Directly correlated microscopy of trench defects in InGaN quantum wells

Area of Science:

• Materials Science
• Semiconductor Physics
• Nanotechnology

Background:

• Indium gallium nitride (InGaN) quantum wells (QWs) are crucial for optoelectronic devices.
• Nanoscale trench defects in InGaN QWs exhibit unique optical properties.
• Understanding the origin of these defects is key to improving device performance.

Purpose of the Study:

• To investigate the relationship between surface morphology, subsurface structure, and light emission in InGaN QW trench defects.
• To elucidate the origin of unusual emission behavior and cathodoluminescence (CL) redshift associated with these defects.
• To correlate defect characteristics with quantum well properties and indium composition.

Main Methods:

• Correlated measurements using scanning probe microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM).
• Focused ion beam-SEM (FIB-SEM) for precise defect localization and lamella preparation.
• Cathodoluminescence (CL) spectroscopy to analyze light emission properties.

Main Results:

• CL redshift correlates with trench width and the prominence of enclosed material.
• Defect location (basal-plane stacking fault position) influences CL redshift and quantum well width.
• Increased indium content observed in enclosed quantum wells, with reduced quantum well width fluctuations.

Conclusions:

• Trench defects significantly alter InGaN QW properties, affecting light emission.
• Defect morphology and subsurface structure dictate the degree of CL redshift and indium distribution.
• Pinning of surface step edges by trenches may contribute to higher indium content in enclosed QWs, mitigating indium loss.