Quantum Optical Studies on Individual Acceptor Bound Excitons in a Semiconductor

We demonstrate the generation of triggered single photons at a predetermined and well defined energy using the radiative recombination of single nitrogen-bound excitons in a semiconductor. The nitrogen atoms are embedded in a ZnSe quantum well structure and were excited by nonresonant optical pumping (82 MHz) at low temperature (4 K). We find resolution-limited photoluminescence lines ($280\mu \mathrm{e}\mathrm{V}$) which display photon antibunching under continuous optical pumping. Our results also suggest that single nitrogen-bound excitons are well suited for cavity quantum electrodynamics experiments.

Figure 1

$\mathrm{\mu }$-PL spectra of sample A for different mesa diameters under cw excitation with $500\mathrm{W}/{\mathrm{c}\mathrm{m}}^2$. All curves are normalized and shifted vertically for a better representation. $T=4\mathrm{K}$.

Figure 2

Measured distribution of coincidence counts $n(\tau )$ for an unstructured part (a) and an etched mesa structure with 160 nm diameter (b) of sample A under cw excitation with $500\mathrm{W}\mathrm{/}{\mathrm{c}\mathrm{m}}^{\mathrm{2}}$. The solid line is a fit of the correlation function $g^{(2)}(\tau )$. The corresponding $\mathrm{\mu }$-PL spectrum for trace (b) is shown in (c). The spectral window for the correlation measurement of trace (b) has been set to the ${\mathrm{I}}_{\mathrm{1}}^{\mathrm{p}\mathrm{a}\mathrm{i}\mathrm{r}}$ emission peak at 2.7891 eV with a FWHM of $800\mathrm{\mu }\mathrm{e}\mathrm{V}$ as marked by the vertical bars. $T=4\mathrm{K}$.

Figure 3

Measured unnormalized correlation function $G^{(2)}(\tau )$ in the energy region of the ${\mathrm{I}}_{\mathrm{1}}^{\mathrm{N}}$ transition for (a) an unstructured part (ensemble average) and for a 95 nm mesa structure of sample A (b) and sample B (c) under pulsed excitation with a Ti:sapphire laser (82 MHz). The corresponding normalized $\mathrm{\mu }$-PL spectra for traces (a)–(c) are shown in (d)–(f), respectively, recorded with an energy resolution of $500\mathrm{\mu }\mathrm{e}\mathrm{V}$ as used for the correlation measurements. $T=4\mathrm{K}$.