Optical properties and evaluation of localized level in gap of In-Ga-Zn-O thin film

Recent studies have shown that an indium gallium zinc oxide (In-Ga-Zn-O: IGZO) thin film is affected by light irradiation in a variety of ways. Such photoresponse properties are considered to result from deep defect levels in the band gap of IGZO, and the defect levels need to be reduced in order to improve the reliability of IGZO. The deep defect levels were measured by low-temperature photoluminescence (low-temperature PL) and a constant photocurrent method (CPM), and the density of states was determined by CPM. As a result, the density of states of the manufactured IGZO film is sufficiently reduced. In addition, an IGZO-FET manufactured through a similar process has sufficient stability against light.