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Al-induced crystallization (AIC) of amorphous SixGe1–x (a-SixGe1–x) alloys with compositions over the entire range of the isomorphous Si–Ge system has been investigated. The crystallization progress was monitored by dedicated in situ x-ray diffraction analysis while gradually increasing the annealing temperature. Auger sputter-depth profiling was applied to investigate the occurrence of Al-induced layer exchange of the Al and a-SixGe1–x sublayers after complete crystallization. A-SixGe1–x alloys with x < 0.13 and x > 0.41 show largely different AIC behaviors with respect to crystallization rate and possible layer exchange of the Al and a-SixGe1–x sublayers upon crystallization. A thermodynamic model for AIC of a-SixGe1–x alloys is presented, which well explains these experimental observations and thereby demonstrates the dominant role of interface thermodynamics in the AIC process of amorphous semiconductors. The model can be used to predict the AIC behaviors of a-SixGe1–x alloys over the entire composition range at specified annealing temperatures. [ABSTRACT FROM PUBLISHER]

A systematic study of a Li atom and four types of SiGe (6,6) nanotubes (NTs) of length ~20 Å has been performed to explore SiGeNTs' viability as anode material in Li-ion batteries. For all structures, full geometry and spin optimizations were performed without any symmetry constraints. We used the hybrid functional B3LYP and an all electron 6-311G**//3-21G* basis set implemented in GAUSSIAN 09 suite of software. All possible internal and external adsorption sites were considered, and it was found that some tubes deformed as a result of the Jahn-Teller effect. Out of all four types, type III NTs were found to retain the tubular shape for most cases of adsorption. Our calculations predict that SiGeNTs attract Li atom on top of Si, on top of Ge, and on top of hollow sites with adsorption energies ranging from 0.888 to 1.657 eV. Most probable sites for external and internal adsorptions were quasi on top of Ge site and quasi hollow site, respectively. After adsorption of the Li atom, Jahn-Teller active orbitals of the systems vanished from the frontier orbital region, indicating that more Li atoms can be adsorbed while keeping the desired tubular shape. In general, the difference between the highest occupied molecular orbital (HOMO) energy level and the lowest unoccupied molecular orbital (LUMO) energy level decreased with respect to the bare SiGeNT values. The decreased HOMO-LUMO gaps vary between 0.685 and 0.930 eV. Charge population analysis indicated that charge generally accumulated around the nearest neighbor atoms to the Li atom. We conclude that with the careful placement of Li atoms, SiGeNTs can be very successful as anode material in Li-ion battery technology. [ABSTRACT FROM AUTHOR]

Highlights: [•] We model boron diffusion in silicon–germanium alloy with Object Kinetic Monte Carlo. [•] We validate our model comparing with experimental results. [•] We report and discuss divergences between a particular experiment and simulation. [•] Boron diffusion in bulk is shown to be independent of a SiGe cap layer. [Copyright &y& Elsevier]

Abstract: NPN silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs) were exposed to 60Co gamma source at different dose rates under two bias conditions. Excess base currents and normalized current gains are used to quantify performance degradation. Experiment results demonstrate that the lower the dose rate, the more the irradiation damage, and some enhanced low dose rate sensitivity (ELDRS) exists in SiGe HBTs. The ELDRS effect is found to depend highly on the bias condition during exposure, and the transistors with forward active mode exhibit a more serious ELDRS effect compared to the floating case. The performance degradation at different dose rates and bias conditions is compared and discussed, and furthermore the underlying physical mechanisms are analyzed and investigated in detail. [Copyright &y& Elsevier]

A combined analytical and numerical process has been developed to model and optimize thermoelements. In this way, the performance of commercial n- and p-type thermoelectric materials can be optimized to deliver the maximum output power and conversion efficiency. The validity of the method is demonstrated using a silicon germanium unicouple. [ABSTRACT FROM AUTHOR]

In this brief, a novel U-shape-channel tunneling field-effect transistor (UTFET) with a SiGe source region is investigated by 2-D technology computer aided design simulation. The enlarged tunneling area and enhanced tunneling rate dramatically increase the tunneling current when the device is turned on. Meanwhile, the off-leakage current of UTFET is suppressed because of the extended physical channel length. The on-state tunneling current of UTFET can be further improved by introducing an n^+-doped Si delta layer under the source region. The inserted delta layer significantly shortens the band-to-band tunneling path, enlarges tunneling area, and thus enhances the tunneling rate of this device. The average value of the subthreshold swing (SS) of the optimized UTFET is 58 mV/dec when V\rm{GS} is varied from 0 to 0.46 V. Using the SiGe-source UTFET structure with a delta layer, the merits of low leakage current, high drive current, and ultralow SS can be realized simultaneously. [ABSTRACT FROM PUBLISHER]

