【Member News】The Team of Tianjin University of Technology has Made New Progress in the Preparation of High-quality β-Ga₂O₃ Films on Si Substrate

      Β phase gallium oxide (β-Ga₂O₃) has been widely studied with its excellent performance such as ultra-wide band width (~ 4.9 eV), extremely high breakdown field (8 MV / cm), stable chemical stability and thermal stability, and has great application potential in high power electronic devices, solar blind ultraviolet detectors and other fields. Monocrystalline silicon (Si) substrate has the advantages of mature preparation process, excellent thermal conductivity and controllable electrical performance. However, due to the large lattice mismatch between β-Ga₂O₃ and single crystal Si, the Ga₂O₃ film prepared by Si substrate has defects such as poor crystallization quality and easy cracking. How to improve the crystallization quality of Ga₂O₃ thin films grown on Si substrate is of great significance to realize the excellent performance of Ga₂O₃ materials and accelerate the commercialization process of Ga₂O₃ devices.

      Therefore, Mi Wei,  Wang Di and their team from Tianjin University of Technology put forward a method combining the deposition Ga₂O₃ seed layer and annealing process, grew β-Ga₂O₃ film and improved the crystallization quality. They used X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM) to explore the effect of different seed layer thickness and annealing temperature on the crystallization quality of Ga₂O₃ film grown on Si (100) substrate.

Figure 1. XRD and SEM test plots of β-Ga₂O₃ samples prepared with different seed crystal layer thickness

      The research team pre-grew Ga₂O₃ seed layer with different thickness on the Si (100) substrate through the RF magnetron sputtering method, then deposited Ga₂O₃ film on the seed layer, and annealed them at different temperatures. It is shown that for the Ga₂O₃ film prepared on the Si substrate, when the seed layer of 9 nm thickness is pre-deposited and the sample is annealed at 800℃, the β-Ga₂O₃ film has the best crystallization quality, with a single out-of-plane epitaxial relationship between the film and the substrate, Si (100) / / β-Ga₂O₃ (01). In addition, the HRTEM and SAED images show that the β-Ga₂O₃ film has a clear and regular lattice arrangement and diffraction point array along the out-of-plane growth direction, and the spacing of the growing (01) plate is about 0.468 nm, indicating that the film has a good crystallization quality. Pre-growth of seed layer with appropriate thickness can provide nucleation sites for β-Ga₂O₃ growth, reduce the effects of lattice mismatch and thermal mismatch between substrate and film, thus promoting film crystallization and preventing cracking, and improving the crystallization quality of the film.

      This work will promote the development of high integration, low cost Si based Ga₂O₃ photoelectric and power devices, and also help to solve the problem of poor heat dissipation of Ga₂O₃ devices, and provide some help for the integration of high-performance Ga₂O₃ devices on Si wafers. Related work has been published on the international journal Vacuum, titled Effects of seed layer thickness and post-annealing process on crystalline quality of β-Ga₂O₃ films prepared on Si (100) substrate by RF magnetron sputtering（214（2023）112235

https://doi.org/10.1016/j.vacuum.2023.112235