Dislocation-assisted electron and hole transport in GaN epitaxial layers

Area of Science:

• Semiconductor Physics
• Materials Science
• Nanotechnology

Background:

• Dislocations in semiconductors critically impact carrier transport, acting as both scattering centers and potential pathways.
• The precise mechanisms of carrier transport along dislocation cores, particularly the differentiation between electron and hole transport, remain incompletely understood.
• Gallium nitride (GaN) is a key material where dislocations significantly influence device performance.

Purpose of the Study:

• To provide the first experimental evidence differentiating electron and hole transport mechanisms along specific dislocation types in GaN.
• To investigate the role of different dislocation densities and types (screw vs. edge) in device degradation, specifically current collapse.
• To elucidate how dislocations influence carrier trapping and transport properties in GaN-based semiconductor devices.

Main Methods:

• Experimental investigation of carrier transport mechanisms in GaN.
• Analysis of the distinct roles of threading screw dislocations and threading edge dislocations.
• Correlation of total dislocation density and the ratio of edge to screw dislocations with device performance metrics like current collapse.

Main Results:

• Demonstrated separate transport mechanisms for electrons and holes mediated by threading screw and threading edge dislocations in GaN.
• Showcased that higher total dislocation density, specifically a larger proportion of edge dislocations, reduces current collapse by mitigating electron trapping.
• Identified screw dislocations as promoting electron leakage via potential barriers and shallow states, while edge dislocations enhance hole transport through extended trap levels.

Conclusions:

• Clarified the long-standing debate on carrier-specific dislocation transport mechanisms in semiconductors.
• Provided critical insights into defect engineering and epitaxial growth for optimizing GaN devices.
• Highlighted the potential for developing dislocation-enhanced semiconductor devices by controlling dislocation types and densities.