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Publications (287) View all
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Dataset: Si tunneling transistors with high on-currents and slopes of 50 mV/dec using segregation doped NiSi 2 tunnel junctions
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ABSTRACT: a b s t r a c t Planar and nanowire (NW) tunneling field effect transistors (TFETs) have been fabricated on ultra thin strained and unstrained SOI with shallow doped nickel disilicide (NiSi 2) source and drain (S/D) contacts. We developed a novel, self-aligned process to form the p-i-n TFETs which greatly simplifies their fabri-cation by tilted dopant implantation using the high-k/metal gate as a shadow mask and dopant segrega-tion. Two methods of dopant segregation are compared: dopant segregation based on the ''snow-plough'' effect of dopants during silicidation and implantation into the silicide (IIS) followed by thermal outdiffu-sion. High drive currents of up to 60 lA/lm of planar p-TFETs were achieved indicating good silicide/sil-icon tunneling junctions. The non-linear temperature dependence of the inverse subthreshold slope S indicates characteristic TFET behavior. Strained Si NW array n-TFETs with omega shaped HfO 2 /TiN gates show high drive currents of 7 lA/lm @ 1 V V dd and steep inverse subthreshold slopes with minimum val-ues of <50 mV/dec due to the smaller band gap of strained Si and optimized electrostatics. -
Article: Si tunneling transistors with high on-currents and slopes of 50 mV/dec using segregation doped NiSi 2 tunnel junctions
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ABSTRACT: a b s t r a c t Planar and nanowire (NW) tunneling field effect transistors (TFETs) have been fabricated on ultra thin strained and unstrained SOI with shallow doped nickel disilicide (NiSi 2) source and drain (S/D) contacts. We developed a novel, self-aligned process to form the p-i-n TFETs which greatly simplifies their fabri-cation by tilted dopant implantation using the high-k/metal gate as a shadow mask and dopant segrega-tion. Two methods of dopant segregation are compared: dopant segregation based on the ''snow-plough'' effect of dopants during silicidation and implantation into the silicide (IIS) followed by thermal outdiffu-sion. High drive currents of up to 60 lA/lm of planar p-TFETs were achieved indicating good silicide/sil-icon tunneling junctions. The non-linear temperature dependence of the inverse subthreshold slope S indicates characteristic TFET behavior. Strained Si NW array n-TFETs with omega shaped HfO 2 /TiN gates show high drive currents of 7 lA/lm @ 1 V V dd and steep inverse subthreshold slopes with minimum val-ues of <50 mV/dec due to the smaller band gap of strained Si and optimized electrostatics.Solid-State Electronics 05/2013; · 1.40 Impact Factor -
Article: Study of dopant activation in biaxially compressively strained SiGe layers using excimer laser annealing
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ABSTRACT: Excimer Laser Annealing (ELA) with a wavelength of 248nm is used to study doping of biaxialy compressively strained Si1�xGex/Si heterostructures. The challenge is to achieve a high activation of As in SiGe, while conserving the elastic strain and suppressing dopant diffusion. Doping of 20 nm Si0.64Ge0.36 layers by ion implantation of 1�1015 Asþ/cm2 and subsequent laser annealing using single 20 ns pulse with an energy density of 0.6 J/cm2 leads to an As activation of about 20% and a sheet resistance of 650X/sq. At this laser energy density, the entire SiGe layer melts and the subsequent fast recrystallization on a nanosecond time scale allows high As incorporation into the lattice. Moreover, using these annealing parameters, the SiGe layer exhibits epitaxial regrowth with negligible strain relaxation. ELA at energy densities greater than 0.6 J/cm2 resembles Pulsed Lased Induced Epitaxy, leading to an intermixing of the SiGe layer with the Si substrate, thus to thicker single-crystalline strained SiGe layers with sheet resistance down to 62X/sq. Effects of energy densities on composition, crystal quality, activation of As and co-doping with B are discussed and related to the spatial and temporal evolution of the temperature in the irradiated zone, as simulated by Finite Element Methods.Journal of Applied Physics 05/2013; 113(20):204902. · 2.17 Impact Factor -
Article: Study of dopant activation in biaxially compressively strained SiGe layers using excimer laser annealing
[show abstract] [hide abstract]
ABSTRACT: Excimer Laser Annealing (ELA) with a wavelength of 248nm is used to study doping of biaxialy compressively strained Si1�xGex/Si heterostructures. The challenge is to achieve a high activation of As in SiGe, while conserving the elastic strain and suppressing dopant diffusion. Doping of 20 nm Si0.64Ge0.36 layers by ion implantation of 1�1015 Asþ/cm2 and subsequent laser annealing using single 20 ns pulse with an energy density of 0.6 J/cm2 leads to an As activation of about 20% and a sheet resistance of 650X/sq. At this laser energy density, the entire SiGe layer melts and the subsequent fast recrystallization on a nanosecond time scale allows high As incorporation into the lattice. Moreover, using these annealing parameters, the SiGe layer exhibits epitaxial regrowth with negligible strain relaxation. ELA at energy densities greater than 0.6 J/cm2 resembles Pulsed Lased Induced Epitaxy, leading to an intermixing of the SiGe layer with the Si substrate, thus to thicker single-crystalline strained SiGe layers with sheet resistance down to 62X/sq. Effects of energy densities on composition, crystal quality, activation of As and co-doping with B are discussed and related to the spatial and temporal evolution of the temperature in the irradiated zone, as simulated by Finite Element Methods.Journal of Applied Physics 05/2013; 113(20):204902. · 2.17 Impact Factor -
Article: Band engineering and growth of tensile strained Ge/(Si)GeSn heterostructures for tunnel field effect transistors
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ABSTRACT: In this letter, we propose a heterostructure design for tunnel field effect transistors with two low direct bandgap group IV compounds, GeSn and highly tensely strained Ge in combination with ternary SiGeSn alloy. Electronic band calculations show that strained Ge, used as channel, grown on Ge1�xSnx(x>9%) buffer, as source, becomes a direct bandgap which significantly increases the tunneling probability. The SiGeSn ternaries are well suitable as drain since they offer a large indirect bandgap. The growth of such heterostructures with the desired band alignment is presented. The crystalline quality of the (Si)Ge(Sn) layers is similar to state-of-the-art SiGe layers.Applied Physics Letters 05/2013; 102:192103. · 3.84 Impact Factor
