2 kV <b> <i>β</i> </b> -Ga2O3 Schottky diode with HfO2/SiO2 dual-layer field plate and mesa termination

Abstract

In this Letter, a vertical β-Ga2O3 Schottky barrier diode (SBD) featuring a composite termination structure with dual-layer field plate and self-aligned etched mesa (DFPM-SBD) is proposed. By combining a high-k HfO2 and SiO2 bilayer dielectric as the field plate termination, the interfacial trap state can be effectively reduced and the electric field crowding effect can be effectively alleviated in β-Ga2O3 SBD. Moreover, the self-aligned etching process is implemented using high-hardness Pt metal as the etching mask, effectively eliminating alignment deviation, thereby contributing to a high breakdown voltage (BV). The experimental result demonstrates that the DFPM-SBD achieves a low Von of 0.68 V (@1 A/cm2), an ideality factor (η) of 1.07, a Schottky barrier height (qΦb) of 1.25 eV, a low specific on-resistance of 3.85 mΩ cm2 along with a high BV of 2050 V, yielding a Baliga's power figure of merit of 1.1 GW/cm2. Furthermore, the interface trap density (Dit) of β-Ga2O3 SBDs is measured, and it is found that the HfO2 layer can effectively reduce the interfacial Dit from 3.25 × 1012 to 4.76 × 1011 cm−2eV−1, showing an 85% reduction, with a trap energy level located at ET in a range of 0.21–0.25 eV below the EC and the time constant ranging from 4.46 to 8.36 × 10−5 ms. Therefore, this work provides important guidance of β-Ga2O3 SBD for high-power applications, pushing the development of ultra-wide gap semiconductors greatly.