TY  - JOUR
A1  - Schubert, D.W.
A1  - Kraus, M.M
A1  - Kenklies, R.
A1  - Becker, Charles R.
A1  - Bicknell-Tassius, R.N.
T1  - Composition and wavelength dependence of the refractive index in Cd\(_{1-x}\)Mn\(_x\)Te epitaxial layers
N2  - We have investigated Cd\(_{1-x}\)Mn\(_x\)Te thin films with Mn concentrations of x=0.12, 0.18, 0.30, 0.52, and 0.70. These single crystal layers were grown by molecular beam epitaxy on [001] CdTe substrates. The real part of the refractive index, n, was determined below the band-gap Eo in the range of 0.5-2.5 eV at T=300 K. The parallel reOectivity was measured near the Brewster angle at the YAG laser wavelength of 1.064 J.Lm (hv= 1.165 eV). Combining these results with the optical pathlength results (nd) of reOection measurements in a Fourier spectrometer we have determined n(x,v) over a wide spectral range by utilizing a three parameter fit. The accuracy of these results for n should improve waveguide designs based on this material.
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37716
ER  - 
TY  - JOUR
A1  - Becker, Charles R.
A1  - He, L.
A1  - Einfeldt, S.
A1  - Wu, Y. S.
A1  - Lérondel, G.
A1  - Heinke, H.
A1  - Oehling, S.
A1  - Bicknell-Tassius, R. N.
A1  - Landwehr, G.
T1  - Molecular beam epitaxial growth and characterization of (100) HgSe on GaAs
N2  - In this paper, we present results on the first MBE growth of HgSe. The influence of the GaAs substrate temperature as well as the Hg and Se fluxes on the growth and the electrical properties has been investigated. It has been found that the growth rate is very low at substrate temperatures above 120°C. At 120°C and at lower temperatures, the growth rate is appreciably higher. The sticking coefficient of Se seems to depend inversely on the Hg/Se flux ratio. Epitaxial growth could be maintained at 70°C with Hg/Se flux ratios between lOO and ISO, and at 160°C between 280 and 450. The electron mobilities of these HgSe epilayers at room temperature decrease from a maximum value of 8.2 x 10^3 cm2 /V' s with increasing electron concentration. The concentration was found to be between 6xlO^17 and 1.6x10^19 cm- 3 at room temperature. Rocking curves from X-ray diffraction measurements of the better epilayers have a full width at half maximum of 5S0 arc sec.
KW  - Physik
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-50947
ER  - 
TY  - JOUR
A1  - Greiner, P.
A1  - Polignone, L.
A1  - Becker, Charles R.
A1  - Geick, R.
T1  - Contactless measurement of the conductivity of II-VI epitaxial layers by means of the partially filled waveguide method
N2  - We report the contactless determination of the conductivity, the mobility and the carrier concentration of II-VI semiconductors by means of the technique of the partially filled waveguide at a microwave frequency of 9 GHz. The samples are CdHgTe epitaxial layers, grown on CdZnTe substrates by molecular beam epitaxy. The conductivity is determined from the transmission coefficient of the sample in the partially filled waveguide. For the analysis of the experimental data, the complex transmission coefficient is calculated by a rigorous multi-mode matching procedure. By varying the conductivity of the sample, we obtain an optimum fit of the calculated data to the experimental results. Comparison with conductivity data determined by the van der Pauw method shows that our method allows to measure the conductivity with good accuracy. The behaviour of the transmission coefficient of the sample is discussed in dependence on the layer conductivity, the layer thickness and the dielectric constant of the substrate. The calculations require to consider in detail the distribution of the electromagnetic fields in the sample region. The usual assumption of a hardly disturbed TE\(_{10}\) mode cannot be used in our case. By applying a magnetic field in extraordinary Voigt configuration. galvanomagnetic measurements have been carried out which yield the mobility and thus the carrier concentration. These results are also in good agreement with van der Pauw transport measurements.
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37838
ER  - 
TY  - JOUR
A1  - Becker, Charles R.
A1  - Lau, Ph.
A1  - GEICK, R.
A1  - Wagner, V.
T1  - Antiferromagnetic Resonance in NiO:Co\(^{2+}\) and NiO:Fe\(^{2+}\)
N2  - No abstract available.
Y1  - 1975
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-30772
ER  - 
TY  - JOUR
A1  - Shanjia, Xu
A1  - Xinzhang, Wu
A1  - Boege, P.
A1  - Schäfer, H.
A1  - Becker, Charles R.
A1  - Geick, R.
T1  - Scattering characteristics of 3-D discontinuity consisting of semiconductor sample filled in waveguide with gaps
N2  - No abstract available
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37964
ER  - 
TY  - JOUR
A1  - Shanjia, Xu
A1  - Xinzhang, Wu
A1  - Greiner, P.
A1  - Becker, Charles R.
A1  - Geick, R.
