Photons meeting: A pathway to high efficiency charge carrier diffusion induced nanowire LEDs

At the next Photons meeting, Yue Zhao will give a seminar. Welcome!

Abstract:

Light-emitting diodes have attracted considerable interest since it substituted the place of incandescent lamp. Other than solid state lighting, its significant role across various applications including displays, optical communications, sensors leads to the urgent need to improve its efficiency and performance in the wavelength of emission spectrum for purpose of different applications. 

Conventional planar LEDs made of semiconductors have been suffered from limits of (1) lattice mismatch during the growth of semiconductors and (2) the total internal reflection resulted from the high refractive index of semiconductors comparing to air. In our configuration, these bottlenecks are solved elegantly by use of tree-shaped nanowires.

Nanowires are essential building blocks for nowadays electronics with the ability to release strain in the radial direction due to their small diameters. In the structure of our tree-shaped nanowires, lower bandgap branches are grown on higher bandgap, axially p-i-n doped core wires. Charge carriers will diffuse into the branches, recombine and emit light there with the core wires being biased. The total internal reflection is impeded since the diameter of branches is subwavelength, so that light will leak out instead of being trapped in the nanowires. Therefore, our tree-shaped nanowire LEDs open the possibility of freedom in materials combination for different emission wavelengths and enhance the efficiency through avoiding the total internal reflection.