Highly doped Si and Ge formed by GILD (gas immersion laser doping); from GILD to superconducting silicon

Cammilleri, D.; Fossard, F.; Débarre, D.; Manh, Cuong-Nguyen; Dubois, C.; Bustarret, Étienne; Marcenat, C.; Achatz, Philipp; Bouchier, D.; Boulmer, J.

doi:10.1016/j.tsf.2008.08.073

Cited by 43 publications

(36 citation statements)

References 16 publications

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“…Unlike for diamond and silicon, boron doping, so far, has failed to establish superconductivity in germanium [19]. Gallium -adjacent to germanium in the periodic table of elements -is a better choice.…”

Section: Preparation Methodsmentioning

confidence: 99%

The impact of heavy Ga doping on superconductivity in germanium

Skrotzki

Herrmannsdörfer

Heera

et al. 2011

Low Temperature Physics

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We report new experimental results on how superconductivity in gallium-doped germanium (Ge:Ga) is influenced by hole concentration and microstructure. Ion implantation and subsequent flash-lamp annealing at various temperatures have been utilized to prepare highly p-doped thin films consisting of nanocrystalline and epitaxially grown sublayers with Ga-peak concentrations of up to 8 at.%. Successive structural investigations were carried out by means of Rutherford-backscattering spectrometry in combination with ion channelling, secondaryion-mass spectrometry, and high-resolution cross-sectional transmission electron microscopy. Hole densities of 1.8·10 20 to 5.3·10 20 cm -3 (0.4 to 1.2 at.%) were estimated via Hall-effect measurements revealing that only a fraction of the incorporated gallium has been activated electrically to generate free charge carriers. The coincidence of a sufficiently high hole and Ga concentration is required for the formation of a superconducting condensate. Our data reflect a critical hole concentration of around 0.4 at.%. Higher concentrations lead to an increase of T c from 0.24 to 0.43 K as characterized by electrical-transport measurements. A short mean-free path indicates superconductivity in the dirty limit. In addition, small critical-current densities of max. 20 kA/m 2 point to a large impact of the microstructure.PACS: 74.10.+v Occurrence, potential candidates; 74.78.-w Superconducting films and low-dimensional structures.

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Section: Preparation Methodsmentioning

confidence: 99%

The impact of heavy Ga doping on superconductivity in germanium

Skrotzki

Herrmannsdörfer

Heera

et al. 2011

Low Temperature Physics

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“…To achieve this goal, donor implantation has been pursued by several groups, 2-8 while other authors emphasize the advantages of in-situ doping. [9][10][11][12][13][14][15][16][17][18][19] Regardless of the specific approach, the implicit assumption underlying this quest is that germanium deviates strongly from the incomplete donor ionization predicted when the doping level is so high that E d -l ) k B T is no longer valid (Here, E d is the donor energy level, l the Fermi level, k B Boltzmann's constant, and T the absolute temperature). Otherwise, a carrier concentration of 5 Â 10 19 cm À3 at room temperature would be unattainable, since it would require an atomic donor concentration of 2 Â 10 21 cm…”

mentioning

confidence: 99%

Frustrated incomplete donor ionization in ultra-low resistivity germanium films

Senaratne

Kouvetakis

et al. 2014

Applied Physics Letters

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The relationship between carrier concentration and donor atomic concentration has been determined in n-type Ge films doped with P. The samples were carefully engineered to minimize non-active dopant incorporation by using specially designed P(SiH3)3 and P(GeH3)3 hydride precursors. The in situ nature of the doping and the growth at low temperatures, facilitated by the Ge3H8 and Ge4H10 Ge sources, promote the creation of ultra-low resistivity films with flat doping profiles that help reduce the errors in the concentration measurements. The results show that Ge deviates strongly from the incomplete ionization expected when the donor atomic concentration exceeds Nd = 1017 cm−3, at which the energy separation between the donor and Fermi levels ceases to be much larger than the thermal energy. Instead, essentially full ionization is seen even at the highest doping levels beyond the solubility limit of P in Ge. The results can be explained using a model developed for silicon by Altermatt and coworkers, provided the relevant model parameter is properly scaled. The findings confirm that donor solubility and/or defect formation, not incomplete ionization, are the major factors limiting the achievement of very high carrier concentrations in n-type Ge. The commercially viable chemistry approach applied here enables fabrication of supersaturated and fully ionized prototypes with potential for broad applications in group-IV semiconductor technologies.

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“…Thin films of boron doped silicon have been prepared by gas-immersion laser doping [3,4]. The surface of a silicon wafer is melted using laser pulses in the presence of a chemisorbed BCl 3 gas.…”

Section: Methodsmentioning

confidence: 99%

The Superconducting Transition in Boron Doped Silicon Films

et al. 2010

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We report on a detailed analysis of the superconducting properties of boron-doped silicon films grown along the 001 direction by gas immersion laser doping. This technique is proved to be a powerful technique to dope silicon in the alloying range 2-10 at.% where superconductivity occurs. The superconducting transitions are sharp and well defined both in resistivity and magnetic susceptibility. The variation of Tc on the boron concentration is in contradiction with a classical exponential dependence on superconducting parameters. Electrical measurements were performed in magnetic field on the sample with cB = 8 at.% (400 laser shots) which has the highest Tc (0.6 K). No hysteresis was found for the transitions in magnetic field, which is characteristic of a type-II superconductor. The corresponding upper critical field was on the order of 1000 G at low temperatures, much smaller than the value previously reported. The temperature dependence of Hc2 is very well reproduced by the linearized Gorkov equations neglecting spin effects in the very dirty limit. These measurements in magnetic field allow an estimation of the electronic mean-free path, the coherence length, and the London penetration depth within a simple two-band free electron model.

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Highly doped Si and Ge formed by GILD (gas immersion laser doping); from GILD to superconducting silicon

Cited by 43 publications

References 16 publications

The impact of heavy Ga doping on superconductivity in germanium

The impact of heavy Ga doping on superconductivity in germanium

Frustrated incomplete donor ionization in ultra-low resistivity germanium films

The Superconducting Transition in Boron Doped Silicon Films

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