@article{BeckerWuWaagetal.1991,
  author    = {Becker, Charles R. and Wu, Y. S. and Waag, A. and Kraus, M. M. and Landwehr, G.},
  title     = {The orientation independence of the CdTe-HgTe valence band offset as determined by x-ray photoelectron spectroscopy},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-30784},
  year      = {1991},
  abstract  = {No abstract available},
  language  = {en}
}
@article{BeckerLatussekHeinkeetal.1993,
  author    = {Becker, Charles, R. and Latussek, V. and Heinke, H. and Regnet, M. M. and Goschenhofer, F. and Einfeldt, S. and He, L. and Bangert, E. and Kraus, M. M. and Landwehr, G.},
  title     = {Molecular beam epitaxial growth and characterization of (001) Hg\(_{1-x}\) Cd\(_x\) Te-HgTe superlattices},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-50959},
  year      = {1993},
  abstract  = {The molecular beam epitaxially growth of (001) Hg\(_{1-x}\) Cd\(_z\) Te-HgTe superlattices has been systematically investigated. The well width as well as the period were determined directly by X-ray diffraction. This was accomphshed for the well width by exploiting the high reflectivity from HgTe and the low reflectivity from CdTe for the (002) Bragg reflection. Knowing the well and barrier thicknesses we have been able to set an upper limit on the aver~ge composition of the barriers, Xl, by annealing the superlattice and then measuring the composition of the. resultmg alloy. Xb was shown to decrease exponentially with decreasing barrier width. Xb is appreciably smaller m. narrow barriers due to the increased significance of interdiffusion in the Hg\(_{1-x}\)Cd\(_x\) Te/HgTe interface in narrow barriers. The experimentally determined optical absorption coefficient for these superlattices is compared WIth theoretical calculations. The absorption coefficient was determined from transmission and reflection spectra at 300, 77 and 5 K. Using the thickness and composition of the barriers and wells, and an interface width due to interdiffusion, the complex refractive index is calculated and compared with the experimental absorption coefficient. The envelope function method based on an 8 x 8 second order k . p band model was used to calculate the superlattice states. These results when inserted into Kubo's formula, yield the dynamic conductivity for interband transitions. The experimental and theoretical values for the absorption coefficient using no adjustable parameters are in good agreement for most of the investigated superlattices. Furthermore the agreement for the higher energetic interband transitions is much worse if values for the barrier composition, which are appreciably different than the experimentally determined values, are used. The infrared photoluminescence was investigated at temperatures from 4.2 to 300 K. Pronounced photoluminescence was observed for all superlattices in this temperature range.},
  subject      = {Physik},
  language  = {en}
}
@article{KrausBeckerScholletal.1993,
  author    = {Kraus, M. M. and Becker, Charles R. and Scholl, S. and Wu, Y. S. and Yuan, S. and Landwehr, G.},
  title     = {Infrared photoluminescence on molecular beam epitaxially grown Hg\(_{1-x}\)Cd\(_x\)Te layers},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-38053},
  year      = {1993},
  abstract  = {No abstract available},
  language  = {en}
}
@article{WuBeckerWaagetal.1991,
  author    = {Wu, Y.S. and Becker, Charles R. and Waag, A. and Kraus, M. M. and Bicknell-Tassius, R. N. and Landwehr, G.},
  title     = {Correlation of the Cd-to-Te ratio on CdTe surfaces with the surface structure},
  isbn      = {0163-1829},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37789},
  year      = {1991},
  abstract  = {We report here that reconstruction on (100), (1lIlA, and (1l1lB CdTe surfaces is either C(2X2), (2X2), and (l X I) or (2X I), (l X I), and (l X I) when they are Cd or Te stabilized, respectively. There is a mixed region between Cd and Te stabilization in which the reflected high-energy electron-diffraction (RHEED) patterns contain characteristics of both Cd- and Te-stabilized surfaces. We have also found that the Cd-to-Te ratio of the x-ray photoelectron intensities of their 3d\(_{3/ 2}\) core levels is about 20\% larger for a Cd-stabilized (1lIlA, (1lIlB, or (100) CdTe surface than for a Te-stabilized one. According to a simple model calculation, which was normalized by means of the photoelectron intensity ratio of a Cd-stabilized (lll)A and aTe-stabilized (1l1lB CdTe surface, the experimental data for CdTe surfaces can be explained by a linear dependence of the photoelectron-intensity ratio on the fraction of Cd in the uppermost monatomic layer. This surface composition can be correlated with the surface structure, i.e., the corresponding RHEED patterns. This correlation can in turn be employed to determine Te and Cd evaporation rates. The Te reevaporation rate is increasingly slower for the Te-stabilized (Ill) A, (l1l)B, and (100) surfaces, while the opposite is true for Cd from Cd-stabilized (Ill) A and (Ill)B surfaces. In addition, Te is much more easily evaporated from all the investigated surfaces than is Cd, if the substrate is kept at normal molecular-beam-epitaxy growth temperatures ranging from 2oo·C to 300 ·C.},
  subject      = {Festk{\"o}rperphysik},
  language  = {en}
}
@article{KrausRegnetBeckeretal.1992,
  author    = {Kraus, M. M. and Regnet, M. M. and Becker, Charles R. and Bicknell-Tassius, R. N. and Landwehr, G.},
  title     = {Comparison of band structure calculations and photoluminescence experiments on HgTe/CdTe superlattices grown by molecular beam epitaxy},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37878},
  year      = {1992},
  abstract  = {We have grown HgTe/CdTe superlattices by molecular beam epitaxy; barrier thicknesses were in the range from 15 to 91 {\AA} and the well thickness was maintained at a constant value of 30 {\AA}. The infrared photoluminescence was investigated by means of Fourier transform infrared spectroscopy in the temperature range from 4.2 to 300 K. All superlattices showed pronounced photoluminescence at temperatures up to 300 K. To gain more detailed insight into the band structure of the HgTe/CdTe superlattices, band structure calculations were performed. The concept of the envelope function approximation was followed. Employing the transfer matrix method, the calculations were completed taking into account an eight band k·p model. An important parameter in these calculations is the natural valence band offset (VBO) between the well and barrier materials. As a general trend, the value for the direct gap decreases with increasing VBO. The experimentally determined energies of the band gap are in reasonable agreement with the values obtained by the theoretical calculations. A comparison between theory and experiment shows that the observed transition energies are closer to calculations employing a large offset (350 meV) as opposed to a small VBO (40 meV).},
  language  = {en}
}
@article{HerrmannHappMoellmannetal.1993,
  author    = {Herrmann, K. H. and Happ, M. and M{\"o}llmann, K.-P. and Tomm, J. W. and Becker, Charles R. and Kraus, M. M. and Yuan, S. and Landwehr, G.},
  title     = {A new model for the absorption coefficient of narrow gap (Hg,Cd)Te that simultaneously considers band tails and band filling},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37894},
  year      = {1993},
  abstract  = {A semiempirical model is presented that correlates the broadening of the absorption edge with both transitions below the energy gap and with transitions by the Kane band model. This model correctly fits both the absorption and luminescence spectra of narrow-gap (Hg,Cd)Te samples that have been grown by the traveling heater method as well as by molecular-beam epitaxy. The accuracy of the band-gap determination is enhanced by this model.},
  language  = {en}
}