Low-voltage cross-sectional EBIC for characterisation of GaN-based light emitting devices

Area of Science:

• Materials Science
• Semiconductor Physics
• Nanotechnology

Background:

• Electron beam induced current (EBIC) characterization is crucial for understanding defects in semiconductors.
• Gallium nitride (GaN) light-emitting devices require advanced cross-sectional analysis due to their complex structures.
• Existing EBIC methods need development for high-resolution defect imaging in GaN.

Purpose of the Study:

• To develop a low-voltage, high-resolution EBIC method for cross-sectional analysis of GaN devices.
• To investigate the influence of crystalline defects on carrier diffusion and recombination in GaN.
• To correlate EBIC findings with cathodoluminescence for precise defect identification.

Main Methods:

• A novel sample preparation technique using low-voltage Argon ion milling to create flat cross-sections.
• Low-voltage, high-resolution EBIC characterization to minimize surface recombination.
• One-dimensional quantification of EBIC signals for spatial resolution analysis.
• Correlation of EBIC images with cathodoluminescence (CL) images.

Main Results:

• The Ar ion milling method produced flat cross-sections with minimal surface recombination, enabling low-voltage EBIC.
• Dark defects, identified as threading dislocations via CL correlation, were observed in EBIC images.
• Significant roughening of the GaN p-n junction was revealed with high spatial resolution.
• Longer minority carrier diffusion lengths were observed along the c-axis at dislocation sites in both p-GaN and multi-quantum well (MQW) regions.

Conclusions:

• Low-voltage cross-sectional EBIC is a promising technique for characterizing point and extended defects in GaN-based devices.
• The observed diffusion length enhancement at dislocations is attributed to point defect gettering and increased quantum well escape rates.
• This technique holds significant potential for analyzing degradation mechanisms in GaN devices.