Transport Anisotropy and Impurity Scattering in Ge at Millikelvin Temperatures: Experimental Study

Olivieri, E.; Dumoulin, L.; Marnieros, S.; Broniatowski, A.

doi:10.1007/s10909-012-0548-0

Cited by 7 publications

(11 citation statements)

References 9 publications

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“…A wide-band electronics (7 MHz) is used for time-resolved measurements of the charge collection signals. Given the location of the energy deposits close to the bottom surface, our setup permits to measure the velocity laws for electrons and holes separately by simply reversing the detector bias [6].…”

Section: Experimental Setup and Methods For Transit Measurementsmentioning

confidence: 99%

“…For optimal signal-to-noise ratio, we use the h measurement channel which collects all the charges at the bottom surface, and therefore delivers the largest signal amplitude compared with the channels at the top surface which are used to measure the carriers straggle [6]. The method to measure the transit time of the carriers is explicited in Fig.…”

Section: Experimental Setup and Methods For Transit Measurementsmentioning

confidence: 99%

“…Our data have been obtained by time-of-flight measurements at 20 mK, with the electric field in the [100] crystallographic direction. Measurements were made with two n-type Ge samples of different crystal purity: one specimen (ID201) is high purity (|N a − N d | < 10 10 cm −3 ), and the other (ID203) is doped to 10 11 cm −3 [6,7]. …”

Section: Introductionmentioning

confidence: 99%

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Hot Carrier Velocities in Doped and in Ultra-pure Germanium Crystals at Millikelvin Temperatures

Olivieri

Broniatowski

2012

J Low Temp Phys

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The velocity laws of electrons and holes in germanium single crystals at millikelvin temperatures are determined as a function of the electric field in the aOE (c) 001 > orientation, based on time-of-flight measurements in cryogenic coplanar grid Ge detectors. Results obtained in two n-type crystals (|N (a) -N (d) |< 10(10) cm(-3) and doped to 10(11) cm(-3)) are compared with the experimental data from previous investigations, and shown to be consistent with Monte-Carlo simulations of carrier transport

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Section: Experimental Setup and Methods For Transit Measurementsmentioning

confidence: 99%

Section: Experimental Setup and Methods For Transit Measurementsmentioning

confidence: 99%

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Hot Carrier Velocities in Doped and in Ultra-pure Germanium Crystals at Millikelvin Temperatures

Olivieri

Broniatowski

2012

J Low Temp Phys

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“…There results a complex, bias dependent pattern of charge collection between the different measurement channels. 2,3 Application of a magnetic field leads to further changes in the collection patterns, as figure 3 (a) shows for the field in the direction normal to the detector axis. On the other hand, minute effects only are observed in the c and d channels when the field is turned parallel to the detector axis ( fig.…”

Section: Resultsmentioning

confidence: 97%

“…Experiments reported elsewhere in these proceedings demonstrate large differences between electron and hole collection in Ge detectors at mK temperatures, with regard to carrier straggling especially. [2][3][4][5] These differences are also reflected in the magnetic field effects ( figs. 2 and 3).…”

Section: Resultsmentioning

confidence: 99%

Effects of a Weak Magnetic Field on Carrier Transport in a Cryogenic Germanium Detector for Dark Matter Search

2012

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A magnetic field of a few gauss produces sizeable effects on carrier transport and charge collection in a germanium dark matter detector operated at millikelvin temperatures. The magnitude of the effects is explained by the large values of the velocities imparted to the carriers, even under the low electric field conditions typical for charge collection in these devices (a few 10 6 cm/s at ~ 1 V/cm). Using a suitable experimental setup, effects of the magnetic field on electron and hole transport were investigated separately. A dependence of these effects on the orientation of the field relative to the detector axis is demonstrated, arising in part from magnetic flux conservation through the superconducting (Al) annular electrodes on these devices.

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Carrier Anisotropy and Impurity Scattering in Ge at mK Temperatures: Modeling and Comparison to Experiment

Broniatowski

2012

J Low Temp Phys

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Improving upon the present background rejection capabilities of the cryogenic germanium detectors for direct dark matter search involves an in-depth comprehension of the charge collection process in these devices. Experimental data point to the combined effects of lattice and impurity scattering on the anisotropy of electron transport in Ge at mK temperatures. A Monte Carlo simulation code has been implemented to incorporate these features in a consistent model for charge collection. In a novel approach to carrier scattering by charged impurities in Ge at cryogenic temperatures, the scattering field of the impurities is treated statistically as a random contribution to the collection field, described by the Holtsmark distribution function with a single adjustable parameter, the mean density of the charged centers. Simulation of charge collection along these lines in devices different by their impurity content shows excellent agreement to experiment. Especially noteworthy is the fact that the strength of impurity scattering is reversed from the known concentration of dopant impurities in the crystals, as the crystal with the higher dopant concentration shows lower scattering at low field than the one with the lower concentration. This raises as an issue for further improvement of these devices, the question of the nature of the scattering centers in high-purity Ge crystals at cryogenic temperatures, associated presumably with deep level impurities or crystal defects. Fig. 1 (Color online) (a) Simulated carrier trajectories for a 60 keV energy deposit from a collimated 241 Am γ source facing the bottom surface of the detector crystal. See Ref. [1] for a full description of the device and of the geometry of the charge collection field especially. Detector bias V p = 2 V; T = 20 mK. Holes are in red and electrons in blue, black, green and magenta depending on their valley of belonging. (b) Same as (a), with the polarity of the electrode biases reversed so that holes instead of electrons are drifted across the full thickness of the detector crystal

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Transport Anisotropy and Impurity Scattering in Ge at Millikelvin Temperatures: Experimental Study

Abstract: Anisotropy effects in hot carrier transport have been investigated in

Cited by 7 publications

References 9 publications

Hot Carrier Velocities in Doped and in Ultra-pure Germanium Crystals at Millikelvin Temperatures

Hot Carrier Velocities in Doped and in Ultra-pure Germanium Crystals at Millikelvin Temperatures

Effects of a Weak Magnetic Field on Carrier Transport in a Cryogenic Germanium Detector for Dark Matter Search

Carrier Anisotropy and Impurity Scattering in Ge at mK Temperatures: Modeling and Comparison to Experiment

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