Use Of SiGe Research Articles

(Electronics and Photonics Division Award) Epitaxy of Group-IV Semiconductors for Nanoelectronics and Optoelectronics

Epitaxy stands for the deposition of a perfectly ordered layer on a monocrystalline substrate, which is typically, for group-IV semiconductors, bulk Si or Silicon-On-Insulator (SOI). If the layer is chemically different from the substrate and lattice parameters are not the same, epitaxy can be of two types. If the atomic columns of the substrate extend into the layer with the same in-plane lattice parameter, the layer will be pseudomorphic. The built-in strain will be compressive if the layer has a larger lattice parameter than that of the substrate or tensile if it is lower. If the layer thickness exceeds the so-called critical thickness for plastic relaxation, it will relax, with the formation of misfit dislocations to accomodate the lattice parameter mimatch.Epitaxy of group-IV semiconductors is key for numerous Si-based nanoelectronics and optoelectronics devices. Although they crystallize in the same diamond structure, C, Si, Ge and Sn bandgaps (5.47, 1.12, 0.66 and -0.41 eV), lattice parameters (3.57, 5.43, 5.66 and 6.49 Å) and fusion temperatures (> 4000°C, 1414°C, 938°C and 232°C) are very different. This can be an advantage (bandgap and mobility engineering in devices) or a difficulty (when growing stacks). Finally, although Si and Ge are miscible in all proportions, solid solubilities of C in Si and Sn in Ge are exceedingly low (less than 10-4 % and 0.8%, respectively). Low growth temperatures and high growth rates will then be mandatory in order to have high quality alloys.In that presentation, I will show how epitaxy can be put to good use in order to boost the properties of devices. Layers or stacks were grown on 200 mm and 300 mm diameter wafers in industrial Reduced-Pressure – Chemical Vapour Deposition tools with temperatures in the 300°C-900°C range and pressures in the 20-100 Torr range, typically. Precursors were mono-methysilane (for C), silane, dichlorosilane or disilane (for Si), germane or digermane (for Ge) and tin tetrachloride (for Sn). Finally, diborane and phosphine were the P-type and N-type dopant precursors, respectively.The electrical properties of p-type Metal Oxyde Semiconductor – Field Effect Transistors (MOSFETs) can be improved by the insertion of a thin pseudomorphic SiGe layer beneath the gate of transistors. The compressive strain in it will boost by a factor of ~2 the hole mobility in pMOSFETs. The use of SiGe:B in the sources and drains regions on each side of such devices will help in minimizing the contact resistivity and increasing the compressive strain in the channel. Ramping-up, at high temperatures, the Ge concentration in microns thick layers grown on Si and capping them with constant composition layers will result in SiGe virtual substrates which are almost fully relaxed (e.g. with a lattice parameter close to that of bulk SiGe), slightly defective (Threading Dislocations Density (TDD) around 105 cm-2) and with surface cross-hatches. Growing thin tensily-strained Si layers on top and transferring them onto oxydized Si will result in strained SOI substrates, with an increase by a factor of two of the electron mobility in n-type MOSFETs built on top. Using low contact resistance tensily-strained SiP sources and drains will further boost nMOSFET performances.Microns-thick Ge layers grown directly on Si thanks to a low temperature/high temperature approach can be used as templates for III-V epitaxy. The surface root mean square roughness will be less than 1 nm and the TDD around 107 cm-2 with some short duration thermal cycling. Ge can also be grown selectively in trenches at the end of Si waveguides and near infra-red photo-detectors processed. Microns-thick SiGe layers (capped with Si) and pure Ge layers (capped with SiGe) can otherwise be used to fabricate mid and long Infra-Red waveguides. Mid-IR supercontinuum light was generated when sending ultrashort light pulses in such waveguides. Finally, germanium can be transformed into a direct bandgap semiconductor thanks to high amounts of tensile strain or some alloying with more than 8% of tin. Optically pumped lasing at room temperature was recently achieved in bonded or pillared micro-disks made of thick, plastically relaxed GeSn 16-17% layers.Finally, the feasability of selectively etching SiGe versus Si can be used to fabricate stacked nanosheet MOSFETs, with superior ION/IOFF tradeoffs for a given footprint. The core structures of such devices are epitaxial Si/SiGe superlattices, with the alternance of typically ten nm thick Si and SiGe layers. SiGe layers are later on selectively etched. The resulting voids are conformally filled with gate dielectrics and metals. We recently succeeded in stacking seven Si nanosheets, with a record nMOSFET saturation current of 2.8mA/µm for a 1V drain voltage. Figure 1

Sensitivity of a Hymenoptera serological immunoglobulin (Ig)E assay for the diagnosis of venom hypersensitivity in dogs.

