Electrical and structural characterization of in situ MOCVD Al2O3/β-Ga2O3 and Al2O3/β-(AlxGa1-x)2O3 MOSCAPs

This study investigates the electrical and structural properties of metal-oxide-semiconductor capacitors (MOSCAPs) with in situ metal-organic chemical vapor deposition-grown Al2O3 dielectrics deposited at varying temperatures on (010) beta-Ga2O3 and beta-(AlxGa1-x)(2)O-3 films with different Al compositions. The Al2O3/beta-Ga2O3 MOSCAPs exhibited a strong dependence of electrical properties on Al2O3 deposition temperature. At 900 degrees C, reduced voltage hysteresis (similar to 0.3 V) with improved reverse breakdown voltage (74.5 V) was observed, corresponding to breakdown fields of 5.01 MV/cm in Al2O3 and 4.11 MV/cm in beta-Ga2O3 under reverse bias. In contrast, 650 degrees C deposition temperature resulted in higher voltage hysteresis (similar to 3.44 V) and lower reverse breakdown voltage (38.8 V) with breakdown fields of 3.69 and 2.87 MV/cm in Al2O3 and beta-Ga2O3, respectively, but exhibited impressive forward breakdown field, increasing from 5.62 MV/cm at 900 degrees C to 7.25 MV/cm at 650 degrees C. High-resolution scanning transmission electron microscopy (STEM) revealed improved crystallinity and sharper interfaces at 900 degrees C, contributing to enhanced reverse breakdown performance. For Al2O3/beta-(AlxGa1-x)(2)O-3 MOSCAPs, increasing Al composition (x) from 5.5% to 9.2% reduced net carrier concentration and improved reverse breakdown field contributions from 2.55 to 2.90 MV/cm in beta-(AlxGa1-x)(2)O-3 and 2.41 to 3.13 MV/cm in Al2O3. The electric field in Al2O3 dielectric under forward bias breakdown also improved from 5.0 to 5.4 MV/cm as Al composition increased from 5.5% to 9.2%. The STEM imaging confirmed the compositional homogeneity and excellent stoichiometry of both Al2O3 and beta-(AlxGa1-x)(2)O-3 layers. These findings demonstrate the robust electrical performance, high breakdown fields, and excellent structural quality of Al2O3/beta-Ga2O3 and Al2O3/beta-(AlxGa1-x)(2)O-3 MOSCAPs, highlighting their potential for high-power electronic applications. (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International (CC BY-NC-ND) license (https://creativecommons.org/licenses/by-nc-nd/4.0/).