Energy band offsets of BeO dielectrics grown via atomic-layer deposition on β-Ga₂O₃ substrates

We report the energy-band alignment of atomic layer-deposited (ALD) beryllium oxide (BeO) films and β-Ga₂O₃ substrates. BeO is a unique oxide with a high dielectric constant and bandgap energy that can be used as a gate dielectric; however, it also has an extremely high thermal conductivity. It has great potential to improve the heat dissipation of β-Ga₂O₃ power devices. In this study, the conduction band offset between the BeO film and β-Ga₂O₃ substrate was found to be 3.4 eV, which was larger than those of conventional high-k gate dielectrics. In addition, the bandgap energies (8.6 eV and 4.7 eV for BeO and β-Ga₂O₃, respectively) were determined using reflection electron energy loss spectroscopy. The valence band offset (0.5 eV) was calculated using Kraut's method with the core level and valence band maximum energies of the BeO film and β-Ga₂O₃ substrate. The high conduction band offset provided by the ALD BeO dielectric on the β-Ga₂O₃ substrate lowered the gate leakage current density of a β-Ga₂O₃ power device.