Enhanced Optical Efficiency and Carrier Dynamics in InGaN/GaN Light-Emitting-Diode Structures through Combination of...

Area of Science:

• Semiconductor Physics
• Materials Science
• Optoelectronics

Background:

• Indium Gallium Nitride (InGaN)/Gallium Nitride (GaN) multiple quantum wells (MQWs) are crucial for efficient light-emitting diodes (LEDs).
• Strain engineering in these MQWs significantly impacts their structural and optical properties.
• Optimizing the buffer layers below the MQWs is essential for improving device performance.

Purpose of the Study:

• To investigate the effect of strain-engineering multilayer regions (L1 and L2) on InGaN/GaN MQW LED structures.
• To compare the performance of LED structures with different configurations of the L2 region, specifically a single layer (S1) versus superlattices (S2).
• To elucidate the relationship between structural characteristics, carrier dynamics, and optical efficiency.

Main Methods:

• Fabrication of two InGaN/GaN MQW LED structures (S1 and S2) with distinct L2 region designs.
• Detailed structural analysis using techniques to examine V-pit dimensions and indium distribution.
• Photoluminescence (PL) and time-resolved PL measurements to assess carrier dynamics and internal quantum efficiency.
• Electroluminescence (EL) measurements to evaluate external quantum efficiency and output power.

Main Results:

• The S2 structure, incorporating superlattices in L2, demonstrated significantly enhanced optical performance compared to S1.
• Superlattices in L2 influenced V-pit dimensions and promoted a more homogeneous indium distribution, preventing In-rich nanosegregation.
• S2 achieved an internal quantum efficiency exceeding 85% and exhibited unique drooping characteristics under high injection, attributed to carrier overflow and V-pit sidewall effects.
• EL measurements showed S2 had 1.6x higher external quantum efficiency and ~66% greater output power than S1.

Conclusions:

• The incorporation of superlattices in the strain-engineering multilayer region (L2) is a highly effective strategy for enhancing the performance of InGaN/GaN MQW LEDs.
• The superlattice structure optimizes indium distribution and manages strain, leading to improved structural quality and carrier dynamics.
• This approach offers a pathway to achieving higher efficiency and output power in next-generation LED devices.