Optimization of hydrothermal growth ZnO Nanorods for enhancement of light extraction from GaN blue LEDs

• Published in: Journal of crystal growth 2010-05, Vol.312 (11), p.1848-1854
• Main Authors: Soh, C.B., Tay, C.B., Chua, S.J., Le, H.Q., Ang, N.S.S., Teng, J.H.
• Format: Article
• Language: English
• Subjects: A2. Hydrothermal crystal growth; A3. Metalorganic chemical vapor deposition; Arrays; B2. Semiconducting II–VI materials; B3. Light emitting diodes; Cross-disciplinary physics: materials science; rheology; Crystal growth; Exact sciences and technology; Extraction; Gallium nitrides; Materials science; Methods of crystal growth; physics of crystal growth; Methods of nanofabrication; Nanorods; Nanoscale materials and structures: fabrication and characterization; Optimization; Oranges; Other topics in nanoscale materials and structures; Physics; Quantum wires; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation; Zinc oxide
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2010.02.041

In this study, we report on the enhancement in the light extraction efficiency of GaN blue LEDs topped with ZnO nanorods. The ZnO nanorods were grown by a two-step hydrothermal synthesis with pre-coated ZnO nanoparticles under optimized condition to give the appropriate size and quality, giving an increase in the light output efficiency of 66%. This improvement is attributed to the optimal rod size and spacing with improved thermal dissipation as compared to light extraction from plain GaN surface. During the ZnO growth on the LEDs, 0.55 M of NH 3 was added and the ZnO sample was later annealed at 475 °C in N 2 ambient, to drive out interstitial oxygen atoms from the tetrahedral unstable site. As a result, a high ratio of UV to orange defect band emission was achieved. The two-step growth of ZnO nanorods on GaN LEDs was effective in generating array of ZnO nanorods which serve as reflector to enhance light extraction from LEDs.