We have studied the low-frequency noise characterizations in 28-nm high-k (HK) pMOSFET with embedded SiGe source/drain (S/D) through 1/f noise and random telegraph noise measurements simultaneously. It is found that uniaxial compressive strain really existed inHK pMOSFET with embedded SiGe S/D.The compressive strain induced the decrease in the tunneling attenuation length reflecting in the oxide trap depth from Si/SiO2 interface to the HK layer, so that the oxide traps at a distance from insulator/semiconductor interface cannot capture carrier in the channel. Consequently, lower 1/f noise level in HK pMOSFET with embedded SiGe S/D is observed, thanks to the less carrier fluctuations from trapping/detrapping behaviors. This result represents an intrinsic benefit of HK pMOSFET using embedded SiGe S/D in low-frequency noise characteristics. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the influence of the Ge content on the {113} defects formed, after a (35 keV, 1 × 1015 Ge+/cm2) preamorphization step followed by annealing at 680 °C, in relaxed SiGe alloys. For that, plan-view Transmission Electron Microscopy (PTEM) under appropriate imaging conditions was used to study the {113} defects evolution as a function of the Ge content. Experimental results show that, increasing the Ge content results in a net reduction of both the density and the size of the {113} defects. Results analysis was performed in the framework of the 'excess interstitials' model which describes perfectly the observed decrease of the {113} defects density in Si. Moreover, through a confrontation between the TEM observations and the predictions of this model, we show that the density of the interstitials contained in the defects (deduced from PTEM images) is a quasi linear function of the density of excess interstitials generated during the preamorphization step beneath the c/a interface, as calculated by the SRIM code. We conclude that collisional arguments can appropriately explain the observed evolution of the {113} defects density as a function of the Ge content. Meanwhile, the observed reduction of the {113} defects size with the Ge content, may be ascribed to a decrease of the transport capacity DiCi*, responsible for the defects growth. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

A new tri-band power amplifier (PA) on a 0.18-\mum SiGe BiCMOS process, operating concurrently in Ku-, K-, and Ka-band, is presented. The concurrent tri-band PA design is based on the distributed amplifier structure with capacitive coupling to enable large device size, while maintaining wide bandwidth, gain cells with the enhanced-gain peaking inductor, and negative-resistance active notch filters for improved tri-band gain response. The concurrent tri-band PA exhibits measured small-signal gain around 15.4, 14.7, and 12.3 dB in the low band (10–19 GHz), midband (23–29 GHz), and high band (33–40 GHz), respectively. In the single-band mode, the PA has maximum output powers of 15, 13.3, and 13.8 dBm at 15, 25, and 35 GHz, respectively. When the PA is operated in dual-band mode, it has maximum output powers of 11.4/8.2 dBm at 15/25 GHz, 13.3/3 dBm at 15/35 GHz, and 8.7/6.7 dBm at 25/35 GHz. In the tri-band mode, it exhibits 8.8/5.4/3.8-dBm maximum output power at 15/25/35 GHz. The concurrent tri-band PA exhibits relatively flat responses in gain and output power across its three frequency bands and good matching up to 40 GHz. [ABSTRACT FROM PUBLISHER]

SiGe epitaxial layers are integrated as an active part in thermal detectors. To improve their performance, deeper understanding of design parameters, such as thickness, well periodicity, quality, and strain amount, of the layers/interfaces is required. Oxygen (2-2500 × 10-9 Torr) was exposed prior or during epitaxy of SiGe/Si multilayers. In this range, samples with 10 nTorr oxygen were processed to investigate layer quality and noise measurements. Temperature coefficient of resistance was also measured to evaluate the thermal response. These results demonstrate sensitivity of SiGe-based devices to size and location of defects in the structure. [ABSTRACT FROM AUTHOR]

A fully integrated push--push voltage controlled oscillator (VCO) working in K-band with a large tuning range and a low phase noise fabricated in a 0.18 μm SiGe BiCMOS technology is presented. Multi-coupled LC tanks are used to improve the tuning range, power consumption and phase noise. Digital tuning varactors are used to maintain a low VCO tuning sensitivity (Kvco) and maximum frequency overlap. The VCO achieves a frequency tuning range (FTR) of 17% at 12 GHz, a phase noise of --106.62 dBc/Hz at 1 MHz offset and consumes 7mW from 1.8 V supply. [ABSTRACT FROM AUTHOR]

