Efficient Dislocation Prevention and Thermal Transport Network Constructed by CNT Films on PSS for GaN-Based UV LEDs

We report the realization of a dislocation prevention and thermal transport network by adopting carbon nanotube (CNT) films on a commercially available patterned sapphire substrate (PSS), using which a high-quality gallium nitride (GaN) epilayer and a device with improved thermal performance are achieved at the same time. High fill factor CNT films with easy accessibility are lifted above the sapphire patterns and introduce a second selective area growth subsequent to the micron-scale selective area growth on PSS, leading to a further reduction in threading dislocation density (TDD) without involving any regrowth process. Under this dislocation prevention effect, the TDD of the GaN epilayer dropped to 3.5 × 107 cm–2 consequently, which is 78% lower than that on PSS. A thermal transporting network of CNTs with high axial thermal conductivity is simultaneously established, contributing to the great improvement in the thermal performance of the near-ultraviolet light-emitting diode (LED) fabricated subsequently. As a result, an 89% increase in saturation light output power and a 55.5% enhancement in internal quantum efficiency were acquired. We thus believe that this convenient yet effective method will be a competitive solution for short-wavelength LED devices that require high efficiency and long lifetime.