Infrared Absorption of Germanium near the Lattice Edge

Macfarlane, G.G.; Roberts, V.

doi:10.1103/physrev.97.1714.2

Cited by 177 publications

(28 citation statements)

References 6 publications

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“…(14). With experimental evidence showing that the Ge material gives the dominant phonon energy for SiGe compositions below 30% Si, 17 we have included a constant phonon energy of 27.7 meV (equivalent to the bulk Ge LA phonon) for each type of material present in our test sample, giving us good fit with our experimental data.…”

Section: Phononssupporting

confidence: 58%

“…For Ge, the dominant phonon is the LA phonon with energy 27.7 meV 18 while the averaged phonon has a slightly lower energy of ∼23 meV. 14,17 The nominally forbidden TA phonon, with only 7.8 meV, also contributes increasingly to the absorption spectra at elevated temperatures (such as room temperature), thus reducing the weighted average phonon. While the TO phonon is symmetry allowed (with energy 30.0 meV), its contribution is much weaker in comparison to the LA (and TA) phonon.…”

Section: Phononsmentioning

confidence: 99%

“…There are three main models that have been effectively used to approximate the indirect absorption spectra in Ge and Si bulk materials: a one-phonon model, 14,17,35,36 a multiple-phonon model 15,16,18,20,37 and an electric-field dependent model. 19 The one-phonon model (Eq.…”

Section: Modeling Indirect Absorptionmentioning

confidence: 99%

“…This additional loss is largely due to indirect absorption and it is important to fully understand this mechanism in detail to optimize future modulator designs in Ge or GeSi. While bulk Ge and Si have been extensively studied with respect to their indirect absorption, [14][15][16][17][18][19][20] how this absorption changes in a quantum well (QW) heterostructures (for QCSE devices ) has not yet been similarly investigated. Only one published paper shows the presence of the longitudinal acoustic (LA) phonon in Ge/SiGe quantum wells with the same energy as that of the bulk material.…”

Section: Introductionmentioning

confidence: 99%

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Indirect absorption in germanium quantum wells

et al. 2011

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Germanium has become a promising material for creating CMOS-compatible optoelectronic devices, such as modulators and detectors employing the Franz-Keldysh effect (FKE) or the quantum-confined Stark effect (QCSE), which meet strict energy and density requirements for future interconnects. To improve Ge-based modulator design, it is important to understand the contributions to the insertion loss (IL). With indirect absorption being the primary component of IL, we have experimentally determined the strength of this loss and compared it with theoretical models. For the first time, we have used the more sensitive photocurrent measurements for determining the effective absorption coefficient in our Ge/SiGe quantum well material employing QCSE. This measurement technique enables measurement of the absorption coefficient over four orders of magnitude. We find good agreement between our thin Ge quantum wells and the bulk material parameters and theoretical models. Similar to bulk Ge, we find that the 27.7 meV LA phonon is dominant in these quantum confined structures and that the electroabsorption profile can be predicted using the model presented by Frova, Phys. Rev., 145 (1966)

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Section: Phononssupporting

confidence: 58%

Section: Phononsmentioning

confidence: 99%

Section: Modeling Indirect Absorptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Indirect absorption in germanium quantum wells

et al. 2011

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“…As a result of indirect allowed transition, treatment considering both the absorption and emission of phonons gives the absorption coefficient α for a single-phonon process in the form [20,21]:…”

Section: Absorption Coefficientmentioning

confidence: 99%

Optical absorption spectra and related parameters of ammonium zinc chloride crystal in the antiferroelectric and commensurate phases

Gaffar¹,

El‐Fadl²,

Anooz³

2003

Cryst. Res. Technol.

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Optical absorption along the three crystallographic axes of (NH 4 ) 2 ZnCl 4 single crystals is reported over a temperature range from 276 K to 350 K. Our results clearly confirm the antiferroelectric to commensurate phase transition at 319 K. Analysis reveals that at the absorption edge the type of transition is the indirect allowed one. The indirect band gaps at various temperatures are determined and their temperature dependence is estimated in the antiferroelectric and commensurate phases. Optical parameters related to the temperature dependence of the energy gap are evaluated. The single-effective oscillator model was used to describe the imaginary part of the dielectric constant, which facilitate calculation of the dipole moment parameters. The steepness parameter is given, its value is used to estimate the temperature dependence of the indirect energy gap and the result is compared with that calculated graphically. In the region of the absorption edge, the absorption coefficient obeys Urbach's rule. Urbach characteristic parameters are determined and their temperature dependence is investigated. Correlation between different parameters is considered. Most of the results confirm the optical isotropic nature of AZC crystals.

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