We have investigated the microstructure and device characteristics of GaAs0.82P0.18 solar cells grown on Si0.20Ge0.80/Si graded buffers. Anti-phase domains (APDs) were largely self-annihilated within the In0.39Ga0.61P initiation layer although a low density of APDs was found to propagate to the surface. A combination of techniques was used to show that the GaAs0.82P0.18 cells have a threading dislocation density of 1.2 ± 0.2 × 107 cm-2. Despite these extended defects, the devices exhibited high open-circuit voltages of 1.10-1.12 V. These results indicate that cascading a GaAs0.82P0.18 top cell with a lower-bandgap Si0.20Ge0.80 cell is a promising approach for high-efficiency dual-junction devices on low-cost Si substrates. [ABSTRACT FROM AUTHOR]

This paper measures the n- and p-MOSFETs fabricated through 65-nm high-k/metal gate CMOSFET process flow. The [110] channels of the Si cap on SiGe with different width (W) and length (L) ratios were compared with Si-only channels. The results show that a high W-L ratio in the [110]~n-channel can alleviate the degradation of biaxial compressive stress. Meanwhile, a low W-L ratio in the p-channel can improve the performance; however, the ratio should at least be below two in this paper. The dominance of the longitudinal or transverse configurations successfully explains this phenomenon because of the reliance of the different levels of piezoresistance coefficient on the channel orientation. The threshold voltage shifts versus the W-L ratio in the p-channel is in agreement with the result. The result is verified by a quantitative current comparison at a high bias in the n-/p-channels between the strained SiGe and Si-only channels, which shows that an extreme W-L ratio in the original biaxially strained SiGe channel can result in longitudinal or transverse strain, thereby leading to different levels of performance degradation/improvement. [ABSTRACT FROM AUTHOR]

A comparative experimental study of series resistance and hole mobility of pMOSFETs with silicon germanium (SiGe) junctions under various silicide techniques is carried out. It is found that using an additional germanium pre-amorphous implant process in the nickel silicide (NiSi) techniques does not affect the hole mobility. However, it increases the source/drain series resistance. On the other hand, an additional silicon capping layer process in the NiSi techniques not only improves the hole mobility, but also reduces the series resistance dramatically. Various MOSFET characterizations from the silicide techniques are mainly due to the differences in the NiSi/SiGe interface structures in those devices. [ABSTRACT FROM AUTHOR]

This paper reports on the use of p-type polycrystalline silicon germanium (poly-Si\rm{1-x}Ge\rm{x}) thin films as a new masking material for the cryogenic deep reactive ion etching (DRIE) of silicon. We investigated the etching behavior of various poly-Si\rm{1-x}Ge\rm{x}{:}B~(01:800). Furthermore, the SiGe mask was etched in SF{6}/O{2} plasma at temperatures \geq-80^\circC and at rates exceeding 8 \mum/min (i.e., more than 37 times faster than SiO{2} or SiN masks). Because of the chemical and thermodynamic stability of the SiGe film as well as the electronic properties of the mask, it was possible to deposit the proposed film at CMOS backend compatible temperatures. The paper also confirms that the mask can easily be dry-removed after the process with high etching-rate by controlling the ICP and RF power and the SF{6} to O{2} ratios, and without affecting the underlying silicon substrate. Using low ICP and RF power, elevated temperatures (i.e., >-80^\circC), and an adjusted O{2}{:}SF{6} ratio (i.e., \approx6\%), we were able to etch away the SiGe mask without adversely affecting the final profile. Ultimately, we were able to develop deep silicon- trenches with high aspect ratio etching straight profiles. \hfill[2012\-0321] [ABSTRACT FROM PUBLISHER]

The role of alloy and phonon scattering is theoretically explored in 5 nm diameter SiGe nanowires at room temperature. Low‐field mobility calculations are performed by utilizing sp3d5ds*‐spin–orbit‐coupled tight binding model for electronic structure and Boltzmann transport formalism. Three different transport orientations 〈100〉, 〈110〉 and 〈111〉 are considered. Alloy scattering is found to play an important role in these Si1–xGex nanowires, leading to a characteristic ‘U’ shaped mobility curve as a function of alloy composition. It is concluded that to extract any advantage of higher Ge hole mobility by alloying, Ge% > 70% is needed. Furthermore, the 〈111〉 channel orientation exhibits the highest hole mobility while 〈100〉 has the lowest hole mobility for any given alloy composition. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) Part of Focus Issue on “Semiconductor Nanowires” (Eds.: Chennupati Jagadish, Lutz Geelhaar, Silvija Gradecak) SiGe is an important material for high mobility p‐type transistors. In this Letter, the role of alloy and phonon scattering on the total hole mobility in SiGe nanowires is studied. At low carrier density, alloy scattering is still found to be relevant leading to an ‘U’ shaped mobility curve as a function of Ge concentration. [ABSTRACT FROM AUTHOR]

Highlights: [•] The (100)/〈110〉 channel direction is more stress sensitive for both N- and PMOS. [•] For high performance application the (100)/〈110〉 channel orientation is optimal. [•] For low-cost and low-power technologies the (100)/〈100〉 orientation is suitable. [ABSTRACT FROM AUTHOR]

