Improved Light Output of AlGaInP-Based Micro-Light Emitting Diode Using Distributed Bragg Reflector

Abstract

We investigated how the performance and reliability of AlGaInP-based red (620 nm) micro-light-emitting diodes (micro-LEDs) ( $25\times 17\,\,\mu \text{m}^{2}$ ) were influenced by the use of $n$ -AlInP ohmic layer and distributed Bragg reflector (DBR). The AlGaAs-based DBR showed reflectivity of 94.9% at 622 nm with a 14 nm-stopband width. The micro-LEDs with $n$ -GaAs gave slightly lower forward voltages by 0.013 – 0.021 V than those with $n$ -Al0.5In0.5P/ $n$ -Al0.6Ga0.4As and $n$ -Al0.5In0.5P/DBR. However, the micro-LEDs with $n$ -Al0.5In0.5P/ $n$ -Al0.6Ga0.4As and $n$ -Al0.5In0.5P/DBR gave 61% and 125% higher light output power at $20~\mu \text{A}$ compared with that with $n$ -GaAs. It was shown that after annealing at 120 °C for 2,000 h, the forward voltage and the light output power at 4.7 A/cm2 of the micro-LEDs with $n$ -Al0.5In0.5P/DBR were degraded by 0.09% and 6.33%, respectively, with reference to those before annealing.