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Your search keyword '"Ager, J. W."' showing total 4 results
Start Over Author "Ager, J. W." Publisher purdue university
4 results on '"Ager, J. W."'

1. Isotopic dependence of the E-0 ' and E-1 direct gaps in the electronic band structure of Si

Author

Tsoi, S., Rodriguez, S., Ramdas, A. K., Ager, J. W., Riemann, H., and Haller, E. E.

Subjects
temperature-dependence, interband transitions, silicon, semiconductors, electroreflectance, ge, modulation, spectra
Abstract

The E-0(') direct transition of Si between its valence band maximum (Gamma(8)(+)) and conduction band minimum (Gamma(6)(-)) and the E-1 direct transition along < 111 > are studied in isotopically enriched Si-28, Si-29, and Si-30 employing photomodulated reflectivity. Their energies (E-G) at low temperature are found to increase with increasing isotopic mass (M) according to E-G(M)=E-G(infinity)-CM-1/2, as predicted in the theory for band gap renormalization by zero-point vibrations through electron-phonon interaction and volume changes associated with anharmonicity. Here E-G(infinity) is the energy gap of the "infinitely" massive isotope, free of renormalization effects.

Published
2005

2. Electron-phonon renormalization of electronic band gaps of semiconductors: Isotopically enriched silicon

Author

Tsoi, S., Alawadhi, H., Lu, X., Ager, J. W., Liao, C. Y., Riemann, H., Haller, E. E., Rodriguez, S., and Ramdas, A. K.

Subjects
Condensed Matter::Materials Science, indirect energy-gap, temperature-dependence, isotope dependence, single-crystal, absorption, diamond, si, ge, luminescence, germanium, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect
Abstract

Photoluminescence and wavelength-modulated transmission spectra displaying phonon-assisted indirect excitonic transitions in isotopically enriched Si-28, Si-29, Si-30, as well as in natural Si, have yielded the isotopic mass (M) dependence of the indirect excitonic gap (E-gx) and the relevant phonon frequencies. Interpreting these measurements on the basis of a phenomenological theory for (partial derivativeE(gx)/partial derivativeM), we deduce E-gx(M=infinity)=(1213.8+/-1.2) meV, the purely electronic value in the absence of electron-phonon interaction and volume changes associated with anharmonicity.

Published
2004

3. Composition dependence of the hydrostatic pressure coefficients of the bandgap of ZnSe1-xTex alloys

Author

Wu, J., Walukiewicz, W., Yu, K. M., Shan, W., Ager, J. W., Haller, E. E., Miotkowski, I., Ramdas, A. K., Su, C. H., Wu, J., Walukiewicz, W., Yu, K. M., Shan, W., Ager, J. W., Haller, E. E., Miotkowski, I., Ramdas, A. K., and Su, C. H.

Abstract

Optical absorption experiments were performed using diamond-anvil cells to measure the hydrostatic pressure dependence of the fundamental bandgap of ZnSe1-xTex alloys over the entire composition range. The first- and second-order pressure coefficients were obtained as a function of composition. The coefficients do not vary linearly between the ZnSe and ZnTe end-point values. Starting from the ZnSe side, the magnitude of both coefficients increases slowly until xapproximate to0.7, which is the point where the ambient-pressure bandgap shows a minimum. At larger values of x the coefficients rapidly approach the values of ZnTe. The large deviations of the pressure coefficients from the linear interpolation between ZnSe and ZnTe are explained in terms of the band anticrossing model.

Published
2003

4. Origin of the large band-gap bowing in highly mismatched semiconductor alloys

Author

Wu, J., Walukiewicz, W., Yu, K. M., Ager, J. W., Haller, E. E., Miotkowski, I., Ramdas, A. K., Su, C. H., Sou, I. K., Perera, R. C. C., Denlinger, J. D., Wu, J., Walukiewicz, W., Yu, K. M., Ager, J. W., Haller, E. E., Miotkowski, I., Ramdas, A. K., Su, C. H., Sou, I. K., Perera, R. C. C., and Denlinger, J. D.

Abstract

Photomodulated reflection, optical absorption, and photoluminescence spectroscopies have been used to measure the composition dependence of interband optical transitions in ZnSe1-xTex and ZnS1-xTex alloys. The results reveal entirely different origins of the large band-gap bowing for small and large Te content. On the Te-rich side, the reduction of the band gap is well explained by the band anticrossing interaction between the Se or S localized states and the ZnTe conduction-band states. On the Se- or S-rich side, an interaction between the localized Te states and the degenerate Gamma valence bands of ZnSe or ZnS is responsible for the band-gap reduction and the rapid increase of the spin-orbit splitting with increasing Te concentration. Results of the soft-x-ray emission experiment provide direct proof of the valence-band anticrossing interaction. The band-gap bowing in the entire composition range is accounted for by a linear interpolation between the conduction-band anticrossing and valence-band anticrossing models.

Published
2003

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