A highly efficient push–push voltage-controlled oscillator (VCO) with a new inductive frequency tuning topology for (sub) terahertz frequencies is presented. The tuning technique is based on a variable inductance seen at the emitter node of a base-degenerated transistor. The variable inductor exhibits high quality factor and high tuning range due to the tunable transistor transconductance via bias current. Fabricated in a 0.13-\mu\m SiGe BiCMOS process, the VCO achieves a tuning range of 3.5% and an output power of -7.2 dBm at 201.5 GHz. The dc power consumption of the VCO is 30 mW, resulting in a high dc to RF power efficiency of 0.6% and a figure of merit (FoMT) of -165, which is the highest FoM for any silicon-based VCO reported to date at this frequency range. To demonstrate the functionality of the tuning technique, three VCO prototypes at different oscillation frequencies, including one operating in the 222.7–229-GHz range, are implemented and measured. [ABSTRACT FROM PUBLISHER]

Based on the empirical pseudo-potential method which incorporates compositional disorder as an effective potential, the band structure of SiGe alloy are calculated for different alloy composition x. The effect of temperature and pressure on the electronic band structure of the considered alloy has been studied. Monotonic decreasing and increasing functions are obtained for the temperature and pressure dependent form factors respectively. Some physical quantities as band gaps, bowing parameters, and the refractive index of the considered alloy with different Ge concentration and under the effect of temperature and pressure are calculated. The results obtained are found in good agreement with the experimental and published data. [ABSTRACT FROM AUTHOR]

An approach to transfer a high-quality SiGe layer for the fabrication of SiGe-on-insulator wafers has been proposed based on the investigation of crack formation in H-implanted Si0.75Ge0.25/B-doped Si0.70Ge0.30/Si structures. The crack formation is found to be closely correlated to the concentration of B atoms doped in the buried Si0.70Ge0.30 layer. For H-implanted Si0.75Ge0.25/Si0.70Ge0.30/Si structures without B doping, no platelets or cracking is observed in the Si0.70Ge0.30 layer. Upon increasing the concentration of B doping in the buried Si0.70Ge0.30 layer to 2 × 1019/cm3, cracking occurs at the interfaces on both sides of Si0.70Ge0.30 interlayer, thus, resulting in the formation of continuous sharp crack confined in the ultrathin Si0.70Ge0.30 interlayer. With B doped ultrathin Si0.70Ge0.30 interlayer, the Si0.75Ge0.25 layer can be transferred to fabricate SiGe-on-insulator by H implantation with a fluence as low as 3 × 1016/cm2, which is only half of the typical fluence required for a conventional ion-cut process. Since cracking is confined in the ultrathin Si0.70Ge0.30 interlayer, the as-cut SiGe-on-insulator possesses a rather smooth surface with a roughness of 1.55 nm. [ABSTRACT FROM AUTHOR]

During molecular beam epitaxial growth of Ge islands on Si(00l) substrates containing pit-patterned areas, an efficient Ge surface diffusion from unpatterned to pit-patterned substrate regions results in position-dependent island growth rates. We exploit this effect to map Out the evolution of strictly ordered Ge islands from prepyramids via pyramids and transition domes into domes by atomic force microscopy. A one-dimensional diffusion model is established which allows a quantitative determination of the Ge surface diffusion Constant and the rates at which Ge atoms are incorporated into the growing islands. We find evidence that during the shape transitions from nonfaceted islands to {105}-faceted pyramids and from pyramids to domes, Ge is incorporated at higher rates than during the growth of pure pyramids or domes. From these data it follows that a Ge atom passes on average several thousand pits before it is incorporated into one. Within our model we show that secondary-island nucleation in the substrate regions between the pits is a consequence of a mismatch between Ge incorporation and deposition rates, which results in a growing wetting layer between the ordered island sites, the thickness of which eventually exceeds the critical one for spontaneous island nucleation. We experimentally demonstrate that by lowering the Ge deposition rate, perfectly ordered islands with large pit periods of around I μm can be grown, in agreement with the model predictions. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we fabricated strain-relaxed Si0.58Ge0.42 thin films on Si substrates by molecular beam epitaxy (MBE) for heterojunction solar cell applications. A combined set of stepwise Si1−x Ge x buffer layers and a Si0.51Ge0.49 strain-inverted layer, in conjunction with rapid thermal annealing (RTA), were employed to confine the dislocations within the buffer layers. Structural characterization of the samples revealed a low dislocation density of less than 105 cm−2 and a relatively smooth surface (0.903nm in root mean square roughness). The results of solar cell characterization showed both an extended absorption edge (1200nm) and improved diode characteristics. For these cells, the short-circuit current density, open-circuit voltage, fill factor, and efficiency were 8.25mA cm−2, 233mV, 0.509, and 0.98%, respectively. [Copyright &y& Elsevier]

