Graphene as transparent electrode for direct observation of hole photoemission from silicon to oxide Appl. Phys. Lett. 102, 123106 (2013) Temperature dependent thermal conductivity of a free-standing graphene nanoribbon Appl. Phys. Lett. 102, 111911 (2013) Directional quantum transport in graphyne p-n junction J. Appl. Phys. 113, 073710 (2013) Charge transport in lightly reduced graphene oxide: A transport energy perspective J. Appl. Phys. 113, 063710 (2013) Effect of chiral property on hot phonon distribution and energy loss rate due to surface polar phonons in a bilayer graphene J. Appl. Phys. 113, 063705 (2013) Additional information on J. Appl. Phys. Shubnikov-de Haas (SdH) and Hall effect measurements performed in a temperature range between 1.8 and 275 K, at an electric field up to 35 kV m À1 and magnetic fields up to 11 T, have been used to investigate the electronic transport properties of monolayer graphene on SiC substrate. The number of layers was determined by the use of the Raman spectroscopy. The carrier density and in-plane effective mass of electrons have been obtained from the periods and temperature dependencies of the amplitude of the SdH oscillations, respectively. The effective mass is in good agreement with the current results in the literature. The two-dimensional (2D) electron energy relaxations in monolayer graphene were also investigated experimentally. The electron temperature (T e ) of hot electrons was obtained from the lattice temperature (T L ) and the applied electric field dependencies of the amplitude of SdH oscillations. The experimental results for the electron temperature dependence of power loss indicate that the energy relaxation of electrons is due to acoustic phonon emission via mixed unscreened piezoelectric interaction and deformation-potential scattering.

The electronic properties of modulation-doped GaAs/Ga 1−x Al x As multiple quantum wells (MWQ) with well width (L z ) in the range between 51 and 145 Å have been investigated by using the Shubnikov-de Haas (SdH) oscillations technique. The carrier density and the Fermi energy have been determined from the period of the SdH oscillations. The in-plane effective mass (m * ) and the quantum lifetime (τ q ) of 2D electrons have been obtained from the temperature and magnetic field dependences of the SdH amplitude. For narrow MQW samples (L z = 51, 75 and 78 Å), m * increases with decreasing L z ; for the samples with L z = 106 and 145 Å, m * is approximately equal to that of electrons in bulk GaAs. The values obtained for τ q show no clear well-width dependence and suggest that interface roughness is the dominating scattering mechanism in GaAs/Ga 1−x Al x As MQWs.

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We investigate electronic transport properties of as-grown and annealed n-type modulationdoped Al 0.15 Ga 0.85 As/GaAs 1−x Bi x (x=0 and 0.04) quantum well (QW) structures using magnetotransport measurements in the temperature range 4.2 K and 60 K and at magnetic fields up to 18 T. Thermal annealing process was applied at two different temperatures, 700 °C and 350 °C during 60 s and 180 s, respectively. We find that electron effective mass and 2D electron density in as-grown Bi-containing sample are slightly lower than that in Bi-free one. Furthermore, quantum electron mobility and quantum scattering time are observed to be decreased in Bi-containing samples. The annealing process at 700 °C causes a slight increase in electron effective mass and 2D electron density. A negligible decrease in electron effective mass and an increase in 2D electron density are determined following annealing at 350 °C. The observed change in electron effective mass following thermal annealing process is attributed to changing 2D electron density in the samples. No improvement on quantum electron mobility and quantum scattering time are observed following thermal annealing at both process temperatures. We determine that one electron subband (e1) for as-grown and annealed (at 700 °C for 60 s) Bicontaining QWs and two electron subbands (e1 and e2) for the annealed (at 350 °C for 180 s) GaAsBi QW sample and the Bi-free QW sample contribute to electronic transport. Our results reveal that there is no significant direct effect of Bi on effective electron mass, but an indirect effect, in which Bi can provoke changes in 2D electron density and hence causes not to observe actual band-edge electron mass but a deviation from its band-edge value. Therefore, it can be concluded that dispersion curve of conduction band does not change as an effect of Bi incorporation in GaAs.

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We report superconductivity in Mg-doped InN grown by molecular beam epitaxy. Superconductivity phase transition temperature occurs Tc=3.97 K as determined by magnetoresistance and Hall resistance measurements. The two-dimensional (2D) carrier density of the measured sample is n2D=9×1014 cm−2 corresponding to a three-dimensional (3D) electron density of n3D=1.8×1019 cm−3 which is within the range of values between Mott transition and the superconductivity to metal transition. We propose a plausible mechanism to explain the existence of the superconductivity in terms of a uniform distribution of superconducting InN nanoparticles or nanosized indium dots forming microscopic Josephson junctions in the heavily compensated insulating bulk InN matrix.

The composition dependence of longitudinal optical (LO) phonon energies in undoped and Mg-doped In 1Àx Ga x N samples are determined using Raman spectroscopy in the range of Ga fraction from x ¼ 0 to x ¼ 56%. The LO phonon energy varies from 73 meV for InN to 83 meV for In 1Àx Ga x N with 56% Ga.Independent measurements of temperature dependent mobility at high temperatures where LO phonon scattering dominates the transport were also used to obtain the LO phonon energy for x ¼ 0 and x ¼ 20%. The results obtained from the two independent techniques compare extremely well.