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

Abstract

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 × 10 7 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 shortwavelength LED devices that require high efficiency and long lifetime.

Unveiling light collection and pump enhancement from quantum wells with plasmonic metasurfaces using power dependent measurements

“…The details on the fabrication can be found in the methods section. The integration of Al metasurfaces with commercial LEDs wafers introduces losses (metal absorption) in comparison with patterned sapphire substrates, which are used in commercial LED devices [37][38][39][40]. Nevertheless, these Al metasurfaces tailor the far-field emission from the blue LED wafer and enhance its intensity by outcoupling the trapped emitted light at angles larger than θ c .…”