The dynamic on-resistance (R_ON) behavior of one commercial GaN HEMT device with p-GaN gate is investigated under hard-switching conditions. The non-monotonic performance of dynamic R_ON with off-state voltage ranging from 50 to 400 V is ascribed to the “leaky dielectric” model. The highest normalized R_ON value of 1.22 appears at 150 and 200 V. The gradual increase and following maximum of dynamic R_ON are found when the device is exposed to a stress voltage for an extended stress time under 100 and 200 V, which is due to a much longer trapping time compared to detrapping time related to deep acceptors and donors. No obvious R_ON degradation, thanks to the suppressed trapping effect, is observed at higher V_DS. From the multi-pulse test, the dynamic R_ON is seen to be insensitive to the frequency. It is demonstrated that the leakage, especially under source and drain contact, is a key issue in the dynamic resistance degradation.

Continuous diamond films with low dislocation density were obtained by two-step epitaxial lateral overgrowth (ELO). Grooves were fabricated by inductively coupled plasma etching. Mo/Pd stripes sputtered in the grooves were used to inhibit the propagation of dislocations originating from the diamond substrate. Coalescent diamond films were achieved by ELO via microwave plasma-enhanced chemical vapor deposition. Etch-pits were formed intentionally to characterize the quality of the epitaxial films and distinguish different growth areas, as dislocations served as preferential sites for etching. In the window regions, a high density of dislocations, displayed as dense etch-pits, was generated. By contrast, the etch-pit density was clearly lower in the overgrowth regions. After the second ELO step, the dislocation density was further decreased. Raman spectroscopy analysis suggested that the lateral overgrowth of diamond is a promising method for achieving low dislocation density films.

Barrier heights of Au on hydrogen-/oxygen-/fluorine-/nitrogen-terminated diamond (H-/O-/F-/N-diamond) have been investigated by X-ray photoelectron spectroscopy. All of the H-/O-/F-/N-diamond surfaces have been formed on different areas of one diamond sample. An Au film with a thickness of 4 nm was evaporated to form Au/diamond contacts. Barrier height values for Au on H-/O-/F-/N-diamond contacts were determined to be −0.19, 1.71, 2.29, and 2.39 eV, respectively. Then, the surface of Au/diamond contacts was treated by 1000 eV Ar⁺ bombardment with different duration of time, resulting in a pinned barrier height of 1.83 eV independent of contact structures. In the end, the spatial distribution of the energy band diagram has been calculated by solving Poisson’s equation.

In this study, contact properties of platinum/gold (Pt/Au) on the surface of hydrogen-terminated single crystal diamond (H-SCD) were studied with several treatment conditions. The electrodes of Pt (20 nm)/Au (100 nm) were deposited on H-SCD surface by electron beam evaporation technique. Then, the specific contact resistance (ρ_c) of the as-fabricated sample was measured by the circular transmission line model, which showed good ohmic properties with the value of 5.65 × 10⁻⁴ Ω·cm². To identify the thermal stability of Pt/Au/H-SCD, the sample was annealed in hydrogen ambient from 200 to 700 °C for 20 min at each temperature. As the temperature increased, ρ_c demonstrated better thermal stability. In addition, the barrier height was evaluated to be −0.67 ± 0.12 eV by X-ray photoelectron spectroscopy (XPS) technique.

In this work, hydrogen-terminated diamond (H-diamond) metal-oxide-semiconductor field-effect-transistors (MOSFETs) on a heteroepitaxial diamond substrate with an Al₂O₃ dielectric and a passivation layer were characterized. The full-width at half maximum value of the diamond (004) X-ray rocking curve was 205.9 arcsec. The maximum output current density and transconductance of the MOSFET were 172 mA/mm and 10.4 mS/mm, respectively. The effect of a low-temperature annealing process on electrical properties was also investigated. After the annealing process in N₂ atmosphere, the threshold voltage (V_th) and flat-band voltage (V_FB) shifts to negative direction due to loss of negative charges. After annealing at 423 K for 3 min, the maximum value of hole field effective mobility (μ_eff) increases by 27% at V_th − V_GS = 2 V. The results, which are not inferior to those based on homoepitaxial diamond, promote the application of heteroepitaxial diamond in the field of electronic devices.

In this paper, two dielectric layers of Al₂O₃ and Gd₂O₃ were prepared by an atomic layer deposition (ALD) and magnetron sputtering deposition (SD), respectively. Based on this, a metal-oxide-semiconductor field-effect transistor (MOSFET) was successfully prepared on a hydrogen-terminated single-crystal diamond (H-diamond), and its related properties were studied. The results showed that this device had typical p-type channel MOSFET output and transfer characteristics. In addition, the maximum current was 15.3 mA/mm, and the dielectric constant of Gd₂O₃ was 24.8. The effective mobility of MOSFET with Gd₂O₃/Al₂O₃ was evaluated to be 182.1 cm²/Vs. To the best of our knowledge, the bilayer dielectric of Gd₂O₃/Al₂O₃ was first used in a hydrogen-terminated diamond MOSFET and had the potential for application.