H<sup>−</sup>-like impurity centers and molecular complexes created by them in semiconductors

Gershenzon, E. M.; Melnikov, A. P.; Rabinovich, R. I.; Serebryakova, N. A.

doi:10.1070/pu1980v023n10abeh005041

Cited by 28 publications

(14 citation statements)

References 9 publications

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“…These "over-charged" states are analogous to the negative hydrogen "anion" (H − ) bound state, which can carry two bound electrons. The negative hydrogen ion was first predicted by Bethe [90], and the semiconductor impurity analogs have been evidenced in germanium [91,92,15]. In this case, the polarizability of the neutral impurity allows for a bound, "anion" state to exist.…”

Section: Neutral Capture Forming Dmentioning

confidence: 99%

Carrier Transport and Related Effects in Detectors of the Cryogenic Dark Matter Search

Sundqvist

2012

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The Cryogenic Dark Matter Search (CDMS) is searching for weakly-interacting massive particles (WIMPS), which could explain the dark matter problem in cosmology and particle physics.By simultaneously measuring signals from deposited charge and the energy in nonequilibrium phonons created by particle interactions in intrinsic germanium crystals at a temperature of 40 mK, a signature response for each event is produced. This response, combined with phonon pulse-shape information, allows CDMS to actively discriminate candidate WIMP interactions with nuclei from electromagnetic radioactive background which interacts with electrons.The challenges associated with these techniques are unique. Carrier scattering is dominated by the spontaneous emission of Luke-Neganov phonons due to zeropoint fluctuations of the lattice ions. Drift fields are maintained at only a few V /cm, else these emitted phonons would dominate the phonons of the original interaction. The dominant systematic issues with CDMS detectors are due to the effects of space charge accumulation. It has been an open question how space charge accrues, and by which of several potential recombination and ionization processes.In this work, we have simulated the transport of electrons and holes in germanium under CDMS conditions. We have implemented both a traditional Monte Carlo technique based on carrier energy, followed later by a novel Monte Carlo algorithm with scattering rates defined and sampled by vector momentum. This vector-based method provides for a full anisotropic simulation of carrier transport including freeflight acceleration with an anisotropic mass, and anisotropic scattering rates.With knowledge of steady state carrier dynamics as a function of applied field, the results of our Monte Carlo simulations allow us to make a wide variety of predictions for energy dependent processes for both electrons and holes.

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Section: Neutral Capture Forming Dmentioning

confidence: 99%

Carrier Transport and Related Effects in Detectors of the Cryogenic Dark Matter Search

Sundqvist

2012

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“…Especially note-worthy 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. The scattering center densities for both devices also exceed by orders of magnitude the values obtained from a thermally stimulated current investigation of the dopant-related (H − -like) centers (∼10 7 cm −3 ) [4,5] in the same crystals at sub-kelvin temperatures. These facts altogether suggest that the scattering centers are not the dopant species but deep level centers associated with still unidentified impurities or crystal defects.…”

Section: Discussionmentioning

confidence: 72%

“…It is doubtful, however, whether any of these models can be applied to the scattering of hot electrons at mK temperatures, given in particular the freeze-out of carrier emission from all, including the shallower (A + /D − ) bound states of the dopant species [4,5]. In the absence of free carrier screening at these temperatures, the long range nature of the Coulomb force makes the conventional model for charged impurity scattering as a succession of two-body encounters equally questionable [6].…”

Section: Impurity Scattering and Electron Anisotropymentioning

confidence: 98%

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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“…Обыч-но такие поправки малы и в ряде случаев ими пре-небрегают [7,8]. Однако они становятся ощути-мыми, если учесть, что пространственно коррелированные заряженные примеси (в пределе -заряженные дислокации) рассеивают электроны слабее, чем разупорядоченные заряженные цен-тры [4,11]. Зная структуру потенциала взаимодействия в области    , представим транспортное сечение σ tr в перенормированном виде Для неполярных молекул (типа CO 2 ), внедрен-ных в междоузлия атомов матрицы, в качестве примесей замещения [12], поправку к σ tr следует учесть в квадрупольном приближении: [γ] -эрг·см 3 .…”

Section: методика расчетаunclassified

Correction to Transport Cross-Section of Charged Carriers in Semiconductors

Muratov¹

2016

Вестник ПГУ. Физика

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H⁻-like impurity centers and molecular complexes created by them in semiconductors

Cited by 28 publications

References 9 publications

Carrier Transport and Related Effects in Detectors of the Cryogenic Dark Matter Search

Carrier Transport and Related Effects in Detectors of the Cryogenic Dark Matter Search

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

Correction to Transport Cross-Section of Charged Carriers in Semiconductors

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H−-like impurity centers and molecular complexes created by them in semiconductors

Cited by 28 publications

References 9 publications

Carrier Transport and Related Effects in Detectors of the Cryogenic Dark Matter Search

Carrier Transport and Related Effects in Detectors of the Cryogenic Dark Matter Search

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

Correction to Transport Cross-Section of Charged Carriers in Semiconductors

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H⁻-like impurity centers and molecular complexes created by them in semiconductors