State-of-the-art and prospects for intense red radiation from core-shell InGaN/GaN nanorods

Area of Science:

• Semiconductor physics
• Materials science
• Optoelectronics

Background:

• Core-shell nanorods (NRs) with Indium Gallium Nitride/Gallium Nitride (InGaN/GaN) quantum wells (QWs) are essential for advanced lighting and display technologies.
• A significant challenge is the weak red light emission intensity from these NRs, hindering their full potential in monolithic white light-emitting diodes (LEDs) and multi-color displays.

Purpose of the Study:

• To investigate the causes of weak red light emission in InGaN/GaN core-shell NRs.
• To identify strategies for enhancing red light output for improved device performance.

Main Methods:

• Photoluminescence measurements were conducted on various NRs under different power, temperature, and time-resolved conditions.
• Calculations of electromagnetic field distribution within the NRs were performed to understand photon state density.
• A novel hybrid nanorod design was proposed based on the experimental and theoretical findings.

Main Results:

• Dominant emission bands were attributed to nonpolar and semipolar QWs, while a broad yellow-red band originated from GaN core defects.
• Emission from polar QWs at the NR tip was suppressed due to low photon state density and overshadowed by defect luminescence.
• Calculations confirmed lower photon state density at the NR tip, further limiting polar QW emission.

Conclusions:

• Defect-related luminescence and low photon state density at the NR tip are primary reasons for weak red emission from polar QWs.
• A proposed hybrid design, placing polar QWs in the cylindrical core with higher photon state density, can convert blue light to red light.
• This approach offers a viable solution to enhance red light generation, addressing a critical need for InGaN/GaN NRs in optoelectronic applications.