Extraction Technique for the Conduction Band Minimum Energy in Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistors

The conduction band minimum energy in amorphous oxide semiconductor-based thin film transistors (AOS TFTs) is a key parameter governing the accurate extraction of energy distribution for the subgap density-of states (DOSs) and carrier mobility. We report a technique for extraction of the gate voltage (V-CBM) and corresponding energy (E-F,E-CBM = EC-EREF) for the quasi-Fermi level (E-F) equal to the conduction band minimum (E-C) as V-CBM = V-GS (E-F = E-C) and E-F,E-CBM = E-F (V-GS = V-CBM). In order to confirm this technique through optoelectronic experimental data, amorphous indium-gallium-zinc-oxide (a-IGZO)based thin film transistor was irradiated with various wavelengths and power, and obtained V-CBM = 7.1 V and E-F CBM = 71 meV in the dark state. This technique is expected to be useful in the accurate characterization of the subgap DOS and the effective mobility in AOS TFTs through a simple and effective extraction process.