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.

  • Simulation analysis of a high efficiency GaInP/Si multijunction solar cell

    M. Benaicha, L. Dehimi, F. Pezzimenti, F. Bouzid

    Available online

    Abstract Full Text PDF

    The solar power conversion efficiency of a gallium indium phosphide (GaInP)/silicon (Si) tandem solar cell has been investigated by means of a physical device simulator considering both mechanically stacked and monolithic structures. In particular, to interconnect the bottom and top sub-cells of the monolithic tandem, a gallium arsenide (GaAs)-based tunnel-junction, i.e. GaAs(n+)/GaAs(p+), which assures a low electrical resistance and an optically low-loss connection, has been considered. The J–V characteristics of the single junction cells, monolithic tandem, and mechanically stacked structure have been calculated extracting the main photovoltaic parameters. An analysis of the tunnel-junction behaviour has been also developed. The mechanically stacked cell achieves an efficiency of 24.27% whereas the monolithic tandem reaches an efficiency of 31.11% under AM1.5 spectral conditions. External quantum efficiency simulations have evaluated the useful wavelength range. The results and discussion could be helpful in designing high efficiency monolithic multijunction GaInP/Si solar cells involving a thin GaAs(n+)/GaAs(p+) tunnel junction.

  • A 0.1–1.5 GHz multi-octave quadruple-stacked CMOS power amplifier

    Shizhe Wei, Haifeng Wu, Qian Lin, Mingzhe Zhang

    Available online

    Abstract Full Text PDF

    In this letter, we design and analyze 0.1–1.5 GHz multi-octave quadruple-stacked CMOS power amplifier (PA) in 0.18 μm CMOS technology. By using two-stage quadruple-stacked topology and feedback technology, the proposed PA realizes an ultra-wideband CMOS PA in a small chip area. Wideband impedance matching is achieved with smaller chip dimension. The effects of feedback resistors on the RF performance are also discussed for this stacked-FET PA. The PA shows measured input return loss (< –10.8 dB) and output return loss (< –9.6 dB) in the entire bandwidth. A saturated output power of 22 dBm with maximum 20% power added efficiency (PAE) is also measured with the drain voltage at 5 V. The chip size is 0.44 mm2 including all pads.

  • Small-signal modeling and parameter extraction method for a multigate GaAs pHEMT switch

    Lin Luo, Jun Liu, Guofang Wang, Yuxing Wu

    Available online

    Abstract Full Text PDF

    This paper presents an accurate small-signal model for multi-gate GaAs pHEMTs in switching-mode. The extraction method for the proposed model is developed. A 2-gate switch structure is fabricated on a commercial 0.5 μm AlGaAs/GaAs pHEMT technology to verify the proposed model. Excellent agreement has been obtained between the measured and simulated results over a wide frequency range.

  • Numerical study of mono-crystalline silicon solar cells with passivated emitter and rear contact configuration for the efficiency beyond 24% based on mass production technology

    Peng Wang, Gaofei Li, Miao Wang, Hong Li, Jing Zheng, Liyou Yang, Yigang Chen, Dongdong Li, Linfeng Lu

    Available online

    Abstract Full Text PDF

    Mono-crystalline silicon solar cells with a passivated emitter rear contact (PERC) configuration have attracted extensive attention from both industry and scientific communities. A record efficiency of 24.06% on p-type silicon wafer and mass production efficiency around 22% have been demonstrated, mainly due to its superior rear side passivation. In this work, the PERC solar cells with a p-type silicon wafer were numerically studied in terms of the surface passivation, quality of silicon wafer and metal electrodes. A rational way to achieve a 24% mass-production efficiency was proposed. Free energy loss analyses were adopted to address the loss sources with respect to the limit efficiency of 29%, which provides a guideline for the design and manufacture of a high-efficiency PERC solar cell.

  • Modelling and optical response of a compressive-strained AlGaN/GaN quantum well laser diode

    A. Menani, L. Dehimi, F. Pezzimenti, S. Dehimi

    Available online

    Abstract Full Text PDF

    The effects of the quantum well (QW) width, carrier density, and aluminium (Al) concentration in the barrier layers on the optical characteristics of a gallium nitride (GaN)-based QW laser diode are investigated by means of a careful modelling analysis in a wide range of temperatures. The device’s optical gain is calculated by using two different band energy models. The first is based on the simple band-to-band model that accounts for carrier transitions between the first levels of the conduction band and valence band, whereas the second assumes the perturbation theory (k.p model) for considering the valence intersubband transitions and the relative absorption losses in the QW. The results reveal that the optical gain increases with increasing the n-type doping density as well as the Al molar fraction of the AlxGa1–xN layers, which originate the GaN compressive-strained QW. In particular, a significant optical gain on the order of 5000 cm–1 is calculated for a QW width of 40 Å at room temperature. In addition, the laser threshold current density is of few tens of A/cm2 at low temperatures.

  • Tubular/helical architectures construction based on rolled-up AlN nanomembranes and resonance as optical microcavity

    Jinyu Yang, Yang Wang, Lu Wang, Ziao Tian, Zengfeng Di, Yongfeng Mei

    Available online

    Abstract Full Text PDF

    Aluminum nitride (AlN) has attracted a great amount of interest due to the fact that these group III–V semiconductors present direct band gap behavior and are compatible with current micro-electro-mechanical systems. In this work, three dimensional (3D) AlN architectures including tubes and helices were constructed by rolling up AlN nanomembranes grown on a silicon-on-insulator wafer via magnetron sputtering. The properties of the AlN membrane were characterized through transmission electron microscopy and X-ray diffraction. The thickness of AlN nanomembranes could be tuned via the RIE thinning method, and thus micro-tubes with different diameters were fabricated. The intrinsic strain in AlN membranes was investigated via micro-Raman spectroscopy, which agrees well with theory prediction. Whispering gallery mode was observed in AlN tubular optical microcavity in photoluminescence spectrum. A postprocess involving atomic layer deposition and R6G immersion were employed on as-fabricated AlN tubes to promote the Q-factor. The AlN tubular micro-resonators could offer a novel design route for Si-based integrated light sources. In addition, the rolled-up technology paves a new way for AlN 3D structure fabrication, which is promising for AlN application in MEMS and photonics fields.

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