Just Accepted

Just Accepted manuscripts are peer-reviewed and accepted for publication. They are posted online prior to technical editing formatting for publication and author proofing.

  • Modeling of tunneling current density of GeC based double barrier multiple quantum well resonant tunneling diode

    Swagata Dey, Vedatrayee Chakraborty, Bratati Mukhopadhyay, Gopa Sen

    Available online

    Abstract Full Text PDF

    In this paper, the double barrier quantum well (DBQW) resonant tunneling diode (RTD) structure made of SiGeSn/GeC/SiGeSn alloys grown on Ge substrate is analyzed. The tensile strained Ge1−zCz on Si1−xy GexSny heterostructure provides a direct band gap type I configuration. The transmission coefficient and tunneling current density have been calculated considering single and multiple quantum wells. A comparative study of tunnelling current of the proposed structure is done with the existing RTD structure based on GeSn/SiGeSn DBH. A higher value of the current density for the proposed structure has been obtained.

  • A 0.19 ppm/°C bandgap reference circuit with high-PSRR

    Jing Leng, Yangyang Lu, Yunwu Zhang, Huan Xu, Kongsheng Hu, Zhicheng Yu, Weifeng Sun, Jing Zhu

    Available online

    Abstract Full Text PDF

    A high-order curvature-compensated CMOS bandgap reference (BGR) topology with a low temperature coefficient (TC) over a wide temperature range and a high power supply reject ratio (PSRR) is presented in this paper. High-order correction is realized by incorporating a nonlinear current INL, which is generated by ∆VGS across resistor into current generated by a conventional first-order current-mode BGR circuit. In order to achieve a high PSRR over a broad frequency range, a voltage pre-regulating technique is applied. The circuit was implemented in CSMC 0.5 μm 600 V BCD process. The experimental results indicate that the proposed topology achieves TC of 0.19 ppm/°C over the temperature range of 165 °C (−40 to 125 °C), PSRR of −123 dB @ DC and −56 dB @ 100 kHz. In addition, it achieves a line regulation performance of 0.017%/V in the supply range of 2.8–20 V.

  • Room-temperature optically pumped InAs/GaAs quantum dots microdisk lasers on SiO2/Si chip

    Pengyi Yue, Xiuming Dou, Xiangbin Su, Zhichuan Niu, Baoquan Sun

    Available online

    Abstract Full Text PDF

    We report on room temperature continuous-wave optically pumped InAs/GaAs quantum dot whispering gallery mode microdisk lasers, heterogeneously integrated on silica/silicon chips. The microdisks are fabricated by photolithography and inductively coupled plasma etching. The lasing wavelength is approximately 1200 nm and the obtained lowest laser threshold is approximately 28 μW. The experimental results show an approach of possible integrated III–V optical active materials on silica/silicon chip for low threshold WGM microdisk lasers.

  • A low standby-power fast carbon nanotube ternary SRAM cell with improved stability

    Gang Li, Pengjun Wang, Yaopeng Kang, Yuejun Zhang

    Available online

    Abstract Full Text PDF

    Power dissipation, speed and stability are the most important parameters for multiple-valued SRAM design. To reduce the power consumption and further improve the performance of the ternary SRAM cell, we propose a low standby-power fast ternary SRAM cell based on Carbon Nanotube Field Effect Transistors (CNFETs). The performance is simulated in terms of three criteria including standby-power, delay (write and read) and stability (RSNM). Compared to the novel ternary SRAM cell, our results show that the average standby-power, write and read delay of the proposed cell are reduced by 78.1%, 39.6% and 58.2%, respectively. In addition, the RSNM under process variations is 2.01x and 1.95x of the conventional and novel ternary SRAM cells, respectively.

  • Photoluminescence and structural analysis of wurtzite (ZnO)1−x(V2O5)x composite

    Amjid Iqbal, Arshad Mahmood, Q. Raza, A. Shah, Rashad Rashid, Zahid Ali, A. Malik, U. Aziz

    Available online

    Abstract Full Text PDF

    This paper demonstrates the structural, vibrational and photoluminescence characteristics of (ZnO)1−x(V2O5)x (x = 0, 3, 6 and 9 mol%) composites semiconductor synthesized by using the solid state reaction method. X-ray diffraction (XRD) studies show that (ZnO)1−x(V2O5)x composites have the poly crystalline wurtzite structure of hexagonal ZnO. It is found from the XRD results that the lattice constants and the crystallite size increase while the dislocation density decreases with increasing doping concentration. The existence of E1 (TO) and E2 (high) Raman modes show that the ZnO still preserve wurtzite structure after doping vanadium oxide, which is in agreement with XRD results. Room temperature photoluminescence (PL) exhibit near band edge and broad deep level emission while indicating the suppression of deep level emission with the incorporation of V2O5 up to a certain concentration, which is less than 9 mol%. Moreover, the optical band gap increases with doping, which is accompanied by the blue shift of the NBE emission.

