Sensitively Site‐Dependent Enhancement of Emissions from Ge Quantum Dots in SiGe Microdisks

Abstract

Herein, the unique emission properties of Ge quantum dots (QDs) SiGe microdisk system are reported on Si substrates. Two types of microdisks embedded with random QDs and radial site‐controlled QDs are realized by top–down and bottom–up methods, respectively. Photoluminescence results demonstrate that the maximum enhancement factor (EF) of emissions from radial site‐controlled QDs is ≈5.2 times of that from random QDs in microdisks. Moreover, the EF dramatically depends on the site of QD in a microdisk. For a single QD in a microdisk, the difference of EF can be more than five orders due to radial site‐dependent Purcell effect. For multiple QDs in a microdisk, both the azimuthal site and the number of QDs also substantially affect EF due to the interference effect of QDs’ emissions coupling into the cavity modes of microdisks. These unique features disclose the critical effect of the spatial matching between the QD site and the cavity mode on light–matter interactions in a microdisk. In addition, the microdisk via the bottom–up method can efficiently suppress nonradiative losses at the sidewall of microdisk. A promising strategy to QDs’ microdisk system is provided in the results, which promises strong coupling between QDs and the cavity modes and the realization of innovative light sources.

Keywords

• microdisks
• photoluminescence
• Purcell factor
• quantum dots
• spatial matching