Amorphous InGaZnO/Poly-Si Coplanar Heterojunction TFT for Memory Applications

We report a heterojunction, nonvolatile memory (NVM) device with amorphous indium-gallium-zinc oxide (a - IGZO) and low-temperature polysilicon (LTPS) stack. The LTPS layer was achieved by blue laser annealing of amorphous silicon. The a - IGZO/LTPS heterojunction NVM exhibits a large threshold voltage (\Delta {\mathsf {V}} {\mathsf {Th}}({\mathsf {V}})) memory window of 19.2 V with prolonged operational stability. An increase in channel length (L) (from 2 to 20\mu \text{m} ) exhibits a stable memory window. The neutral oxygen vacancy states in a - IGZO trap the carriers at a - IGZO/LTPS interface and then transforms into a metastable state, ( {\mathsf {D}} {\mathsf {O}}+ {\mathsf {h}} {+}(2 {\mathsf {h}} {+})\to {\mathsf {D}} {+}/ {\mathsf {D}} {++} or {\mathsf {D}} {\mathsf {O}}+ {\mathsf {e}} {-}(2 {\mathsf {e}} {-})\to {\mathsf {D}} {-}/ {\mathsf {D}} { - } ), which is the key to the operation of a - IGZO/LTPS heterojunction NVM.