Growth of Highly-Ordered-Crystalline Indium-Gallium-Oxide Thin-Film via Plasma-Enhanced ALD for High Performance Top-Gate Field-Effect Transistors

This study introduces a novel method for achieving highly ordered-crystalline In_2-xGa_xO₃ [0 ≤ x ≤ 0.6] thin films on Si substrates at 250 °C using plasma-enhanced atomic-layer-deposition (PEALD) with dual seed crystal layers (SCLs) of γ-Al₂O₃ and ZnO. Field-effect transistors (FETs) with random polycrystalline In_2-xGa_xO₃ channels (grown without SCLs) show a mobility (µFE) of 85.1 cm² V^-1s^-1, attributed to high indium content. In contrast, FETs with highly ordered In_2-xGa_xO₃ grown via SCLs exhibit superior performance, with µFE reaching 95.5 cm² VV^-1s^-1 and enhanced reliability due to the uniform growth of high-quality bixbyite films. The role of γ-Al₂O₃ and ZnO SCLs in enabling this growth and the correlation between cation composition, crystalline structure, and electrical properties are comprehensively analyzed. This approach provides new insights into the high-quality bixbyite In_2-xGa_xO₃ system, offering an alternative to conventional amorphous or polycrystalline structures. The highly ordered crystalline structure paves the way for advanced applications in 3D heterogeneous semiconductor chips, expanding beyond displays to include memory, logic, and artificial intelligence devices.