Strain engineering and the crystalline quality of semiconductor nanostructures are important issues for electronic and optoelectronic devices. We report on defect-free SiGe island arrays resulting from Ge coverages of up to 38 monolayers grown on prepatterned Si(001) substrates. This represents a significant expansion of the parameter space known for the growth of perfect island arrays. A cyclic development of the Ge content and island shape was observed while increasing the Ge coverage. Synchrotron-based x-ray diffraction experiments and finite element method calculations allow us to study the strain behavior of such islands in great detail. In contrast to the oscillatory changes of island shape and average Ge content, the overall strain behavior of these islands exhibits a clear monotonic trend of progressive strain relaxation with increasing Ge coverage. [ABSTRACT FROM AUTHOR]

This paper presents the design and the implementation of a fully monolithic coupled-oscillator array, operating at 6 GHz with close to zero coupling phase, in 0.25 μm BICMOS silicon germanium process. This array is made of four LC-NMOS differential VCOs coupled through a resistor. The single LC-NMOS VCO structure is designed and optimized in terms of phase noise with a graphical optimization approach while satisfying design constraints. At 2.5 V power supply voltage, and a power dissipation of only 125 mW, the coupled oscillators array features a simulated phase noise of −127.3 dBc/Hz at 1 MHz frequency offset from a 6 GHz carrier, giving a simulated phase progression that was continuously variable over the range −64° < Δϕ < 64° and −116° < Δϕ < 116°. This constant phase progression can be established by slightly detuning the peripheral array elements, while maintaining mutual synchronization. [ABSTRACT FROM AUTHOR]

We studied the plastic deformation of an ultrathin silicon-on-insulator with epitaxial Si1-xGex by transmission electron microscopy, Raman spectroscopy, and finite-element method. We analyzed a top Si layer of 10 nm (testing also a 2 nm layer) with epitaxial Si0.64Ge0.36 stressors of 50 and 100 nm. SiGe plastically deforms the top Si layer, and this strain remains even when Si1-xGex is removed. For low dislocation densities, dislocations are gettered close to the Si/SiO2 interface, while the SiGe/Si interface is coherent. Beyond a threshold dislocation density, interactions between dislocations force additional dislocations to position at the Si1-xGex/Si interface. [ABSTRACT FROM AUTHOR]

This paper presents a novel InP-SiGe BiCMOS technology using wafer-scale heterogeneous integration. The vertical stacking of the InP double heterojunction bipolar transistor (DHBT) circuitry directly on top of the BiCMOS wafer enables ultra-broadband interconnects with <0.2~dB insertion loss from 0–100 GHz. The 0.8\times 5~\mum^2 InP DHBTs show fT/f\max of 400/350 GHz with an output power of more than 26 mW at 96 GHz. These are record values for a heterogeneously integrated transistor on silicon. As a circuit example, a 164-GHz signal source is presented. It features a voltage-controlled oscillator in BiCMOS, which drives a doubler-amplifier chain in InP DHBT technology. [ABSTRACT FROM AUTHOR]

In this article, the small-signal equivalent circuit model of SiGe:C heterojunction bipolar transistors (HBTs) has directly been extracted fromS-parameter data. Moreover, in this article, we present a new modelling approach using ANFIS (adaptive neuro-fuzzy inference system), which in general has a high degree of accuracy, simplicity and novelty (independent approach). Then measured and model-calculated data show an excellent agreement with less than 1.68 × 10−5% discrepancy in the frequency range of higher than 300 GHz over a wide range of bias points in ANFIS. The results show ANFIS model is better than ANN (artificial neural network) for redeveloping the model and increasing the input parameters. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Impact of Ge content on Vt, β, and Id mismatches in advanced PMOSFETs. [•] Global improvement ofelectrical parameters mismatchobserved in PMOSETs with SiGe channel. [•] The reduction of Coulomb scatteringwith the introduction of Ge improves β mismatch. [Copyright &y& Elsevier]

A new technique to measure the thermal conductivity of thermoelectric materials at the microscale has been developed. The structure allows the electrical conductivity, thermal conductivity, and Seebeck coefficient to be measured on a single device. The thermal conductivity is particularly difficult to measure since it requires precise estimation of the heat flux injected into the material. The new technique is based on a differential method where the parasitic contributions of the supporting beams of a Hall bar are removed. The thermal measurements with integrated platinum thermometers on the device are cross-checked using thermal atomic force microscopy and validated by finite-element analysis simulations. [ABSTRACT FROM AUTHOR]

