MicroLEDs have been considered as one of the promising candidates for various emerging applications. Due to their better optical transparency, tunnel junctions (TJs) offer higher light extraction efficiency than conventional current spreading layers, such as indium tin oxide (ITO). However, TJs grown by MOCVD suffer from high voltage penalty attributed to hydrogen passivation in the p-GaN during the TJ regrowth, resulting in poor wall-plug efficiency that is impractical for most applications.
The recent progress in MOCVD-grown TJ optoelectronic devices from 2020 will be presented. First, a novel sidewall activation method with chemical treatments will be revealed and the TJ microLED performances will be discussed. By employing this activation method, the efficiency characteristic of TJ microLEDs is better than that of ITO devices. TJs grown by MOCVD can be utilized for microLEDs as well as for laser diodes. The device performances of TJ and ITO laser diodes on m-plane GaN substrates are compared, where the preliminary laser results suggest TJs can be advantageous with further optimizations. Lastly, a novel TJ design that uses AlGaN layer will be introduced to improve the electrical performance of GaN TJ while maintaining good optical characteristics.