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Evaluation of local free carrier concentrations in individual heavily-doped GaN:Si micro-rods by micro-Raman spectroscopy (2016)

M. S. Mohajerani, S. Khachadorian, T. Schimpke, C. Nenstiel, J. Hartmann, J. Ledig, A. Avramescu, M. Strassburg, A. Hoffmann and A. Waag

American Institute of Physics (AIP)

In: Applied Physics Letters

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Publikationsdatum: 2016-03-05

Beschreibung: Three-dimensional III-nitride micro-structures are being developed as a promising candidate for the future opto-electrical devices. In this study, we demonstrate a quick and straight-forward method to locally evaluate free-carrier concentrations and a crystalline quality in individual GaN:Si micro-rods. By employing micro-Raman mapping and analyzing lower frequency branch of A 1 (LO)- and E 1 (LO)-phonon-plasmon-coupled modes (LPP – ), the free carrier concentrations are determined in axial and planar configurations, respectively. Due to a gradual doping profile along the micro-rods, a highly spatially resolved mapping on the sidewall is exploited to reconstruct free carrier concentration profile along the GaN:Si micro-rods. Despite remarkably high free carrier concentrations above 1 × 10 20 cm −3 , the micro-rods reveal an excellent crystalline quality, without a doping-induced stress.

Print ISSN: 0003-6951

Digitale ISSN: 1077-3118

Thema: Physik

Publiziert von American Institute of Physics (AIP)

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Accurate strain measurements in highly strained Ge microbridges (2016)

A. Gassenq, S. Tardif, K. Guilloy, G. Osvaldo Dias, N. Pauc, I. Duchemin, D. Rouchon, J.-M. Hartmann, J. Widiez, J. Escalante, Y.-M. Niquet, R. Geiger, T. Zabel, H. Sigg, J. Faist, A. Chelnokov, F. Rieutord, V. Reboud and V. Calvo

American Institute of Physics (AIP)

In: Applied Physics Letters

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Publikationsdatum: 2016-06-14

Beschreibung: Ge under high strain is predicted to become a direct bandgap semiconductor. Very large deformations can be introduced using microbridge devices. However, at the microscale, strain values are commonly deduced from Raman spectroscopy using empirical linear models only established up to ε 100 = 1.2% for uniaxial stress. In this work, we calibrate the Raman-strain relation at higher strain using synchrotron based microdiffraction. The Ge microbridges show unprecedented high tensile strain up to 4.9% corresponding to an unexpected Δω = 9.9 cm −1 Raman shift. We demonstrate experimentally and theoretically that the Raman strain relation is not linear and we provide a more accurate expression.

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Digitale ISSN: 1077-3118

Thema: Physik

Publiziert von American Institute of Physics (AIP)

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1.9% bi-axial tensile strain in thick germanium suspended membranes fabricated in optical germanium-on-insulator substrates for laser applications (2015)

A. Gassenq, K. Guilloy, G. Osvaldo Dias, N. Pauc, D. Rouchon, J.-M. Hartmann, J. Widiez, S. Tardif, F. Rieutord, J. Escalante, I. Duchemin, Y.-M. Niquet, R. Geiger, T. Zabel, H. Sigg, J. Faist, A. Chelnokov, V. Reboud and V. Calvo

American Institute of Physics (AIP)

In: Applied Physics Letters

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Publikationsdatum: 2015-11-12

Beschreibung: High tensile strains in Ge are currently studied for the development of integrated laser sources on Si. In this work, we developed specific Germanium-On-Insulator 200 mm wafer to improve tolerance to high strains induced via shaping of the Ge layers into micro-bridges. Building on the high crystalline quality, we demonstrate bi-axial tensile strain of 1.9%, which is currently the highest reported value measured in thick (350 nm) Ge layer. Since this strain is generally considered as the onset of the direct bandgap in Ge, our realization paves the way towards mid-infrared lasers fully compatible with CMOS fab technology.

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Digitale ISSN: 1077-3118

Thema: Physik

Publiziert von American Institute of Physics (AIP)

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