Endurance Characteristics of Amorphous-InGaZnO Transparent Flash Memory With Gold Nanocrystal Storage Layer

The amorphous indium–gallium–zinc-oxide (a-IGZO) thin-film transistor (TFT)-based nonvolatile transparent Flash memory devices were fabricated with gold (Au) nanocrystal storage layer. The performance and the reliability of transparent memory devices have been characterized by experiment and technology computer-aided design simulation. This memory device shows a large-enough memory window $\Delta V = \hbox{4.7} \ \hbox{V}$ at the program/erase (P/E) voltage ${V_{ \rm PGM}/V_{\rm ERS}} = \hbox{35}/-\hbox{35} \ \hbox{V}$ for the P/E time ${T_{\rm PGM}/ T_{\rm ERS}} = \hbox{3/25} \ \hbox{s}$ . The memory window was kept almost the same after 1050 P/E cycles; however, the center voltage of the memory window $(V_{C})$ was shifted in a negative direction. The cycling effect was explained by the change in the density of states (DOS) and the acceptor-like interface-trap density $D_{\rm itA}(E)$ in the a-IGZO channel layer with increasing P/E cycles. The main mechanism for the change in $V_{C}$ was found to be the accelerated injection of holes into the gate insulator due to the energy band bending during the erase operation.