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Mathias Kaschel

Bio: Mathias Kaschel is an academic researcher from University of Stuttgart. The author has contributed to research in topics: Molecular beam epitaxy & Photodetector. The author has an hindex of 15, co-authored 35 publications receiving 1006 citations.

Papers
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Journal ArticleDOI
TL;DR: GeSn heterojunction photodetectors on Si substrates were grown with Sn concentration up to 4, fabricated for vertical light incidence, and characterized in this paper, where the complete layer structure was grown by means of ultra low temperature (100 °C) molecular beam epitaxy.
Abstract: GeSn heterojunction photodetectors on Si substrates were grown with Sn concentration up to 4%, fabricated for vertical light incidence, and characterized. The complete layer structure was grown by means of ultra low temperature (100 °C) molecular beam epitaxy. The Sn content shifts the responsivity into the infrared, about 310 nm for the 4% Sn sample. An increase of the optical responsivity for wavelengths higher than 1550 nm can be observed with increasing Sn content. At 1600 nm, the optical responsivity is increased by more than a factor of 10 for the GeSn diode with 4% Sn in comparison to the Ge reference diode.

173 citations

Journal ArticleDOI
TL;DR: GeSn heterojunction p-i-n diodes with a Sn content of 0.5% are grown with a very low temperature growth step in order to suppress Sn surface segregation.
Abstract: GeSn heterojunction p-i-n diodes with a Sn content of 0.5% are grown with a special low temperature molecular beam epitaxy. The Sn incorporation in Ge is facilitated by a very low temperature growth step in order to suppress Sn surface segregation. Diodes with sharp doping transitions are realized as double mesa structures with a diameter from 1.5 up to 80 μm. An optical responsivity of these GeSn diodes of 0.1 A/W at a wavelength of λ=1.55 μm is measured. In comparison with a pure Ge detector the optical responsivity is increased by factor of 3 as a result of Sn caused band gap reduction.

171 citations

Journal ArticleDOI
TL;DR: In this paper, fast Ge-on-Si p-i-n photodiodes are fabricated and their frequency response is measured up to 67 GHz at a wavelength of 1550 nm.
Abstract: Fast Ge-on-Si p-i-n photodiodes are fabricated and their frequency response is measured up to 67 GHz at a wavelength of 1550 nm. At a bias voltage of -2 V, a 3-dB bandwidth (BW) of 49 GHz is achieved. This is to the best of the authors' knowledge the highest BW ever published for Ge photodiodes.

102 citations

Journal ArticleDOI
TL;DR: In this article, a GeSn light-emitting pin diode integrated on Si via a Ge buffer is demonstrated and it is compared with a lightemitting Pin diode made from pure, unstrained Ge on Si.
Abstract: In this letter, a GeSn light-emitting pin diode integrated on Si via a Ge buffer is demonstrated and it is compared with a light-emitting pin diode made from pure, unstrained Ge on Si. The diode layer structures are grown with a special low-temperature molecular beam epitaxy process. The pseudomorphic GeSn layers (1.1% Sn content) on the Ge buffer are compressively strained. Both light-emitting pin diodes clearly show direct bandgap electroluminescence emission at room temperature. The electroluminescence peak of the GeSn light-emitting pin diode is shifted by 20 meV into the infrared region compared to the electroluminescence peak of the unstrained Ge light-emitting pin diode. The shift is due to the lower bandgap of GeSn and the influence of strain.

92 citations

Journal ArticleDOI
TL;DR: All detectors had bandwidth above 40 GHz at enough reverse voltage which increased from zero to -5 V within the given Sn range and caused the depletion of the nominal intrinsic absorber at increasing reverse voltages.
Abstract: GeSn (Sn content up to 4.2%) photodiodes with vertical pin structures were grown on thin Ge virtual substrates on Si by a low temperature (160 °C) molecular beam epitaxy. Vertical detectors were fabricated by a double mesa process with mesa radii between 5 µm and 80 µm. The nominal intrinsic absorber contains carrier densities from below 1·1016 cm−3 to 1·1017 cm−3 for Ge reference detectors and GeSn detectors with 4.2% Sn, respectively. The photodetectors were investigated with electrical and optoelectrical methods from direct current up to high frequencies (40 GHz). For a laser wavelength of 1550 nm an increasing of the optical responsivities (84 mA/W −218 mA/W) for vertical incidence detectors with thin (300 nm) absorbers as function of the Sn content were found. Most important from an application perspective all detectors had bandwidth above 40 GHz at enough reverse voltage which increased from zero to −5 V within the given Sn range. Increasing carrier densities (up to 1·1017 cm−3) with Sn contents caused the depletion of the nominal intrinsic absorber at increasing reverse voltages.

