Enhancement of visible light detection for indium-gallium-zinc oxide-based transparent phototransistor via application of porous-structured polytetrafluoroethylene

In this paper, a transparent phototransistor with improved visible light detection by applying sub gap states engineering and a porous polytetrafluoroethylene (PTFE) layer on the indium-gallium-zinc oxide (IGZO) thin film is introduced. The porous PTFE film was sputtered with the selective etching process through an oxygen plasma process after removing nickel nanoparticles dispersed by a magnetic field with a liftoff process. The photoresponse characteristics of porous PTFE/IGZO (PPI) phototransistors were tested with various thicknesses of PTFE (15-75; 15 nm steps). The PPI phototransistor with the PTFE thickness of 30 nm showed the highest photoresponse properties. Although the measured optical bandgap energy of the IGZO film was 3.87 eV, the PPI phototransistors could detect visible light due to the trap-assisted electron/hole pair generation by the sub gap states of the IGZO film induced by plasma damage during PTFE deposition. In addition, it was possible to maximize the efficiency of detecting visible light by capturing and scattering light with the porous structure of PTFE. The PPI phototransistors had a photoresponsivity of 73.45 ± 16.14 A/W, photosensitivity of (1.60 ± 0.57) × 106, and detectivity of (2.62 ± 2.37) × 1010 Jones under illumination by red light with a wavelength of 635 nm and an intensity of 10 mW/mm2.