High crystalline quality homoepitaxial Si-doped β-Ga₂O₃(010) layers with reduced structural anisotropy grown by hot-wall MOCVD

Authors

• D. Gogova, Linköping University
• D. Q. Tran, Linköping University
• V. Jokubavicius, Linköping University
• L. Vines, Oslo University
• M. Schubert, Lund University, University of Nebraska-LincolnFollow
• R. Yakimova, Linköping University
• P. P. Paskov, Linköping University
• V. Darakchieva, Linköping University, Lund University

Document Type

Article

Date of this Version

1-29-2024

Citation

J. Vac. Sci. Technol. A 42(2) Mar/Apr 2024; doi: 10.1116/6.0003424

Comments

Open access.

Abstract

A new growth approach, based on the hot-wall metalorganic chemical vapor deposition concept, is developed for high-quality homoepitaxial growth of Si-doped single-crystalline β-Ga₂O₃ layers on (010)-oriented native substrates. Substrate annealing in argon atmosphere for 1 min at temperatures below 600 ^oC is proposed for the formation of epi-ready surfaces as a cost-effective alternative to the traditionally employed annealing process in oxygen-containing atmosphere with a time duration of 1 h at about 1000 ^oC. It is shown that the on-axis rocking curve widths exhibit anisotropic dependence on the azimuth angle with minima for in-plane direction parallel to the [001] and maximum for the [100] for both substrate and layer. The homoepitaxial layers are demonstrated to have excellent structural properties with a β-Ga₂O₃(020) rocking curve full-widths at half-maximum as low as 11 arc sec, which is lower than the corresponding one for the substrates (19 arc sec), even for highly Si-doped (low 10¹⁹ cm^-3 range) layers. Furthermore, the structural anisotropy in the layer is substantially reduced with respect to the substrate. Very smooth surface morphology of the epilayers with a root mean square roughness value of 0.6 nm over a 5 x 5 μm² area is achieved along with a high electron mobility of 69 cm² V^-1 s^-1 at a free carrier concentration n = 1.9 x 10¹⁹ cm^-3. These values compare well with state-of-the-art parameters reported in the literature for β-Ga₂O₃(010) homoepitaxial layers with respective Si doping levels. Thermal conductivity of 17.4Wm^-1K^-1 is determined along the [010] direction for the homoepitaxial layers at 300 K, which approaches the respective value of bulk crystal (20.6Wm^-1K^-1). This result is explained by a weak boundary effect and a low dislocation density in the homoepitaxial layers.