Hymenoptera envenomation with honey bee (Apis mellifera) and paper wasp (Polistes spp.) may cause life-threatening anaphylaxis in dogs. In human patients, clinical history, intradermal testing (IDT) and measurement of allergen-specific serological immunoglobulin (Ig)E (sIgE) are used to support a diagnosis of Hymenoptera venom hypersensitivity. The utility of venom allergen-specific sIgE has not yet been evaluated for this purpose in dogs. The objective of the study was to investigate the sensitivity (sn), specificity (sp) and positive predictive value (PPV) of honey bee and paper wasp serological titres using a commercially available sIgE assay [VARL (Veterinary Allergen Reference Laboratory) Liquid Gold] against clinical history for a diagnosis of Hymenoptera hypersensitivity in dogs. Honeybee and paper wasp IgE serum titres were measured in 15 client-owned dogs with a diagnosis of Hymenoptera venom hypersensitivity based on a history of anaphylaxis, owner observation of Hymenoptera, and positive IDT to bee and/or wasp; and in 10 client-owned dogs with no known history of anaphylaxis or Hymenoptera exposure and a negative IDT to bee and wasp. Analysis of receiver operating characteristic (ROC) curves demonstrate that a VARL score cut-off of one of six for honeybee yields Sn, Sp and PPV of 40%, 60% and 60%, respectively, and two of six for wasp yields Sn, Sp and PPV of 25%, 78% and 60%, respectively. Owing to the poor sensitivity and PPV of sIgE assays for both bee and wasp hypersensitivity in dogs with known envenomation and anaphylaxis, the use of sIgE cannot be recommended as a tool for venom identification.

Modern approaches to the diagnosis and management of children with allergy to cow’s milk proteins

Allergy to cow’s milk proteins is the most common cause of allergic reactions in young children, with a significant impact on the quality of life of children and their families. The most significant biomarker of herbivore milk allergy is allergen-specific IgE (sIgE), which can be assessed both for the whole allergen (for example, cow’s milk (CM), mare’s milk, goat’s milk, etc.) and a specific molecule, included in their composition. This article focuses on the use of sIgE in infants with suspected cow’s milk protein allergy.

Review of Ordering Practices for Single-Allergen and Serum-Specific Immunoglobulin E Panel Tests for Food Allergy

To review food allergen serum–specific immunoglobulin E (sIgE) ordering practices, single foods versus food panel, by allergists versus nonallergist providers.Food allergen sIgE laboratory tests performed at a children’s hospital clinical laboratory from January 1 to December 31, 2018.This study was a follow-up retrospective review of food allergen sIgE laboratory tests performed. The test was considered a multiallergen panel if >1 food was included. Ordering practices were compared between allergists and nonallergists. Allergists were made up of both allergists at the institution and community allergists who used that laboratory.A total of 12 345 sIgE tests were ordered by 400 unique practitioners, including 13 allergists at the institution and 41 community allergists. A total of 89% were single-food sIgE tests, and 11% were panels. The top diagnoses associated with sIgE food panels were dermatitis, allergy to other foods, and unspecified abdominal pain. Allergists ordered 8986 tests, of which only 1.2% were panels. Nonallergists ordered 3368 tests, of which 37.5% were panels. The proportion of sIgE tests ordered as panels by community allergists was higher than that by academic allergists (1.9% vs 0.75%). Compared with a similar study from the same center in 2013, there was a 55% decrease in the overall number of panels ordered in 2018.Appropriate diagnosis of an IgE-mediated food allergy requires an appropriate clinical history after ingestion of the suspected food supported by skin-prick tests and/or sIgE tests. The use of sIgE as a screening test is not recommended because of its low positive predictive value. Panels of food sIgE tests are readily available and ordered more by nonallergists than by allergists. Because more individuals will have detectable IgE sensitization than true symptoms, this leads to overdiagnosis and misdiagnosis. This, in turn, can lead to nutritional deficiencies and increased health care costs.Although IgE-mediated food allergies appear to be increasing, overdiagnosis is a concern. Most of these food panels were ordered by nonallergists for complaints not typical of an IgE-mediated food allergy. Families are given lists of positive results without truly understanding the limitations of testing. Trying to determine true allergies versus sensitization without clinical symptoms often requires referral to an allergist who will perform additional tests, including oral food challenges. This can be time consuming and invoke additional costs to the families. Although it is reassuring to see the number is going down, at least at this laboratory, there is still a long way to go regarding educating families and nonallergist providers on the appropriate approaches to diagnosis of IgE-mediated food allergies.

