Electron traps in amorphous In-Ga-Zn-O thin films studied by isothermal capacitance transient spectroscopy

Electron traps in amorphous In-Ga-Zn-O (a-IGZO) thin films were studied using isothermal capacitance transient spectroscopy (ICTS). Broad peaks that shifted toward a longer elapsed time with an increase in the filling pulse width were detected from the ICTS spectra for metal-oxide-semiconductor diodes consisting of a Mo/SiO2/a-IGZO structure. The time constant of the peak position at 180K was found to be from similar to 1m to similar to 100 ms, corresponding to a range of energy level from similar to 170 to similar to 230 meV below the conduction band edge. The total trap density around the peak was estimated to be similar to 1 x 10(16) cm(-3).eV(-1). Further, according to the biasing voltage dependence of the ICTS signal, the density of the trap states increases by about three orders of magnitude near the interface between the a-IGZO and the gate dielectric layers. The electron transport in electronic devices using an a-IGZO could be influenced by the trap states detected in the present study. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3691923]