【Member Papers】 (100) Microcracks induced by (1 ± 11) stacking faults in halide vapor deposited (001) β-Ga₂O₃: Origin of reverse leakage current in Schottky barrier diodes observed by high-sensitive emission microscopy and synchrotron x-ray topography

      Researchers from the Saga University and Novel Crystal Technology have published a dissertation titled "(100) Microcracks induced by (1 ± 11) stacking faults in halide vapor deposited (001) β-Ga₂O₃: Origin of reverse leakage current in Schottky barrier diodes observed by high-sensitive emission microscopy and synchrotron x-ray topography " in Journal of Applied Physics.

Background

      This study focuses on β-Ga₂O₃, an ultra-wide bandgap semiconductor with a bandgap of 4.8 eV and a high breakdown field of 8 MV/cm, making it a promising candidate for high-power and high-efficiency electronic devices. N-type β-Ga₂O₃ can be achieved through Si or Sn doping, and high-performance Schottky barrier diodes (SBDs) have been demonstrated with breakdown voltages up to 2.89 kV and low on-resistance values. These devices typically utilize β-Ga₂O₃ epitaxial layers grown by the halide vapor phase epitaxy (HVPE) technique, which enables high growth rates and high-quality thick drift layers suitable for vertical power devices.

      However, despite these advantages, SBDs often suffer from high reverse leakage current and reduced breakdown voltage due to so-called “killer defects,” whose origins remain unclear. Various types of defects have been reported in β-Ga₂O₃, including voids, polycrystalline regions, stacking faults, dislocations, and microgrooves. Building upon these findings, this study identifies microcracks induced by stacking faults in HVPE-grown (001) β-Ga₂O₃ epitaxial layers for the first time. The research further reveals the facet planes and associated dislocation networks around these microcracks, demonstrating that such stacking-fault-induced microcracks act as critical killer defects responsible for the reverse leakage behavior in HVPE-grown β-Ga₂O₃ SBDs.

Abstract

      This study reports that microcracks on a halide vapor-phase epitaxy (HVPE)-deposited (001) β-Ga₂O₃ epitaxial layer are killer defects in Schottky barrier diodes (SBDs). The microcracks are (100) cracks with a typical length of 1.7–5.1 μm and depth of 0.48–2.2 μm. They are accompanied by (111) or (1-11) stacking faults and dislocation networks, causing a large reverse-leakage-current flow in SBDs. The stacking faults were generated during HVPE growth. The microcracks were considered to be formed by tensile strain caused by the difference in thermal expansion coefficients between the [100] and [010] directions during growth, annealing, etc. The electric field at the bottom of the microcrack was 6.0 MV/cm at −80 V, which resulted in a reverse leakage current in the SBD.

Conclusion

      In this paper, we found that microcracks on an HVPE (001) β-Ga₂O₃ epitaxial layer grown on an EFG (001) β-Ga₂O₃ substrate were killer defects in SBDs. The microcracks were (100) cracks with a typical length of 1.7–5.1 μm and depth of 0.48–2.2 μm. They were induced by stacking faults and cause reverse leakage current paths [896 nA (8.87 μA/cm²) at −80 V]. The stacking faults were (1±11) facets. This indicates that they occurred during HVPE growth. Subsequently formed dislocation networks were observed around microcracks and stacking faults.

      In the simulation, we proved that the electric field concentrated at the end of the microcrack reached 6.0 MV/cm at −80 V, about five times higher than that of the flat surface. This suggests that the electric field concentration at the end of microcracks in the HVPE layer caused a reverse leakage current.