Comparison of first principles and semi-empirical models of the structural and electronic properties of $$\hbox {Ge}_{1-x}\hbox {Sn}_{x}$$ alloys

O'Halloran, Edmond J.; Broderick, Christopher A.; Tanner, Daniel S. P.; Schulz, Stefan; O’Reilly, Eoin P.

doi:10.1007/s11082-019-1992-8

Cited by 26 publications

(72 citation statements)

References 63 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This value is consistent with the energy expected at low temperature for the optical transition through the fundamental indirect band gap of bulk Ge [30], thereby suggesting the prominence of the indirect-band-gap recombination in all the observed spectra of our coherent Ge 1−x Sn x films. The emergence of the indirect PL in Ge 1−x Sn x is also in line with the -L hybridization of the conduction-band edge pointed out by recent calculations [31,32].…”

Section: A Photoluminescence Measurementssupporting

confidence: 86%

“…The measured carrier lifetime τ corresponds to an effective lifetime for photogenerated carriers and encapsulates contributions from radiative (τ R ) and nonradiative (τ NR ) recombination processes: τ −1 = τ −1 R + τ −1 NR [44]. Recent analyses [31,32,45] have shown that the evolution of the Ge 1−x Sn x band gap is driven by Sn-induced hybridization between the Ge -point and L-point conduction-band-edge states. A direct band gap then emerges continuously with increasing Sn content, as the alloy conduction-band edge acquires increasing direct ( ) character.…”

Section: B Hanle Measurements and Carrier Lifetimementioning

confidence: 99%

See 1 more Smart Citation

Continuous-Wave Magneto-Optical Determination of the Carrier Lifetime in Coherent Ge1−xSnx/Ge Heterostructures

et al. 2020

Self Cite

View full text Add to dashboard Cite

We present a magneto-optical study of the carrier dynamics in compressively strained Ge 1−x Sn x films with Sn content up to 10% epitaxially grown on Ge on Si(001) virtual substrates. We leverage the Hanle effect under steady-state excitation to study the spin-dependent optical transitions in the presence of an external magnetic field. This allows us to obtain direct access to the dynamics of the optically induced carrier population. Our approach reveals that at cryogenic temperatures the effective lifetime of the photogenerated carriers in coherent Ge 1−x Sn x is on the subnanosecond timescale. Supported by a model estimate of the radiative lifetime, our measurements indicate that carrier recombination is dominated by nonradiative processes. Our results thus provide central information to improve the fundamental understanding of carrier kinetics in this advanced direct-band-gap group-IV-material system. Such knowledge can be a stepping stone in the quest for the implementation of Ge 1−x Sn x -based functional devices.

show abstract

Section: A Photoluminescence Measurementssupporting

confidence: 86%

Section: B Hanle Measurements and Carrier Lifetimementioning

confidence: 99%

Continuous-Wave Magneto-Optical Determination of the Carrier Lifetime in Coherent Ge1−xSnx/Ge Heterostructures

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…4(a) we compare the calculated Raman spectra of ordered and disordered supercells having the same Sn composition, x = 6.25%: an ordered 16-atom Ge 15 Sn 1 supercell (upper panel), and configuration averaging over 25 distinct, disordered 512-atom Ge 480 Sn 32 supercells (lower panel). Figure 4(b) shows the distribution of relaxed nearest-neighbour bond lengths in these supercells, sorted into bins of width 0.01 Å, 46,72 where the distribution for the disordered Ge 480 Sn 32 supercells has again been obtained via configurational averaging. Note that in Fig.…”

Section: B Impact Of Alloy Disordermentioning

confidence: 99%

Raman spectroscopy of group-IV Ge$_{1-x}$Sn$_{x}$ alloys: theory and experiment

Tanner¹,

Raha²,

Doherty³

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

Ge 1−x Sn x alloys are a promising candidate material to realise direct-gap group-IV semiconductors for applications in Si-compatible electronic and photonic devices. Here, we present a combined theoretical and experimental analysis of Raman spectroscopy in Ge 1−x Sn x alloys. We describe liquid-vapour-solid growth and structural characterisation of Ge 1−x Sn x (x ≤ 8%) nanowires displaying high crystalline quality, and investigate the structural and vibrational properties of the nanowires using Raman spectroscopy. Our theoretical analysis is based on a fully analytic anharmonic valence force field (VFF) potential, which describes exactly -i.e. without recourse to numerical fitting -the secondorder elastic constants, third-order bulk modulus, selected second-and third-order inner elastic constants and, as a consequence, the zone-centre transverse optical phonon mode frequency and its hydrostatic and axial strain dependence. We compute bulk elastic properties via density functional theory to parametrise the VFF potential for Ge 1−x Sn x alloys, and apply the VFF potential to explicitly compute the Raman spectra of realistic, disordered Ge 1−x Sn x alloy supercells. Our atomistic theoretical calculations quantitatively capture: (i) the evolution of the measured Raman spectra with Sn composition x, (ii) demonstrate explicitly that the presence of short-range alloy disorder can significantly impact the shift coefficients a and b that respectively describe the dependence of the Raman shift on Sn composition and pseudomorphic strain, (iii) elucidate the origin of the so-called "disorder activated" mode identified in previous experimental investigations, and (iv) allow for detailed atomic-scale interpretation of measured Raman spectra. Overall, our analysis provides insight relevant to the characterisation of this emerging material system.

