Optimizing performance and yield of vertical GaN diodes using wafer scale optical techniques.

Area of Science:

• Materials Science
• Semiconductor Physics
• Power Electronics

Background:

• Gallium Nitride (GaN) is a key material for high-power electronic devices.
• Defects in GaN substrates can significantly impact device performance and reliability.
• Non-destructive characterization techniques are essential for understanding these defects.

Purpose of the Study:

• To investigate the impact of substrate defects on the performance of vertical GaN P-i-N diodes.
• To correlate non-destructive characterization results with device electrical measurements.
• To identify critical defect types that lead to device failure.

Main Methods:

• Utilized Raman spectroscopy to detect crystal stress and conductivity variations.
• Employed optical profilometry to identify surface topography like bumps and pits.
• Fabricated and electrically tested vertical GaN P-i-N diodes on areas with and without defects.

Main Results:

• Devices consistently blocked over 1000 V with on-resistance below 2 mΩ cm².
• High crystal stress increased device failure probability from 6% to 20%.
• Surface bumps and pits could induce low-voltage catastrophic failures, correlating with crystal stress.

Conclusions:

• Substrate defects, particularly high crystal stress and specific surface topographies, critically affect vertical GaN device reliability.
• Non-destructive techniques like Raman spectroscopy and optical profilometry are vital for predicting and mitigating device failures.
• Optimizing GaN substrate quality is essential for advancing high-performance power electronics.