  • Al-free cladding-layer blue laser diodes with a low aspect ratio in far-field beam pattern

    Meixin Feng, Qian Sun, Jianping Liu, Zengcheng Li, Yu Zhou, Hongwei Gao, Shuming Zhang, Hui Yang

    Available online

    Abstract Full Text PDF

    c-plane GaN-based blue laser diodes (LDs) were fabricated with Al-free cladding layers (CLs) and deepened etching depth of mesa structure, so the aspect ratio of the far-field pattern (FFP) of the laser beam can be reduced to as low as 1.7, which is nearly the same as conventional AlGaInP-based red LDs. By using GaN CLs, the radiation angle of the laser beam θ is only 10.1° in the direction perpendicular to the junction plane. After forming a deeply etched mesa, the beam divergence angle parallel to the junction plane of FFP, θ//, increases from 4.9° to 5.8°. After using the modified structure, the operation voltage of LD is effectively reduced by 2 V at an injection current of 50 mA, but the threshold current value increases. The etching damage may be one of the main reasons responsible for the increase of the threshold current.

  • Influence of deposition rate on the structural, optical and electrical properties of electron beam evaporated SnO2 thin films for transparent conducting electrode applications

    Nitin Kumar, Bhawana Joshi, K. Asokan

    Available online

    Abstract Full Text PDF

    In this work, the role of deposition rate in the structural, optical and electrical properties of SnO2 thin films deposited by electron beam evaporation method is investigated by varying the deposition powers viz. 50, 75, and 100 W. The structural characterization of the films is done by X-ray diffraction (XRD) technique. The surface morphology of the films is studied by scanning electron microscopy (SEM). Rutherford back scattering (RBS) measurements revealed the thickness of the films ranging from 200 nm to 400 and also a change in the concentration of oxygen vacancies which is found to be the maximum in the film deposited at the lowest deposition rate. Optical absorption spectrum is recorded using the UV–Vis spectroscopy and the films are found to be transparent in nature. A shift in the absorption edge is observed and is attributed to a different level of allowed energy states in conduction band minimum. The Hall effect and electrical measurements show a variation in the carrier concentrations, mobility and resistivity of the films. In order to explore a better compromise in electrical and optical properties for transparent electrode applications, skin depths calculations are also done to find the optimized values of carrier concentration and mobility.

  • Band structure of monolayer of graphene, silicene and silicon-carbide including a lattice of empty or filled holes

    N. Nouri, G. Rashedi

    Available online

    Abstract Full Text PDF

    We have developed a \begin{document}$\pi$\end{document} -orbital tight-binding Hamiltonian model taking into account the nearest neighbors to study the effect of antidot lattices (two dimensional honeycomb lattice of atoms including holes) on the band structure of silicene and silicon carbide (SiC) sheets. We obtained that the band structure of the silicene antidot superlattice strongly depends on the size of embedded holes, and the band gap of the silicene antidot lattice increases by increasing of holes diameter. The band gap of SiC antidot lattice, except for the lattice of the small unit cell, is independent of the holes diameter and also depends on the distance between holes. We obtained that, the band gap of the SiC antidot lattice is the same as the band gap of the corresponding sheet without hole. Also, the electronic properties of the SiC antidot superlattice occupied either by carbon or by silicon atoms are investigated, numerically. Furthermore, we study the effect of occupation of graphene antidot by Si atoms and vice versa. Also, we have calculated the band structure of graphene and silicene antidot lattice filled by Si + C atoms. Finally, we compute the band structure of the SiC antidot lattice including the holes which are filled by C or by Si atoms. Really, in this paper we have generalized the method of paper[38] about graphene antidot with empty holes to the cases of filled holes by different atoms and also to the case of silicene and silicon carbide antidot lattices.

  • Design and comparison of new fault-tolerant majority gate based on quantum-dot cellular automata

    Xiaoyang Wang, Guangjun Xie, Feifei Deng, Yu Quan, Hongjun Lü

    Available online

    Abstract Full Text PDF

    Quantum-dot cellular automata (QCA) is increasingly valued by researchers because of its nanoscale size and very low power consumption. However, in the manufacture of nanoscale devices prone to various forms of defects, which will affect the subsequent circuits design. Therefore, fault-tolerant QCA architectures have become a new research direction. The purpose of this paper is to build a novel fault-tolerant three-input majority gate based on normal cells. Compared with the previous structures, the majority gate shows high fault tolerance under single-cell and double-cell omission defects. In order to examine the functionality of the proposed structure, some physical proofs under single cell missing defects are provided. Besides, two new fault-tolerant decoders are constructed based on the proposed majority gate. In order to fully demonstrate the performance of the proposed decoder, the previous decoders were thoroughly compared in terms of fault tolerance, area and delay. The result shows that the proposed design has a good fault tolerance characteristic, while the performance in other aspects is also quite good.

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