Evaluation of oxygen-vacancy concentration through simulated hydrogen diffusion in amorphous In-Ga-Zn-O

Abstract

A multiscale approach is presented to calculate the hydrogen diffusion in amorphous In-Ga-Zn-O (a-IGZO). Based on the fact that the presence of oxygen vacancy (VO) defects suppresses the hydrogen diffusion in a-IGZO, the simulated H diffusion depth is utilized to evaluate the VO concentration (nVo). The kinetic Monte Carlo (kMC) simulation is carried out to obtain the depth profiles of H diffusion in a-IGZO, which uses input of the H migration energy barriers (EA) calculated within the density functional theory (DFT) method. The DFT calculations showed that when H occupies the VO defects, its EA becomes higher than that of the interstitial H, which eventually suppresses H diffusion. The H diffusion function depending on nVo and temperature, fD(nVo,T), is readily obtained fitting the complementary error function to the simulated H diffusion profile. It is observed that fD(nVo,T) can closely reproduce the experimentally measured H diffusion from literature with nVo being comparable to the measured carrier concentration that can be speculated as the upper limit of nVo. The properties of H diffusion in a-IGZO are examined in detail to address the application of the presented approach for estimation of nVo.