Interface engineering for minimizing trapped charge density in β-Ga₂O₃ Schottky barrier diodes for high-performance power devices

• Published in: Materials today physics 2025-01, Vol.50, Article 101605
• Main Authors: Dahiya, Shivani, Chakkar, Atul G., Kumar, Pradeep, Kumar, Mukesh
• Format: Article
• Language: English
• Subjects: Gallium oxide; Interface study; Power devices; Schottky contact; Ultra-wide bandgap
• ISSN: 2542-5293; 2542-5293
• DOI: 10.1016/j.mtphys.2024.101605

Gallium oxide (Ga2O3), with its ultra-wide bandgap and high breakdown voltage, has emerged as a leading candidate for next-generation power devices. The performance and the Baliga figure-of-merit for power devices critically depend on breakdown voltage sustained by Schottky contact of metal with ultra-wide gap materials. However, high-quality Schottky contacts with Ga2O3 presents a significant challenge due to the presence of surface defects and formation of metal induced mid-gap defects states in Ga2O3. In this study, we investigate the electrical properties and defects at the interface between Ni metal and β-Ga₂O₃ thin films. Additionally, a 20 nm MgO thin films with various oxygen contents were deposited on β-Ga2O3 using radio-frequency magnetron sputtering and Ni/MgO/β-Ga2O3 metal-insulator-semiconductor Schottky diodes were fabricated. The frequency dependent C-V characteristic and surface-sensitive XPS depth profile is employed to study the interface of Ni/Ga2O3 and Ni/MgO/Ga2O3 Schottky barrier diodes. Our results show that the Ni/MgO/Ga₂O₃ Schottky barrier diode with 66 % O₂ in the MgO thin film during synthesis attains a barrier height of 0.87 eV. Subsequent post-metallization annealing at 300 °C in an Ar ambient for 30 min enhances the barrier height up to 1.1 eV. Also, a reduced on-resistance of 11.65 mΩ cm2 and a lower on-voltage of 0.3V was obtained after annealing in Ar. The frequency dependent C-V characteristic results show no dispersion in capacitance for the annealed sample which signify the passivation of interface defects density (Διτ) and oxide charges density (Nf) in the dielectric layer (MgO). The minimum value of Dit and Nf achieved for the sample having highest barrier height (1.1eV) are 5.41 × 1011/eV/cm2 and 2.91 × 1010/cm3, respectively. This study establishes a vigorous foundation for the expanded utilization of Ga2O3 in power electronics devices, emphasizing the vital role of interface engineering. [Display omitted] •The defects at the Ni/Ga₂O₃ interface are thoroughly investigate.•The MgO layer enhances device properties and reduces defects at the Ni/Ga₂O₃ interface.•The MgO device achieved a 1.01 eV barrier height, 11.65 mΩ cm2 Ron, and 0.3V Von.•Frequency-dependent C-V characteristics were used to quantify interface defects.•XPS depth profile reveals oxygen defects as the main cause of barrier height variation.