Observation of strain in pseudomorphic Si1−xGex by tracking phonon participation in Si∕SiGe resonant interband tunnel diodes via electron tunneling spectroscopy

Yu, Rui; Anisha, R.; Jin, Niu; Chung, Sung-Yong; Berger, Paul R.; Gramila, T. J.; Thompson, Phillip E.

doi:10.1063/1.3187832

Cited by 3 publications

(2 citation statements)

References 33 publications

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“…The peaks are positioned at slightly higher biases (19 and 63 mV) than the literature values of ±18 (TA) and ±57 mV (TO) . It is tempting to use the observed upshift in phonon energies to directly quantify the strain in the nanowire. However, in our current setup, the aforementioned contact resistance of our device and the limited signal intensity would hamper such an analysis.…”

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confidence: 81%

Silicon Nanowire Esaki Diodes

et al. 2012

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We report on the fabrication and characterization of silicon nanowire tunnel diodes. The silicon nanowires were grown on p-type Si substrates using Au-catalyzed vapor-liquid-solid growth and in situ n-type doping. Electrical measurements reveal Esaki diode characteristics with peak current densities of 3.6 kA/cm(2), peak-to-valley current ratios of up to 4.3, and reverse current densities of up to 300 kA/cm(2) at 0.5 V reverse bias. Strain-dependent current-voltage (I-V) measurements exhibit a decrease of the peak tunnel current with uniaxial tensile stress and an increase of 48% for 1.3 GPa compressive stress along the <111> growth direction, revealing the strain dependence of the Si band structure and thus the tunnel barrier. The contributions of phonons to the indirect tunneling process were probed by conductance measurements at 4.2 K. These measurements show phonon peaks at energies corresponding to the transverse acoustical and transverse optical phonons. In addition, the low-temperature conductance measurements were extended to higher biases to identify potential impurity states in the band gap. The results demonstrate that the most likely impurity, namely, Au from the catalyst particle, is not detectable, a finding that is also supported by the excellent device properties of the Esaki diodes reported here.

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confidence: 81%

Silicon Nanowire Esaki Diodes

et al. 2012

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“…27 However, e TA and D TA are altered with strain due to the distorted crystal structure affecting the atomic lattice vibration, which has been studied experimentally on Si and SiGe. [28][29][30] To correctly model indirect BTBT in strained Ge, a modified Keating model 31 is using to calculate e TA as a function of tensile strain (e TA ¼ 7.6-0.96 Â e // meV). D TA variation in strained Ge is taken into account by 30…”

Section: B Btbt Parametersmentioning

confidence: 99%

Tensile strained Ge tunnel field-effect transistors: k · p material modeling and numerical device simulation

Kao

Verhulst

Put

et al. 2014

Journal of Applied Physics

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Group IV based tunnel field-effect transistors generally show lower on-current than III-V based devices because of the weaker phonon-assisted tunneling transitions in the group IV indirect bandgap materials. Direct tunneling in Ge, however, can be enhanced by strain engineering. In this work, we use a 30-band k Á p method to calculate the band structure of biaxial tensile strained Ge and then extract the bandgaps and effective masses at C and L symmetry points in k-space, from which the parameters for the direct and indirect band-to-band tunneling (BTBT) models are determined. While transitions from the heavy and light hole valence bands to the conduction band edge at the L point are always bridged by phonon scattering, we highlight a new finding that only the light-holelike valence band is strongly coupling to the conduction band at the C point even in the presence of strain based on the 30-band k Á p analysis. By utilizing a Technology Computer Aided Design simulator equipped with the calculated band-to-band tunneling BTBT models, the electrical characteristics of tensile strained Ge point and line tunneling devices are self-consistently computed considering multiple dynamic nonlocal tunnel paths. The influence of field-induced quantum confinement on the tunneling onset is included. Our simulation predicts that an on-current up to 160 (260) lA/lm can be achieved along with on/off ratio > 10 6 for V DD ¼ 0.5 V by the n-type (p-type) line tunneling device made of 2.5% biaxial tensile strained Ge. V

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Compressively strained SiGe band-to-band tunneling model calibration based on p-i-n diodes and prospect of strained SiGe tunneling field-effect transistors

Kao

Verhulst²,

Rooyackers³

et al. 2014

Journal of Applied Physics

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Band-to-band tunneling parameters of strained indirect bandgap materials are not well-known, hampering the reliability of performance predictions of tunneling devices based on these materials. The nonlocal band-to-band tunneling model for compressively strained SiGe is calibrated based on a comparison of strained SiGe p-i-n tunneling diode measurements and doping-profile-based diode simulations. Dopant and Ge profiles of the diodes are determined by secondary ion mass spectrometry and capacitance-voltage measurements. Theoretical parameters of the band-to-band tunneling model are calculated based on strain-dependent properties such as bandgap, phonon energy, deformation-potential-based electron-phonon coupling, and hole effective masses of strained SiGe. The latter is determined with a 6-band kÁp model. The calibration indicates an underestimation of the theoretical electron-phonon coupling with nearly an order of magnitude. Prospects of compressively strained SiGe tunneling transistors are made by simulations with the calibrated model. V C 2014 AIP Publishing LLC. [http://dx.

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Observation of strain in pseudomorphic Si1−xGex by tracking phonon participation in Si∕SiGe resonant interband tunnel diodes via electron tunneling spectroscopy

Cited by 3 publications

References 33 publications

Silicon Nanowire Esaki Diodes

Silicon Nanowire Esaki Diodes

Tensile strained Ge tunnel field-effect transistors: k · p material modeling and numerical device simulation

Compressively strained SiGe band-to-band tunneling model calibration based on p-i-n diodes and prospect of strained SiGe tunneling field-effect transistors

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