Direct-bandgap GeSn grown on silicon with 2230 nm photoluminescence

Ghetmiri, Seyed Amir; Du, Wei; Margetis, Joe; Mosleh, Aboozar; Cousar, Larry; Conley, Benjamin R.; Domulevicz, Lucas; Nazzal, Amjad; Sun, Greg; Soref, Richard A.; Tolle, John; Li, Baohua; Naseem, Hameed A.; Yu, Shui-Qing

doi:10.1063/1.4898597

Cited by 191 publications

(142 citation statements)

References 24 publications

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“…The indirect-to-direct transition point locates at the Sn composition slightly below 10%, which agrees well with the discovery that was reported in Ref. 3; however, for relaxed GeSn samples, the transition point could happen for Sn compositions around 6%. The deviation between the Gaussian fitting points and the fitted lines are mainly due to the strain of the samples.…”

Section: Photoluminescencesupporting

confidence: 81%

“…While for the samples with higher Sn compositions, the indirect and direct peaks cannot be identified due to the small separation between the indirect and direct bandgap energies, resulting in a single peak PL spectrum with broad peak line-width. In addition, the indirect-to-direct transition occurs at the Sn composition of 10%, 3 beyond which the GeSn alloy becomes the direct bandgap material, and therefore only a direct peak with narrowed peak line-width can be observed. Note that the noisy PL spectra of GeSn samples with Sn compositions from 8% to 12% is due to the use of PbS detector, which features a 3.0 lm cut-off but with low signal-tonoise ratio.…”

Section: Photoluminescencementioning

confidence: 99%

“…5d, which reveals the direct bandgap material of GeSn with 12% Sn. 3 Since the U-valley minimum is lower than that of L-valley in direct bandgap GeSn, most electrons tend to populate on U-valley; therefore, the indirect transition was dramatically reduced, resulting in the single peak PL spectra. The PL behavior of the n-doped GeSn samples with Sn compositions of 5%, 8%, and 10% were investigated.…”

Section: Photoluminescencementioning

confidence: 99%

See 2 more Smart Citations

Optical Characterization of Si-Based Ge1−x Sn x Alloys with Sn Compositions up to 12%

Al-Kabi

Ghetmiri

Margetis

et al. 2015

Journal of Elec Materi

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Optical properties of germanium tin (Ge 1Àx Sn x ) alloys have been comprehensively studied with Sn compositions from 0 (Ge) to 12%. Raman spectra of the GeSn samples with various Sn compositions were measured. The room temperature photoluminescence (PL) spectra show a gradual shift of emission peaks towards longer wavelength as Sn composition increases. Temperature dependent PL shows the PL intensity variation along with the temperature change, which reveals the indirectness or directness of the bandgap of the material. As temperature decreases, the PL intensity decreases with Sn composition less than 8%, indicating the indirect bandgap Ge 1Àx Sn x ; while the PL intensity increases with Sn composition higher than 10%, implying the direct bandgap Ge 1Àx Sn x . Moreover, the PL study of n-doped samples shows bandgap narrowing compared to the unintentionally (Boron) doped thin film with similar Sn compositions due to the doping.

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Section: Photoluminescencesupporting

confidence: 81%

Section: Photoluminescencementioning

confidence: 99%

Section: Photoluminescencementioning

confidence: 99%

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Optical Characterization of Si-Based Ge1−x Sn x Alloys with Sn Compositions up to 12%

Al-Kabi

Ghetmiri

Margetis

et al. 2015

Journal of Elec Materi

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“…Experimental evidence of the tendency towards a direct band structure was partially obtained in early studies. [10][11][12][13][14] However, only recently has Wirths et al demonstrated a direct bandgap alloy conclusively, with strong photoluminescence and a lasing effect at a Sn content of %11 at: %. 15 The aforementioned properties, together with the possibility of full compatibility with current Si technology, make Ge 1Àx Sn x an attractive material.…”

Section: Introductionmentioning

confidence: 99%

“…However, achieving high quality crystalline Ge 1Àx Sn x with above 6:5 at: %Sn is challenging as the material is unstable at high Sn concentration because the solid solubility of Sn in Ge at ambient temperature is about 0:5 at: % . 16 For this reason, a non-equilibrium technique is essential for growing the alloy, such as molecular beam epitaxy (MBE), 10,11,17 sputter deposition, 18 or chemical vapour deposition (CVD). 15,19,20 Alternatively, ion-beam synthesis combined with nanosecond pulsed laser melting (PLM) can also provide a condition far from equilibrium 21 for achieving supersaturated Sn concentrations in Ge.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Ge1−xSnx alloys by ion implantation and pulsed laser melting: Towards a group IV direct bandgap material

