Band parameters of CdS and CdSe single crystals determined from optical exciton spectra

Voigt, J.; Spiegelberg, F.; Senoner, Mathias

doi:10.1002/pssb.2220910120

Cited by 116 publications

(34 citation statements)

References 18 publications

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“…14 There is a substantial literature of optical studies of CdS designed to extract the parameters of exciton polaritons. 15 These studies are in good agreement with the present results after due account is taken of Ref. 13.…”

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confidence: 94%

Measurement of the damping dispersion of exciton polaritons in CdS

Dagenais¹,

Sharfin²

1987

Phys. Rev. Lett.

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At 2 K, at low intensity, and in good-quality samples, the source of the exciton-polariton dipole dephasing time (or phase-coherence time) is found to be extrinsic in nature and due to dephasing elastic collisions for excitation below the transverse-^-exciton frequency, and purely intrinsic and due to quasielastic collisions with acoustical phonons for excitation above the longitudinal-^4-exciton frequency. The damping increases linearly with detuning for excitation above the longitudinal-^-exciton frequency.PACS numbers: 72.10.Di, 78.50.Ge In this Letter, we report detailed measurements and a comprehensive study of the damping dispersion of both the A and B exciton polaritons in CdS over a wide frequency range. We identify the source of the damping and we demonstrate for the first time that, at low temperatures and in high-quality samples, the source of the damping is completely different for excitation above and below the lowest transverse-exciton frequency (w^). It is found that the damping below the co TA frequency is extrinsic in nature and is governed by the impurity (and point defects) content of the sample. Above the coj A resonance, the dephasing is intrinsic and the results can be well explained by an exciton-acoustic-phonon interaction through the deformation-potential mechanism. This leads to a damping coefficient above the CO T A frequency proportional to the detuning from the COTA resonance. These results challenge the common use of a constant, detuning-independent, phenomenological damping coefficient in the expression of the exciton contribution to the complex dielectric function. Our approach for extracting the exciton-polariton damping is based on the precise measurement of the optical transmission of high-quality CdS platelets. By working in a spectral region away from the longitudinal (&>/,) and transverse (COT) excitons, the present study deliberately avoids the need of determining the correct additional boundary condition and the appropriate dead-layer thickness. 1,2 Given the sample thickness and purity used in the experiment, the additional wave is of too small amplitude to perturb significantly the observed Fabry-Perot fringes. Future work in and around the CO L T region should provide a means of testing different additional boundary conditions, as was already suggested by Broser, Pantke, and Rosenzweig, 3 but this is not the present intent.We have restricted our present studies in CdS to light polarized perpendicular to the c axis and to frequencies around the A and B excitons. The dispersion relation, expressed by the dielectric function e(k,co), is given by the following expression 4 " 6 :

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confidence: 94%

Measurement of the damping dispersion of exciton polaritons in CdS

Dagenais¹,

Sharfin²

1987

Phys. Rev. Lett.

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“…These results are summarized in Table I, together with those reported in the literature. 8,9,38,39 There are two additional structures K and I observed in the lower energy side of the PR spectra ͑Figs. 5 and 6͒.…”

Section: ͑6͒mentioning

confidence: 97%

Photoreflectance spectroscopy of wurtzite CdS

Imada

Ozaki

Adachi

2002

Journal of Applied Physics

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Photoreflectance (PR) spectra have been measured to determine the lowest direct-band edge E0α (α=A, B, and C) of wurtzite CdS single crystal in the temperature range T=13–300 K for both E⊥c and E∥c polarizations. The measured PR spectra can be interpreted by the three-dimensional (3D) excitonic plus one-electron line shapes over the entire temperature range. The temperature dependence of the excitonic and critical-point parameters (energy, amplitude, and broadening parameter) have been determined and analyzed using the Varshni [Physica (Amsterdam) 34, 149 (1967)] equation and an analytical four-parameter expression recently developed for the explanation of the band-gap shrinkage effect in semiconductors. The 3D- exciton binding energies have also been determined to be 27 (A), 31 (B), and 30 meV (C), respectively.

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“…As seen from this transition scheme, there is a complete agreement concerning the number of lines, their succession as well as their q-dependence. 5) The constant G was determined from the oscillator strength of the free A-exciton: fex = = 2.56 x [19]. Accepting such an explanation of the excited states the observation of distinct a-and b-lines represents to our knowledge the first experimental proof of the A-B coupling in CdS.…”

Section: Y(ro Rh R H ) = V L S ( R E ) M 1 8 ( R I ) X(rh)mentioning

confidence: 99%

Excited states of bound excitons in wurtzite‐type semiconductors

Puls¹,

Henneberger²,

Voigt

1983

Physica Status Solidi (b)

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Excitons bound to neutral impurities are studied with respect to excited states by means of excitation spectroscopy in CdS single crystals a t 1.8 K. The symmetry of the four excited states of the exciton bound to neutral donor (placed energetically below the free exciton) can be deduced from the observed dependence of their optical transitions on the direction of the wave vector and the polarization. Theoretical considerations taking into account the complex valence band structure of wurtzite-type semiconductors lead to an explanation of these states in terms of excited (p-and d-like) hole states of the bound exciton. With respect to the exciton bound t o neutral acceptor only the well-known I1B-states are found experimentally arising from the incorporation of a hole from the lower B-subvalence band in the complex. Mit Hilfe der Anregungsspektroskopie werden angeregte Zustiinde von gebundenen Exzitonen in

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Band parameters of CdS and CdSe single crystals determined from optical exciton spectra

Cited by 116 publications

References 18 publications

Measurement of the damping dispersion of exciton polaritons in CdS

Measurement of the damping dispersion of exciton polaritons in CdS

Photoreflectance spectroscopy of wurtzite CdS

Excited states of bound excitons in wurtzite‐type semiconductors

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