Silicon-Germanium (SiGe) technology effectively merges the desirable attributes of conventional silicon-based CMOS manufacturing (high integration levels, at high yield and low cost) with the extreme levels of transistor performance attainable in classical III-V heterojunction bipolar transistors (HBTs). SiGe technology joins together on-die high-speed bandgap-engineered SiGe HBTs with conventional Si CMOS to form SiGe BiCMOS technology, including all the requisite RF passive elements and multi-level thick-Al metalization required for high-speed circuit design. Such an silicon-based integrated circuit technology platform presents designers with an ideal division of labor for realizing optimal solutions to many performance-constrained mixed-signal (analog + digital + RF) systems. The unique bandgap-engineered features of SiGe HBTs enable several key merits with respect to operation across a wide variety of so-called “extreme environments”, potentially with little or no process modification, ultimately providing compelling advantages at the circuit and system level, across a wide class of envisioned commercial and defense applications. Here we give an overview of this interesting field, focusing primarily on the intersection of SiGe HBTs, and circuits built from them, with radiation-intense environments such as space. [ABSTRACT FROM PUBLISHER]

This paper reports a simulation study investigating the drive current of a prototypical SiGe n-type FinFET built on a relaxed SiGe substrate for different values of the Ge content x in the Si(1-x)Gex active layer. To this purpose, we performed strain simulations, band-structure calculations, and multisubband Monte Carlo transport simulations accounting for the effects of the Ge content on both the band-structure and the scattering rates in the transistor channel. Our results suggest that the largest on-current may be obtained with a simple Si active layer, because of the beneficial strain induced by the SiGe substrate. A SiGe channel instead is less performing because of strain relaxation and alloy scattering. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Analytical model of subthreshold current is derived for strained-Si on SGOI MOSFET. [•] Analytical subthreshold swing model is developed for strained-Si on SGOI MOSFET. [•] Parabolic approximation is used for determination of the 2D channel potential. [•] ATLAS simulation data are used for the verification of theoretical results. [•] Theoretical results are in good agreement with simulation results. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present the unique features exhibited by a novel nanoscale SiGe-on-insulator metal-oxide-semiconductor field-effect transistor (MOSFET) with modified channel band energy. The key idea in this work is to modify the band energy in the channel for improving electrical performances. Graded Ge composition profile is employed in the channel that leads to call the proposed structure as GC-SGOI structure. Using two-dimensional two-carrier simulation we demonstrate that the GC-SGOI structure has higher saturation velocity in comparison with stepped (SC-SGOI) and uniform (UC-SGOI) germanium composition due to the high conduction and valence bands slopes by using graded Ge composition profile. Also, our results show that the GC-SGOI exhibit excellent properties not only higher mobility, drain current and saturation velocity but also hot electron degradation improvement and better reliability. Therefore, refer to the results, the GC-SGOI structure has superior performances in comparison with the SC- and UC-SGOI structures which leads to be a good candidate for VLSI circuits. [Copyright &y& Elsevier]

Abstract: We present a review of recent advances in deterministic solvers for the Boltzmann transport equation for electrons and holes in a 3D and quasi 2D -space and demonstrate the capabilities of deterministic solvers by two new examples: a THz SiGe HBT and a quantum well PMOSFET. Compared to the standard approach, the Monte Carlo method, these deterministic solvers have certain advantages. They yield exact stationary solutions and they allow small-signal and noise analysis directly in the frequency range from 0 to THz. Inclusion of magnetic fields, the Pauli principle or rare events causes no problems. Thus, it is now possible to calculate certain key figures of merit for devices based on the Boltzmann transport equation, which was previously very difficult or not possible at all. On the other hand, the deterministic solvers are more memory intensive and more difficult to code than the Monte Carlo method. [Copyright &y& Elsevier]

An analytical study to quantify the substrate parasitic effects on SiGe HBT amplifiers in both common-base and commonemitter configuration is presented. The power gain relations and stability factors are derived from the modelled S-parameters which are computed at a fixed bias point from the small-signal hybrid model of SiGe HBT in both configurations. It has been shown that the power gains of SiGe HBT amplifiers in both configurations are degraded when extrinsic and substrate parasitics are taken into account. The degradation in power gains is found to be more pronounced for CB configuration, which makes the design of HBT amplifiers, particularly in the CB mode, difficult. Close matching of the modelled data with the reported experimental results validates the proposed methodology. [ABSTRACT FROM AUTHOR]

