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For the first time, an epitaxial beryllium oxide (BeO) film was grown on 4H silicon carbide (4H-SiC) by atomic layer deposition (ALD) at a low temperature of 250 °C. The BeO film had a large lattice mismatch with the substrate (>7–8%), but it was successfully grown to a single crystal by domain-matching epitaxy (DME). The bandgap energy, dielectric constant, and thermal conductivity properties of crystalline BeO are suitable for power transistors that require low leakage currents and fast heat dissipation in high electric fields. Physical characterization confirmed the single-crystalline BeO (0 0 2). Raman analysis showed that the E1 and A1 phonon modes of ALD BeO were intermixed with the E2 and A1 phonon modes of SiC, resulting in a significant increase in phonon intensity. After heat treatment at a high temperature, a small amount of SiO2 interfacial oxide was formed but the stoichiometry of BeO was maintained. From the capacitance-voltage (C-V) curves, we obtained a dielectric constant of 6.9 and calculated a low interface trap density of 6 × 1010 cm−2·eV−1 using the Terman method at Ec-Et = 0.6 eV. The high bandgap, thermal conductivity, and excellent crystallinity reduced the dangling bonds at the interface of BeO-on-SiC.

This paper reports the first-time evaluation of the time-dependent dielectric breakdown of recessed AlGaN/GaN-on-Si metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with plasma enhanced chemical vapor deposition (PECVD) SiO2 gate oxide. The interface fixed charge density and oxide bulk charge density extracted from the flat-band voltage characteristics were 2.7 × 1011 ± 6.54 × 1010 cm−2 and -9.71 × 1017 ± 5.18 × 1016 cm−3, respectively. The time dependent dielectric breakdown (TDDB) characteristics exhibited longer lifetime estimation as the SiO2 thickness increased. The excellent reliability of the PECVD SiO2 film was validated for use as the gate oxide of recessed AlGaN/GaN MOS-HFET.

A high quality SiO 2 deposition process using a plasma enhanced chemical vapor deposition system has been developed for the gate insulator process of normally-off recessed-gate AlGaN/GaN metal–oxide–semiconductor-heterostructure field-effect transistors (MOS-HFETs). SiO 2 films were deposited by using SiH 4 and N 2 O mixtures as reactant gases. The breakdown field increased with increasing the N 2 O flow rate. The optimum SiH 4 /N 2 O ratio was 0.05, which resulted in a maximum breakdown field of 11 MV/cm for the SiO 2 film deposited on recessed GaN surface. The deposition conditions were optimized as follows; a gas flow rate of SiH 4 /N 2 O (=27/540 sccm), a source RF power of 100 W, a pressure of 2 Torr, and a deposition temperature of 350 °C. A fabricated normally-off MOS-HFET exhibited a threshold voltage of 3.2 V, a specific on-resistance of 4.46 mΩ cm 2 , and a breakdown voltage of 810 V.

We have investigated the effects of a silicon nitride (SiNx) passivation process using plasma-enhanced chemical vapor deposition (PECVD) on a ultra-thin-barrier AlGaN/GaN heterostructure field-effect transistors (HFETs). The bulk charge characteristics of the PECVD SiNx films were dependent on the film deposition conditions, which strongly influenced the sheet resistance (Rsh) and flat-band voltage characteristics of AlGaN/GaN HFETs. The reduction in Rsh is a strong function of the amount of positive bulk charges in the SiNx passivation film. An optimized PECVD SiNx process was used to drastically decrease the Rsh from 45,450 Ω/sq to 732 Ω/sq. A Mo/Au Schottky-gate device fabricated with PECVD SiNx passivation exhibited a maximum drain current density of 172 mA/mm, quasi-normally-off operation, and breakdown voltage of > 1100 V

In this study, we have investigated the effects of SF6 plasma treatment on the isolation leakage current characteristics of AlGaN/GaN heterojunction field-effect transistors (HFETs). The device isolation was performed by Cl2/BCl3-based plasma etching process followed by SF6 plasma treatment for 1 min. It was found that the SF6 plasma post-etching treatment was an effective method to improve the electrical isolation characteristics. X-ray photoelectron spectroscopy analysis was carried out to investigate the chemical bonding states of the etched GaN surfaces.