Luminescence and local photonic confinement of single ZnSe:Mn nanostructure and the shape dependent lasing behavior

One-dimensional Mn-ZnSe nanostructures with high crystallite quality were synthesized by the CVD method. Transmission electron microscopy was used to study the defect state, crystal lattice and growth direction of as-prepared nanostructures. Raman spectra under varied excitation wavelengths confirmed the dopant modes of Mn(II) and the inhomogeneity. The micro-photoluminescence (PL) spectra of individual nanostructures under CW laser excitation with different powers showed the dominant trapped state emission with periodic multi-peaks. The selected peak mapping indicated that there were many integrated Fabry-Perot cavities and whispering gallery mode cavities within the nanowires/nanoneedles and nanobelts, respectively, which can be accounted for by inhomogeneous optical phases in the Mn-ZnSe nanostructure. The phase may be introduced by both Mn doping and structural relaxation. The micro-PL spectra under nanosecond pulse laser excitation produce low threshold lasing lines near the band edge of Mn-ZnSe nanostructures. The lasing occurs due to the dominant interaction between bound excitons at high density, evidenced by its appearance close to the LO phonon replica. The belts show much stronger lasing emission due to larger 2D coherent space than the wires due to the inhomogeneity induced by the doping process. The different optical behavior with changing excitation pulses may find applications in future photonic devices of II-VI nanostructures.

Impurity absorption in CVD ZnSe

Fourier transmission spectroscopic and laser calorimetric measurements have been used to characterize bulk and surface impurity bands in CVD ZnSe. Temperature dependence studies indicate that, while absorption between 1200 cm-(l) and 1800 cm-(1) is mainly from bulk molecular impurities, surface impurities also contribute and introduce a departure from the expected exponential dependence of multiphonon absorption with frequency above 850 cm-(1).