A comparative study of threading dislocations in AlGaN/GaN heterostructures grown on Si substrates with different buffer structures

Abstract

Effective characterization and suppression of threading dislocations (TDs) via optimized buffer architectures represent critical objectives in developing high-performance GaN high electron mobility transistor (HEMT) electronic devices. This study presents a comparative investigation of TDs characterization in GaN/AlGaN heterostructure grown on Si substrate with two buffer architectures: superlattice (SL) and step-graded (SG) AlGaN. Combining electron channeling contrast imaging (ECCI), defect-selective etching, high-resolution X-ray diffraction (HRXRD), and transmission electron microscopy (TEM), we systematically evaluate both near-surface and bulk threading dislocation behaviors. The integration of ECCI with a Python script enabled automated TD quantification, enhancing measurement precision. All results consistently demonstrate that SL-buffered heterostructures exhibit ∼46 % lower near-surface TD density compared to SG-AlGaN counterparts. Cross-sectional TEM analysis revealed that the discrepancy in dislocation density between two GaN-on-Si epitaxial samples originates from the buffer structure governed stress control and dislocation filtering efficacy, with SL-buffered GaN-on-Si samples demonstrating superior TDs blocking effect and near-surface TD reduction. Our study establishes a framework for efficient and precise TD assessment via multi-technique characterizations, demonstrating superior TD filtering capability of the SL-buffered structure for fabricating high-performance GaN/AlGaN heterostructure HEMT devices with reduced dislocation densities.