Fig. 3

Directness parameter (GS_L-GS_Γ) variation as a function of the Ge_0.72Sn_0.28 QD size and Sn composition of the Ge_0.65-xSi_0.35Sn _x surrounding layer. The dotted line indicates the thermal energy at room temperature. The inset represents a schematic definition of the directness parameter