T1  - Microwave transmission and reflection of stratified lossy dielectric segments partially filled waveguide
N2  - The microwave transmission and reßection is evaluated for stratified lossy dielectric segments partially filling the rectangular waveguide by the method which combines the multimode network theory with the rigorous mode matching procedure. As an example, we investigate in detail the microwave scattering properties of II-VI-epitaxial layer on a lossy dielectric substrate inserted in the rectangular waveguide. The experimental data verify the accuracy and the effectiveness of the present method. Extensive numerical results are presented to establish useful guidelines for the contactless microwave measurement of the conductivity of the epitaxiallayer.
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37958
ER  - 
TY  - JOUR
A1  - Wu, Y. S.
A1  - Becker, Charles R.
A1  - Waag, A.
A1  - Bicknell-Tassius, R. N.
A1  - Landwehr, G.
T1  - Thermal effects on (100) CdZnTe substrates as studied by x-ray photoelectron spectroscopy and reflection high energy electron diffraction
N2  - The influence of different CdZnTe substrate treatments prior to II-VI molecular beam epitaxial growth on surface stoichiometry, oxygen, and carbon contamination has been studied using x-ray photoelectron spectroscopy and reflection high energy electron diffraction. Heating the substrate at 300 °C can eliminate oxygen contamination, but cannot completely remove carbon from the surface. Heating at higher temperatures decreases the carbon contamination only slightly, while increasing the Zn-Cd ratio on the surface considerably. The magnitude of the latter effect is surprising and is crucial when one is using lattice matched CdZnTe (Zn 4%) substrates.
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37801
SN  - 0003-6951
ER  - 
TY  - JOUR
A1  - Wu, Y. S.
A1  - Becker, Charles R.
A1  - Waag, A.
A1  - von Schierstedt, K.
A1  - Bicknell-Tassius, R. N.
A1  - Landwehr, G.
T1  - Surface sublimation of zinc blende CdTe
N2  - The surface sublimation of Cd and Te atoms from the zinc blende (111)A CdTe surface has been investigated in detail by reflection high energy electron diffraction and x-ray photoelectron spectroscopy. These experiments verify that Te is much easier to evaporate than Cd. The experimental value for the Te activation energy from a Te stabilized (111)A CdTe surface is 1.41 ±0.1O eV, which is apparently inconsistent with recent theoretical results.
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37829
ER  - 
TY  - JOUR
A1  - He, L.
A1  - Becker, Charles R.
A1  - Bicknell-Tassius, R. N.
A1  - Scholl, S.
A1  - Landwehr, G.
T1  - Molecular beam epitaxial growth of (100) Hg\(_{0.8}\)Cd\(_{0.2}\)Te on Cd\(_{0.96}\)Zn\(_{0.04}\)Te
N2  - No abstract available
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-38044
ER  - 
TY  - JOUR
A1  - Rösch, M.
A1  - Atzmüller, R.
A1  - Schaack, G.
A1  - Becker, Charles R.
T1  - Resonant Raman scattering in a zero-gap semiconductor: Interference effects and deformation potentials at the E\(_1\) and E\(_1\) + \(\Delta_1\) gaps of HgTe
N2  - No abstract available
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-38062
ER  - 
TY  - JOUR
A1  - Wu, Y. S.
A1  - Becker, Charles R.
A1  - Waag, A.
A1  - Bicknell-Tassius, R. N.
A1  - Landwehr, G.
T1  - Removal of oxygen and reduction of carbon contamination on (100) Cd\(_{0.96}\)Zn\(_{0.04}\)Te
N2  - No abstract available
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-38014
ER  - 
TY  - JOUR
A1  - He, L.
A1  - Becker, Charles R.
A1  - Bicknell-Tassius, R. N.
A1  - Scholl, S.
A1  - Landwehr, G.
T1  - Molecular beam epitaxial growth and evaluation of intrinsic and extrinsically doped (100) Hg\(_{0.8}\)Cd\(_{0.2}\)Te on (100) Cd\(_{0.96}\)Zn\(_{0.04}\)Te
N2  - No abstract available.
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37885
ER  - 
TY  - JOUR
A1  - Kraus, M. M.
A1  - Regnet, M. M.
A1  - Becker, Charles R.
A1  - Bicknell-Tassius, R. N.
A1  - Landwehr, G.
T1  - Comparison of band structure calculations and photoluminescence experiments on HgTe/CdTe superlattices grown by molecular beam epitaxy
N2  - We have grown HgTe/CdTe superlattices by molecular beam epitaxy; barrier thicknesses were in the range from 15 to 91 Å and the well thickness was maintained at a constant value of 30 Å. 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).
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37878
ER  - 
TY  - JOUR
A1  - Wu, Y. S.
A1  - Becker, Charles R.
A1  - Waag, A.
A1  - Schmiedl, R.
A1  - Einfeldt, S.
A1  - Landwehr, G.