show abstract

“… 7 − 11 Recent theoretical calculations have also supported that the indirect-gap to direct-gap transition proceeds via the continuous transition–with increasing x . 11 , 12 The optical and optoelectronic properties of an alloy can be influenced by the alloy composition, as demonstrated both theoretically 13 and experimentally. 14 − 16 A definitive transition to a direct bandgap is required, with large enough Sn incorporation, for the use of Ge 1– x Sn x in efficient optoelectronic devices, such as photodiodes and photodetectors and photonic devices without the need for any external force such as induced strain.…”

Section: Introductionmentioning

confidence: 96%

Stretching the Equilibrium Limit of Sn in Ge_1–xSn_x Nanowires: Implications for Field Effect Transistors

Biswas

Doherty

Galluccio

et al. 2021

ACS Appl. Nano Mater.

View full text Add to dashboard Cite

Ge 1– x Sn x nanowires incorporating a large amount of Sn would be useful for mobility enhancement in nanoelectronic devices, a definitive transition to a direct bandgap for application in optoelectronic devices and to increase the efficiency of the GeSn-based photonic devices. Here we report the catalytic bottom-up fabrication of Ge 1– x Sn x nanowires with very high Sn incorporation ( x > 0.3). These nanowires are grown in supercritical toluene under high pressure (21 MPa). The introduction of high pressure in the vapor–liquid–solid (VLS) like growth regime resulted in a substantial increase of Sn incorporation in the nanowires, with a Sn content ranging between 10 and 35 atom %. The incorporation of Sn in the nanowires was found to be inversely related to nanowire diameter; a high Sn content of 35 atom % was achieved in very thin Ge 1– x Sn x nanowires with diameters close to 20 nm. Sn was found to be homogeneously distributed throughout the body of the nanowires, without apparent clustering or segregation. The large inclusion of Sn in the nanowires could be attributed to the nanowire growth kinetics and small nanowire diameters, resulting in increased solubility of Sn in Ge at the metastable liquid–solid interface under high pressure. Electrical investigation of the Ge 1– x Sn x ( x = 0.10) nanowires synthesized by the supercritical fluid approach revealed their potential in nanoelectronics and sensor-based applications.

show abstract

Comparison of first principles and semi-empirical models of the structural and electronic properties of $$\hbox {Ge}_{1-x}\hbox {Sn}_{x}$$ alloys

Cited by 26 publications

References 63 publications

Continuous-Wave Magneto-Optical Determination of the Carrier Lifetime in Coherent Ge1−xSnx/Ge Heterostructures

Continuous-Wave Magneto-Optical Determination of the Carrier Lifetime in Coherent Ge1−xSnx/Ge Heterostructures

Raman spectroscopy of group-IV Ge$_{1-x}$Sn$_{x}$ alloys: theory and experiment

Stretching the Equilibrium Limit of Sn in Ge_1–xSn_x Nanowires: Implications for Field Effect Transistors

Contact Info

Product

Resources

About

Comparison of first principles and semi-empirical models of the structural and electronic properties of $$\hbox {Ge}_{1-x}\hbox {Sn}_{x}$$ alloys

Cited by 26 publications

References 63 publications

Continuous-Wave Magneto-Optical Determination of the Carrier Lifetime in Coherent Ge1−xSnx/Ge Heterostructures

Continuous-Wave Magneto-Optical Determination of the Carrier Lifetime in Coherent Ge1−xSnx/Ge Heterostructures

Raman spectroscopy of group-IV Ge$_{1-x}$Sn$_{x}$ alloys: theory and experiment

Stretching the Equilibrium Limit of Sn in Ge1–xSnx Nanowires: Implications for Field Effect Transistors

Contact Info

Product

Resources

About

Stretching the Equilibrium Limit of Sn in Ge_1–xSn_x Nanowires: Implications for Field Effect Transistors