Colloidal Synthesis, Energy Gap Tuning and Carrier Dynamics of Ge-Si-Sn Nanoalloys with Visible to Near IR Photoluminescence

Group IV semiconductor quantum dots have gained noteworthy interest in optoelectronic applications due to their high natural abundance, low-cost of elemental components, and low-to-non-toxicity. A number of chemical syntheses for colloidal Si and Ge quantum dots have been reported and new methods continue to appear. However, these methods generally lack the wide tunability of nanocrystal size and consequently absorption and emission energies resulting in minimal exploration of photophysical properties. To address this issue, we have recently studied the incorporation of elemental Si and Sn into Ge nanocrystals to produce homogeneous Ge_1-x-ySi_ySn_x ternary alloy and quantum dots that exhibit size and composition-tunable absorption and emission across visible to near-infrared spectrum. Herein, the physical characterization of the quantum-confined and non-quantum-confined Ge_1-x-ySi_ySn_x alloys using powder X-ray diffraction, transmission and scanning electron microscopy, energy dispersive spectroscopy, steady-state and time-resolved absorption and emission spectroscopy, and computational electronic structure calculations will be presented. The effect of synthetic parameters on nanocrystal size, shape, composition, absorption and emission energy, and carrier dynamics will be discussed in light of their application in silicon-based visible to near-infrared optoelectronics.