Strained Si, SiGe, and Ge channels for high-mobility metal-oxide-semiconductor field-effect transistors
TL;DR: A review of the history and current progress in highmobility strained Si, SiGe, and Ge channel metal-oxide-semiconductor field effect transistors (MOSFETs) can be found in this article.
Abstract: This article reviews the history and current progress in high-mobility strained Si, SiGe, and Ge channel metal-oxide-semiconductor field-effect transistors (MOSFETs). We start by providing a chronological overview of important milestones and discoveries that have allowed heterostructures grown on Si substrates to transition from purely academic research in the 1980’s and 1990’s to the commercial development that is taking place today. We next provide a topical review of the various types of strain-engineered MOSFETs that can be integrated onto relaxed Si1−xGex, including surface-channel strained Si n- and p-MOSFETs, as well as double-heterostructure MOSFETs which combine a strained Si surface channel with a Ge-rich buried channel. In all cases, we will focus on the connections between layer structure, band structure, and MOS mobility characteristics. Although the surface and starting substrate are composed of pure Si, the use of strained Si still creates new challenges, and we shall also review the litera...
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TL;DR: A solution-processing technique in which lattice strain is used to increase charge carrier mobilities by introducing greater electron orbital overlap between the component molecules should aid the development of high-performance, low-cost organic semiconducting devices.
Abstract: A solution-processing method known as solution shearing is used to introduce lattice strain to organic semiconductors, thus improving charge carrier mobility. Solution-processed organic semiconductors show great promise for application in cheap and flexible electronic devices, but generally suffer from greatly reduced electronic performance — most notably charge-carrier mobilities — compared with their inorganic counterparts. Borrowing a trick from the inorganic semiconductor community, Giri et al. show how the introduction of strain into an organic semiconductor, through a simple solution-processing technique, modifies the molecular packing within the material and hence its electronic performance. For one material studied, the preparation of a strained structure is shown to more than double the charge-carrier mobility. Circuits based on organic semiconductors are being actively explored for flexible, transparent and low-cost electronic applications1,2,3,4,5. But to realize such applications, the charge carrier mobilities of solution-processed organic semiconductors must be improved. For inorganic semiconductors, a general method of increasing charge carrier mobility is to introduce strain within the crystal lattice6. Here we describe a solution-processing technique for organic semiconductors in which lattice strain is used to increase charge carrier mobilities by introducing greater electron orbital overlap between the component molecules. For organic semiconductors, the spacing between cofacially stacked, conjugated backbones (the π–π stacking distance) greatly influences electron orbital overlap and therefore mobility7. Using our method to incrementally introduce lattice strain, we alter the π–π stacking distance of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) from 3.33 A to 3.08 A. We believe that 3.08 A is the shortest π–π stacking distance that has been achieved in an organic semiconductor crystal lattice (although a π–π distance of 3.04 A has been achieved through intramolecular bonding8,9,10). The positive charge carrier (hole) mobility in TIPS-pentacene transistors increased from 0.8 cm2 V−1 s−1 for unstrained films to a high mobility of 4.6 cm2 V−1 s−1 for a strained film. Using solution processing to modify molecular packing through lattice strain should aid the development of high-performance, low-cost organic semiconducting devices.
965 citations
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...For inorganic semiconductors, a general method of increasing charge carrier mobility is to introduce strain within the crystal lattic...
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TL;DR: It is reported that Si nanowires possess an unusually large piezoresistance effect compared with bulk, which may have significant implications in nanowire-based flexible electronics, as well as in nanoelectromechanical systems.
