Experimental Demonstration of the Purcell Effect in Silicon Mie-resonators with Embedded Ge(Si) Quantum Dots

CMOS-compatible light emitters are intensely investigated for integrated active silicon photonic circuits. One of the approaches to achieve on-chip light emitters is the epitaxial growth of Ge(Si) QDs on silicon.  Their... [ view full abstract ]

CMOS-compatible light emitters are intensely investigated for integrated active silicon photonic circuits. One of the approaches to achieve on-chip light emitters is the epitaxial growth of Ge(Si) QDs on silicon.  Their broad emission in 1.3-1.5 um range is attractive for the telecomm applications. 

We investigate optical properties of Ge(Si) QD multilayers, that are grown in a thin Si slab on a SOI wafer, by steady-state and time-resolved micro-photoluminescence. We identify Auger recombination as the governing mechanism of carrier dynamics in such heterostructures. 

Then we demonstrate the possibility of light manipulation at the nanoscale by resonant nanostructures investigating Si nanodisks with embedded Ge(Si) QDs. The nanodisks were fabricated using either focused ion beam milling or by the combination of electron-beam lithography wit reactive ion etching (Figure 1). We show that the Mie resonances of the disks govern the enhancement of the photoluminescent signal from the embedded QDs due to a good spatial overlap of the emitter position with the electric field of Mie modes (Figure 2). Furthermore, we engineer collective Mie-resonances in a nanodisk trimer resulting in an increased Q-factor and an up to 10-fold enhancement of the luminescent signal due to the excitation of anti-symmetric magnetic and electric dipole modes (Figure 3). 

Using time-resolved measurements we show that the minima of the effective lifetime coincide with the positions of the Mie resonances for a large variation of disk sizes confirming the impact of the Purcell effect on QD emission rate (Figure 4). Purcell factors at the different Mie-resonances are determined and agree well with the modelled ones.