Academic and industry research progress in germanium nanodevices
TL;DR: Germanium-based transistors have the potential to operate at high speeds with low power requirements and might therefore be used in non-silicon-based semiconductor technology in the future.
Abstract: Silicon has enabled the rise of the semiconductor electronics industry, but it was not the first material used in such devices. During the 1950s, just after the birth of the transistor, solid-state devices were almost exclusively manufactured from germanium. Today, one of the key ways to improve transistor performance is to increase charge-carrier mobility within the device channel. Motivated by this, the solid-state device research community is returning to investigating the high-mobility material germanium. Germanium-based transistors have the potential to operate at high speeds with low power requirements and might therefore be used in non-silicon-based semiconductor technology in the future.
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TL;DR: A series of germanes Ar3GeX, containing electron-withdrawing substituents [Ar = p-FC6H4, 1a, 1b, 2b, 3c, 4, 5] were synthesized and used to prepare symmetrical digermanes as mentioned in this paper.
25 citations
TL;DR: In this paper, the authors performed a quantitative in situ study of explosive crystallization in amorphous germanium using dynamic transmission electron microscopy, and showed that the diffusivity of the material locally/immediately in advance of the exploding crystallization front is inconsistent with those of a liquid phase.
Abstract: The crystallization of amorphous semiconductors is a strongly exothermic process. Once initiated the release of latent heat can be sufficient to drive a self-sustaining crystallization front through the material in a manner that has been described as explosive. Here, we perform a quantitative in situ study of explosive crystallization in amorphous germanium using dynamic transmission electron microscopy. Direct observations of the speed of the explosive crystallization front as it evolves along a laser-imprinted temperature gradient are used to experimentally determine the complete interface response function (i.e., the temperature-dependent front propagation speed) for this process, which reaches a peak of 16 m/s. Fitting to the Frenkel-Wilson kinetic law demonstrates that the diffusivity of the material locally/immediately in advance of the explosive crystallization front is inconsistent with those of a liquid phase. This result suggests a modification to the liquid-mediated mechanism commonly used to describe this process that replaces the phase change at the leading amorphous-liquid interface with a change in bonding character (from covalent to metallic) occurring in the hot amorphous material.
24 citations
TL;DR: In this paper, the oleylamine capping ligand can be replaced by dodecanethiol without loss of Bi, and a positive correlation between the lattice parameter and the concentration of Bi content (0.5-2.0 mol %) is shown via powder X-ray diffraction and selected area electron diffraction.
Abstract: Nanogermanium is a material that has great potential for technological applications, and doped and alloyed Ge nanocrystals (NCs) are actively being considered. New alloys and compositions are possible in colloidal synthesis because the reactions are kinetically rather than thermodynamically controlled. Most of the Group V elements have been shown to be n-type dopants in Ge to increase carrier concentration; however, thermodynamically, Bi shows no solubility in crystalline Ge. Bi-doped Ge NCs were synthesized for the first time in a microwave-assisted solution route. The oleylamine capping ligand can be replaced by dodecanethiol without loss of Bi. A positive correlation between the lattice parameter and the concentration of Bi content (0.5–2.0 mol %) is shown via powder X-ray diffraction and selected area electron diffraction. X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), scanning TEM, and inductively coupled plasma–mass spectroscopy are consistent with the Bi solubility up to ...
24 citations
TL;DR: In this article, an advanced nano-scale transfer length method was used to extract the specific contact resistivity ρc between the metal and the heavily doped p-Ge0.95Sn0.05 layer.
Abstract: A heavily Ga-doped Ge0.95Sn0.05 layer was grown on the Ge (100) substrate by molecular beam epitaxy (MBE), achieving an active doping concentration of 1.6 × 1020 cm−3 without the use of ion implantation and high temperature annealing that could cause Sn precipitation or surface segregation. An advanced nano-scale transfer length method was used to extract the specific contact resistivity ρc between the metal and the heavily doped p-Ge0.95Sn0.05 layer. By incorporating Sn into Ge and in-situ Ga doping during the MBE growth, an ultra-low ρc of 1.4 × 10−9 Ω·cm2 was achieved, which is 50% lower than the ρc of p+-Ge control and is also the lowest value obtained for metal/p-type semiconductor contacts.
23 citations
TL;DR: In this article, a wave-like wrinkled geometry with uniform periodicity and amplitude on elastomeric substrates is proposed to enhance the flexibility of the germanium-based devices.
