High mobility of IGO/IGZO double-channel thin-film transistors by atomic layer deposition

In this paper, top-gate thin-film transistors (TFTs) of two stacked double-channel layers derived from atomic layer deposition in combination with the plasma-enhanced chemical vapor deposition (PECVD) process were fabricated. The Hall measurement shows that the Hall mobility of the indium gallium oxide (IGO)/indium gallium zinc oxide (IGZO) active layer is 1.6 times more that of the amorphous In-rich IGZO/IGZO layer due to superior carrier percolation conduction paths from the polycrystalline IGO layer. Furthermore, x-ray photoelectron spectroscopy analysis indicates that the IGO/IGZO film has much less oxygen vacancy concentration, which is advantageous in improving not only mobility but also stability. The optimized IGO/IGZO TFT showed both high mobility (38.0 cm2 V−1 s−1) and high stability (ΔVTH = +0.14 V) of a positive bias stress under post-deposition annealing at 250 °C. This strategy provides a feasible process for realizing high-performance TFTs that is compatible with ALD-derived oxides and commercial PECVD techniques in the industry.