We explored the multicomponent oxide semiconductor of Hf-In-Zn-O (HIZO) using vacuum deposition technique and carried out the in-depth study on the light-induced instability of HIZO transistor under the bias thermal stress. A higher level of Hf or Zn incorporation in HIZO materials was found to be critical for improving the photostability of HIZO transistors under negative bias thermal stress conditions, which can be explained by either band-gap modulation of the HIZO film or changes in the oxygen vacancy concentration in the HIZO channel. This result is consistent with the trapping or injection model of photocreated hole carriers. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3552700] All rights reserved.