Wave-function engineering and absorption spectra in Si0.16Ge0.84/Ge0.94Sn0.06/Si0.16Ge0.84 strained on relaxed Si0.10Ge0.90 type I quantum well

et al. 2014

Phys. Status Solidi C

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We report a theoretical investigation of strained Ge1−xSnx/Ge (001)‐oriented quantum wells as a bulding block in active region of infrared photodetector. The electronic band parameters, gaps, discontinuities and effective masses for heterointerfaces between compressively strained Ge1−xSnx and relaxed Ge have beencomputed at room temperature. From this preliminary and mendatory work, we conclude that pseudomorphic Ge1−xSnx alloys become direct band gap semiconductors at a Sn‐fraction of 15.3%, e.g. a lattice mismatch as high as 2.3%. Due to achievable critical layer thickness and mainly solid solubility limit, a type‐I compressively strained Ge/Ge0.92Sn0.08/Ge (double) quantum well is studied by solving Schrödinger equation without and applied bias voltage. A strong absorption coefficient (> 1×104 cm−1) and a Stark shift of the direct transition between 2.01 μm and 2.25 μm at large external fields (40kV/cm) are attractive characteristics for the design of infrared photodetectors (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Section: Introductionmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 88%

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Band engineering and absorption spectra in compressively strained Ge_0.92Sn_0.08/Ge (001) double quantum well for infrared photodetection

et al. 2014

Phys. Status Solidi C

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“…x Sn x is taken from our calculations in [21]. All the other parameters for the Ge 1−x Sn x material systems are calculated using a simple linear interpolation between Ge, and α-Sn, whose values are taken form references [22][23][24] …”

Section: Calculation Of Materials Parametersmentioning

confidence: 99%

Stark shift of the absorption spectra in Ge/Ge1−Sn /Ge type-I single QW cell for mid-wavelength infra-red modulators

Superlattices and Microstructures

et al. 2015

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For mid-wavelength infra-red (MWIR) modulation or detection applications, we propose α-Sn rich Ge/Ge 1-x Sn x /Ge a type-I single quantum wells (SQW) partially strain compensated on Ge 1-y Sn y relaxed layers grown onto (001)-oriented Ge substrate. Such elementary cells with W-like potential profiles of conduction and valence bands have been modeled by solving the one-dimensional Schrödinger equation under an applied external electrical field. First, strain effects on electrons, heavy holes (hh) and light holes (lh) energy bands for strained/relaxed Ge 1-x Sn x /Ge 1-y Sn y heterointerfaces are investigated using the modelsolid theory in the whole ranges (0  x, y  1) of Sn compositions. From the obtained band-discontinuities, band gaps and effective masses, Ge 1-y Sn y /Ge/Ge 0.80 Sn 0.20 /Ge/Ge 1-y Sn y cells are computed as a function of the Ge 0.80 Sn 0.20 well width for three compositions of the Ge 1-y Sn y buffer layer (y=0.05, 0.07 and 0.09) in order to get the optimum quantum confinement of electrons and holes levels while keeping a reasonable amount of averaged strain in the cell. The electric field effect on the absorption spectra is given. An absorption coefficient in the 6  to 3  10 3 cm −1 range is reasonably obtained for a SQW at room temperature with a rather large Stark shift of the direct transition between 0.46 and 0.38 eV (i.e., λ=3.26-2.70 μm) at large external fields (50 kV/cm). These characteristics are attractive for the design of MWIR optical modulators.

“…The device is sketched in figure 2. The material parameters used are taken from [23][24][25] and summarized in table 2. The compressive lattice mismatch between Ge 0.964 Sn 0.036 and Ge is 0.52% while the average mismatch of the 200 nm-thick stacks is 0.26%.…”

Section: Studied Structure and Modelingmentioning

confidence: 99%

Performance evaluation of high-detectivity p-i-n infrared photodetector based on compressively-strained Ge_0.964Sn_0.036/Ge multiple quantum wells by quantum modelling

Semicond. Sci. Technol.

et al. 2015

GeSn/Ge p-i-n photodetectors with practical Ge 0.964 Sn 0.036 active layers are theoretically investigated. First, we calculated the electronic band parameters for the heterointerfaces between strained Ge 1−x Sn x and relaxed (001)-oriented Ge. The carrier transport in a p-i-n photodiode built on a ten-period Ge 0.964 Sn 0.036 /Ge multiple quantum well absorber was then analyzed and numerically simulated within the Tsu−Esaki formalism by self-consistently solving the Schrödinger and Poisson equations, coupled to the kinetic rate equations. Photodetection up to a 2.1 μm cut-off wavelength is achieved. High responsivities of 0.62 A W −1 and 0.71 A W −1 were obtained under a reverse bias voltage of −3 V at peak wavelengths of 1550 nm and 1781 nm, respectively. Even for this low Sn-fraction, it is found that the photodetector quantum efficiency (49%@1.55 μm) is higher than those of comparable pure-Ge devices at room temperature. Detectivity of 3.8 × 10 10 cm Hz 1/2 W −1 and 7.9 × 10 10 cm Hz 1/2 W −1 at −1 V and −0.5 V, respectively, is achievable at room temperature for a 1550 nm wavelength peak of responsivity. This work represents a step forward in developing GeSn/Ge based infrared photodetectors.