We report on ultrascaled (LG = 23 nm) compressively strained SiGe-based FDSOI pMOSFET with ultrathin body. The devices have been fabricated using a high-K metal gate (TiN/HfSiON) process flow. SiGe channels (3.4 nm) have been epitaxially grown on 3-nm thick 300-mm SOI wafers and combined with embedded Si0.7Ge0.3(:B) raised source and drain (RSD) for Vth,p tuning and smart strain management. Indepth electrical characterizations point out the +120-mV Vth,p tuning, the excellent short-channel, and DIBL control (similar to SOI reference), and show for the first time extremely low variability for SiGe-based FD pMOSFETs. Furthermore, we investigate hole-transport properties as a function of gate length and temperature and demonstrate 60% Raccess reduction with SiGe RSD and +330% mobility enhancement at 23-nm gate length with respect to 7-nm thick SOI reference. [ABSTRACT FROM AUTHOR]

Abstract: A variable optical attenuator based on a 2D MEMS grating is described. The device is a perforated and suspended poly-SiGe membrane with fixed islands within the perforations. It specularly reflects light in the non-actuated state, whereas after actuation the membrane deflects downwards forming a grating which diffracts light in higher orders reducing the intensity of the specular reflection. Using a laser of 400nm wavelength, we could obtain an attenuation level of 20dB with 0.11dB of polarization dependent loss. A close match was obtained between the experimental and simulated mechanical behavior of the device showing the possibility of efficiently extending its use in the NIR regime. Additionally, as the device is made of poly-SiGe deposited at low temperature, it can be monolithically integrated with CMOS in the future. [Copyright &y& Elsevier]

This article presents a 24/77-GHz transmitter chipset for automotive radar sensors implemented in a 160/175-GHz fT/fmax SiGe BiCMOS technology. The chipset adopts a dual-band architecture consisting of a 24-GHz section for ultra-wideband short-range radar operation, which is also exploited to drive the 77-GHz long-range radar transmitter front-end. The proposed design adopts a single 24-GHz frequency synthesizer to implement both radar operation modes. The transmitter chipset is able to deliver a maximum output power of 3 dBm and 12 dBm at 24 GHz and 77 GHz, respectively. The 24-GHz transmitter demonstrates to operate with pulse widths of 0.5 ns and 1 ns in compliance with the transmission mask designed by ETSI. The 77-GHz transmitter exhibits a power gain of 20 dB, an output power of 12 dBm, and an output referred 1-dB compression point of 9.5 dBm, while drawing 155 mA from a 2.5-V supply voltage. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:782-786, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27425 [ABSTRACT FROM AUTHOR]

The total-dose-effects of gamma and proton irradiations on high-voltage silicon–germanium heterojunction bipolar transistors with the collector electrode elicited from the backside of the substrate are investigated. Pre- and post-radiation DC characteristics of the transistors are used to quantify the dose tolerance to the two different irradiation sources. Measurement results indicate that the devices exhibit a total dose tolerance up to Mrad level. The device response is indeed radiation source dependent and the proton irradiation can produce a more significant damage than the gamma irradiation, causing more pronounced performance degradation. The experimental results from both irradiations are compared and discussed in detail, and furthermore the underlying physical mechanisms are analyzed and investigated. The considerably different degradation behaviors are attributed to the extra displacement damage besides ionizing damage induced by the proton irradiation. [ABSTRACT FROM AUTHOR]

We investigate the nucleation and growth of anisotropic and strained quantum dots in heteroepitaxy by means of kinetic Monte Carlo simulations. Surface energy anisotropy is introduced in order to depict Ge- like dots with (105) facets growing on a Si (100) substrate. Three dimensional islands, mainly in the form of square-base pyramids, are reported and their coarsening is found to be interrupted during annealing. The resulting island density follows the scaling law ρ∼(D/F)−α with α≃0.6 as a function of the diffusion D to flux F ratio. The island size distribution follows the scaling law resulting from the assumption of a single length scale. [ABSTRACT FROM AUTHOR]

Abstract: Linearity characteristics of common-emitter (CE) and common-base (CB) configuration SiGe HBTs are analyzed and compared under different matching, bias and frequency conditions. Impedance matching is demonstrated to have significant effect on the configuration-dependent linearity characteristics. Moreover, with source and load impedance matched for maximum output power, CE and CB configurations not only show different power gain relation but also different linearity characteristics dependence on frequency. Theoretical expressions show good agreement of the RF linearity property for simulation and experimental results. Further dc bias study reveals that both higher power-gain and better linearity can be obtained from the CB than the CE configuration under certain bias and operation conditions. A potential tradeoff between the two configurations in terms of linearity and power gain is also demonstrated. [Copyright &y& Elsevier]

We investigate the morphological evolution of SiGe quantum dots deposited on Si(100) during long-time annealing. At low strain, the dots' self-organization begins by an instability and interrupts when (105) pyramids form. This evolution and the resulting island density are quantified by molecular-beam epitaxy. A kinetic model accounting for elasticity, wetting, and anisotropy is shown to reproduce well the experimental findings with appropriate wetting parameters. In this nucleationless regime, a mean-field kinetic analysis explains the existence of nearly stationary states by the vanishing of the coarsening driving force. The island size distribution follows in both experiments and theory the scaling law associated with a single characteristic length scale. [ABSTRACT FROM AUTHOR]

