Comparative study of LEDs conformally overgrown on multi-facet GaN NWs vs. conventional c-plane LEDs

Abstract

Over the last decade, considerable efforts have gone into researching techniques to improve the efficiency of light emitting diodes (LEDs) based on the III-nitride material system. These efforts can be classified into two main approaches : improving the internal quantum efficiency (IQE) and increasing the light extraction efficiency of the LED devices. In the work outlined below, we demonstrate a unique LED structure that has a significantly enhanced light output intensity compared to c-plane LEDs by tackling both approaches simultaneously. We investigated the ratio of light output intensity of the NWs LED vs the c-plane LED as a function of current density. At lower current densities, the lower QCSE in NWs LED is responsible for a large ratio. This reduces with increasing current density as carrier screening of the polarization field in the c-plane LED negates the QCSE effect. The ratio saturates at higher current densities where the mechanism for higher light output is dominated by the light extraction efficiency that depends only on the device geometry and is independent of the current density in the NWs LED.