Abstract: Germanium nanomembranes are suitable for flexible electronics, including high-mobility nonsilicon transistors, fast radio-frequency switches, microwave diodes, and high-performance photodetectors. In order to enhance the flexibility of the germanium-based devices, we present a strategy to integrate single-crystalline germanium nanomembranes into a wave-like wrinkled geometry with a uniform periodicity and amplitude on elastomeric substrates. Wrinkled single-crystalline germanium nanomembranes are realized with a reversible and large deformation up to 10%, and the stretchable metal–germanium–metal photodetectors have been demonstrated. Optoelectronic response studies reveal that the wrinkled germanium-based photodetectors exhibit enhanced efficiency of optoelectronic interactions compared with planar photodetectors using flat germanium nanomembranes. Furthermore, the wrinkled photodetectors reveal high response speed and stretchable capability of up to 8.56%. This paper may pave the way for the integration of germanium nanomembranes into the field of flexible/wearable optoelectronics.
23 citations
Cites background from "Academic and industry research prog..."
...mobility [15], low-field drift velocity [16], small bandgap, and superior mechanical properties [17], nanoscale germanium membranes are desirable in flexible transistors [18], radiofrequency diodes [19], [20], and photodetectors [21], [22]....
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References
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01 Dec 2007
TL;DR: In this paper, a 45 nm logic technology is described that for the first time incorporates high-k + metal gate transistors in a high volume manufacturing process, resulting in the highest drive currents yet reported for NMOS and PMOS.
Abstract: A 45 nm logic technology is described that for the first time incorporates high-k + metal gate transistors in a high volume manufacturing process. The transistors feature 1.0 nm EOT high-k gate dielectric, dual band edge workfunction metal gates and third generation strained silicon, resulting in the highest drive currents yet reported for NMOS and PMOS. The technology also features trench contact based local routing, 9 layers of copper interconnect with low-k ILD, low cost 193 nm dry patterning, and 100% Pb-free packaging. Process yield, performance and reliability are demonstrated on 153 Mb SRAM arrays with SRAM cell size of 0.346 mum2, and on multiple microprocessors.
973 citations
08 Dec 2003
TL;DR: In this article, the authors describe a novel strained transistor architecture which is incorporated into a 90nm logic technology on 300mm wafers, which features an epitaxially grown strained SiGe film embedded in the source drain regions.
Abstract: This paper describes the details of a novel strained transistor architecture which is incorporated into a 90nm logic technology on 300mm wafers The unique strained PMOS transistor structure features an epitaxially grown strained SiGe film embedded in the source drain regions Dramatic performance enhancement relative to unstrained devices are reported These transistors have gate length of 45nm and 50nm for NMOS and PMOS respectively, 12nm physical gate oxide and Ni salicide World record PMOS drive currents of 700/spl mu/A//spl mu/m (high V/sub T/) and 800/spl mu/A//spl mu/m (low V/sub T/) at 12V are demonstrated NMOS devices exercise a highly tensile silicon nitride capping layer to induce tensile strain in the NMOS channel region High NMOS drive currents of 126mA//spl mu/m (high VT) and 145mA//spl mu/m (low VT) at 12V are reported The technology is mature and is being ramped into high volume manufacturing to fabricate next generation Pentium/spl reg/ and Intel/spl reg/ Centrino/spl trade/ processor families
729 citations
TL;DR: In this paper, a method of controlling threading dislocation densities in Ge on Si involving graded SiGe layers and chemical-mechanical polishing (CMP) is presented.
Abstract: A method of controlling threading dislocation densities in Ge on Si involving graded SiGe layers and chemical-mechanical polishing (CMP) is presented. This method has allowed us to grow a relaxed graded buffer to 100% Ge without the increase in threading dislocation density normally observed in thick graded structures. This sample has been characterized by transmission electron microscopy, etch-pit density, atomic force microscopy, Nomarski optical microscopy, and triple-axis x-ray diffraction. Compared to other relaxed graded buffers in which CMP was not implemented, this sample exhibits improvements in threading dislocation density and surface roughness. We have also made process modifications in order to eliminate particles due to gas-phase nucleation and cracks due to thermal mismatch strain. We have achieved relaxed Ge on Si with a threading dislocation density of 2.1×106 cm−2, and we expect that further process refinements will lead to lower threading dislocation densities on the order of bulk Ge su...
620 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