Influence of the quantum confined Stark effect on photoluminescence spectra of PbTe nanodots embedded in a CdTe matrix

The quantum confined Stark effect induced by electric fields is of outstanding importance for nanostructure properties. In embedded quantum dots, it occurs as consequence of internal electric fields related to interface charges. A quantum dot model including the quantum confined Stark effect is proposed. It is applied to PbTe/CdTe quantum dot precipitates. The predicted photoluminescence spectra are compared with results of photoluminescence experiments. The unexpected photoluminescence intensity drop at low temperatures is interpreted to be a consequence of the internal quantum confined Stark effect.

Figure 1

(Color online) (a) Model of a PbTe QD embedded in CdTe matrix. To enhance the visibility in the first quadrant no matrix atoms are shown. (b) Schematic representation of the occurring dot-matrix interface facets. Different terminations are indicated by different colors.

Figure 2

Schematic confinement potential of an embedded QD with internal electric field. The lowest electron and hole levels are indicated by horizontal solid lines. The spatial separation ${\Delta }_{\text{wav}}$ of the maxima between the HONO and LUNO probability distributions and the energy shift ${\Delta }_{\text{Stark}}$ due to the field-induced potential are indicated.

Figure 3

(Color online) Electron-hole transition energies for a 29-nm PbTe/CdTe QD as function of temperature. The black solid line depicts the calculated ground-state transition energy $E_{\text{trans}}^{00}$, while the excited-state transition energy $E_{\text{trans}}^{33}$ is given as black dashed line. The red lines represent the unstrained (dash-dotted line) and strained (dashed line) bulk PbTe band gap.

Figure 4

Temperature-dependent PL spectra:(a) Theoretical prediction for a 29-nm PbTe QD; (b) Experimental observation for PbTe/CdTe QDs formed from an initially 5-nm-thick PbTe layer—taken from Schwarzl et al. (Ref. 14).

Figure 5

Theoretical (black dots) peak energies of PL emission spectra of PbTe/CdTe QDs as function of temperature. The full and dashed lines depict calculated ground-state and excited-state transition energies, respectively.

Figure 6

Normalized integrated PL intensity. Left panel: theoretical prediction for a 18-nm QD (solid line) and a 29-nm QD (dashed line). Right panel: experimental data of optimum annealed 3-nm (squares) and 5-nm (circles) PbTe/CdTe samples. Vertical dotted lines indicate the maxima