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Full-Text Articles in Physics

Quantum Transport In In0.75Ga0.25As Quantum Wires, P. J. Simmonds, F. Sfigakis, H. E. Beere, D. A. Ritchie, M. Pepper, D. Anderson, G. A.C. Jones Apr 2008

Quantum Transport In In0.75Ga0.25As Quantum Wires, P. J. Simmonds, F. Sfigakis, H. E. Beere, D. A. Ritchie, M. Pepper, D. Anderson, G. A.C. Jones

Paul J. Simmonds

In addition to quantized conductance plateaus at integer multiples of 2e2/h, the differential conductance G=dI/dV shows plateaus at 0.25(2e2/h) and 0.75(2e2/h) under applied source-drain bias in In0.75Ga0.25As quantum wires defined by insulated split gates. This observation is consistent with a spin-gap model for the 0.7 structure. Using a tilted magnetic field to induce Landau level crossings, the g factor was measured to be ~9 by the coincidence method. This material, with a mobility of 1.8×105 ...


Growth-Temperature Optimization For Low Carrier-Density In0.75Ga0.25As-Based High Electron Mobility Transistors On Inp, Paul J. Simmonds, H. E. Beere, D. A. Ritchie, S. N. Holmes Oct 2007

Growth-Temperature Optimization For Low Carrier-Density In0.75Ga0.25As-Based High Electron Mobility Transistors On Inp, Paul J. Simmonds, H. E. Beere, D. A. Ritchie, S. N. Holmes

Paul J. Simmonds

Two-dimensional electron gases (2DEGs) were formed in undoped In0.75Al0.25As / In0.75Ga0.25As / In0.75Al0.25As quantum wells. The optimal growth temperature for this structure is 410°C, with peak 2DEG electron mobility and density values of μ = 221000 cm2/V s and n = 1.36 × 1011 cm−2 at 1.5 K. This electron mobility is equal to the highest previously published for these undoped structures but with a factor of 2 reduction in n. This has been achieved through the use of a ...


Quantum Dot Resonant Tunneling Diodes For Telecom Wavelength Single Photon Detection, H. W. Li, Paul J. Simmonds, H. E. Beere, B. E. Kardynał, D. A. Ritchie, A. J. Shields Sep 2007

Quantum Dot Resonant Tunneling Diodes For Telecom Wavelength Single Photon Detection, H. W. Li, Paul J. Simmonds, H. E. Beere, B. E. Kardynał, D. A. Ritchie, A. J. Shields

Paul J. Simmonds

Single photon detection was realized at a telecom wavelength with quantum dot resonant tunneling diodes grown on an InP substrate. The structure contains a AlAs/In0.53Ga0.47As/AlAs quantum well with InAs quantum dots grown on the top AlAs barrier. The single photon detection efficiency of the device under 1310 nm illumination was measured to be about 0.35% ± 0.07% with a dark count rate of 1.58×10-6 ns-1. This corresponds to an internal efficiency of 6.3%.


Quantum Dot Resonant Tunneling Diode For Telecommunication Wavelength Single Photon Detection, H. W. Li, B. E. Kardynał, P. See, A. J. Shields, P. Simmonds, H. E. Beere, D. A. Ritchie Aug 2007

Quantum Dot Resonant Tunneling Diode For Telecommunication Wavelength Single Photon Detection, H. W. Li, B. E. Kardynał, P. See, A. J. Shields, P. Simmonds, H. E. Beere, D. A. Ritchie

Paul J. Simmonds

The authors present a quantum dot (QD) based single photon detector operating at a fiber optic telecommunication wavelength. The detector is based on an AlAs/In0.53Ga0.47As/AlAs double-barrier resonant tunneling diode containing a layer of self-assembled InAs QDs grown on an InP substrate. The device shows an internal efficiency of about 6.3% with a dark count rate of 1.58 × 10−6 ns−1 for 1310 nm photons.


Growth By Molecular Beam Epitaxy Of Self-Assembled Inas Quantum Dots On Inalas And Ingaas Lattice-Matched To Inp, Paul J. Simmonds, H W. Li, H E. Beere, P See, A J. Shields, D A. Ritchie Apr 2007

Growth By Molecular Beam Epitaxy Of Self-Assembled Inas Quantum Dots On Inalas And Ingaas Lattice-Matched To Inp, Paul J. Simmonds, H W. Li, H E. Beere, P See, A J. Shields, D A. Ritchie

Paul J. Simmonds

The authors report the results of a detailed study of the effect of growth conditions, for molecular beam epitaxy, on the structural and optical properties of self-assembled InAs quantum dots (QDs) on In0.524Al0.476As. InAs QDs both buried in, and on top of, In0.524Al0.476As were analyzed using photoluminescence (PL) and atomic force microscopy. InAs QD morphology and peak PL emission wavelength both scale linearly with deposition thickness in monolayers (MLs). InAs deposition thickness can be used to tune QD PL wavelength by 170 nm/ML, over a range of ...