SINGLE ZERO-DIMENSIONAL EXCITONS IN CDSE/ZNSE NANOSTRUCTURES

Zero-dimensional excitons (0DXs) in CdSe/ZnSe nanostructures have been studied by time- and spatially resolved photoluminescence spectroscopy. The three-dimensional confinement is confirmed by an exciton lifetime up to 550 ps, independent of temperature up to 130 K. By preparing mesa structures with diameters down to 50 nm as local probes, an extremely high spatial resolution is achieved, giving experimental access to single 0DXs. A splitting of the ground state into a linearly polarized doublet with an energy spacing up to 1.5 meV is found, varying from dot to dot in sign and magnitude. This indicates a noncircular shape with no preferential orientation of the dots. The dot density is estimated to increase from 5×1010 to 1.5×1011 cm−2, when changing the nominal CdSe layer thickness from 1 to 3 ML, i.e., close to the critical thickness.

[1]  Dawson,et al.  Linewidth dependence of radiative exciton lifetimes in quantum wells. , 1987, Physical review letters.

[2]  A. Forchel,et al.  Lateral quantization effects in lithographically defined CdZnSe/ZnSe quantum dots and quantum wires , 1995 .

[3]  Kazuhiro Ohkawa,et al.  CdSe/ZnSe Quantum Dot Structures: Structural and Optical Investigations , 1997 .

[4]  Egorov,et al.  Ultranarrow Luminescence Lines from Single Quantum Dots. , 1995, Physical review letters.

[5]  G. Bastard,et al.  Photoluminescence of single InAs quantum dots obtained by self-organized growth on GaAs. , 1994, Physical review letters.

[6]  J. Merz,et al.  Visible photoluminescence from N-dot ensembles and the linewidth of ultrasmall AlyIn1-yAs/AlxGa1-xAs quantum dots. , 1994, Physical review. B, Condensed matter.

[7]  Cosman,et al.  Fine structure of excitons in type-II GaAs/AlAs quantum wells. , 1990, Physical review. B, Condensed matter.

[8]  E. Betzig,et al.  Near-Field Spectroscopy of the Quantum Constituents of a Luminescent System , 1994, Science.

[9]  Gammon,et al.  Fine structure splitting in the optical spectra of single GaAs quantum dots. , 1996, Physical review letters.

[10]  Kazuhiro Ohkawa,et al.  CdSe/ZnSe quantum structures grown by migration enhanced epitaxy: Structural and optical investigations , 1997 .

[11]  F. Henneberger,et al.  Self‐Assembled Visible‐Bandgap II–VI Quantum Dots , 1997 .

[12]  Y. Arakawa,et al.  Highly uniform InGaAs/GaAs quantum dots (∼15 nm) by metalorganic chemical vapor deposition , 1994 .

[13]  James L. Merz,et al.  Formation of self‐assembling CdSe quantum dots on ZnSe by molecular beam epitaxy , 1996 .

[14]  D. Awschalom,et al.  ZERO-DIMENSIONAL EXCITONIC CONFINEMENT IN LOCALLY STRAINED ZN1-XCDXSE QUANTUM WELLS , 1997 .

[15]  Weimann,et al.  Quantum dots formed by interface fluctuations in AlAs/GaAs coupled quantum well structures. , 1994, Physical review letters.