Effects of Wavelength and Geometrical Condition on Photosensitivity of Self-Aligned Top-Gate Amorphous InZnO Thin Film Transistors

We study the wavelength and geometrical condition (channel width and length) dependent photoresponses of self-aligned top-gate amorphous InZnO (IZO) thin-film transistors (TFTs). Under illumination with wavelength ranging from 350~550 nm, with the decreasing of wavelength $(\lambda)$, the responsivity is improved obviously but the subthreshold swing deteriorates significantly. The photoelectric properties of a-IZO TFT under monochromatic illumination with various channel width (W) and length (L) are also investigated. The responsivity (R) is found to increase with the decreasing of L and almost irrelevant to W. High $\mathrm{I}_{\mathrm{ph}}/\mathrm{I}_{\mathrm{dark}}$ ratio (3.48×105) and R (287 A/W) were achieved. Further performance enhancement will be led by continuous scaling of the channel length.