Figure 1

(Color online) Extraction of SSC profiles by XSTM measurements and modeling. (a) A shape of model QD using base length and height extracted from XSTM measurements. The composition profile ${\text{C}}_{\text{In}}\left(\text{x},\text{y},\text{z}\right)$ is constructed by fitting In composition at four points $\left({\text{X}}_{\text{Base}},{\text{X}}_{\text{Base}R},{\text{X}}_{Top},{\text{X}}_{\text{Top}R}\right)$, $C_{\text{In}}\left(x,y,z\right)=X_0+{\left[{\left(x/{\text{b}}_{\text{geom}}\right)}^2+{\left(y/{\text{b}}_{\text{geom}}\right)}^2\right]}^{1/2}\left(X_R-X_0\right)$, where $X_0=X_{\text{Base}}+\left(X_{\text{Top}}-X_{\text{Base}}\right)\left(z/h_{\text{geom}}\right)$, $X_R=X_{\text{Base}R}+\left(X_{\text{Top}R}-X_{\text{Base}R}\right)\left(z/h_{\text{geom}}\right)$. (b) Measured outward relaxation curve (black) is fitted by a few models that vary the composition profile for a given shape using continuum elasticity simulation. This produces (c) model SSC profiles of five model QDs. Indium composition profile is shown by contour plot where 20% of In is represented by cyan (light gray) color, 40% of In concentration by green (gray), and 100% by red (dark gray). (d) Spectroscopically deduced model QDs via the barcoding approach (Ref. 21). In parts (c) and (d) the error of the calculated relaxation profile relative to measured relaxation (b) is judged by the RMS deviations.Reuse & Permissions

Figure 2

(Color online) Measured and assigned photoluminescence energy vs gate voltage (upper panel) from which a multiexciton sequence (bottom panel) is extracted for two prototype QDs emitting around $\sim 1\text{eV}$. Multiexcitonic transition energies are given relative to monoexciton energy (for QD A ${\text{E}}_X^0=1.071\text{eV}$, and for QD B ${\text{E}}_X^0=1.081\text{eV}$).Reuse & Permissions

Figure 3

(Color online) Calculated emission spectra for exciton charges ${\text{X}}^0$, ${\text{XX}}^0$, ${\text{X}}^{-1}$, and ${\text{X}}^{-2}$ of the XSTM deduced models 1–5 QDs [shown in Fig. 2c]. QDs T1 and T2 are spectroscopically deduced via the barcoding procedure (Ref. 21). These are compared with experiment.Reuse & Permissions

Figure 4

(Color online) (a) Phase diagram of sequence of emission lines as a function of QD height $\left({\text{h}}_{\text{Spectr}}\right)$ and spectroscopic base-length $\left({\text{b}}_{\text{Spectr}}\right)$ for average In composition ${\overline{C}}_{\text{In}}\ge 80\%$. ${\text{h}}_i=\text{f}\left({\overline{C}}_{\text{In}}\right)$, where $\text{i}=1,2,3$. For example for ${\overline{C}}_{\text{In}}=80\%$, ${\text{h}}_1=3.5\text{nm}$, ${\text{h}}_2=4.5\text{nm}$, and ${\text{h}}_3=5.5\text{nm}$. Regions I–IV represent different type of line sequences. Only region I satisfies spectral HRs. (b) ${\text{C}}_{\text{In}}\left(\text{z}\right)$ in the growth direction of model 5 (red dotted lines) and model T2 (blue solid curve). (c) Calculated effective confining potential for electrons and holes obtained for model 5 (black) and model T2 (red) QDs. In the QD region the offsets are irregular (jagged) due to alloy fluctuations. Atomic-scale alloy randomness (Ref. 28) presents slight variations of effective confining potential, but does not influence the spectral HRs (Ref. 21).Reuse & Permissions