Silver antimony Ohmic contacts to moderately doped n-type germanium

Dumas, Derek C. S.; Gallacher, Kevin; Millar, Ross W.; MacLaren, Ian; Myronov, Maksym; Leadley, D. R.; Paul, Douglas J.

doi:10.1063/1.4873127

Cited by 12 publications

(9 citation statements)

References 35 publications

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“…NiGe alloys have demonstrated contact resistivities of 2 × 10 −7 Ω-cm 2 but only for contact n-type doping of 3 × 10 19 cm −3 . A better choice is Ag (1% Sb) which has demonstrated sufficiently low resistivity contacts even at n-Ge contact doping of 10 18 cm −3 [43]. The Ag is also ideal for plasmon waveguides at THz frequencies as explained above.…”

Section: Materials Choice and Thz Optical Datamentioning

confidence: 99%

“…First is Au to allow a direct comparison with many III-V THz QCLs [11]. Al and Cu are chosen as they are silicon foundry compatible and Ag is chosen as it provides the lowest losses in III-V THz QCLs [38] and also forms a good Ohmic contact to n-Ge [43]. The 300 K refractive index data used in the simulations for Al and Cu were taken from Ref.…”

Section: Materials Choice and Thz Optical Datamentioning

confidence: 99%

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Design and simulation of losses in Ge/SiGe terahertz quantum cascade laser waveguides

Gallacher¹,

Ortolani²,

Rew³

et al. 2020

Opt. Express

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The waveguide losses from a range of surface plasmon and double metal waveguides for Ge/Si 1−x Ge x THz quantum cascade laser gain media are investigated at 4.79 THz (62.6 µm wavelength). Double metal waveguides demonstrate lower losses than surface plasmonic guiding with minimum losses for a 10 µm thick active gain region with silver metal of 21 cm −1 at 300 K reducing to 14.5 cm −1 at 10 K. Losses for silicon foundry compatible metals including Al and Cu are also provided for comparison and to provide a guide for gain requirements to enable lasers to be fabricated in commercial silicon foundries. To allow these losses to be calculated for a range of designs, the complex refractive index of a range of nominally undoped Si 1−x Ge x with x = 0.7, 0.8 and 0.9 and doped Ge heterolayers were extracted from Fourier transform infrared spectroscopy measurements between 0.1 and 10 THz and from 300 K down to 10 K. The results demonstrate losses comparable to similar designs of GaAs/AlGaAs quantum cascade laser plasmon waveguides indicating that a gain threshold of 15.1 cm −1 and 23.8 cm −1 are required to produce a 4.79 THz Ge/SiGe THz laser at 10 K and 300 K, respectively, for 2 mm long double metal waveguide quantum cascade lasers with facet coatings.

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Section: Materials Choice and Thz Optical Datamentioning

confidence: 99%

Section: Materials Choice and Thz Optical Datamentioning

confidence: 99%

Design and simulation of losses in Ge/SiGe terahertz quantum cascade laser waveguides

Gallacher¹,

Ortolani²,

Rew³

et al. 2020

Opt. Express

Self Cite

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“…Photolithography was used before a mesa pattern was etched using SF 6 and C 4 F 8 mixed etch process (18) which has demonstrated very low levels of damage (19). Metal contacts were patterned using Ag (1% Sb) annealed at 400 ˚C at the top and bottom of the mesa to provide electrical Ohmic contacts (20). On top of the mesa a thin 50 nm Si 3 N 4 layer is deposited by PECVD before a four terminal thermometer was deposited using Ti/Pt metals.…”

Section: Methodsmentioning

confidence: 99%

(Invited) The Use of Silicon-Germanium Superlattices in Thermoelectric Devices and Microfabricated Generators

et al. 2016

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Ferre Llin, L. et al. (2016) The use of silicon-germanium superlattices for thermoelectric devices and microfabricated generators. ECS Transactions, 75(8), pp. 469-478. (doi:10.1149/07508.0469ecst) This is the author's final accepted version.There may be differences between this version and the published version. Low dimensional structures such as superlattices have the potential to improve the thermoelectric properties of materials by engineering the scattering of phonons to reduce the thermal conductivity and therefore improve the thermeoelectric performance. Here we demonstrate the reduction in thermal conductivity in Ge/SiGe superlattices using multiple barrier engineering to scatter acoustic phonons at the key wavelengths for thermal transport. The approach allows ZT to be increased in wide quantum well superlattices through the reduction of heterointerfaces which scatter both electrons and phonons.

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“…First a mesa structure was patterned by photolithography and etched using a fluorine-based reactive ion etch process [17]. Next Ohmic contacts were produced at the top and bottom of the mesa using photolithography followed by deposition of Ag (1% Sb) [18] Two SR830 lock-in amplifiers were used to monitor the change in voltage in the Pd resistor, which was translated into a temperature after performing the calibration. The Seebeck voltage in open circuit was measured by probing the two contacts, whose terminals were connected to an external voltmeter.…”

Section: Device Fabrication and Characterizationmentioning

confidence: 99%

Thermoelectric cross-plane properties on p- and n-Ge/SixGe1-x superlattices

et al. 2016

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-Silicon and germanium materials have demonstrated an increasing attraction for energy harvesting, due to their sustainability and integrability with complementary metal oxide semiconductor and micro-electro-mechanical-systems technology. The thermoelectric efficiencies for these materials, however, are very poor at room temperature and so it is necessary to engineer them in order to compete with telluride based materials, which have demonstrated at room temperature the highest performances in literature [1].Micro-fabricated devices consisting of mesa structures with integrated heaters, thermometers and Ohmic contacts were used to extract the cross-plane values of the Seebeck coefficient and the thermal conductivity from p-and n-Ge/Si x Ge 1-x superlattices. A second device consisting in a modified circular transfer line method structure was used to extract the electrical conductivity of the materials. A range of p-Ge/Si 0.5 Ge 0.5 superlattices with different doping levels was investigated in detail to determine the role of the doping density in dictating the thermoelectric properties. A second set of n-Ge/Si 0.3 Ge 0.7 superlattices was fabricated to study the impact that quantum well thickness might have on the two thermoelectric figures of merit, and also to demonstrate a further reduction of the thermal conductivity by scattering phonons at different wavelengths. This technique has demonstrated to lower the thermal conductivity by a 25% by adding different barrier thicknesses per period.

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Silver antimony Ohmic contacts to moderately doped n-type germanium

Cited by 12 publications

References 35 publications

Design and simulation of losses in Ge/SiGe terahertz quantum cascade laser waveguides

Design and simulation of losses in Ge/SiGe terahertz quantum cascade laser waveguides

(Invited) The Use of Silicon-Germanium Superlattices in Thermoelectric Devices and Microfabricated Generators

Thermoelectric cross-plane properties on p- and n-Ge/SixGe1-x superlattices

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