Abstract: The piezoresistance effect of silicon1 has been widely used in mechanical sensors2,3,4, and is now being actively explored in order to improve the performance of silicon transistors5,6. In fact, strain engineering is now considered to be one of the most promising strategies for developing high-performance sub-10-nm silicon devices7. Interesting electromechanical properties have been observed in carbon nanotubes8,9. In this paper we report that Si nanowires possess an unusually large piezoresistance effect compared with bulk. For example, the longitudinal piezoresistance coefficient along the 〈111〉 direction increases with decreasing diameter for p-type Si nanowires, reaching as high as −3,550 × 10−11 Pa–1, in comparison with a bulk value of −94 × 10−11 Pa−1. Strain-induced carrier mobility change and surface modifications have been shown to have clear influence on piezoresistance coefficients. This giant piezoresistance effect in Si nanowires may have significant implications in nanowire-based flexible electronics, as well as in nanoelectromechanical systems.
693 citations
TL;DR: In this review, the key points for development of high mobility OFETs are highlighted from aspects of molecular engineering, process engineering and interface engineering, and the importance of other factors, such as impurities and testing conditions is also addressed.
Abstract: Remarkable progress has been made in developing high performance organic field-effect transistors (OFETs) and the mobility of OFETs has been approaching the values of polycrystalline silicon, meeting the requirements of various electronic applications from electronic papers to integrated circuits. In this review, the key points for development of high mobility OFETs are highlighted from aspects of molecular engineering, process engineering and interface engineering. The importance of other factors, such as impurities and testing conditions is also addressed. Finally, the current challenges in this field for practical applications of OFETs are further discussed.
677 citations
TL;DR: In this paper, a detailed theoretical model for the physics of strain effects in bulk semiconductors and surface Si, Ge, and III-V channel metal-oxide-semiconductor field effect transistors is presented.
Abstract: A detailed theoretical picture is given for the physics of strain effects in bulk semiconductors and surface Si, Ge, and III–V channel metal-oxide-semiconductor field-effect transistors. For the technologically important in-plane biaxial and longitudinal uniaxial stress, changes in energy band splitting and warping, effective mass, and scattering are investigated by symmetry, tight-binding, and k⋅p methods. The results show both types of stress split the Si conduction band while only longitudinal uniaxial stress along ⟨110⟩ splits the Ge conduction band. The longitudinal uniaxial stress warps the conduction band in all semiconductors. The physics of the strain altered valence bands for Si, Ge, and III–V semiconductors are shown to be similar although the strain enhancement of hole mobility is largest for longitudinal uniaxial compression in ⟨110⟩ channel devices and channel materials with substantial differences between heavy and light hole masses such as Ge and GaAs. Furthermore, for all these materials,...
467 citations
TL;DR: In this article, the opportunities and challenges of high-k/Ge MOSFETs are discussed on the basis of the material properties of Ge oxide to provide insights for future progress.
443 citations
References
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Book•
01 Jan 1979
TL;DR: In this article, Bertotti, Ferro, and Mazetti proposed a theory of dislocation drag in covalent crystals and formed a model of the formation and evolution of dislocations during irradiation.
Abstract: Preface. Electrical noise associated with dislocations and plastic flow in metals (G. Bertotti, A. Ferro, F. Fiorillo, P. Mazetti). Mechanisms of dislocation drag (V.I. Alshits, V.L. Indenbom). Dislocations in covalent crystals (H. Alexander). Formation and evolution of dislocation structures during irradiation (B.O. Hall). Dislocation theory of martensitic transformations (G.B. Olsen, M. Cohen). Author index. Subject index. Cumulative index.
2,752 citations
TL;DR: It is shown that the islands formed in Stranski-Krastanow (SK) growth of Ge on Si(100) are initially dislocation free, and the limiting critical thickness of coherent SK islands is shown to be higher than that for 2D growth.
Abstract: We show that the islands formed in Stranski-Krastanow (SK) growth of Ge on Si(100) are initially dislocation free. Island formation in true SK growth should be driven by strain relaxation in large, dislocated islands. Coherent SK growth is explained in terms of elastic deformation around the islands, which partially accommodates mismatch. The limiting critical thickness, ${\mathit{h}}_{\mathit{c}}$, of coherent SK islands is shown to be higher than that for 2D growth. We demonstrate growth of dislocation-free Ge islands on Si to a thickness of \ensuremath{\approxeq}500 \AA{}, 50\ifmmode\times\else\texttimes\fi{}higher than ${\mathit{h}}_{\mathit{c}}$ for 2D Ge/Si epitaxy.
