The Experts below are selected from a list of 31047 Experts worldwide ranked by ideXlab platform
Yee-chia Yeo - One of the best experts on this subject based on the ideXlab platform.
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Realizing steep subthreshold swing with Impact Ionization Transistors
2009 International Symposium on VLSI Technology Systems and Applications, 2009Co-Authors: Yee-chia YeoAbstract:Recent developments in Impact Ionization Transistors (I-MOS) will be discussed here, including strained Impact Ionization transistors realized on the nanowire or multiple-gate device architecture. I-MOS devices achieve excellent subthreshold swings well below 5 mV/decade at room temperature. Techniques for enhancing Impact Ionization rate and reducing the breakdown voltage V BD for device performance improvement will be discussed. Challenges faced by I-MOS will be highlighted. Some challenges may be addressed through the strain and materials engineering. Limitations of the I-MOS will also be discussed.
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Reduction of Impact-Ionization threshold energies for performance enhancement of complementary Impact-Ionization metal-oxide-semiconductor transistors
Applied Physics Letters, 2007Co-Authors: Eng Huat Toh, Grace Huiqi Wang, Lap Chan, Ganesh Samudra, Yee-chia YeoAbstract:We explore the improvement of electrical performance of Impact-Ionization metal-oxide-semiconductor (I-MOS) transistors by the reduction of Impact-Ionization threshold energy through incorporation of materials with smaller bandgaps. Silicon-germanium (SiGe) I-MOS transistors were demonstrated. The lower bandgap of SiGe, as compared to Si, contributes to lower electron and hole Impact-Ionization threshold energies, leading to avalanche breakdown at a much reduced source voltage and enhanced device performance. Both n- and p-channel I-MOS devices were fabricated on Si0.60Ge0.40-on-insulator substrates using a complementary metal-oxide-semiconductor compatible process flow. Excellent subthreshold swings as low as 5mV/decade were achieved for the SiGe I-MOS devices. Reduction in breakdown voltage VBD was as large as 1.3 and 1.6V, respectively, for the n- and p-channel Si0.60Ge0.40 I-MOS devices.
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Device Design and Scalability of an Impact Ionization MOS Transistor with an Elevated Impact Ionization Region
Simulation of Semiconductor Processes and Devices 2007, 1Co-Authors: Eng Huat Toh, Grace Huiqi Wang, Lap Chan, Ganesh Samudra, Yee-chia YeoAbstract:This paper reports a novel L-shaped Impact-Ionization MOS (LI-MOS) transistor structure that achieves a subthreshold swing of well below 60 mV/decade at room temperature and operates at a low supply voltage. The device features an L-shaped or elevated Impact-Ionization region (I-region) which displaces the hot carrier activity away from the gate dielectric region to improve hot carrier reliability and VT stability problems. Device physics and design principles for the LI-MOS transistor are detailed through extensive two-dimensional device simulations. The LI-MOS transistor exhibits excellent scalability, making it suitable for augmenting the performance of standard CMOS transistors in future technology generations.
Ronald Redmer - One of the best experts on this subject based on the ideXlab platform.
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Impact Ionization and high-field effects in wide-band-gap semiconductors
Physica B-condensed Matter, 2001Co-Authors: M. Reigrotzki, J. R. Madureira, A. Kuligk, N. Fitzer, Ronald Redmer, Stephen M. Goodnick, M. Dür, Wolfgang SchattkeAbstract:Impact Ionization is important for electron transport in wide-band-gap semiconductors at high electric fields. We consider a realistic band structure as well as high-field quantum corrections such as the intracollisional field effect in the calculation of the microscopic scattering rate. A pronounced softening of the Impact Ionization threshold is obtained. This field-dependent Impact Ionization rate is included within a full-band ensemble Monte Carlo simulation of high-field transport in ZnS. Although the Impact Ionization rate itself is strongly affected, little effect is observed on measurable quantities such as the Impact Ionization coefficient.
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Impact Ionization AND HIGH FIELD EFFECTS IN WIDE BAND GAP SEMICONDUCTORS
International Journal of High Speed Electronics and Systems, 2001Co-Authors: M. Reigrotzki, J. R. Madureira, A. Kuligk, N. Fitzer, Ronald Redmer, Stephen M. Goodnick, M. DürAbstract:Impact Ionization plays a crucial role for electron transport in wide-bandgap semiconductors at high electric fields. Therefore, a realistic band structure has to be used in calculations of the microscopic scattering rate, as well as high field quantum corrections such as the intercollisional field effect. Here we consider both, and evaluate the Impact Ionization rate for wide-bandgap materials such as ZnS. A pronounced softening of the Impact Ionization threshold is obtained, as found earlier for materials like Si and GaAs. This field dependent Impact Ionization rate is included within a full-band ensemble Monte Carlo simulation of high field transport in ZnS. Although the Impact Ionization rate itself is strongly affected, little effect is observed on measurable quantities such as the Impact Ionization coefficient or the electron distribution function itself.