Analytical study of electrical performance of SiGe-based n+-p-p+ solar cells with BaSi2 BSF structure

This manuscript reports on an analytical study required to determine and enhance the effect of the high–low junction based back surface field (BSF) of thin n-CdS/p-SiGe/p + -BaSi2 heterojunction solar cell. A 0.3 µm thick BSF layer made of extensively available and low-cost barium silicide (BaSi2) is introduced into the basic SiGe solar cell for the first time. SCAPS-1D simulator is employed to analyze different parameters such as open circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), quantum efficiency (QE) and conversion efficiency (η) of the device. The SiGe absorber layer thickness is varied from 2 to 50 µm to analyze the device performance, however optimum results are observed between 10 and 15 µm. The BSF BaSi2 layer thickness changing from 0.1 to 0.8 µm to check the viability of device for optimal efficiency. The present structure anticipates an efficiency of 17.05% for BSF layer thickness of 0.8 µm. In addition, the use of SiGe earth abundant material instead of CIGS having rare earth metals indium and gallium, reduces the overall fabrication cost of the solar cell.

Coconut allergy: Characteristics of reactions and diagnostic predictors in a pediatric tertiary care center

BackgroundLittle is known on the clinical manifestations of coconut allergy. Our knowledge to date is mainly based on case reports. ObjectiveTo characterize the allergic reactions to coconut and suggest diagnostic cutoffs for specific immunoglobulin E (sIgE) and skin prick testing (SPT) to predict clinically reactive coconut allergy. MethodsMethods include retrospective chart review at an urban tertiary care center of patients with positive testing result for coconut. Probability curves were computed by logistic regression for SPT and coconut sIgE. ResultsOf 275 records reviewed, 69 patients reported coconut reactions and 206 were sensitized only or nonallergic. The reactions occurred with breastfeeding (n = 2), contact (n = 10), or oral ingestion (n = 57). Approximately 50% of oral ingestion reactions were associated with mild/moderate anaphylaxis. Clinical reactivity vs sensitization was more common in topical coconut users (2-fold) (P = .02). Although not statistically significant, there was a trend toward more coconut allergy vs sensitization in Asian and African American patients. The probability of allergy with positive SPT result was approximately 50% and with sIgE was approximately 60%. At an SPT of 9 mm wheal or sIgE of 58 kU of allergen/L, there is a 95% probability of reaction. Cosensitization with tree nuts, legumes, and seeds was common. Macadamia nut had the strongest correlation with coconut (r = 0.81, P < .001, n = 101). ConclusionAlthough the rate of reactivity to coconut in sensitized individuals is low, half of the reactions from consumption met the criteria for anaphylaxis. Clinicians should be aware of the spectrum of reactions and diagnostic use of sIgE and SPT.

Immunological methods for diagnosis and monitoring of IgE-mediated allergy caused by industrial sensitizing agents (IMExAllergy).

