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oe1(光电查) - 科学论文

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  • Electroresistance of Pt/BaTiO<sub>3</sub>/LaNiO<sub>3</sub> ferroelectric tunnel junctions and its dependence on BaTiO<sub>3</sub> thickness

    摘要： Recently, ferroelectric tunnel junctions (FTJs) have attracted considerable attention due to their great potential in next generation non-volatile memories. In this work, we report on thickness-dependent tunneling electroresistance (TER) and corresponding evolution of transport behavior in Pt/BaTiO3/LaNiO3 FTJs with various BaTiO3 thicknesses of 2.0, 3.2, and 4.8 nm. The TER effect is observed in the 3.2 nm-thick Pt/BaTiO3/LaNiO3 tunnel junction and an ON/OFF current ratio of ~170 is achieved due to the modulation of barrier height by polarization reversal. When the BaTiO3 is increased to 4.8 nm in thickness, the ferroelectric-modulation of the barrier profile becomes more pronounced and the dominant transport mechanism changes from electron tunneling to thermally-activated thermionic injection. As a result, the OFF state current is significantly reduced due to the suppression of the Fowler-Nordheim tunneling with increased width and height of the BaTiO3 barrier. A greatly improved ON/OFF current ratio of ~12500 is thus achieved in the 4.8 nm-thick Pt/BaTiO3/LaNiO3 FTJ device. These results facilitate deeper understanding of the TER effects from the viewpoint of not only the barrier profile but also the transport mechanism.

    关键词： Pulsed laser deposition,Ferroelectric tunnel junctions,Ferroelectric memory,Resistive switching

    更新于2025-09-23 15:23:52

  • Low-temperature growth of n<sup>++</sup>-GaN by metalorganic chemical vapor deposition to achieve low-resistivity tunnel junctions on blue light emitting diodes

    摘要： We report on low-resistivity GaN tunnel junctions (TJ) on blue light-emitting diodes (LEDs). Si-doped n++-GaN layers are grown by metalorganic chemical vapor deposition directly on LED epiwafers. Low growth temperature (< 800 °C) was used to hinder Mg-passivation by hydrogen in the p++-GaN top surface. This allows achieving low-resistivity TJs without the need for post-growth Mg activation. TJs are further improved by inserting a 5 nm thick In0.15Ga0.85N interlayer (IL) within the GaN TJ thanks to piezoelectric polarization induced band bending. Eventually, the impact of InGaN IL on the internal quantum efficiency of blue LEDs is discussed.

    关键词： metalorganic chemical vapor deposition,GaN tunnel junctions,blue light-emitting diodes

    更新于2025-09-23 15:21:01

  • Complementary Resistive Switching Using Metal-Ferroelectric-Metal Tunnel Junctions

    摘要： Complementary resistive switching (CRS) devices are receiving attention because they can potentially solve the current-sneak and current-leakage problems of memory arrays based on resistive switching (RS) elements. It is shown here that a simple anti-serial connection of two ferroelectric tunnel junctions, based on BaTiO3, with symmetric top metallic electrodes and a common, floating bottom nanometric film electrode, constitute a CRS memory element. It allows nonvolatile storage of binary states (“1” = “HRS+LRS” and “0” = “LRS+HRS”), where HRS (LRS) indicate the high (low) resistance state of each ferroelectric tunnel junction. Remarkably, these states have an identical and large resistance in the remanent state, characteristic of CRS. Here, protocols for writing information are reported and it is shown that non-destructive or destructive reading schemes can be chosen by selecting the appropriate reading voltage amplitude. Moreover, this dual-tunnel device has a significantly lower power consumption than a single ferroelectric tunnel junction to perform writing/reading functions, as is experimentally demonstrated. These findings illustrate that the recent impressive development of ferroelectric tunnel junctions can be further exploited to contribute to solving critical bottlenecks in data storage and logic functions implemented using RS elements.

    关键词： ferroelectric tunnel junctions,BaTiO3,complementary resistive switching,ferroelectric

    更新于2025-09-19 17:15:36

  • Buried‐Tunnel Junction Current Injection for InP‐Based Nanomembrane Photonic Crystal Surface Emitting Lasers on Silicon

    摘要： Herein, the design, metal-organic vapor-phase epitaxial growth, fabrication, and characterization of buried-tunnel junction (BTJ) current injection structures for InP/Si hybrid nanomembrane photonic crystal surface emitting lasers (PCSELs) are reported. Corresponding BTJ-light-emitting diodes on InP substrate show low series resistance and uniform carrier injection over square-shaped device areas with side length ranging from 15 up to 250 μm, whereas BTJ-PCSEL structures with similar current injection con?guration fabricated on photonic-crystal silicon-on-insulator substrate using transfer print technology show signi?cant linewidth narrowing at low current density.

