Metalorganic chemical vapor deposition grown n-InGaN/n-GaN tunnel junctions for micro-light-emitting diodes with very low forward voltage
Panpan Li, Haojun Zhang, Hongjian Li, Yuewei Zhang, Yifan Yao, Nathan Palmquist, Mike Iza, James S. Speck, Shuji Nakamura, Steven P. DenBaars
Abstract
Abstract High performance GaN-based micro-light-emitting diodes (µLEDs) with epitaxial n-InGaN/n-GaN tunnel junctions (InGaN TJs) were grown by metalorganic chemical vapor deposition (MOCVD). The InGaN TJs µLEDs show a significant reduction of forward voltage (V f ) by ∼0.6 V compared to the common TJs µLEDs. The V f at 20 A cm −2 is very low varied from 3.15 V to 3.19 V in small InGaN TJ µLEDs with a size less than 40 × 40 µ m 2 , and then significantly increases in large LEDs. Selective area growth (SAG) of TJs can overcome such size limitation by vertical out diffusion of hydrogen through the apertures on top of p-GaN. The InGaN TJ µLEDs overgrown by SAG show a size-independent low V f ranged from 3.08 V to 3.25 V. The external quantum efficiency (EQE) of the packaged TJ µLEDs was improved by 6% compared to the common µLEDs with indium tin oxide (ITO) contact. This work solves the key challenges of MOCVD-grown TJs.