Trap Density of States Measured by Photon Probe on Amorphous-InGaZnO Thin-Film Transistors

Trap density of states (DOS) for two amorphous InGaZnO thin-film transistors are measured by photoexcited charge-collection spectroscopy (PECCS); free charges trapped at a certain energy level are liberated by the corresponding energetic photons and then electrically collected at the source/drain electrodes. During this photoelectric process, the threshold voltage of TFT shifts and its magnitude provides the DOS information of charge traps. According to the PECCS analysis, the TFT with a channel deposited under high sputtering power appeared more stable than the other device prepared with low sputtering power, showing even less than ~10 ¹⁰ cm ^-2 as its totally integrated trap density.