Effect of layers of carbon-nanotube-patterned substrate on GaN-based light-emitting diodes

Abstract

In this paper, the high-performance GaN-based light-emitting diodes (LEDs) with coated carbon nanotubes (CNTs) on sapphire substrates, fabricated by metal–organic chemical vapor deposition (MOCVD), were demonstrated. The different layers of a CNT-patterned sapphire substrate (CNPSS) grown by an optimized growth process were discussed. Results of X-ray diffraction (XRD) showed the threading dislocations to be suppressed, thus the crystal quality of the GaN film was improved by introducing the carbon nanotube films. The LEDs with a CNPSS exhibited lower reverse-bias current and divergent angle, and larger enhancement of the light output power (LOP) compared with the conventional LEDs. With the increase in the number of layers of CNTs, the CNPSS-LED exhibited better crystal quality and photoelectric property, but more layers of CNTs also absorbed more light. There is a trade-off between the crystalline quality of the LED and light absorption.