    关键词： photonic-crystal surface emitting lasers,buried-tunnel junctions,photonic bandedge lasers,silicon photonics,surface emitting lasers

    更新于2025-09-19 17:13:59

  • Band engineering of III-nitride-based deep-ultraviolet light-emitting diodes: A review

    摘要： III-nitride deep ultraviolet (DUV) light-emitting diodes (LEDs) are identified as the promising candidate for energy-efficient, environment-friendly and robust UV lighting source in the application of water/air purification, sterilization, and bio-sensing. However, the state-of-art DUV LED performance is far from satisfaction for commercialization owing to its low internal quantum efficiency, large current leakage and efficiency droop at high current injection, etc. Extensive efforts have been devoted to properly designing the band structures of such luminescent devices to enhance their output power. In this review, we summarize the recent progress on various energy band designs and engineering of DUV LEDs, with particular of interest is paid on the various approaches in band engineering of the electron-blocking layer, quantum well, quantum barrier and the implementation of many novel structures such as tunnel junctions, ultrathin quantum heterostructures to enhance their efficiency. Those inspirational approaches pave the way towards the next generation of greener and efficient UV sources for practical applications.

    关键词： Quantum well,Quantum barrier,Deep ultraviolet light-emitting diode,Ultrathin quantum heterostructures,Band engineering,Electron-blocking layer,Tunnel junctions,III-nitride

    更新于2025-09-19 17:13:59

  • Asymmetric Resistive Switching Dynamics in BaTiO <sub/>3</sub> Tunnel Junctions

    摘要： The resistive switching associated with polarization reversal is studied in detail in ferroelectric BaTiO3 tunnel junctions, with focus on the dynamics of the ferroelectric domain switching. It is observed that the transition between the high-resistance state (HRS) and the low-resistance state (LRS) is largely asymmetric being smooth from LRS to HRS, but proceeds via avalanches in the HRS-to-LRS transitions. It is shown that this distinct behavior is related to the presence of an imprint field in the junction and has important consequences on the junction’s performance.

    关键词： ferroelectric tunnel junctions,ferroelectric dynamics,neuromorphic computing,BaTiO3 films,memristors

    更新于2025-09-09 09:28:46

  • Spin splitting in EuO(111)/Si(111) spin-filter tunnel junctions with atomically sharp interface

    摘要： We demonstrate the tunneling in spin-split barriers made of ferromagnetic EuO grown on Si(111) substrates by molecular beam epitaxy. For 6 nm thick EuO films with high crystal quality and atomically sharp interfaces, we find a barrier height lowering driven by the spin splitting below the Curie temperature of 35 K. We determined the splitting energy to be 0.56 + 0.03 eV at 20 K which results in a spin polarization above 90%.

    关键词： molecular beam epitaxy,atomically sharp interface,EuO(111)/Si(111),spin splitting,spin-filter tunnel junctions

    更新于2025-09-04 15:30:14

  • High germanium doping of GaN films by ammonia molecular beam epitaxy

    摘要： Doping Gallium nitride (GaN) with elemental Germanium (Ge) grown by ammonia molecular beam epitaxy is presented. Growth studies varying the GaN growth rate, substrate growth temperature and the elemental Ge flux reveal several incorporation dependencies. Ge incorporation increases with flux, as expected, and a doping range from ~1017 cm-3 to 1020 cm-3 was readily achieved. A strong substrate temperature dependence on the electrical properties of films grown is observed, with an optimal growth temperature of 740 °C, lower than standard GaN growth conditions for the ammonia molecular beam epitaxy. Compensation effects at higher growth temperatures are suspected, as observed with other techniques. Crystallographic defects are apparent at the highest doping concentrations from electrical and optical measurements, however thin layers of such highly doped films are of great interest for contact layers and tunnel junctions in devices.

    关键词： Ammonia Molecular Beam Epitaxy,Molecular Beam Epitaxy,Tunnel Junctions,Germanium Doping,Gallium Nitride

    更新于2025-09-04 15:30:14