Optical polarization properties of (11-22) semi-polar InGaN LEDs with a wide spectral range

Area of Science:

• Solid State Physics
• Materials Science
• Optoelectronics

Background:

• Semi-polar Gallium Nitride (GaN) based Light Emitting Diodes (LEDs) are crucial for advanced lighting and display technologies.
• Understanding electroluminescence polarization is key to optimizing LED performance and color tuning.
• High crystal quality InGaN grown on semi-polar (11-22) templates offers unique optoelectronic properties.

Purpose of the Study:

• To investigate the influence of indium content and injection current on the electroluminescence polarization of semi-polar InGaN LEDs.
• To identify any polarization switching phenomena across a wide spectral range.
• To correlate polarization properties with material characteristics and device operation.

Main Methods:

• Fabrication of high-quality semi-polar InGaN LEDs on (11-22) templates.
• Electroluminescence polarization measurements across a spectral range of 443 nm to 555 nm.
• Systematic variation of injection current to study its effect on polarization degree.

Main Results:

• Observed clear polarization switching around 470 nm.
• Shortest wavelength LED (443 nm) showed positive polarization (0.15), longest (555 nm) showed negative (-0.33).
• Longer wavelength LEDs (>470 nm) exhibited negative polarization degrees, with increasing dependence on injection current and decreasing absolute value with higher current. The 443 nm LED polarization remained constant.

Conclusions:

• Polarization behavior is strongly dependent on emission wavelength and injection current.
• The observed discrepancy in polarization dependence on current is attributed to differences in the density of states (DOS) of valence subbands.
• These findings provide critical insights for designing and fabricating high-performance, wavelength-tunable semi-polar InGaN LEDs.