric field polarity across the junction can be flipped. This study demonstrates a zero-bias near-infrared (NIR) photodetector with a high photoresponsivity of 538.9 mA W -1 , a fast rise time of 25.2 ms, and a decay time of 25.08 ms. Furthermore, we observed a detectivity ( D ) of 8.4 × 10 9 Jones, a normalized photocurrent to dark current ratio (NPDR) of 2.8 × 10 10 W -1 , and a noise equivalent power (NEP) of 2.2 × 10 -14 W Hz -1/2 . Our strategy opens alternative possibilities for scalable, low-cost, multifunctional transparent near-infrared photosensors with selective wavelength photodetection.