Electrical Instability of p-Channel SnO Thin-Film Transistors Under Light Illumination

Abstract

We investigated the effects of illumination and bias illumination stresses on the electrical performance of p-type tin monoxide (SnO) thin-film transistors (TFTs). The transfer curve shifts in the positive direction with an increase of the subthreshold slope (SS) and OFF-current ( $I_{\mathrm {OFF}}$ ) under light illumination, where the increase in SS and $I_{\mathrm {OFF}}$ under illumination was attributed to the photoconductivity in SnO, especially at the back channel region. The positively shifted transfer curve by light illumination recovers to the initial one within 3000 s after turning OFF the light source. The trapping and detrapping of the photogenerated electrons in bulk defect states of SnO were considered as the most probable mechanism for the illumination-induced positive shift of the transfer curve and persistent photoconductivity in p-type SnO TFTs. There was no significant difference in the degree of light-induced-degradation between the TFTs with and without a passivation layer, which was mainly attributed to the weak chemisorption of oxygen molecules on SnO. Threshold voltage shift ( $\Delta V_{\mathrm {th}}$ ) is much decreased under negative bias illumination stresses than under negative bias stresses, but $\Delta V_{\mathrm {th}}$ increases under positive bias illumination stresses than under positive bias stresses in p-type SnO TFTs.