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

Abstract

This study introduces a novel method for achieving highly ordered-crystalline In2-xGaxO3 [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 In2-xGaxO3 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 In2-xGaxO3 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 In2-xGaxO3 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.