Depth-resolved transport measurements and atom-probe tomography of heterogeneous, superconducting Ge:Ga films

Heera, V.; Fiedler, J.; Naumann, M.; Skrotzki, R.; Kölling, Sebastian; Wilde, L.; Herrmannsdörfer, T.; Skorupa, W.; Wosnitza, J.; Helm, M.

doi:10.1088/0953-2048/27/5/055025

Cited by 11 publications

(7 citation statements)

References 27 publications

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“…Figure 4a displays a cross-sectional bright-field TEM image taken from Al-doped Ge after annealing. In this case, both single dislocations within the implanted layer and end-of-range defects are detected [33]. Figure 4b the recrystallized Ge is single-crystalline.…”

Section: Microstructurementioning

confidence: 84%

Section: Microstructurementioning

confidence: 97%

See 1 more Smart Citation

Superconductivity in single-crystalline aluminum- and gallium-hyperdoped germanium

Prucnal

Heera

Hübner

et al. 2019

Phys. Rev. Materials

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Superconductivity in group IV semiconductors is desired for hybrid devices combining both semiconducting and superconducting properties. Following boron doped diamond and Si, superconductivity has been observed in gallium doped Ge, however the obtained specimen is in polycrystalline form [Herrmannsdörfer et al., Phys. Rev. Lett. 102, 217003 (2009)]. Here, we present superconducting single-crystalline Ge hyperdoped with gallium or aluminium by ion implantation and rear-side flash lamp annealing. The maximum concentration of Al and Ga incorporated into substitutional positions in Ge is eight times higher than the equilibrium solid solubility. This corresponds to a hole concentration above 10 21 cm -3 . Using density functional theory in the local density approximation and pseudopotential plane-wave approach, we show that the superconductivity in p-type Ge is phonon-mediated. According to the ab initio calculations the critical superconducting temperature for Al-and Ga-doped Ge is in the range of 0.45 K for 6.25 at.% of dopant concentration being in a qualitative agreement with experimentally obtained values.

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Section: Microstructurementioning

confidence: 84%

Section: Microstructurementioning

confidence: 97%

Superconductivity in single-crystalline aluminum- and gallium-hyperdoped germanium

Prucnal

Heera

Hübner

et al. 2019

Phys. Rev. Materials

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“…The lines show Ga concentration (per cm 3 ) vs. depth for E IMP = 25, 35, 45, and 80 keV all experimentally implemented in this study. The grey line represents Ga distribution for E IMP = 100 keV, serving as a reference to the previous reports on superconducting Ge 16,21,37 .…”

Section: Resultsmentioning

confidence: 99%

Observation of Distinct Superconducting Phases in Hyperdoped p-type Germanium

Sardashti¹,

Nguyen²,

Sarney³

et al. 2020

Preprint

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Realization of superconductivity in Group IV semiconductors could have a strong impact in the direction quantum technologies will take in the future. Therefore, it is imperative to understand the nature of the superconducting phases in materials such as Silicon and Germanium. Here, we report systematic synthesis and characterization of superconducting phases in hyperdoped Germanium prepared by Gallium ion implantation beyond its solubility limits. The resulting structural and physical characteristics have been tailored by changing the implantation energy and activation annealing temperature. Surprisingly, in addition to the poly-crystalline phase with weakly-coupled superconducting Ga clusters we find a nano-crystalline phase with quasi-2D characteristics consisting of a thin Ga film constrained near top surfaces. The new phase shows signatures of strong disorder such as anomalous Bc temperature dependence and crossings in magentoresistance isotherms. Apart from using hyperdoped Ge as a potential testbed for studying signatures of Quantum phase transitions (e.g. quantum Griffith singularity), our results suggest the possibility of integration of hyperdoped Ge nano-crystalline phase into superconducting circuits due to its 2D nature.

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“…In light of this, the solubility characteristics of Ga in Ge, depending on the thin film processing techniques, could be higher in thin films than those in bulk. [53][54][55] For example, a single phase homogeneous amorphous GaGe thin film with a Ga composition of 5 at% has been prepared by Nath et al 53 employing physical vapor deposition.…”

Section: Resultsmentioning

confidence: 99%

Droplet-induced dot, dot-in-hole, and hole structures in GaGe thin films grown by MOCVD on GaAs substrates

2016

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We report observations and origins of Ga-rich GaGe droplets and the localized etching of Ge-rich GaGe thin films grown on GaAs (100) substrates by metalorganic chemical vapor deposition. Micron and sub-micron dots, dot-in-holes, and holes have been fabricated by controlling the partial pressures of the Ga and Ge precursors as well as the substrate temperatures. The dot-in-hole features can also be converted to empty holes via post-growth sonication in hot deionized water due to the low melting point of the Ga-rich dots. Enhanced Raman scattering (ERS) of the Ge-Ge lattice vibrational mode has been observed at the wall of the concentric dot-in-hole structures as well as in the empty holes. To interpret the ERS mechanism, we have carried out finite-difference time-domain (FDTD) simulations, which reveal an enhanced electrical field for the obtained structures as a result of interference between the incident and reflected waves at the surface of the thin films that, in turn, results in the observed ERS. These findings greatly enrich the conventional droplet epitaxy and etching techniques and widen their applications.

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Depth-resolved transport measurements and atom-probe tomography of heterogeneous, superconducting Ge:Ga films

Cited by 11 publications

References 27 publications

Superconductivity in single-crystalline aluminum- and gallium-hyperdoped germanium

Superconductivity in single-crystalline aluminum- and gallium-hyperdoped germanium

Observation of Distinct Superconducting Phases in Hyperdoped p-type Germanium

Droplet-induced dot, dot-in-hole, and hole structures in GaGe thin films grown by MOCVD on GaAs substrates

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