Temperature dependence of energy gap of Ge1−xSnxalloys withx  &lt;  0.11 studied by photoreflectance

Żelazna, K.; Wełna, M.; Misiewicz, J.; Dekoster, J; Kudrawiec, R.

doi:10.1088/0022-3727/49/23/235301

Cited by 8 publications

(7 citation statements)

References 32 publications

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“…However, due to the reduced PL intensity with increasing temperature, the Γ HH and L HH peaks were not resolved on the spectra measured above 200 To confirm our understanding, temperature dependent PL measurements were performed to examine the relative peak intensity of direct (Γ HH ) and indirect (L HH ) transitions as a function of temperature (Figure 7). A red shift of both Γ HH and L HH peaks is seen with increasing temperature, which agrees with the bandgap shrinkage [24,25]. The peak intensities and their positions were determined again by fitting each measured spectrum with two Gaussian functions.…”

Section: Photoluminescence From Samples With the Same Sn Composition But Different Level Of Strain And Measurement Of ∆Esupporting

confidence: 70%

Impact of Long-Term Annealing on Photoluminescence from Ge1−xSnx Alloys

et al. 2021

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We report on the connection between strain, composition, defect density and the photoluminescence observed before and after annealing at 300 °C for GeSn samples with Sn content of 8% to 10%. Results show how the composition and level of strain influenced the separation between the indirect and direct optical transitions, while changes in the level of strain also influenced the density of misfit dislocations and surface roughness. The effect of annealing is observed to lower the level of strain, decreasing the energy separation between the indirect and direct optical transitions, while also simultaneously increasing the density of misfit/threading dislocations and surface roughness. The reduction in energy separation leads to an increase of photoluminescence (PL) emission, while the increase of misfit/threading dislocations density and surface roughness results in a decrease of PL. Consequently, the competition between these factors is observed to determine the impact of annealing on the PL. As a result, annealing increases the collected PL for small (≤40 meV) separation between the indirect to direct optical transitions in the as-grown sample while decreases the PL for larger (≥60 meV) separations. More generally, these numbers have a small dependence on the level of strain in the as-grown samples.

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Section: Photoluminescence From Samples With the Same Sn Composition But Different Level Of Strain And Measurement Of ∆Esupporting

confidence: 70%

Impact of Long-Term Annealing on Photoluminescence from Ge1−xSnx Alloys

et al. 2021

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“…In line with the expected Ge-like band structure, deformation potential theory suggests that the low-temperature PL is dominated by the indirect band-gap recombination involving conduction band electrons at the L -point of the Brillouin zone and valence band heavy holes (HH) at the zone center (see Supporting Information). The built-in compressive strain removes the HH degeneracy with the light hole (LH) band, yielding a HH–LH separation of ∼100 meV. , This strain-induced splitting and the weak dipole matrix element conceal the observation of high-energy features due to transitions involving LH states at any of the pump power densities employed in this work (see Supporting Information).…”

mentioning

confidence: 82%

“…By increasing the temperature, the PL features experience a well-known red-shift , as a result of the band-gap shrinking (see also Supporting Information for a detailed discussion), while the concomitant integrated PL intensity discloses a nontrivial temperature behavior that differs drastically for the three Ge 0. 91 Sn 0.09 epilayers.…”

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confidence: 99%

Temperature-Dependent Photoluminescence Characteristics of GeSn Epitaxial Layers

et al. 2016

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Ge1−xSnx epitaxial heterostructures are emerging as prominent candidates for the monolithic integration of light sources on Si substrates. Here we propose a judicious explanation for their temperature-dependent photoluminescence (PL) that is based upon the so far disregarded optical activity of dislocations. By working at the onset of plastic relaxation, which occurs whenever the epilayer releases the strain accumulated during growth on the lattice mismatched substrate, we demonstrate that dislocation nucleation can be explicitly seen in the PL data. Notably, our findings point out that a monotonous thermal PL quenching can be observed in coherent films, in spite of the indirect nature of the Ge1−xSnx bandgap. Our investigation, therefore, contributes to a deeper understanding of the recombination dynamics in this intriguing group IV alloy and offers insights into crucial phenomena shaping the light emission efficiency.

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“…The main drawback of that legacy method is that the coefficients

α_{GeSn}^{Γ}

and

β_{GeSn}^{Γ}

have to be calibrated for each Sn concentration as shown in refs. [].…”

Section: Eight‐band K·p Model Theorymentioning

confidence: 99%

Experimental Calibration of Sn‐Related Varshni Parameters for High Sn Content GeSn Layers

et al. 2019

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From temperature-dependent photoluminescence of a single Ge 0.84 Sn 0.16 sample, Sn-related Varshni parameters are extracted and used as input parameters in an 8-band k·p model, and predict direct bandgap energies of high Sn content GeSn alloys with concentration varying from 8% to 16%. Then, exhaustively compared are the calculated direct -valley bandgap energies to photoluminescence results of 13% and 16% Sn content alloys and to direct bandgap energies found in literature. The agreement between k·p modeling and experimental datasets is close to 3% for different strain conditions of GeSn epilayers. The outcome of this study is an 8-band k·p model with a fixed set of parameters, the model being self-sufficient to describe the direct bandgap of Ge 1−x Sn x layers with x varying from 8% to 16% for large ranges of strain and temperature.

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Temperature dependence of energy gap of Ge_1−xSn_xalloys withx < 0.11 studied by photoreflectance

Cited by 8 publications

References 32 publications

Impact of Long-Term Annealing on Photoluminescence from Ge1−xSnx Alloys

Impact of Long-Term Annealing on Photoluminescence from Ge1−xSnx Alloys

Temperature-Dependent Photoluminescence Characteristics of GeSn Epitaxial Layers

Experimental Calibration of Sn‐Related Varshni Parameters for High Sn Content GeSn Layers

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