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) ofn-channel amorphous GaInZnO (a-GIZO) thin-film transistors based on the combination of subbandgap optical charge pumping andC-Vcharacteristics 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 ofC-Vcharacteristics. The extracted DOS shows the superposition of the exponential tail states and the Gaussian deep states (NTA=2times1018eV-1ldrcm-3,NDA=4times1015eV-1ldrcm-3,kTTA=0.085 eV,kTDA=0.5 eV ,EO=1 eV). The TCAD simulation results incorporated by the extracted DOS show good agreements with the measured transfer and output characteristics of a-GIZO thin-film transistors with a single set of process-controlled parameters.