Imaging dislocations in gallium nitride across broad areas using atomic force microscopy.

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Gallium Nitride (GaN) is a critical material for electronic and optoelectronic devices.
• Understanding the distribution of threading dislocations (TDs) is essential for optimizing GaN material quality.
• Surface pits are often associated with TDs, but their detailed imaging and analysis can be challenging.

Purpose of the Study:

• To develop and apply high-resolution imaging techniques for detailed analysis of threading dislocations (TDs) in Gallium Nitride (GaN).
• To identify and map the spatial distribution of TDs using atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM).
• To introduce an automated software tool for efficient TD coordinate identification.

Main Methods:

• Utilizing atomic force microscopy (AFM) with a high sampling rate to image GaN samples.
• Employing silane and ammonia treatments to enlarge surface pits linked to TDs.
• Applying Kelvin probe force microscopy (KPFM) at high pixel density to analyze surface potential variations.
• Developing an automated software tool for identifying TD coordinates within AFM images.

Main Results:

• High pixel density AFM images successfully identified TDs in tens of microns sized GaN samples.
• The spatial distribution of TDs was accurately mapped, providing detailed insights.
• Kelvin probe force microscopy (KPFM) revealed local surface potential changes associated with hundreds of dislocations.
• An automated software tool efficiently determined the coordinates of TDs in the images.

Conclusions:

• High-resolution AFM and KPFM are effective for detailed characterization of TDs in GaN.
• The developed automated software tool enhances the efficiency of TD analysis.
• This study provides valuable data on TD distribution and surface potential for GaN material optimization.