Thermal analysis of degradation in Ga₂O₃-In ₂O₃-ZnO thin-film transistors

Degradation of Ga₂O₃-In2O₃-ZnO (GIZO) thin-film transistors (TFTs), which are promising for driving circuits of next-generation displays, was studied. We found a degradation mode that was not observed in silicon TFTs. A parallel shift without any change of the transfer curve was observed under gate voltage stress. Judging from the bias voltage dependences we confirmed that the mode was mainly dominated by a vertical electric field. Thermal distribution was measured to analysis the degradation mechanism. Joule heating caused by drain current was observed; however, a marked acceleration of degradation by drain bias was not found. Therefore, we concluded that Joule heating did not accelerate degradation. Recovery of electrical properties independent of stress voltage were observed.