Industrial sensitizing agents (allergens) in living and working environments play an important role in eliciting type 1 allergic disorders including asthma and allergic rhinitis. Successful management of allergic diseases necessitates identifying their specific causes (ie, identify the causative agent(s) and the route of contact to allergen: airborne, or skin contact) to avoid further exposure. Identification of sensitization by a sensitive and validated measurement of specific IgE is an important step in the diagnosis. However, only a limited number of environmental and occupational allergens are available on the market for use in sIgE testing. Accordingly, specific in‐house testing by individual diagnostic and laboratory centers is often required. Currently, different immunological tests are in use at various diagnostic centers that often produce considerably divergent results, mostly due to lack of standardized allergen preparation and standardized procedures as well as inadequate quality control. Our review and meta‐analysis exhibited satisfactory performance of sIgE detection test for most high molecular weight (HMW) allergens with a pooled sensitivity of 0.74 and specificity of 0.71. However, for low molecular weight (LMW) allergens, pooled sensitivity is generally lower (0.28) and specificity higher (0.89) than for HMW tests. Major recommendations based on the presented data include diagnostic use of sIgE to HMW allergens. A negative sIgE result for LMW agents does not exclude sensitization. In addition, the requirements for full transparency of the content of allergen preparations with details on standardization and quality control are underlined. Development of standard operating procedures for in‐house sIgE assays, and clinical validation, centralized quality control and audits are emphasized. There is also a need for specialized laboratories to provide a custom service for the development of tests for the measurement of putative novel occupational allergens that are not commercially available.

(Invited) Extending Advanced CMOS Scaling with SiGe Channel Materials

Advanced CMOS Scaling has benefited from the introduction of novel materials and integration techniques over the past two decades. Consumer demand for more connectivity and real-time information continues to drive the need for product solutions with advanced power management and increased functionality while maintaining low cost. New device architectures such as FINFET and Fully Depleted Silicon-On-Insulator are part of the solution, however these device architectures still rely on advanced channel strain engineering to meet power, performance, and scaling requirements. The use of SiGe as a channel material is attractive due to enhanced mobility and compatibility with standard CMOS processing. PFET drive current enhancement has already been realized to enable platforms based on high performance planar FDSOI devices, while SiGe as part of the channel is also a top solution to enable next generation FINFET and Gate-All-Around devices. In this invited paper we will provide an in-depth look into the device benefits and challenges of SiGe as a channel material.

(Invited) Extending Advanced CMOS Scaling with SiGe Channel Materials

Advanced CMOS Scaling has benefited from the introduction of novel materials and integration techniques over the past two decades. Consumer demand for more connectivity and real-time information continues to drive the need for product solutions with advanced power management and increased functionality while maintaining low cost. New device architectures such as FINFET and Fully Depleted Silicon-On-Insulator are part of the solution, however these device architectures still rely on advanced channel strain engineering to meet power, performance, and scaling requirements. The use of SiGe as a channel material is attractive due to enhanced mobility and compatibility with standard CMOS processing. PFET drive current enhancement has already been realized to enable platforms based on high performance planar FDSOI devices, while SiGe as part of the channel is also a top solution to enable next generation FINFET and Gate-All-Around devices. In this invited paper we will provide a look into the device benefits and challenges of SiGe as a channel material.

SiGe Integrated Circuit Developments for SQUID/TES Readout

SiGe integrated circuits dedicated to the readout of superconducting bolometer arrays for astrophysics have been developed since more than 10 years at APC. Whether for Cosmic Microwave Background (CMB) observations with the QUBIC ground-based experiment (Aumont et al. in astro-ph.IM, 2016. arXiv:1609.04372 ) or for the Hot and Energetic Universe science theme with the X-IFU instrument on-board of the ATHENA space mission (Barret et al. in SPIE 9905, space telescopes & instrumentation 2016: UV to $$\gamma $$ Ray, 2016. https://doi.org/10.1117/12.2232432 ), several kinds of Transition Edge Sensor (TES) (Irwin and Hilton, in ENSS (ed) Cryogenic particle detection, Springer, Berlin, 2005) arrays have been investigated. To readout such superconducting detector arrays, we use time or frequency domain multiplexers (TDM, FDM) (Prele in JINST 10:C08015, 2016. https://doi.org/10.1088/1748-0221/10/08/C08015 ) with Superconducting QUantum Interference Devices (SQUID). In addition to the SQUID devices, low-noise biasing and amplification are needed. These last functions can be obtained by using BiCMOS SiGe technology in an Application Specific Integrated Circuit (ASIC). ASIC technology allows integration of highly optimised circuits specifically designed for a unique application. Moreover, we could reach very low-noise and wide band amplification using SiGe bipolar transistor either at room or cryogenic temperatures (Cressler in J Phys IV 04(C6):C6-101, 1994. https://doi.org/10.1051/jp4:1994616 ). This paper discusses the use of SiGe integrated circuits for SQUID/TES readout and gives an update of the last developments dedicated to the QUBIC telescope and to the X-IFU instrument. Both ASIC called SQmux128 and AwaXe are described showing the interest of such SiGe technology for SQUID multiplexer controls.

