Plenarvorträge - DPG-Tagungen

Halbleiterphysik Donnerstag
HL 44.70 Do 16:30 Poster A
Übergangsmetall-Donator Paare in Si — •R. Vianden 1 , D.
Brett 2 , A. Byrne 3 und M. Ridgway 2 — 1 Helmholtz-Institut für
Strahlen- und Kernphysik, Nußallee 14-16, D-53115 Bonn — 2 Dep.
of Electronic Materials Engineering — 3 Dep. of Nuclear Physics,
RSPhysSE, Australian National University, Canberra ACT 0200,
Australia
Die Wechselwirkungen zwischen Übergangsmetallverunreinigungen
und Dotierungsatomen können die Funktion von Halbleiterbauelementen
gravierend beeinflussen. Da die Löslichkeit der Übergangsmetalle in
Halbleitern wie Si und Ge sehr klein ist, ist es oft unmöglich, ihr Verhalten
mit klassischen Methoden zu beobachten. Die Methode der gestörten
γ-γ Winkelkorrelation (PAC) kommt dagegen mit extrem geringen Fremdatomkonzentrationen
aus. Wir haben das PAC-Sondenatom 100 Pd in As
dotiertes Silizium implantiert, um die Wechselwirkung geringer Pd Verunreinigungen
mit den Donatoratomen zu beobachten. Erste Ergebnisse
zeigen, dass bis zu 30% der Pd Sonden an As Donatoratomen eingefangen
werden. Die beobachtete Quadrupolwechselwirkung, νQ = 10,2(1) MHz,
η = 0 und eine 〈111〉 Orientierung des elektrischen Feldgradienten legen
den Einbau auf einem dem As benachbarten substitutionellen Gitterplatz
nahe.
HL 44.71 Do 16:30 Poster A
Ab-initio investigation of the high-pressure phase transition
cd→β-tin under nonhydrostatic pressure in Si and Ge —
•Katalin Gaál-Nagy and Dieter Strauch — Institut für
Theoretische Physik, Universität Regensburg, 93040 Regensburg
In this contribution we present an ab-initio study of the high-pressure
phase transition from the cubic-diamond (cd) to the β-tin phase in Si and
Ge. Our main interest is here the influence of non-hydrostatic pressure
to the transition. In a first step we calculated the full curve of the equation
of state from a enthalpy surface including energies and enthalpies for
the complete set of parameters which are allowed to vary. This the H(p)
curve is calculated by evaluating the hydrostatic pressure concerning the
components of the diagonal stress tensor beeing equal. Next a similar procedure
can be done for non-equal components for non-hydrostatic pressure.
Last we included the effect of strain in our calculations. We find
an essentual lowering of the transition pressure under non-hydrostatic
conditions. The calculations were performed within the framework of
the density functional theory using ultrasoft pseudopotentials and the
local density as well as the generalized gradient approximation for the
exchange-correlation potential implemented in VASP [1].
[1] G. Kresse, J. Furthmüller, Comput. Mat. Scie. 6, 15 (1996)
HL 44.72 Do 16:30 Poster A
Hydrogen-induced platelets in Ge — •Martin Hiller, Edward
Lavrov, and Jörg Weber — Institut für Angewandte Physik - Halbleiterphysik,
TU Dresden, 01062 Dresden
Germanium treated in hydrogen and/or deuterium plasmas has been
investigated by means of Raman scattering at RT. Two Raman lines
at ∼ 2000 and 4150 cm −1 are observed after H-plasma treatment at
150 ◦ C. The former is identified as local vibrational modes (LVMs) of
Ge–H bonds, whereas the latter was shown to originate from a LVM of
H2. Polarization Raman measurements revealed that both lines possess
a trigonal symmetry. Based on this and the similarity of the two signals
in Ge and Si we identify the 2000 cm −1 line as hydrogen-induced {111}
platelets, whereas the 4150 cm −1 line belongs to H2 trapped within these
platelets.
HL 44.73 Do 16:30 Poster A
XRD analysis of Ge- and GexSi1−x-layers grown by surfactant
mediated epitaxy — •T. Wietler and K.R. Hofmann — Institute
for Semiconductor Devices and Electronic Materials, University of
Hannover, Appelstr. 11A, 30167 Hannover, Germany
Strained Si/Ge-heterodevices provide the opportunity to combine enhanced
carrier mobilities with silicon technology. The controlled growth
of relaxed virtual GexSi1−x substrates with high Ge content is a vital precondition
for the fabrication of strained layer structures. By surfactant
mediated epitaxy (SME) employing Sb as surfactant relaxed GexSi1−x
films can be realized.
