Breakthrough in Dislocation-Assisted Electron and Hole Transport in Gallium Nitride Epitaxial Layers

Gallium nitride (GaN)-based electronic devices exhibit high-frequency operation, high efficiency, high-temperature resistance, and radiation hardness, making them core components for next-generation high-efficiency power electronics and radio-frequency electronic systems. These devices have already demonstrated significant advantages in applications such as 5G/6G communications and smart consumer electronics. GaN-based devices are primarily fabricated using heteroepitaxial materials. Due to severe lattice and thermal mismatches between the epitaxial substrate and GaN-based epitaxial layers (e.g., AlGaN/GaN heterostructures), the epitaxial thin films inevitably contain a high density of linear dislocations (~10^8 cm^-2), far exceeding those in semiconductor materials like silicon and silicon carbide. Screw dislocations, edge dislocations, and their mixed types are the most common dislocation types in GaN-based heteroepitaxial structures. The leakage current and reliability degradation induced by these dislocations pose critical challenges to extending GaN-based electronic devices to higher-voltage and higher-power applications.

A collaborative effort led by the Institute of Microelectronics of the Chinese Academy of Sciences (CAS), together with the Institute of Semiconductors of CAS, Peking University, the Hong Kong University of Science and Technology, the University of Cambridge, Wuhan University, and Suzhou Nanowin High-Tech Semiconductor Co., Ltd., has for the first time clarified the impact mechanisms of screw and edge dislocations in GaN heteroepitaxial structures on the key reliability issue—dynamic on-resistance degradation—in GaN-based power electronic devices. The team developed a "dual-channel dislocation transport" model, revealing that screw and edge dislocations in GaN epitaxial layers can serve as independent transport paths for electrons and holes, respectively, exerting opposing effects on device leakage current and dynamic resistance degradation.

Leveraging advanced characterization techniques such as deep-level transient spectroscopy, low-temperature photoluminescence, conductive/potential atomic force microscopy, and first-principles calculations, the research team elucidated at the atomic level that screw dislocations induce longitudinally connected ultra-shallow electronic states along their open-core sidewalls, while forming electron potential wells in the dislocation core regions, creating an "electron channel" penetrating the epitaxial layer. In contrast, edge dislocations induce continuously distributed hole traps around them, which couple with carbon-related defects (e.g., CN) in carbon-doped GaN buffer layers, forming a "hole channel."

The team validated these findings through electrical testing on 650-V-class GaN-based HEMT devices. Even with a low total dislocation density, devices dominated by screw dislocations exhibited significantly greater dynamic on-resistance degradation under high-voltage switching stress compared to those dominated by edge dislocations. This phenomenon confirms that screw dislocations facilitate electron leakage, charge accumulation, and current collapse, whereas edge dislocation-assisted hole redistribution helps mitigate electron accumulation in the buffer layer, thereby alleviating dynamic performance degradation. The study suggests that adjusting the ratio of screw to edge dislocations through epitaxial process optimization could achieve an optimal balance between leakage current and dynamic reliability in GaN power devices while maintaining overall crystal quality.

This research opens new avenues for "defect engineering" in GaN devices, proposing that dislocations can be treated as engineerable one-dimensional carrier conduits rather than merely harmful structural defects. This strategy may extend to other semiconductor material systems, laying the foundation for establishing a theoretical framework for "dislocation electronics."