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Field effect on the Impact Ionization rate in semiconductors
Journal of Applied Physics, 2000Co-Authors: Ronald Redmer, J. R. Madureira, N. Fitzer, Stephen M. Goodnick, Wolfgang Schattke, Eckehard SchöllAbstract:Impact Ionization plays a crucial role for electron transport in semiconductors at high electric fields. We derive appropriate quantum kinetic equations for electron transport in semiconductors within linear response theory. The field-dependent collision integral is evaluated for the process of Impact Ionization. A known, essentially analytical result is reproduced within the parabolic band approximation [W. Quade et al., Phys. Rev. B 50, 7398 (1994)]. Based on the numerical results for zero field strengths but realistic band structures, a fit formula is proposed for the respective field-dependent Impact Ionization rate. Explicit results are given for GaAs, Si, GaN, ZnS, and SrS.
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Impact Ionization in ZnS
Physical review. B Condensed matter, 1995Co-Authors: M. Reigrotzki, Ronald Redmer, Michael Stobbe, Wolfgang SchattkeAbstract:The Impact Ionization rate and its orientation dependence in k space is calculated for ZnS. The numerical results indicate a strong correlation to the band structure. The use of a q-dependent screening function for the Coulomb interaction between conduction and valence electrons is found to be essential. A simple fit formula is presented for easy calculation of the energy dependent transition rate.
Wolfgang Schattke - One of the best experts on this subject based on the ideXlab platform.
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Impact Ionization and high-field effects in wide-band-gap semiconductors
Physica B-condensed Matter, 2001Co-Authors: M. Reigrotzki, J. R. Madureira, A. Kuligk, N. Fitzer, Ronald Redmer, Stephen M. Goodnick, M. Dür, Wolfgang SchattkeAbstract:Impact Ionization is important for electron transport in wide-band-gap semiconductors at high electric fields. We consider a realistic band structure as well as high-field quantum corrections such as the intracollisional field effect in the calculation of the microscopic scattering rate. A pronounced softening of the Impact Ionization threshold is obtained. This field-dependent Impact Ionization rate is included within a full-band ensemble Monte Carlo simulation of high-field transport in ZnS. Although the Impact Ionization rate itself is strongly affected, little effect is observed on measurable quantities such as the Impact Ionization coefficient.
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Field effect on the Impact Ionization rate in semiconductors
Journal of Applied Physics, 2000Co-Authors: Ronald Redmer, J. R. Madureira, N. Fitzer, Stephen M. Goodnick, Wolfgang Schattke, Eckehard SchöllAbstract:Impact Ionization plays a crucial role for electron transport in semiconductors at high electric fields. We derive appropriate quantum kinetic equations for electron transport in semiconductors within linear response theory. The field-dependent collision integral is evaluated for the process of Impact Ionization. A known, essentially analytical result is reproduced within the parabolic band approximation [W. Quade et al., Phys. Rev. B 50, 7398 (1994)]. Based on the numerical results for zero field strengths but realistic band structures, a fit formula is proposed for the respective field-dependent Impact Ionization rate. Explicit results are given for GaAs, Si, GaN, ZnS, and SrS.
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Impact Ionization in ZnS
Physical review. B Condensed matter, 1995Co-Authors: M. Reigrotzki, Ronald Redmer, Michael Stobbe, Wolfgang SchattkeAbstract:The Impact Ionization rate and its orientation dependence in k space is calculated for ZnS. The numerical results indicate a strong correlation to the band structure. The use of a q-dependent screening function for the Coulomb interaction between conduction and valence electrons is found to be essential. A simple fit formula is presented for easy calculation of the energy dependent transition rate.
Chihiro Hamaguchi - One of the best experts on this subject based on the ideXlab platform.
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Impact Ionization model for full band Monte Carlo simulation in GaAs
Journal of Applied Physics, 1996Co-Authors: H. K. Jung, K. Taniguchi, Chihiro HamaguchiAbstract:The Impact Ionization rate in GaAs is derived from a first principle’s calculation which includes realistic band structure and a wave‐vector‐ and frequency‐dependent dielectric function. The Impact Ionization rate is highly anisotropic at low electron energy, while it becomes isotropic at higher energy range in which Impact Ionization events frequently occur. The calculated Impact Ionization rate is well fitted to a modified Keldysh formula with two sets of power exponents of 7.8 and 5.6, indicating very soft threshold characteristics. Using a full band Monte Carlo simulation which includes the empirical phonon scattering rate based on first principles theory, we derived the Impact Ionization coefficient. The calculated Impact Ionization coefficients agree well with available experimental data. Our isotropic model shows better agreement with reported experimental data than a previous anisotropic model, especially in low electric field. The mean energy of secondary generated electrons is found to be expres...
