Facile Polydimethylsiloxane Treatment of Indium Gallium Zinc Oxide Phototransistor for Visible Light-Based Multilevel Photomemory

For visible light-based multilevel photomemories, indium-gallium-zinc-oxide (IGZO, In:Ga:Zn = 1:2.8:1.4)-based phototransistors capable of detection and storage in the visible light region are fabricated through the facile polydimethylsiloxane (PDMS) treatment, a process of exfoliating the hardened PDMS after coating on the gate insulator (GI) via a drop-casting process. Here, PDMS residues form on the GI by exfoliation induced subgap states in the front channel of IGZO. Subgap states are composed of interface trap states by the less-hardened PDMS and organic-related trap states by diffusion of organic residues into the IGZO front region during the 300 degrees C annealing step. PDMS-treated IGZO phototransistors exhibit improved optoelectronic characteristics due to increased subgap states. Photoresponsivity, photosensitivity, and detectivity under red light irradiation with an intensity of 5 mW mm(-2) are improved compared with untreated IGZO phototransistors, from 69.56 to 718.15 A W-1, from 7.64 x 10(3) to 4.63 x 10(7), and from 3.16 x 10(8) to 1.25 x 10(12) Jones, respectively. Additionally, the possibility of multilevel photomemory is evaluated using the same devices. These devices are able to not only hold data for 18 000 s after red light irradiation for 1 s but also exhibit stable operation for up to 60 repetitive programming/erasing cycles.