Photocurrent analysis of In-Ga-Zn-O (IGZO) film

We investigated the electrical properties of the In-Ga-Zn-O (IGZO) film under light illumination. We measured the photoconductivity of a-IGZO thin film under light illumination with various intensities. We extracted the photoexcitation activation energy and dark relaxation activation energy through extended stretched exponential analysis. Dark relaxation characteristics, which are related to the recombination process, show longer time constant, τ, larger effective activation energy E_ac, and lower stretching exponent, β, with wider activation energy bandwidth, Δ_ac, than those corresponding to those of photoexcitation. These indicate that recombination takes place more slowly and through more deeply bound activation processes with the broader distribution of activation energies than those corresponding to photogeneration process. The wider distribution for the dark relaxation energy for the higher light intensity suggests that the metastable state distribution is related to the distribution of the oxygen vacancy state, V_o. We also concluded that the usage of the right value of the attempt-to-escape frequency is important to estimate the exact value of E_ac. (author)