Date

2017

Document Type

Thesis

Degree

Master of Science

Department

Electrical Engineering

First Adviser

Tansu, Nelson

Abstract

In this thesis, we investigate the efficiency enhancement of surface plasmon (SP) coupling to the InGaN/ GaN QWs LED based on the strongly localized optical field and highly enhanced photon density of states near the SP frequency (ωsp) according to Purcell enhancement factor. Based on the Purcell effect, when the emission frequency approaches the surface plasmon frequency coupled to the active region, the energy coupled to the SP will notably increase and hence IQE will be strongly enhanced. In order to achieve the desirable long-wavelength emission and enhance the radiative efficiency for InGaN QWs LED, TiN and Au are selected as the appropriate materials for allowing the design of the surface plasmon frequency in the long-wavelength spectral regime (green-red). Such optimum design for engineering the surface plasmon frequency of the nano-metallic structures will result in enhanced radiation recombination rate from the active region. In this thesis, we investigate both single and double metallic layers structure to get the optimized model for Purcell enhancement in long-wavelength range. The effect of the metallic layer thicknesses has been exhibited in the computational studies. The Au and TiN single-layer structures can achieve the strong Purcell factor of ~1000 times and ~550 times in green and amber regime, respectively. The tunability of the SP frequency can be achieved by using the TiN/Au double-metallic layer structures for achieving optimized design to cover the peak Purcell factor ~ 500 times across the range of the surface plasmon frequencies of Au and TiN. The effect of different spacer separation between the InGaN QWs and metallic layer is also investigated. The variation of the spacer thickness affects the coupling efficiency, and this increased thickness also reduces the Purcell enhancement factor and decreases the surface plasmon frequency.

Share

COinS