Au metalization schemes were deposited on AlGaN/ GaN heterostructures. The dependence of the specific contact resistance on the annealing conditions and the V:Al thickness ratio was shown. For an optimized electrode stack, a low specific contact resistance of 8.9 Â 10 À6 X cm 2 was achieved at an annealing temperature of 650 C. Compared to the conventional Ti/Al/Ni/Au contact, this is a reduction of 150 K. The microstructure and contact formation at the AlGaN/metal interface were investigated by transmission electron microscopy including high-resolution micrographs and energy dispersive X-ray analysis. It was shown that for low-resistive contacts, the resistivity of the metalization has to be taken into account. The V:Al thickness ratio has an impact on the formation of different intermetallic phases and thus is crucial for establishing ohmic contacts at reduced annealing temperatures. V
A four-fold segmented n-type point-contact "Broad Energy" high-purity germanium detector, SegBEGe, has been characterised at the Max-Planck-Institut für Physik in Munich. The main characteristics of the detector are described and first measurements concerning the detector properties are presented. The possibility to use mirror pulses to determine source positions is discussed as well as charge losses observed close to the core contact.
Hot-phonon effects on hot-electron noise and transport are investigated in nominally undoped two-dimensional Al 0.23 Ga 0.77 N/GaN channel with electron density of 7.4 × 10 12 cm −2 . The electrons are subjected to electric field applied in the channel plane. The dependence of noise temperature on supplied electric power yields hot-phonon lifetime of (370 ± 100) fs at low levels of power (<1 nW/electron). Monte Carlo simulation of hot-electron drift velocity with the same lifetime value as a model parameter confirms the experimental findings. The lifetime decreases as the supplied power increases until the values below 50 fs are deduced at high level of power (>10 nW/electron). These values are substantially lower than the plasmon-free lifetime, and the experimental data are interpreted in terms of plasmon-assisted conversion of hot phonons into acoustic phonons and to other vibration modes.
The open-source software package
SolidStateDetectors.jl to calculate the fields and simulate
the drifts of charge carriers in solid state detectors, especially
in large volume high-purity germanium detectors, together with the
corresponding pulses, is introduced. The package can perform all
calculations in full 3D while it can also make use of detector
symmetries. The effect of the surroundings of a detector can also be
studied. The package is programmed in the user friendly and
performance oriented language julia, such that 3D field
calculations and drift simulations can be executed efficiently and
in parallel. The package was developed for high-purity germanium
detectors, but it can be adjusted by the user to other types of
semiconductors. The verification of the package is shown for an
n-type segmented point-contact germanium detector. Additional
features of SolidStateDetectors.jl, which are under
development are listed.
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