Silicon nanocrystal-based photonic crystal slabs with broadband and efficient directional light emission

L Ondič,J Valenta,R G Elliman,A Kromka,I Pelant,M Varga

doi:10.1038/s41598-017-05973-y

Abstract

Light extraction from a thin planar layer can be increased by introducing a two-dimensional periodic pattern on its surface. This structure, the so-called photonic crystal (PhC) slab, then not only enhances the extraction efficiency of light but can direct the extracted emission into desired angles. Careful design of the structures is important in order to have a spectral overlap of the emission with extraction (leaky) modes. We show that by fabricating PhC slabs with optimized dimensions from silicon nanocrystals (SiNCs) active layers, the extraction efficiency of vertical light emission from SiNCs at a particular wavelength can be enhanced ∼ 11 times compared to that of uncorrugated SiNCs-rich layer. More importantly, increased light emission can be obtained in a broad spectral range and, simultaneously, the extracted light can stay confined within relatively narrow angle around the normal to the sample plane. We demonstrate experimentally and theoretically that the physical origin of the enhancement is such that light originating from SiNCs first couples to leaky modes of the PhCs and is then efficiently extracted into the surrounding.

Highlights

Light-emitting silicon nanocrystals (SiNCs) are a material of great importance due to their biocompatibility as well as the compatibility with standard electronic and communication platforms[1]
By comparing the experimental and computational results we show that the enhancement originates from the coupling of light emitted by SiNCs into the leaky modes of the Photonic crystal (PhC) which are efficiently extracted into surrounding
PhC structures were etched into the surface of the SiNC-rich layer by the means of electron beam lithography (EBL) and subsequent reactive ion etching (RIE)

Summary

Introduction

Light-emitting silicon nanocrystals (SiNCs) are a material of great importance due to their biocompatibility as well as the compatibility with standard electronic and communication platforms[1]. On the other hand, structuring the surface of these devices in a periodic manner offers the potential for further increase of the external quantum efficiency and for controlling the radiation pattern of the extracted luminescence. The PhCs were fabricated with high Si implantation dose in order to increase the refractive index value of the SiNC-rich SiO2 layer up to 1.8 and to obtain spectral separation of the TE and TM fundamental leaky modes. As demonstrated even such an imperfect structure can possess high performance with respect to the light extraction

Methods

Results

Conclusion