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During this lab-course one gets insight into
transport measurements of semiconductor structures. It will
be possible to perform measurements in a He-3 cryostat as well
as in a He-3/He-4 dilution fridge. The principle of operation
will be explained in detail. If own samples are available,
they can be measured during stay in Jülich.
Contact person: Thomas Schäpers
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SQUID Magnetometry (Jülich)
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For the characterisation of dilute magnetic
semiconductors SQUID (superconducting quantum interference
device) measurements are of central importance. By means of
a SQUID magnetometer the magnetisation of a semiconductor layer
system can be determined as a function of temperatur and of
an external magnetic field. In dilute magnetic semiconductors
the saturation magnetization of often extremely small. During
the lab-course it will be explained how measurements with sufficient
sensitivity can be performed and how measurement errors can
be prevented.
Contact person: Vitaliy Guzenko
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GaN Molecular Beam Epitaxy (Jülich)
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Molecular Beam Epitaxy (MBE) is a versatile
technique for growing thin epitaxial structures made of semiconductors,
metals or insulators. The aim of our work is the fabrication
of optimized GaN layers grown on different substrates by MBE,
in order to realize semiconductor/ ferromagnet heterostructures
for spintronic applications. During the lab course we will
discuss the most important aspects of MBE apparatus and the
growth mechanisms of GaN-based heterostructures.
Contact person: Raffaella Calarco
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MBE and RHEED (Göttingen)
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Molecular Beam Epitaxy (MBE) is the technique
of creating single-crystalline compund semiconductor films
in an ultrahigh vacuum (UHV) enviroment. Complex, multilayer
structures can be deposited sequentially onto a heated substrate
in a MBE reactor. The composition, thickness, and dopant species
of each layer can be independently and very precisely controlled.
In this experiment the growth of GaN will be performed on a GaN
template layer in a Modular Gen II MBE system. The MBE process
for GaN critically depends on the Ga and N flux parameters, which
have to be set up for optimum growth conditions. Reflection High
Energy Electron Diffraction (RHEED) allows to control the substrate
surface preparation and furthermore to follow the growth in real
time. The diffraction pattern, in particular the intensity oscillations
of the reflected spot are quantitatively analyzed to determine
the growth rate of GaN and the Ga flux for optimum growth. .
Contact person: Angela Rizzi
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