Tran

Pastor

Gandhi

et al. 2016

Journal of Applied Physics

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The germanium-tin (Ge1−xSnx) material system is expected to be a direct bandgap group IV semiconductor at a Sn content of 6.5−11 at. %. Such Sn concentrations can be realized by non-equilibrium deposition techniques such as molecular beam epitaxy or chemical vapour deposition. In this report, the combination of ion implantation and pulsed laser melting is demonstrated to be an alternative promising method to produce a highly Sn concentrated alloy with a good crystal quality. The structural properties of the alloys such as soluble Sn concentration, strain distribution, and crystal quality have been characterized by Rutherford backscattering spectrometry, Raman spectroscopy, x ray diffraction, and transmission electron microscopy. It is shown that it is possible to produce a high quality alloy with up to 6.2 at. %Sn. The optical properties and electronic band structure have been studied by spectroscopic ellipsometry. The introduction of substitutional Sn into Ge is shown to either induce a splitting between light and heavy hole subbands or lower the conduction band at the Γ valley. Limitations and possible solutions to introducing higher Sn content into Ge that is sufficient for a direct bandgap transition are also discussed.

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Room‐Temperature Negative Differential Resistance and High Tunneling Current Density in GeSn Esaki Diodes

et al. 2022

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distribution. Novel devices with different operational principles for a sharper SS than 60 mV per decade have been extensively investigated, such as impact ionization MOS (I-MOS) transistors, [1] negative-capacitance field-effect transistors (NC-FETs), [2] or tunnel field-effect transistors (TFETs). [3] While an SS of sub-60 mV per decade has been demonstrated for those devices, the issues of the required high gate biases for I-MOS transistors or the hysteresis for NC-FETs are critical issues for the reliability of integrated circuits. For TFETs, whose device structures are similar to conventional CMOS transistors, a steep SS is achieved by band-toband tunneling (BTBT) processes between the source and channel regions. The major issue for TFETs is their low drive current. For group-IV materials such as silicon (Si) or germanium (Ge), the device performance of TFETs is poor due to their large bandgap energies and effective masses of carriers, and the requirement of phonon participation for the momentum reservation in the BTBT process. [4,5] For III-V materials, while the tunneling current is high because of their direct-bandgap characteristics, [6,7] the poor quality of oxide interface could lead to the instability of device operations. Moreover, the compatibility with the Si-based VLSI technology is still a critical issue. [8] Recently, germanium-tin (GeSn) has attracted much attention for electronic, optoelectronic, and spintronic device applications owing to its direct-bandgap characteristics, [9] high carrier mobility, [10] strong spin-orbit coupling (SOC) effects, [11] and compatibility with the VLSI technology. Simulations on GeSn TFETs showed strong current enhancement than Si-or Gebased devices owing to the direct BTBT process and the smaller bandgap and effective carrier masses in GeSn. [12,13] To justify the BTBT process and calibrate the tunneling rates, Esaki diodes with negative differential resistance (NDR) are used to characterize the peak current density. Thus far, there is no NDR demonstrated in any GeSn-based Esaki diodes at room temperature. To observe NDR, the Fermi levels must be higher or lower than the conduction band minimum or the valence band maximum at the n-type or p-type regions, respectively. If the doping levels or the activation rates of dopants are not high enough, NDR will not be observed. Moreover, if there exists a large amount of defect states in the bandgap, electrons can tunnel across the junction via those states with the assistance of thermal processes, Tunnel field-effect transistors (TFETs) are a promising candidate for lowpower applications owing to their steep subthreshold swing of sub-60 mV per decade. For silicon-or germanium-based TFETs, the drive current is low due to the indirect band-to-band tunneling (BTBT) process. Direct-bandgap germanium-tin (GeSn) can boost the TFET performance since phonon participation is not required during the tunneling process. Esaki diodes with negative differential resistance (NDR) are used to characterize the BTBT properties and calibr...

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Direct-bandgap GeSn grown on silicon with 2230 nm photoluminescence

Cited by 191 publications

References 24 publications

Optical Characterization of Si-Based Ge1−x Sn x Alloys with Sn Compositions up to 12%

Optical Characterization of Si-Based Ge1−x Sn x Alloys with Sn Compositions up to 12%

Synthesis of Ge1−xSnx alloys by ion implantation and pulsed laser melting: Towards a group IV direct bandgap material

Room‐Temperature Negative Differential Resistance and High Tunneling Current Density in GeSn Esaki Diodes

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