Two-step growth of β-Ga₂O₃ films on (100) diamond via low pressure chemical vapor deposition

One of the major challenges in β-Ga₂O₃-based high power and high frequency devices is anticipated to be related to the low thermal conductivity of the material which is on the order of 10–30 W/m K. The use of diamond (thermal conductivity ∼2000 W/m K) as a substrate can be one effective approach for achieving better thermal management in β-Ga₂O₃-based devices. In this work, low pressure chemical vapor deposition was used to grow β-Ga₂O₃ films on (100) oriented, single-crystalline diamond substrates. A two-step growth technique was employed to avoid the oxidation of the diamond surface at high temperatures. From x-ray diffraction measurements, the β-Ga₂O₃ films grew along the $⟨−201⟩$ crystalline axis with the β-Ga₂O₃ (002) planes rotated by ±24.3–27° with respect to the diamond (111) planes. High-magnification scanning transmission electron microscopy imaging revealed an abrupt β-Ga₂O₃/diamond interface without any voids which is essential for the high rate of heat transfer across the interface. N-type electrical conductivity was measured in a Si-doped β-Ga₂O₃ film with 1.4 × 10¹⁹ cm⁻³ electron concentration and ∼3 cm²/V s electron mobility. This work demonstrates the feasibility of heteroepitaxy of β-Ga₂O₃ films on diamond substrates for potential device design and device fabrication with efficient thermal management.