Light output performance of red AlGaInP-based light emitting diodes with different chip geometries and structures

Area of Science:

• Optoelectronics
• Semiconductor devices

Background:

• Red aluminum gallium indium phosphide (AlGaInP) light-emitting diodes (LEDs) are essential for various display and lighting applications.
• Miniaturization of LEDs into micro-LEDs presents challenges in maintaining optical and electrical performance.

Purpose of the Study:

• To investigate the impact of chip size, p-cladding layer thickness, and multi-quantum well (MQW) count on the performance of red AlGaInP LEDs.
• To understand the underlying mechanisms of efficiency loss in smaller LED devices.

Main Methods:

• Experimental characterization of optical and electrical properties of AlGaInP LEDs with varying chip sizes and MQW structures.
• Device simulations to analyze carrier dynamics and recombination mechanisms.
• Analysis of external quantum efficiency (EQE), ideality factor, and S parameter (∂lnL/∂lnI).

Main Results:

• EQE decreased significantly with smaller chip sizes, attributed to increased Shockley-Read-Hall nonradiative recombination at sidewall defects.
• Ideality factor increased from 1.47 to 1.95 as chip size reduced from 350 μm to 15 μm.
• Smaller LEDs with 5 pairs of MQWs exhibited over 30% higher internal quantum efficiency (IQE) at 5 A/cm² compared to those with 20 pairs.

Conclusions:

• Chip size is a critical factor affecting LED performance, with smaller devices suffering from higher carrier losses.
• Optimizing the number of MQWs is essential for achieving maximum EQE in micro-LEDs, balancing efficiency and device structure.
• Further research into mitigating sidewall effects is necessary for advanced micro-LED development.