This paper analyses substrate-related spurious tones in fractional-N phase-locked loops with integrated VCOs. Spur positions are calculated and experimentally verified as a function of the divider ratios of prescaler and programmable divider. For an integrated wideband PLL in SiGe BiCMOS technology the spur power levels are measured and compared with theoretical expectations. The power in these spurs is minimized by layout techniques shielding the reference input buffer. Spur minimization by using a variable reference frequency is experimentally demonstrated. Based on this observation, a programmable integer- N PLL for driving the fractional-N synthesizer is suggested to reduce the worst-case spur level significantly. [ABSTRACT FROM AUTHOR]

We report on the electro-refractive effect in Ge/SiGe multiple quantum wells grown by low energy plasma enhanced chemical vapor deposition. The electro-refractive effect was experimentally characterized by the shift of Fabry-Perot fringes in the transmission spectra of a 64 μm long slab waveguide. A refractive index variation up to 1.3 × 10-3 was measured with an applied electric field of 88 kV/cm at 1475 nm, 50 meV below the excitonic resonance, with a VπLπ figure of merit of 0.46 V cm. The device performances are promising for the realization of Mach Zehnder modulators in the Ge-Si material platform. [ABSTRACT FROM AUTHOR]

In semiconductor manufacturing, we expect the cause of defects to be process or tool related. However, at the 90 nm technology node and beyond we find that defects can be caused by issues related to the wafers' environment, such as processing of other wafers in the same tool or in the same carrier, or by seemingly innocuous actions. We pay special attention to the role of the mini-environment, which is deemed essential to achieving low particle counts for advanced technology nodes. We show defects that are caused by the environment, and some which are specifically related to the use of the mini-environment. We discuss several ways to reduce the sensitivity to environmental factors. Process and tool changes are found that eliminate yield detractors. We also present a workaround that has helped reduce the impact of queue time restrictions on cycle time. [ABSTRACT FROM PUBLISHER]

Abstract: This study proposes a novel HfO2 nanocrystal memory on epi-SiGe (Ge: 15%) channel. Because SiGe has a smaller bandgap than that of silicon, it increases electron/hole injection and the enhances program/erase speeds. This study compares the characteristics of HfO2 nanocrystal memories with different oxynitride tunnel oxide thicknesses on Si and epi-SiGe substrate. Results show that the proposed nonvolatile memory possesses superior characteristics in terms of considerably large memory window for two-bits operation, high speed program/erase for low power applications, long retention time, excellent endurance, and strong immunity to disturbance. [Copyright &y& Elsevier]

Power amplifier (PA) design for 160-GHz applications in an advanced SiGe heterojunction bipolar transistor (HBT) technology with saturated output power (Psat) in excess of 10 dBm is presented. The architecture is based on a three-stage pseudodifferential configuration that was implemented in SiGe HBT evaluation technology with f\max of 400 GHz. At saturation, a PA breakout circuit delivers 10 dBm with 20-dB gain. From 150 to 170 GHz, the small-signal gain is within 20–32 dB and the output referred 1-dB compression point (P1\ dB) is 8.5 dBm at 160 GHz. High output power was possible due to optimum device sizing, efficient layout, and accurate EM modeling. To our best knowledge, this is the highest output power reported for silicon PAs operating beyond 120 GHz. [ABSTRACT FROM AUTHOR]

This paper presents holistic design of a novel four-way differential power-combining transformer for use in millimeter-wave power-amplifier (PA). The combiner with an inner radius of 25 \mum exhibits a record low insertion loss of 1.25 dB at 83.5 GHz. It is designed to simultaneously act as a balanced-to-unbalanced converter, removing the need for additional BALUNs typically required in differential circuits. A complete circuit comprised of a power splitter, two-stage differential cascode PA array, a power combiner as well as input and output matching elements was designed and realized in SiGe technology with fT/f\max 170/250 GHz. Measured small-signal gain of at least 16.8 dB was obtained from 76.4 to 85.3 GHz with a peak 19.5 dB at 83 GHz. The prototype delivered 12.5 dBm output referred 1 dB compression point and 14 dBm saturated output power when operated from a 3.2 V dc supply voltage at 78 GHz. [ABSTRACT FROM AUTHOR]

The article is dedicated to the review and analysis of the effects and processes occurring in Si-Ge quantum size semiconductor structures upon particle irradiation including ion implantation. Comparisons to bulk materials are drawn. The reasons of the enhanced radiation hardness of superlattices and quantum dots are elucidated. Some technological applications of the radiation treatment are reviewed. [ABSTRACT FROM AUTHOR]