Extraction of Density of States in Amorphous GaInZnO Thin-Film Transistors by Combining an Optical Charge Pumping and Capacitance—Voltage Characteristics.

A technique for extracting the acceptorlike density of states (DOS) of n-channel amorphous GaInZnO (a-GIZO) thin-film transistors based on the combination of subbandgap op- tical charge pumping and C-V characteristics is proposed. While the energy level is scanned by the photon energy and the gate voltage sweep, its density is extracted from the optical response of C-V characteristics. The extracted DOS shows the superpo- sition of the exponential tail states and the Gaussian deep states (NTA = 2 x 1018 eV' . cm3, NDA = 4 x iO'5 eV' . cm3, kTTA = 0.085 eV, kTDA = 0.5 eV, E0 = 1 eV). The TCAD simulation results incorporated by the extracted DOS show good agreements with the measured transfer and output characteris- tics of a-GIZO thin-film transistors with a single set of process- controlled parameters. [ABSTRACT FROM AUTHOR]