  A whole series of complementary studies have been performed on the same,
single nanowire containing a quantum dot: cathodoluminescence spectroscopy and
imaging, micro-photoluminescence spectroscopy under magnetic field and as a
function of temperature, and energy-dispersive X-ray spectrometry and imaging.
The ZnTe nanowire was deposited on a Si 3 N 4 membrane with Ti/Al patterns. The
complete set of data shows that the CdTe quantum dot features the heavy-hole
state as a ground state, although the compressive mismatch strain promotes a
light-hole ground state as soon as the aspect ratio is larger than unity
(elongated dot). A numerical calculation of the whole structure shows that the
transition from the heavy-hole to the light-hole configuration is pushed toward
values of the aspect ratio much larger than unity by the presence of a
(Zn,Mg)Te shell, and that the effect is further enhanced by a small valence
band offset between the semiconductors in the dot and around it.
