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

We investigated the optical and electrical properties of red AlGaInP light-emitting diodes (LEDs) as functions of chip size, p-cladding layer thickness, and the number of multi-quantum wells (MQWs). External quantum efficiency (EQE) decreased with decreasing chip size. The ideality factor gradually increased from 1.47 to 1.95 as the chip size decreased from 350 mu m to 15 mu m. This indicates that the smaller LEDs experienced larger carrier loss due to Shockley-Read-Hall nonradiative recombination at sidewall defects. S parameter, defined as partial derivative lnL/partial derivative lnI, increased with decreasing chip size. Simulations and experimental results showed that smaller LEDs with 5 pairs of MQWs had over 30% higher IQE at 5 A/cm(2) than the LED with 20 pairs of MQWs. These results show that the optimization of the number of QWs is needed to obtain maximum EQE of micro-LEDs. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.