Identification of type of threading dislocation causing reverse leakage in GaN p-n junctions after continuous forward...

Area of Science:

• Materials Science
• Semiconductor Physics
• Device Engineering

Background:

• Power devices face degradation under high current/voltage stress.
• Previous work showed increased reverse leakage current in Gallium Nitride (GaN) p-n junctions after forward current stress.

Purpose of the Study:

• Identify specific threading dislocations causing reverse leakage in GaN p-n diodes under forward current stress.

Main Methods:

• Metalorganic vapor phase epitaxy (MOVPE) growth of GaN p-n diodes on freestanding GaN substrates.
• Optical emission microscopy to identify leakage sites.
• Cross-sectional transmission electron microscopy (TEM) and large-angle convergent-beam electron diffraction (LACBED) to analyze dislocation type and Burgers vector.

Main Results:

• GaN p-n diodes exhibited ~200 V breakdown voltage and avalanche capability.
• Forward current injection led to rapid reverse leakage increase in some diodes.
• Optical emission microscopy localized leakage sites.
• Cross-sectional TEM identified closed-core threading screw dislocations (TSDs) at leakage sites.
• LACBED confirmed TSDs have Burgers vector [0001] (b=1c).

Conclusions:

• Threading screw dislocations (TSDs) with Burgers vector [0001] are confirmed as the primary pathways for reverse leakage current in GaN p-n diodes subjected to forward current stress.
• Understanding these dislocation-related leakage mechanisms is crucial for improving the reliability of GaN power devices.