Investigation of electrical properties of MOS structures with silicon nitride films doped with rare earth elements

One of the main problems of MOS devices in electronics is improving the stability of their characteristics. This problem is considered in this work. This solution is ensured by a decrease in the density of the surface states due to the use of silicon nitride films doped with rare earth elements as a tunneling and barrier layer and due to use of SiGe and Ge solid solutions as a storage medium of nanoclusters. CV-studies of the electrophysical parameters of MOS structures of Me-Si3N4 (rare earth elements)-Ge(SiGe)-Si3N4 (rare earth elements)-nSi nanoclusters, where rare earth elements with a different atomic radius are used as alloying components, are performed. The regularity of the influence of the atomic radius of rare earth elements on the electrical characteristics of MOS structures is revealed.

Component‐resolved diagnosis of wasp (yellow jacket) venom allergy

Wasp venom allergy is a potentially life-threatening condition with serious consequences of diagnostic error. To assess whether component-resolved diagnosis, using non-glycosylated recombinant allergen components from yellow jacket can add to the diagnosis of wasp venom allergy. In total, 148 patients with a wasp (yellow jacket) allergy were included, 91 with unequivocal tests, 26 with double positivity of serum-specific IgE (sIgE) to both venoms, 21 with discrepant sIgE and skin test results and finally 10 having their diagnosis only confirmed by basophil activation test (negative sIgE and skin test results). Specific IgE to recombinant species-specific allergen components Ves v 1 and Ves v 5 from yellow jacket, Api m 1 from honeybee and Ves v 5 complemented wasp venom were tested by ImmunoCAP. Overall, combined use of sIgE to rVes v 1 and rVes v 5 allowed correct diagnosis in 139 of the 148 patients (94%) and rApi m 1 was demonstrable in only one patient. Supplementing the traditional yellow jacket allergosorbent with rVes v 5 allowed to correctly diagnose wasp allergy in patients sensitized to Ves v 5 but demonstrating a negative sIgE to wasp venom. Component-resolved diagnoses with the wasp-specific recombinant allergen components Ves v 1 and Ves v 5 is a reliable method to diagnose yellow jacket allergy and can help to take out the sting of difficult cases. However, as the number of patients with doubt after conventional tests is small, larger collaborative studies are needed to draw more definitive conclusions. Whether the rVes v 5 supplemented yellow jacket allergosorbent constitutes an asset in the diagnostic management of wasp venom allergy remains to be further established.

Theoretical Calculation of the Magnetic Resonance Frequency of the Electron Spin Embedded Inside a Silicon Host for Solid-State Quantum Computing

The electron-spin magnetic resonance frequency of an electron-spin qubit structure that is proposed for the realization of a quantum computer is rigorously determined by a numerical method. The potential distribution inside the silicon qubit structure is accurately calculated by an electromagnetic simulation method, and the perturbation theory to the second order is formulated to obtain the magnetic resonance frequency of a phosphorus donor electron spin. Our results showed that, for the same qubit structure (Si:P), as originally proposed by Kane for a nuclear-spin qubit quantum computer, a smaller static magnetic field <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> is in favor of producing a wider tunable bandwidth for the magnetic resonance frequency of the electron spin. Our results also reveal that the use of SiGe as an alternative insulation material to the A-gate structure can improve the control efficiency of the A-gate voltage.

