Roles of Hot Carriers in Dynamic Self-Heating Degradation of a-InGaZnO Thin-Film Transistors

The dynamic self-heating (SH) degradation was investigated on a-InGaZnO (a-IGZO) thin-film transistors (TFTs) under constant drain bias and varied gate pulses. Besides the negative shift of threshold voltage (
${V}_{{\mathrm {th}}}$
), similar with that under DC SH stress, the asymmetric degradations near drain and source revealed the concomitant hot-carrier (HC) effect. The HC-induced local barrier near drain could compensate certain SH-induced
${V}_{{\mathrm {th}}}$
shift, while a drastic SH effect would in turn enhance the HC barrier to high enough to cause hard breakdown. For a-IGZO TFTs under dynamic SH stresses, the interactions between SH and HC effects dominate the degradation behaviors and can be sensitively tuned by the falling time of gate pulse, suggesting a feasible method of lessening the dynamic instability.