GexSi1−x films with Ge content variying from x=0.7 to 1 were grown
by SME on Si(111) substrates. The crystalline quality and the degree
of strain relaxation were studied by high resolution X-ray diffraction
(HXRD). X-Ray reflection (XRR) was used to measure the surface roughness
and film thickness. The X-ray analysis results are compared to those
obtained by etch pit density (EPD), auger electron spectroscopy (AES)
depth profiling and atomic force microscopy (AFM).
HL 44.74 Do 16:30 Poster A
Contactless determination of temperature variations in single
junction thermal converters — •V. Schlosser 1 , G. Heine 2 , W.
Waldmann 2 , M. Garcocz 2 , and G. Klinger 3 — 1 Institut für Materialphysik,
Universität Wien — 2 Bundesamt für Eich- und Vermessungswesen,
Wien — 3 Institut für Meteorologie und Geophysik, Universität Wien
The ac-dc transfer standard is one of the basic electrical standards,
by which the ac voltage and ac current are deduced from their dc counterparts.
A well established method is the comparison of electric power
between ac- and dc- voltage by converting the power to force or heat.
Converters may be recognised as reference standard and the system is
called the ”ac-dc transfer standard”. Differences in the signal between
ac- and dc- power generation depend on frequency and waveform. In
the low frequency regime the thermal ripple dominates the error introduced
by the thermal converter. The purpose of this work was to develop
an experimental set up which is capable to record the time dependend
temperature fluctuations caused by ac- currents. The infrared radiation
which is emitted by the heated filament and bead of a thermal converter
was monitored using a scanning infrared radiation imaging set up. The
method will be presented and first results will be discussed.
HL 44.75 Do 16:30 Poster A
Investigations of the local and temporal temperature changes
in precision shunt resistors — •G. Klinger 1 , V. Schlosser 2 , G.
Heine 3 , W. Waldmann 3 , and M. Garcocz 3 — 1 Institut für Meteorologie
und Geophysik, Universität Wien — 2 Institut für Materialphysik,
Universität Wien — 3 Bundesamt für Eich- und Vermessungswesen, Wien
The most accurate determination of alternating electrical currents or
voltages is based on a comparison with direct current measurements
which can be resolved with a far higher precision. A widely used method
is the conversion of the electric power to heat in a thermal converter.
Because the range of thermal converters is restricted to currents below
15 mA and voltages of less than 3 V higher currents and voltages are
measured by a step-up transformation. In the case of high currents precision
shunt resistors are used. The knowledge of the temporal and spatial
temperature distribution of the resistor during operation is an essential
prerequisite to (i) perform an error correction and to (ii) optimize the
design of the resistor. In the present work we used a thermo camera to
investigate the temperature distribution of shunt resistors. Additional
measurements with thermo couples were carried out in order to correct
measurement deviations caused by optical surface properties. The results
of the measurements and model calculations of the resistor’s temperature
dependence will be discussed.
HL 44.76 Do 16:30 Poster A
Herstellung und Vermessung von lateralen p-n-Übergängen —
C. Werner, D. Reuter, A.D. Wieck, •C. Werner, D. Reuter
und A.D. Wieck — Lehrstuhl für Angewandte Festkörperphysik der
Ruhr-Universität Bochum
Wir haben auf Basis von Al0,33Ga0,67As/In0,1Ga0,9As/GaAs-
Heterostrukturen laterale p-n-Übergänge erzeugt, indem wir eine in der
MBE gewachsene und mit Kohlenstoff modulationsdotierte Heterostruktur
überkompensiert haben. Dieses geschieht durch lokale Implantation
von Silizium-Atomen in einer Anlage zur Erzeugung fokussierter Ionenstrahlen.
Für laterale p-n-Übergänge wurden interessante Voraussagen
bezüglich des Verhaltens der Ausbreitung der Verarmungszone und
der Sperrschichtkapazität als Funktion der angelegten Sperrspannung
gemacht. So sollte sich die Verarmungszone linear mit der Sperrspannung
ausbreiten [1, 2]. Um dies nachzuprüfen, wurde an diesen Proben der
optisch induzierte Sperrstrom gemessen und daraus die Länge der
Verarmungszone bestimmt. Die Sperrschichtkapazität hingegen sollte
nur sehr schwach von der Sperrspannung abhängen [2]. Dieses wurde
mittels Kapazitätsmessungen überprüft.
[1] U. Dötsch, A.D. Wieck, Nanodevices produced with focussed ion
beams, Nuclear Instruments and Methods in Physics Research B 139, 12
(1998)
[2] A.Sh. Achoyan et al., Two-Dimensional p-n Junction under Equlibrium
Conditions, Semiconductors 36, 903 (2002)