Estimation of Dislocation Densities With Nondestructive Scanning Electron Microscope Techniques: Application to...

Area of Science:

• Semiconductor Materials Science
• Materials Characterization
• Solid State Physics

Background:

• Threading dislocations (TDs) significantly impact gallium nitride (GaN) semiconductor device performance and reliability.
• Accurate characterization of TD densities and types is essential for optimizing GaN-based electronic and optoelectronic devices.
• Existing characterization methods may have limitations in comprehensively evaluating TDs.

Purpose of the Study:

• To comparatively evaluate the effectiveness of electron channeling contrast imaging (ECCI) and high-resolution electron backscattered diffraction (HR-EBSD) for characterizing threading dislocations (TDs) in GaN.
• To determine the performance of ECCI and HR-EBSD in assessing TD densities and types in GaN epitaxial layers.
• To establish a complementary approach for comprehensive TD analysis.

Main Methods:

• Utilized a scanning electron microscope (SEM) equipped with both ECCI and HR-EBSD.
• Performed comparative analysis of TD densities and types using ECCI for counting and HR-EBSD for crystallographic orientation and strain analysis.
• Investigated dislocation line vectors, types (edge, mixed, screw), and their distribution relative to the growth direction ([0001]).

Main Results:

• Dislocation line vectors predominantly deviate from the GaN growth direction ([0001]).
• Edge-type dislocations, with lines parallel to [0001], and mixed-type dislocations were identified within dislocation clusters.
• HR-EBSD, with a spatial resolution of 50 nm, could not resolve individual dislocations but provided insights into lattice rotations and residual elastic strain fields.

Conclusions:

• ECCI and HR-EBSD are complementary techniques for counting and characterizing TDs in GaN.
• Combining ECCI's counting capability with HR-EBSD's description of geometrically necessary dislocation density provides a comprehensive measure of total TD density and dislocation type proportions.
• While HR-EBSD has limitations in resolving individual TDs at the nanoscale, its analysis of strain and rotation complements ECCI for a thorough understanding of TD impact.