A research team has developed high-performance diamond/ε-Ga₂O₃ heterojunction pn diodes based on ultrawide bandgap semiconductors, achieving breakdown voltages exceeding 3 kV. This work was published in Nano Letters.

The research was led by Prof. YE Jichun from the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS), together with researchers from Zhengzhou University, Nanjing University, Harbin Institute of Technology, and Yongjiang Laboratory.

Ultrawide bandgap semiconductors comprising Ga₂O₃ and diamond demonstrate notable potential for high-power applications due to their ultrawide bandgap, high breakdown field, radiation resistance, and carrier mobility. Bipolar devices, such as pn diodes and bipolar junction transistors, hold promising potential in the high-power electronics industry due to their ability to withstand reverse voltage currents.

However, effective bipolar doping in ultrawide bandgap semiconductors is limited by the substantial ionization energies of dopants. To overcome this bottleneck, the researchers proposed a heterojunction strategy. This approach integrates p-type diamond with n-type ε-Ga₂O₃ for fabricating power pn diodes.

The heteroepitaxial n-type ε-Ga₂O₃ film was grown on the p-type diamond single-crystal substrate by coordinating multi-domains and confining the crystallization pathway. This process alleviates lattice mismatch. The heterojunction interface between ε-Ga₂O₃ and diamond is atomically sharp without observable interfacial element diffusion, enabling highly efficient rectification and low reverse leakage current in the heterojunction diodes.

Compared with previously reported diamond-based diodes, the fabricated diamond/ε-Ga₂O₃ heterojunction diode exhibits notable rectifying characteristics, with an on−off ratio exceeding 10⁸. It achieves a maximum breakdown voltage surpassing 3,000 V, even without edge termination.

Additionally, a thermal boundary conductance of up to 64 MW/m²·K at 500 K was achieved, demonstrating the thermal management capability of the diamond/ε-Ga₂O₃ heterojunction diode. This study introduces an innovative methodology for fabricating high-performance ultrawide bandgap semiconductor-based bipolar devices. The resulting devices demonstrate exceptional breakdown voltages and efficient thermal management, making them highly suitable for ultra-high-power applications.

This research was funded through multiple programs, including the National Key R&D Program of China, the National Natural Science Foundation of China, the Zhejiang Provincial Natural Science Foundation of China, and the Ningbo Yongjiang Talent Introduction Programme.