1,751 citations
Book•
01 Jan 1972TL;DR: The Solid State Electronic Devices (SSED) as discussed by the authors is an introductory book on semiconductor materials, physics, devices, and technology, which aims to: 1) develop basic semiconductor physics concepts, and 2) provide a sound understanding of current semiconductor devices and technology.
Abstract: For undergraduate electrical engineering students or for practicing engineers and scientists interested in updating their understanding of modern electronics One of the most widely used introductory books on semiconductor materials, physics, devices and technology, Solid State Electronic Devices aims to: 1) develop basic semiconductor physics concepts, so students can better understand current and future devices; and 2) provide a sound understanding of current semiconductor devices and technology, so that their applications to electronic and optoelectronic circuits and systems can be appreciated. Students are brought to a level of understanding that will enable them to read much of the current literature on new devices and applications. Teaching and Learning Experience This program will provide a better teaching and learning experience-for you and your students. It will help: *Provide a Sound Understanding of Current Semiconductor Devices: With this background, students will be able to see how their applications to electronic and optoelectronic circuits and systems are meaningful. *Incorporate the Basics of Semiconductor Materials and Conduction Processes in Solids: Most of the commonly used semiconductor terms and concepts are introduced and related to a broad range of devices. *Develop Basic Semiconductor Physics Concepts: With this background, students will be better able to understand current and future devices.
1,632 citations
IBM1
TL;DR: In this article, the authors compute the band structure and shear deformation potentials of strained Si, Ge, and SiGe alloys, and fit the theoretical results to experimental data on the phonon-limited carrier mobilities in bulk Si and Ge.
Abstract: Using nonlocal empirical pseudopotentials, we compute the band structure and shear deformation potentials of strained Si, Ge, and SiGe alloys. Fitting the theoretical results to experimental data on the phonon‐limited carrier mobilities in bulk Si and Ge, the dilatation deformation potential Ξd is found to be 1.1 eV for the Si Δ minima, −4.4 eV for the Ge L minima, corresponding to a value for the valence band dilatation deformation potential a of approximately 2 eV for both Si and Ge. The optical deformation potential d0 is found to be 41.45 and 41.75 eV for Si and Ge, respectively. Carrier mobilities in strained Si and Ge are then evaluated. The results show a large enhancement of the hole mobility for both tensile and compressive strain along the [001] direction, but only a modest enhancement (approximately 60%) of the electron mobility for tensile biaxial strain in Si. Finally, from a fit to carrier mobilities in relaxed SiGe alloys, the effective alloy scattering potential is determined to be about 0...
1,500 citations
TL;DR: In this paper, the inversion layer mobility in n-and p-channel Si MOSFETs with a wide range of substrate impurity concentrations (10/sup 15/ to 10/sup 18/ cm/sup -3/) was examined.
Abstract: This paper reports the studies of the inversion layer mobility in n- and p-channel Si MOSFET's with a wide range of substrate impurity concentrations (10/sup 15/ to 10/sup 18/ cm/sup -3/). The validity and limitations of the universal relationship between the inversion layer mobility and the effective normal field (E/sub eff/) are examined. It is found that the universality of both the electron and hole mobilities does hold up to 10/sup 18/ cm/sup -3/. The E/sub eff/ dependences of the universal curves are observed to differ between electrons and holes, particularly at lower temperatures. This result means a different influence of surface roughness scattering on the electron and hole transports. On substrates with higher impurity concentrations, the electron and hole mobilities significantly deviate from the universal curves at lower surface carrier concentrations because of Coulomb scattering by the substrate impurity. Also, the deviation caused by the charged centers at the Si/SiO/sub 2/ interface is observed in the mobility of MOSFET's degraded by Fowler-Nordheim electron injection. >
1,389 citations