Band gap energy and binding energies of Z3-excitions in CuCl

Saito, Koya; Hasuo, Masahiro; Hatano, T.; Nagasawa, Nobukata

doi:10.1016/0038-1098(95)00007-0

Cited by 47 publications

(30 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The calculated transition energy to the (2P, 1s) state as a function of the dot size is plotted by the solid curve in Fig. 4, together with our experimental value (closed circle), the experimental data from [3] (open circles), and that for bulk crystals [8] (dashed line). The peak energy of the IRTA originating from the biexciton eventually Photon Energy (meV) Fig.…”

mentioning

confidence: 97%

See 1 more Smart Citation

Infrared transient absorption of excitons and biexcitons confined in CuCl quantum dots

Miyajima

Edamatsu

Itoh

2003

phys. stat. sol. (c)

View full text Add to dashboard Cite

We have measured the mid-infrared transient absorption of CuCl quantum dots embedded in a NaCl matrix with picosecond temporal resolution. The transient absorption exhibited two decay components that are attributable to confined excitons and biexcitons. This result indicates the existence of stable excited states of biexcitons confined in the quantum dots, although the energy separation between the ground and excited states of a biexciton is larger than its binding energy in bulk crystals.1 Introduction The optical properties of semiconductor quantum dots (QDs) have attracted much interest in recent years. The three-dimensional confinement of electrons and holes dramatically changes the electronic structure with a continuous energy spectrum in bulk crystals to that with discrete energy levels in QDs. To date, the optical properties of the lowest-energy state of an electron−hole (e−h) pair (1S Rydberg exciton) confined in QDs have been investigated extensively. However, it is also very important and interesting to study excited-state properties of confined excitons because of larger or anisotropic extension of their wavefunctions. In QDs, the transitions between sublevels of confined excitons are expected to show large optical nonlinearity because of the discrete energy levels and large correlation between excited carriers that are spatially confined in a QD. Utilizing this nonlinearity, the optical response concerned with the confined excited states is applicable to novel infrared (IR) optical devices. A number of studies on the excited exciton states were carried out in materials in the 'strong-confinement' regime, in which the properties of confined excitons are much different from those of free excitons in bulk crystals [1,2]. On the other hand, there are fewer reports on the excited exciton states in the 'weakconfinement' regime, in which the quantum confinement affects essentially the center-of-mass motion of the excitons with less influence on the relative motion of the e−h pair.CuCl QDs show a typical character of the weak confinement because of the very small exciton Bohr radius a B = 0.7 nm. For CuCl QDs, the infrared transient absorption (IRTA) ascribed to the transition from the lowest Rydberg 1S state to the 2P state of the confined exciton was observed and the results showed that the Rydberg energy of the confined exciton depends on the size of the QD [3,4]. However, there are a number of unresolved questions to be clarified. First, since the temporal resolution of the previous measurements was not sufficient to resolve the decay time of the IRTA, the attribution of the IRTA to the confined exciton was still ambiguous. Thus, it is necessary to confirm that the IRTA is actually induced by the exciton, and to examine other possibilities of the origin of the IRTA. Especially, it is interesting to examine the excited states of the confined excitons in the case where two or more excitons are created in a QD. Second, the observed IRTA spectra had large spectral widths and the absorption

show abstract

mentioning

confidence: 97%

“…The solid line indicates the theoretical transition energy from 1S to 2P exciton states [4,7]. The broken line indicates that for the bulk crystal [8].…”

mentioning

confidence: 98%

Infrared transient absorption of excitons and biexcitons confined in CuCl quantum dots

Miyajima

Edamatsu

Itoh

2003

phys. stat. sol. (c)

View full text Add to dashboard Cite

show abstract

“…CuCl is an appropriate material for the study of fundamental properties of the exciton and biexciton since they are very stable because of their large binding energy (197 meV for the exciton [2] and 32 meV for the biexciton [4]) compared to the other semiconductors. The exciton Rydberg states have been investigated by one-and twophoton absorption measurements [2].…”

mentioning

confidence: 99%

“…This energy structure can be observed by two methods. One is the one-and two-photon absorption measurements to detect the exciton states associated with Rydberg s-and p-series [2]. The other is a transient absorption from the lowest 1s state to the excited states associated with p-series [3].…”

mentioning

confidence: 99%

Infrared transient absorption spectra for excited transition of excitons and biexcitons in CuCl

