The misfit dislocations and strain fields at a Ge/Si heterostructure interface were investigated experimentally using a combination of high-resolution transmission electron microscopy and quantitative electron micrograph analysis methods. The type of misfit dislocation at the interface was determined to be 60° dislocation and 90° full-edge dislocation. The full-field strains at the Ge/Si heterostructure interface were mapped by using the geometric phase analysis (GPA) and peak pairs analysis (PPA), respectively. The effect of the mask size on the GPA and PPA results was analyzed in detail. For comparison, the theoretical strain fields of the misfit dislocations were also calculated by the Peierls-Nabarro and Foreman dislocation models. The results showed that the optimal mask sizes in GPA and PPA were approximately three tenths and one-tenth of the reciprocal lattice vector, respectively. The Foreman dislocation model with an alterable factor a = 4 can best describe the strain field of the misfit dislocation at the Ge/Si heterostructure interface.
We report a novel common gate stack solution for Ge 1-x Sn x P-MOSFET and In 0.7 Ga 0.3 As N-MOSFET, featuring sub-400°C Si 2 H 6 passivation, sub-1.3 nm EOT, and single TaN metal gate. Symmetric V TH , high performance, low gate leakage, negligible hysteresis, and excellent reliability were realized. Using this gate stack, the world's first GeSn short-channel device with gate length L G down to 250 nm was realized. Drive current of more than 1000 μA/μm was achieved, with peak intrinsic transconductance of ~465 μS/μm at V DS of -1.1 V.
Ge photodetector is very success in the Si-based photonics. Butdue to the limitation of the bandgap, Ge photodetector can’t beoperated at light wavelength longer than 1600nm. Theincorporation of Sn into Ge adjusts the band structures, andeffectively shrinks the bandgap relative to pure Ge. This makesGeSn photodetector a promising device for short-wave infraredlight detection (about 2000nm wavelength). In this paper, growthof GeSn alloys on Si and Ge substrates by MBE and sputtering willbe introduced. GeSn PIN photodetectors were fabricated by CMOScompatible process. The performance of the GeSn PDs, such asdark current, response spectra and quantum efficiency will bepresented and discussed.
The valley degree of freedom, like the spin degree of freedom in spintronics, is regarded as a new information carrier, promoting the emerging valley photonics. Although there exist topologically protected valley edge states which are immune to optical backscattering caused by defects and sharp edges at the inverse valley Hall phase interfaces composed of ordinary optical dielectric materials, the dispersion and the frequency range of the edge states cannot be tuned once the geometrical parameters of the materials are determined. In this paper, we propose a chirped valley graphene plasmonic metamaterial waveguide composed of the valley graphene plasmonic metamaterials (VGPMs) with regularly varying chemical potentials while keeping the geometrical parameters constant. Due to the excellent tunability of graphene, the proposed waveguide supports group velocity modulation and zero group velocity of the edge states, where the light field of different frequencies focuses at different specific locations. The proposed structures may find significant applications in the fields of slow light, micro–nano-optics, topological plasmonics, and on-chip light manipulation.
We report the demonstration of strained GeSn channel pMOSFETs on (111)- and (100)-oriented Ge substrates. The Sn composition is 4.1%. The device interface is passivated using (NH4)2S solution. Compared to devices on Ge(100), GeSn pMOSFETs on Ge(111) demonstrate a 20% enhancement in effective hole mobility at an inversion charge density (Qinv) of 2 × 1013 cm-2.
Abstract Topological circuits play an important role in exploring high-order topological insulators. In this work, we demonstrate that defects in the bulk without changing the parameters can increase zero-admittance states. Furthermore, the coupling parameters affect the distribution of the zero-admittance states are demonstrated. The impedance is measured to verify the existence of these states. The experimental results agree well with the theoretical results, both showing the strong resonance peak, as well as the impedance distribution of different parameters is mainly concentrated at the 2π/3 corner, 2π/6 corner, or edge. Our work paves the way for the research and experimentation of honeycomb topological circuits.
We propose the monolayer graphene plasmonic waveguide (MGPW), which is composed of graphene core sandwiched by two graphene metamaterial (GMM) claddings and investigate the properties of plasmonic modes propagating in the waveguide. The effective refraction index of the GMMs claddings takes negative (or positive) at the vicinity of the Dirac-like point in the band structure. We show that when the effective refraction index of the GMMs is positive, the plasmons travel forward in the MGPW with a positive group velocity (vg > 0, vp > 0). In contrast—for the negative refraction index GMM claddings—a negative group velocity of the fundamental mode (vg < 0, vp > 0) appears in the proposed waveguide structure when the core is sufficiently narrow. A forbidden band appears between the negative and positive group velocity regions, which is enhanced gradually as the width of the core increases. On the other hand, one can overcome this limitation and even make the forbidden band disappear by increasing the chemical potential difference between the nanodisks and the ambient graphene of the GMM claddings. The proposed structure offers a novel scheme of on-chip electromagnetic field and may find significant applications in the future high density plasmonic integrated circuit technique.
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