【Member Papers】4.3-kV Fully Vertical β-Ga2O3 Heterojunction Barrier Schottky Diode With Sputtered p-GaN

      Researchers from Xidian University have published a dissertation titled " 4.3-kV Fully Vertical β-Ga₂O₃ Heterojunction Barrier Schottky Diode With Sputtered p-GaN " in IEEE Transactions on Electron Devices.

Background

      With the rapid advancement of modern electronic technology, the demand for high-breakdown-voltage and high-power electronic devices is continuously increasing in fields such as power transmission, communication, and aerospace. In this context, β-phase gallium oxide (β-Ga₂O₃) has emerged as one of the most promising next-generation ultrawide bandgap (UWBG) semiconductor materials. It features a wide bandgap of 4.9 eV and an exceptionally high critical electric field of 8 MV/cm, which theoretically allows β-Ga₂O₃-based devices to operate at higher voltages and power densities than conventional semiconductors such as Si, SiC, and gallium nitride (GaN). Furthermore, β-Ga₂O₃ offers significant advantages in scalability and cost-effectiveness, owing to the feasibility of large-area bulk crystal growth via edge-defined film-fed growth (EFG) and epitaxial layer fabrication using hydride vapor phase epitaxy (HVPE). These characteristics make it highly attractive for cost-sensitive and large-scale deployment in power electronic applications. However, despite its intrinsic advantages, β-Ga₂O₃ still faces a critical material challenge: the lack of shallow acceptors and strong self-trapping effects of holes prevent the realization of effective p-type conduction in the valence band.

Abstract

      In this article, a fully vertical β-Ga₂O₃ hetero junction barrier Schottky (HJBS) diode utilizing a sputtered p-gallium nitride (GaN) layer is reported. The device exhibits a high destructive breakdown voltage (BV) of 4335 V, a turn-on voltage (V_on) of 0.8 V, and a specific ON-resistance (R_on,sp) of 6.79 mΩ· cm², resulting in an outstanding Baliga’s figure of merit (BFOM) of 2.77 GW/cm². This high performance is primarily attributed to the effective electric-field modulation introduced by the p-GaN layer beneath the anode, which suppresses peak electric-field crowding and significantly delays the onset of breakdown. To further validate the material quality and structural integrity of the sputtered p-GaN layer, com prehensive characterization using scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM) was conducted, demonstrating a dense morphology and well-oriented crystalline structure. These results confirm that sputtering is a viable and promising approach for integrating p-GaN, which is particularly important in the absence of effective p-type doping technology in β-Ga₂O₃. Furthermore, temperature-dependent–current–voltage (I–V–T) measure ments were carried out to investigate the reverse leakage transport mechanisms. It was found that in the low reverse voltage range (−1 to −20 V), the Poole–Frenkel (PF) emission dominates, with a trap barrier height of 0.74 eV. With increasing reverse bias (−20 to −200 V), the dominant transport mechanism transitions to 3-D Mott variable-range hopping (3-D Mott–VRH).

Conclusion

      In this work, we first present the fabrication of fully vertical p-GaN/n-Ga₂O₃ HJBS utilizing sputtered p-GaN. Benefiting from the well-oriented crystalline structure of the sputtered p-GaN layer and the effective modulation of the electric field, the proposed HJBS achieves a BV of 4335 V and a BFOM of 2.77 GW/cm². Compared with previously reported fully vertical HJBS diodes, the proposed p-GaN/n-Ga₂O₃ HJBS demonstrates superior performance with the highest BV and BFOM. These findings highlight the promising potential of p-GaN as an effective p-type material in Ga₂O₃-based heterostructures, offering a novel approach to address the long standing challenge of the lack of p-Ga₂O₃ materials. This advancement is expected to significantly contribute to the development of Ga₂O₃ diodes for high-voltage applications.