Improved Properties of Post-Deposition Annealed Ga2O3/SiC and Ga2O3/Al2O3/SiC Back-Gate Transistors Fabricated by Radio Frequency Sputtering

Abstract

The high breakdown electric field, n-type doping capability, availability of high-quality substrates, and high Baliga’s figure of merit of Ga2O3 demonstrate its potential as a next-generation power semiconductor material. However, the thermal conductivity of Ga2O3 is lower than that of other wide-bandgap materials, resulting in the degradation of the electrical performance and reduced reliability of devices. The heterostructure formation on substrates with high thermal conductivity has been noted to facilitate heat dissipation in devices. In this work, Ga2O3 thin films with an Al2O3 interlayer were deposited on SiC substrates by radio frequency sputtering. Post-deposition annealing was performed at 900 °C for 1 h to crystallize the Ga2O3 thin films. The Auger electron spectroscopy depth profiles revealed the interdiffusion of the Ga and Al atoms at the Ga2O3/Al2O3 interface after annealing. The X-ray diffraction (XRD) results displayed improved crystallinity after annealing and adding the Al2O3 interlayer. The crystallite size increased from 5.72 to 8.09 nm as calculated by the Scherrer equation using the full width at half maximum (FWHM). The carrier mobility was enhanced from 5.31 to 28.39 cm2 V−1 s−1 in the annealed Ga2O3 thin films on Al2O3/SiC. The transfer and output characteristics of the Ga2O3/SiC and Ga2O3/Al2O3/SiC back-gate transistors reflect the trend of the XRD and Hall measurement results. Therefore, this work demonstrated that the physical and electrical properties of the Ga2O3/SiC back-gate transistors can be improved by post-deposition annealing and the introduction of an Al2O3 interlayer.