Improved Electrical Stability in the Al Doped ZnO Thin-Film-Transistors Grown by Atomic Layer Deposition

Bottom-gate oxide thin-film-transistors (TFTs) with improved electrical stability were fabricated with Al doped ZnO (AZO) channel layers grown by atomic layer deposition (ALD) at a relatively low temperature. The ALD growth at and the addition of 1–5 atom % Al dopant provided the thin films with reliable semiconducting characteristics, and the TFT devices fabricated with the 1 and 3 atom % AZO films showed a good field effect mobility and on–off current ratio. The transfer curves for the AZO channel TFTs exhibited improved hysteresis loop and positive gate bias stress results compared to those for the pure ZnO TFTs. The improved electrical stability was attributed to the coarsening of the crystal size and the preferred orientation along the nonpolar direction afforded by the addition of Al.