T1  - Oxygen on the (100) CdTe surface
N2  - We have investigated oxygen on CdTe substrates by means of x-ray photoelectron spectroscopy (XPS) and reflection high-energy electron diffraction (RHEED). A Te oxide layer that was at least 15 A thick was found on the surface of as-delivered CdTe substrates that were mechanically polished. This oxide is not easily evaporated at temperatures lower than 350°C. Furthermore, heating in air, which further oxidizes the CdTe layer, should be avoided. Etching with HCI acid (15% HCl) for at least 20 s and then rinsing with de-ionized water reduces the Te oxide layer on the surface down to 4% of a monoatomic layer. However, according to XPS measurements of the 0 Is peak, 20%-30% of a monoatomic layer of oxygen remains on the surface, which can be eliminated by heating at temperatures ranging between 300 and 340 cC. The RHEED patterns for a molecular beam epitaxially (MBE)-grown CdTe film on a (lOO) CdTe substrate with approximately one monoatomic layer of oxidized Te on the surface lose the characteristics of the normal RHEED pattems for a MBE-grown CdTe film on an oxygen-free CdTe substrate.
Y1  - 1993
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37869
ER  - 
TY  - CHAP
A1  - Boege, P.
A1  - Schäfer, H.
A1  - Shanjia, Xu
A1  - Xinzhang, Wu
A1  - Einfeldt, S.
A1  - Becker, Charles R.
A1  - Hommel, D.
A1  - Geick, R.
T1  - Improved conductivity-measurement of semiconductor epitaxial layers by means of the contactless microwave method
N2  - Measurements and calculations of the scattering-characteristics of stratified lossy dielectric blocks completely filling a waveguide cross section are presented. The method is used for contactless conductivity measurements of MBE-grown II-VI semiconductor layers.
KW  - Millimeterwelle
KW  - Kongreß
KW  - San Diego <Calif.
KW  - 1994>
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37763
ER  - 
TY  - JOUR
A1  - Wu, Y.S.
A1  - Becker, Charles R.
A1  - Waag, A.
A1  - Kraus, M. M.
A1  - Bicknell-Tassius, R. N.
A1  - Landwehr, G.
T1  - Correlation of the Cd-to-Te ratio on CdTe surfaces with the surface structure
N2  - 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.
KW  - Festkörperphysik
Y1  - 1991
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37789
SN  - 0163-1829
ER  - 
TY  - CHAP
A1  - Bicknell-Tassius, R. N.
A1  - Scholl, S.
A1  - Becker, Charles R.
A1  - Landwehr, G.
T1  - High magnetic field transport in II-VI heterostructures
N2  - In the present work we report the results of magneto-transport measurements on some Hg-based li-VI semiconductor epitaxiallayers grown by molecular beam epitaxy. The transport measurement were carried out at temperatures in the range 0.4 - 4.2 K in magnetic fields up to 10.0 T. Further, we point out the necessity of using multicarrier models for data interpretation and show finally some Shubnikov-de-Haas results on sampies with high mobility carners.
Y1  - 1992
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-37797
ER  - 
TY  - JOUR
A1  - Geis, G.
A1  - Geick, R.
A1  - Becker, Charles R.
A1  - Wagner, V.
T1  - Antiferromagnetic resonance in CoO/NiO mixed crystals
N2  - We have studied the lowest magnetic excitation of Ni\(_{1-x}\)Co\(_x\)O mixed crystals for 0.94 \(\leq\) x \(\leq\) 1. Together with previous results for 0.02 \(\leq\) x \(\leq\) 0.07 and neutron data for x = 0.14 and x = 0.30, the results are discussed by means of a model, especially the variation of AFMR frequency and preferred spin direction with Co concentration x.
Y1  - 1977
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-31239
ER  - 
TY  - JOUR
A1  - Wu, Y. S.
A1  - Becker, Charles R.
A1  - Waag, A.
A1  - Bicknell-Tassius, R. N.
A1  - Landwehr, G.
T1  - The effects of laser illumination and high energy electrons on molecular-beam epitaxial growth of CdTe
N2  - We report the results of a detailed investigation on the Te-stabilized (2 x 1) and the Cdstabilized c( 2 X 2) surfaces of ( 100) CdTe substrates. The investigation demonstrates for the first time that both laser illumination and, to a greater extent, high-energy electron irradiation increase the Te desorption and reduce the Cd desorption from ( 100) CdTe surfaces. Thus it is possible by choosing the proper growth temperature and photon or electron fluxes to change the surface reconstruction from the normally Te-stabilized to a Cd-stabilized phase.
Y1  - 1991
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-30795
ER  - 
TY  - JOUR
A1  - Xu, Shanjia
A1  - Sheng, Xinqing
A1  - Greiner, P.
A1  - Becker, Charles R.
A1  - Geick, R.
T1  - High-order finite-element analysis of scattering properties of II-VI semiconductor materials
N2  - The sattering characteristics ot the n-VI semiconductors were analyzed by a method which combines the second-order finite-element method with the rigorous mode matching procedure. The method avolds the difficulty of solving the complex transcendental equation introduced in the multimode network method and calculates all the eigenvalues and eigenfunctions simultaneously which are needed for the mode matching treatment in the longitudinal direction. As a result, the whole solution procedure is significantly simplified. A comparison is given between the experimental data and the calculated results obtained with this analysis and tbe network method. Very good agreement has been achieved, the accuracy and efficiency of the present method are thus verified.
KW  - Halbleiter
KW  - II-VI semiconductor
KW  - scattering characteristics
KW  - high-order finite element
KW  - mode matching method
Y1  - 1994
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86283
ER  -