Yoshioka

Miyajima

Ashida

et al. 2008

Phys. Status Solidi (c)

View full text Add to dashboard Cite

Infrared transient absorption (IRTA) spectra for excitons and biexcitons in CuCl bulk crystal have been measured by pump‐probe spectroscopy. The IRTA peak energy of the exciton agrees with the transition energy between Rydberg 1s to 2p states reported in one‐ and two‐photon absorption measurement. On the other hand, the IRTA peak energy of the biexcitons locates in energy higher than that of the excitons, which is reasonable by taking hydrogen molecule model into account. In addition, our results support the enhancement of the transition energy between 1s and 2p states in quantum dots compared to the bulk case. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

show abstract

“…In GaAs quantum well [1,2] and type II superlattices [3], the binding energy of biexcitons over 2 meV has been observed, whereas in ZnSe quantum well [4] and CuCl single crystals [5][6][7] much higher binding energies have been measured. The first observation of biexcitons was made by Haynes [8] in crystalline silicon, and on the basis of his previous work on a neutral donor complex [9], Haynes used the ratio of the binding energy of a biexciton (E xx b ) to that of an exciton (E x b ) in silicon as 0.1.…”

mentioning

confidence: 99%

On the validity of Haynes rule for the binding of excitonic complexes in low dimensions

Singh

1998

Phys. Solid State

View full text Add to dashboard Cite

Using a two-dimensional geometrical model and fractional dimension approach, it is found analytically that the ratio of the binding energy of a biexciton to that of an exciton is 0.228 in quantum wells and it is independent of the quantum well width. This agrees very well with the results in GaAs and ZnSe quantum wells, and CuCl crystals and large quantum dots. It is suggested that while Haynes rule may be valid for bulk, much higher ratios may be expected in lower dimensions. 1.Much interest has recently generated in studying the excitonic complexes like biexcitons and trions in narrow dimensions, because of their applications in quantum confined optoelectronic devices. In GaAs quantum well in silicon as 0.1. Eversince this ratio, commonly known as the Haynes Rule, has been assumed to be applicable for all solids, including quantum wells [10]. However, as biexcitons are observed more frequently in confined systems, a desirable question arises if there is a constant ratio for the binding energy of a biexciton to that of an exciton, which can be applied for both bulk and confined systems.In this paper we have presented a brief account of determining the ratio of the binding energy of quasi-two-dimensional biexcitons to that of an exciton analytically [11] using the fractional dimension approach [12], and compared it with some of the known experimental results on quantum wells. As the Bohr radius of biexcitons is much larger than that of excitons, it may be expected that the effect of confinement will be more pronounced on biexcitons than on excitons. Therefore, while the Haynes rule may be regarded as applicable in bulk crystals, a higher ratio may be expected in lower dimensions.2. In quantum wells of widths smaller than the biexcitonic diameter, a biexciton is confined into a 2D space. In this situation a planar square geometrical configuration [11] for the electrons and holes involved in the formation of a biexciton can be assumed. Assuming that the quantum well plane is parallel to the xy-plane, the 2D biexciton is free to move only in this plane. Transforming the Hamiltonian of such a geometrical structure into the six relative co-ordinates and a centre of mass coordinate, we get the biexciton Hamiltonian as [11]where are the Laplacians with respect to the relative co-ordinates between electron and hole, electron and electron, and hole and hole, respectively, and ∇ 2 R is that with respect to the centre of mass co-ordinate. V is the Coulomb potential of interaction among the electrons and holes of the biexciton. Applying another co-ordinate transformation to the relative co-ordinates that ensures a square structure of the 2D biexciton, the Hamiltonian (1) reduces into [11]where µ xx = 2 3 µ eh , ε xx = √ 2/(4 − √ 2) ε, and ε is the dielectric constant of the material. The kinetic energy operator of the centre of mass motion is excluded from the Hamiltonian (2). The energy eigenvalue of the Hamiltonian (2) can be obtained be applying the fractional dimension approach [12] in solving the following Schrödinger ...

show abstract

Band gap energy and binding energies of Z3-excitions in CuCl

Cited by 47 publications

References 12 publications

Infrared transient absorption of excitons and biexcitons confined in CuCl quantum dots

Infrared transient absorption of excitons and biexcitons confined in CuCl quantum dots

Infrared transient absorption spectra for excited transition of excitons and biexcitons in CuCl

On the validity of Haynes rule for the binding of excitonic complexes in low dimensions

Contact Info

Product

Resources

About