Novel SiGe Source/Drain for Reduced Parasitic Resistance in Ge NMOS

Parasitic resistance issues are an important limitation of Germanium n-channel MOSFETs. We have experimentally investigated the use of SiGe as source/drain material to reduce the parasitic resistance. We have utilized circular TLM (transmission line method) measurement structures to extract the parasitic resistances of these SiGe layers. Results show about two orders of magnitude improvement in specific contact resistivity for insitu-doped n+ SiGe (20% Ge) over 100% n+ Ge layers, thus making it suitable for utilization as source/drain material in Ge NMOS transistors to reduce parasitic resistance, among other benefits.

Novel analog pulse‐width‐modulated 15‐μm SiGe micromirrors

Abstract— A novel six‐electrode SiGe micromirror pixel enabling analog pulse‐width modulation (PWM) in display applications is presented. Instead of utilizing bitplanes, arbitrary duty cycles can be realized, resulting in an analog gray‐level distribution. This eliminates the posterization (contouring) effect that is typical for digital micromirrors. Moreover, the pixel design does not require the incorporation of electronic comparators and the gamma compensation can be processed externally. Two out of the six electrodes are used as landing electrodes. The other four attracting electrodes are driven by two anti‐phase saw‐tooth signals and two fixed analog voltage signals. By applying this signal scheme, the duty cycle of the mirror is modulated in an analog manner. Test vehicles were manufactured where SiGe is the microelectromechanical systems (MEMS) material. The use of SiGe as a structural layer is advantageous to build MEMS since the CMOS and MEMS layers can be deposited in a monolithic manner. Measurements using a Laser Doppier Vibrometer (LDV) have confirmed the feasibility of analog PWM for 15‐μm SiGe micromirrors.

Investigation of Capacitorless Double-Gate Single-Transistor DRAM: With and Without Quantum Well

We characterize and optimize double-gate single-transistor DRAM via extensive simulations. We propose a new kind of DRAM, namely, the single-transistor (1T) quantum well (QW) DRAM, which has a ¿storage pocket¿ for holes within the body. This memory employs the QW as a way of energy band engineering to introduce the storage pocket within the body of the device, which also gives the opportunity to engineer spatial hole distribution within the device, which is not possible with the conventional 1T DRAMs. With this ¿storage pocket¿ and spatial hole distribution engineering approach, we demonstrate improvement in the drain current ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> ) difference between the reads of two states of the memory and, hence, improvement in sense margin and scalability characteristics. Furthermore, it is found that the use of SiGe instead of pure germanium to form the QW has added advantages in terms of retention, erase scheme, and fabrication.

The Versatile Use of SiGe for High-Performance Devices

Apart from the widely used bandgap engineering in the base of Hetero-junction Bipolar Transistors (HBTs) and strain engineering in CMOS SiGe has many other possible application in Si technology. This paper will discuss several examples, both within and outside (Bi)CMOS technology. For instance, SiGe bandgap engineering can be used in power diodes. Other possibilities make use of the fact that SiGe can be etched selectively towards Si. This allows, for example, creation of cavities in the silicon substrate. These can be used for, e.g., reduction of parasitic capacitance, device isolation, or electric field shaping.

The Versatile use of SiGe for High-performance Devices

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Polysilicon thin film transistors using sputtered HfO2 gate dielectric and SiGe source/drain

We have fabricated polysilicon thin film transistors (TFTs) using sputtered HfO2 gate dielectric and SiGe as source/drain. The polysilicon film is formed by low temperature furnace recrystallization of amorphous silicon. The effective dielectric constant of the HfO2 in the TFTs is 17.7, and the transconductance of the TFTs is about 4.5 times that of those using SiO2 as gate dielectric. The use of SiGe as source/drain requires a lower thermal budget than the conventional technique of impurity implantation in the polysilicon film.

Morphological study of polycrystalline SiGe alloy deposited by vertical LPCVD

As device dimensions shrink to the deep-submicron scale, new challenges arises from the very small scale used and even poly crystalline silicon (poly-Si) presents problems as gate electrode. The use of SiGe as gate material can present many advantages over the poly-Si, as it leads to a lower boron penetration and gate depletion. In this paper authors present some morphological studies of polycrystalline SiGe thin films deposited in a vertical LPCVD (Low Pressure Chemical Vapor Deposition) reactor for using as MOS (Metal Oxide Semiconductor) gate electrode.