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Impact Ionization model for full band Monte Carlo simulation
Journal of Applied Physics, 1994Co-Authors: Yoshinari Kamakura, H. Mizuno, Mitsuru Yamaji, Masato Morifuji, K. Taniguchi, Chihiro Hamaguchi, Tatsuya Kunikiyo, M. TakenakaAbstract:The Impact Ionization rate in silicon is numerically derived from wave functions and energy band structure based on an empirical pseudopotential method. The calculated Impact Ionization rate is well fitted to an analytical formula with a power exponent of 4.6, indicating soft threshold of Impact Ionization rate, which originates from the complexity of the Si band structure. The calculated Impact Ionization rate shows strong anisotropy at low electron energy (e
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Theoretical calculation of Impact Ionization rate in SiO2
Journal of Applied Physics, 1993Co-Authors: H. Mizuno, Masato Morifuji, Kenji Taniguchi, Chihiro HamaguchiAbstract:Impact Ionization rate in SiO2 was numerically calculated using both pseudo‐wave functions and energy band structure based on a self‐consistent pseudopotential method. To avoid numerical complexity due to amorphous structure, SiO2 was assumed to be a crystalline α‐quartz. The calculated Impact Ionization rate shows a strong wave vector anisotropy near a threshold energy regime, primary electrons existing at Γ point yield the strongest Impact Ionization rate. It was found that calculated results are not expressed by a Keldysh formula since SiO2 has complex band structure (e.g., indirect transition gap and nonparabolic bands). The magnitude of the theoretical Impact Ionization rate was very close to the experimental results recently reported by E. Cartier and F.R. McFeely [Phys. Rev. B 44, 10689 (1991)]. Detailed theoretical study clearly demonstrates that the average energy of secondary generated carriers depends linearly on the energy of primary electrons.
J. R. Madureira - One of the best experts on this subject based on the ideXlab platform.
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Impact Ionization and high-field effects in wide-band-gap semiconductors
Physica B-condensed Matter, 2001Co-Authors: M. Reigrotzki, J. R. Madureira, A. Kuligk, N. Fitzer, Ronald Redmer, Stephen M. Goodnick, M. Dür, Wolfgang SchattkeAbstract:Impact Ionization is important for electron transport in wide-band-gap semiconductors at high electric fields. We consider a realistic band structure as well as high-field quantum corrections such as the intracollisional field effect in the calculation of the microscopic scattering rate. A pronounced softening of the Impact Ionization threshold is obtained. This field-dependent Impact Ionization rate is included within a full-band ensemble Monte Carlo simulation of high-field transport in ZnS. Although the Impact Ionization rate itself is strongly affected, little effect is observed on measurable quantities such as the Impact Ionization coefficient.
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Impact Ionization AND HIGH FIELD EFFECTS IN WIDE BAND GAP SEMICONDUCTORS
International Journal of High Speed Electronics and Systems, 2001Co-Authors: M. Reigrotzki, J. R. Madureira, A. Kuligk, N. Fitzer, Ronald Redmer, Stephen M. Goodnick, M. DürAbstract:Impact Ionization plays a crucial role for electron transport in wide-bandgap semiconductors at high electric fields. Therefore, a realistic band structure has to be used in calculations of the microscopic scattering rate, as well as high field quantum corrections such as the intercollisional field effect. Here we consider both, and evaluate the Impact Ionization rate for wide-bandgap materials such as ZnS. A pronounced softening of the Impact Ionization threshold is obtained, as found earlier for materials like Si and GaAs. This field dependent Impact Ionization rate is included within a full-band ensemble Monte Carlo simulation of high field transport in ZnS. Although the Impact Ionization rate itself is strongly affected, little effect is observed on measurable quantities such as the Impact Ionization coefficient or the electron distribution function itself.
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Field effect on the Impact Ionization rate in semiconductors
Journal of Applied Physics, 2000Co-Authors: Ronald Redmer, J. R. Madureira, N. Fitzer, Stephen M. Goodnick, Wolfgang Schattke, Eckehard SchöllAbstract:Impact Ionization plays a crucial role for electron transport in semiconductors at high electric fields. We derive appropriate quantum kinetic equations for electron transport in semiconductors within linear response theory. The field-dependent collision integral is evaluated for the process of Impact Ionization. A known, essentially analytical result is reproduced within the parabolic band approximation [W. Quade et al., Phys. Rev. B 50, 7398 (1994)]. Based on the numerical results for zero field strengths but realistic band structures, a fit formula is proposed for the respective field-dependent Impact Ionization rate. Explicit results are given for GaAs, Si, GaN, ZnS, and SrS.