91 citations


Cited by
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Journal ArticleDOI
TL;DR: Zhou et al. as discussed by the authors assess the three main contenders for on-chip light sources: erbium-based light sources, germanium-on-silicon lasers and III-V-based silicon lasers.
Abstract: Hybrid silicon lasers based on bonded III–V layers on silicon are currently the best contenders for on-chip lasers for silicon photonics. On-chip silicon light sources are highly desired for use as electrical-to-optical converters in silicon-based photonics. Zhiping Zhou and Bing Yin of Peking University in China and Jurgen Michel of Massachusetts Institute of Technology assess the three main contenders for such light sources: erbium-based light sources, germanium-on-silicon lasers and III-V-based silicon lasers. They consider operating wavelength, pumping conditions, power consumption, thermal stability and fabrication process. The scientists regard the power efficiencies of electrically pumped erbium-based lasers as being too low and the threshold currents of germanium lasers as being too high. They conclude that III–V quantum dot lasers monolithically grown on silicon show the most promise for realizing on-chip lasers.

448 citations

Journal ArticleDOI
TL;DR: The low intrinsic capacitance of this photodiode may enable the elimination of transimpedance amplifiers in future optical data communication receivers, creating ultra low power consumption optical communications.
Abstract: We present a compact 13 × 4 μm2 Germanium waveguide photodiode, integrated in a CMOS compatible silicon photonics process flow This photodiode has a best-in-class 3 dB cutoff frequency of 45 GHz, responsivity of 08 A/W and dark current of 3 nA The low intrinsic capacitance of this device may enable the elimination of transimpedance amplifiers in future optical data communication receivers, creating ultra low power consumption optical communications

298 citations

Journal ArticleDOI
TL;DR: A comprehensive summary of the recent progress mainly on photodetectors based on inorganic p-type semiconductor materials is presented.
Abstract: Photoelectric detectors are the central part of modern photodetection systems with numerous commercial and scientific applications. p-Type semiconductor materials play important roles in optoelectronic devices. Photodetectors based on p-type semiconductor materials have attracted a great deal of attention in recent years because of their unique properties. Here, a comprehensive summary of the recent progress mainly on photodetectors based on inorganic p-type semiconductor materials is presented. Various structures, including photoconductors, phototransistors, homojunctions, heterojunctions, p-i-n junctions, and metal-semiconductor junctions of photodetectors based on inorganic p-type semiconductor materials, are discussed and summarized. Perspectives and an outlook, highlighting the promising future directions of this research field, are also given.

290 citations

Journal ArticleDOI
TL;DR: A rigorous approach for designing a highly efficient coupling between single mode optical fibers and silicon nanophotonic waveguides based on diffractive gratings based on cost-effective CMOS process flow is presented.
Abstract: We present a rigorous approach for designing a highly efficient coupling between single mode optical fibers and silicon nanophotonic waveguides based on diffractive gratings. The structures are fabricated on standard SOI wafers in a cost-effective CMOS process flow. The measured coupling efficiency reaches −1.08 dB and a record value of −0.62 dB in the 1550 nm telecommunication window using a uniform and a nonuniform grating, respectively, with a 1dB-bandwidth larger than 40 nm.

231 citations

Journal ArticleDOI
12 Jan 2011-Sensors
TL;DR: The recent progress in the development and integration of Ge-photodetectors on Si-based photonics will be comprehensively reviewed, along with remaining technological issues to be overcome and future research trends.
Abstract: High speed photodetectors are a key building block, which allow a large wavelength range of detection from 850 nm to telecommunication standards at optical fiber band passes of 1.3-1.55 μm. Such devices are key components in several applications such as local area networks, board to board, chip to chip and intrachip interconnects. Recent technological achievements in growth of high quality SiGe/Ge films on Si wafers have opened up the possibility of low cost Ge-based photodetectors for near infrared communication bands and high resolution spectral imaging with high quantum efficiencies. In this review article, the recent progress in the development and integration of Ge-photodetectors on Si-based photonics will be comprehensively reviewed, along with remaining technological issues to be overcome and future research trends.

220 citations