Ultrawide Bandgap β-Ga₂O₃/p-GaN Heterojunction Barrier Schottky Rectifiers for Efficient Power Electronic Applications

Ultrawide bandgap (UWBG) semiconductor β-Ga₂O₃ has attracted tremendous research interest in power electronics, RF electronics, and photonics due to its large bandgap of 4.9 eV and higher breakdown field of ~ 8 MV/cm. However, due to the lack of p-type doping, most of the demonstrated power devices are unipolar such as Schottky barrier diodes (SBDs). However, SBDs suffer from high leakage current, low breakdown voltages, and thermal instability due to low Schottky barrier. To overcome these issues, this work aims at studying β-Ga₂O₃based junction barrier Schottky (JBS) rectifiers, which combines the advantages of SBDs and p-n diodes.<br/>Other p-type materials such as GaN and NiO have been investigated to form heterojunctions with β-Ga₂O₃. Among them, GaN is a very promising candidate since both materials have wide bandgaps, and they can be epitaxially grown on each other using metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). Our preliminary work on mechanically exfoliated β-Ga₂O₃/GaN p-n junction showed decent electrical properties. In this work, β-Ga₂O₃/p-GaN JBS rectifiers are systematically investigated for efficient power electronics applications using SILVACO TCAD simulation. The JBS devices will be compared with conventional β-Ga₂O₃ SBD and β-Ga₂O₃ SBD with p-GaN guard rings (GR). All the devices have 500 nm heavily doped β-Ga₂O₃ contact layer and 5 µm unintentionally doped β-Ga₂O₃ drift layer. Platinum (Pt) with a work function of 5.65 eV is used as the top contact (anode/Schottky contact), and titanium/gold (Ti/Au) metal stacks are used as the bottom contact (cathode/ohmic contact). The forward characteristics such as on-resistance and turn-on voltage and the reverse breakdown voltages of the three devices will be compared to demonstrate the advantages of JBS rectifiers. The JBS structure will be optimized with different p-GaN widths, depths, shapes, and spacing between p-GaN regions. This work can provide critical guidance for the development of advanced β-Ga₂O₃ based high-voltage and high-power rectifiers.