Large Photoresponse in Amorphous In-Ga-Zn-O and Origin of Reversible and Slow Decay

Photoresponses of an amorphous oxide semiconductor, In-Ga-Zn-O (a-IGZO), are investigated by continuous-wave photocurrent measurements, which are discussed in terms of mobility-lifetime products (eta mu tau). It shows that a-IGZO has eta mu tau values larger than those of amorphous silicon, which originate from high Fermi levels as well as long photocarrier lifetime. Reversible and very slow photocurrent decays are observed with time constants > 10(3) s and associated activation energies similar to 0.9 eV. A metastable donor model and a photoreduction model are proposed to explain it. These results provide fundamental physical data for optoelectronic applications of a-IGZO. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3460302] All rights reserved.