The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
M S Wartak - One of the best experts on this subject based on the ideXlab platform.
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8 Band and 14 Band kp modeling of Electronic Band Structure and material gain in ga in asbi quantum wells grown on gaas and inp substrates
Journal of Applied Physics, 2015Co-Authors: M Gladysiewicz, R Kudrawiec, M S WartakAbstract:The Electronic Band Structure and material gain have been calculated for GaAsBi/GaAs quantum wells (QWs) with various bismuth concentrations (Bi ≤ 15%) within the 8-Band and 14-Band kp models. The 14-Band kp model was obtained by extending the standard 8-Band kp Hamiltonian by the valence Band anticrossing (VBAC) Hamiltonian, which is widely used to describe Bi-related changes in the Electronic Band Structure of dilute bismides. It has been shown that in the range of low carrier concentrations n < 5 × 1018 cm−3, material gain spectra calculated within 8- and 14-Band kp Hamiltonians are similar. It means that the 8-Band kp model can be used to calculate material gain in dilute bismides QWs. Therefore, it can be applied to analyze QWs containing new dilute bismides for which the VBAC parameters are unknown. Thus, the energy gap and electron effective mass for Bi-containing materials are used instead of VBAC parameters. The Electronic Band Structure and material gain have been calculated for 8 nm wide GaInAs...
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Electronic Band Structure and Material Gain of Dilute Nitride Quantum Wells Grown on InP Substrate
IEEE Journal of Quantum Electronics, 2015Co-Authors: M Gladysiewicz, R Kudrawiec, M S WartakAbstract:The eight-Band kp Hamiltonian is applied to calculate Electronic Band Structure and material gain in dilute nitride quantum wells (QWs) grown on InP substrate. Three N-containing QW materials (GaInNAs, GaNAsSb, and GaNPSb) and different N-free barriers (GaInAs, GaAsSb, GaPSb, AlGaInAs, GaInPAs, AlGaAsSb, GaPAsSb, and AlGaPSb) lattice matched to InP are analyzed. It is shown that Ga0.17In0.83Ny As1-y-QWs with Ga0.47In0.53As, Al0.23Ga0.24In0.53As, or Ga0.17In0.83P0.63As0.37 barriers are a very good gain medium for long-wavelength lasers grown on InP substrates. For N-free QWs the transverse electric (TE) mode of the material gain develops at 2.1 μm. This gain peak shifts toward longer wavelengths upon the incorporation of nitrogen and reaches the wavelength of ~2.8 Mm for 3% N. For GaNyAs0.26-ySb0.74-QWs no quantum confinement or very weak quantum confinement exist for electrons in N-free QWs with the ternary barrier (i.e., GaAs0.51Sb0.49) and quaternary (Al0.23Ga0.77As0.51Sb0.49 and GaP0.25As0.15Sb0.60) barriers, respectively. However, the quantum confinement in the conduction Band strongly increases after incorporation of nitrogen. For GaNyAs0.26-ySb0.74-QWs with 3% N gain peak for TE mode exists at 3.2 μm. Very similar changes in Electronic Band Structure and material gain are noticed for GaNyP0.26-ySb0.74-QWs with GaP0.35Sb0.65, Al0.23Ga0.77As0.52Sb0.48, and GaP0.25As0.15 Sb0.60 barriers. In that case gain peak (TE mode) for GaN0.03P0.23Sb0.74-QW with GaP0.35Sb0.65 barrier is at 3.6 μm. The intensity and the shape of material gain spectra in the three QW system vary with changes of the nitrogen concentration and the barrier content. At carrier concentration of 5 × 1018 cm-3, the largest material gain exists for Ga0.17In0.83NyAs1-y-QWs with Al0.23Ga0.24In0.53As and Ga0.17In0.83As0.37Ga0.63 barriers.
Se Hyuk Oh - One of the best experts on this subject based on the ideXlab platform.
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Electronic Band Structure and photocatalytic activity of ln2ti2o7 ln la pr nd
Journal of Physical Chemistry B, 2003Co-Authors: Dong Won Hwang, Wei Li, Se Hyuk OhAbstract:Photocatalytic activity in the water splitting of Ln2Ti2O7 (Ln = La, Pr, Nd) with a layered Structure was highly dependent on their Electronic Band Structure. The conduction Band of La2Ti2O7 consisted mainly of Ti 3d and La 5d, whereas the valence Band consisted mainly of O 2p and Ti 3d. The empty La 4f level was found to be located ca. 3.6 eV above the bottom of the conduction Band from both the Electronic Band-Structure calculation and the XPS measurement. The occupied and unoccupied Ln 4f level in Ln2Ti2O7 was shifted to lower energy as the number of 4f electrons increased. This shift of the Ln 4f Band made it possible for the Band-gap energy of both Pr2Ti2O7 and Nd2Ti2O7 to be decreased. For Nd2Ti2O7, the unoccupied Nd 4f level located between the conduction Band and the valence Band was found to be detrimental to photocatalytic activity in water splitting because it could act as an electron-trapping site.
Robert Vajtai - One of the best experts on this subject based on the ideXlab platform.
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evolution of the Electronic Band Structure and efficient photo detection in atomic layers of inse
ACS Nano, 2014Co-Authors: Liehui Ge, Rajesh Kappera, Antony George, Sina Najmaei, Robert Vajtai, Manish Chhowalla, Hisato Yamaguchi, Gautam Gupta, Aditya D Mohite, Pulickel M AjayanAbstract:Atomic layers of two-dimensional (2D) materials have recently been the focus of extensive research. This follows from the footsteps of graphene, which has shown great potential for ultrathin optoElectronic devices. In this paper, we present a comprehensive study on the synthesis, characterization, and thin film photodetector application of atomic layers of InSe. Correlation between resonance Raman spectroscopy and photoconductivity measurements allows us to systematically track the evolution of the Electronic Band Structure of 2D InSe as its thickness approaches few atomic layers. Analysis of photoconductivity spectra suggests that few-layered InSe has an indirect Band gap of 1.4 eV, which is 200 meV higher than bulk InSe due to the suppressed interlayer electron orbital coupling. Temperature-dependent photocurrent measurements reveal that the suppressed interlayer interaction also results in more localized pz-like orbitals, and these orbitals couple strongly with the in-plane E′ and E″ phonons. Finally, ...
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Evolution of the Electronic Band Structure and efficient photo-detection in atomic layers of InSe
ACS Nano, 2014Co-Authors: Sidong Lei, Rajesh Kappera, Antony George, Liehui Ge, Sina Najmaei, Manish Chhowalla, Jun Lou, Hisato Yamaguchi, Gautam Gupta, Robert VajtaiAbstract:Atomic layers of two-dimensional (2D) materials have recently been the focus of extensive research. This follows from the footsteps of graphene, which has shown great potential for ultrathin optoElectronic devices. In this paper, we present a comprehensive study on the synthesis, characterization, and thin film photodetector application of atomic layers of InSe. Correlation between resonance Raman spectroscopy and photoconductivity measurements allows us to systematically track the evolution of the Electronic Band Structure of 2D InSe as its thickness approaches few atomic layers. Analysis of photoconductivity spectra suggests that few-layered InSe has an indirect Band gap of 1.4 eV, which is 200 meV higher than bulk InSe due to the suppressed interlayer electron orbital coupling. Temperature-dependent photocurrent measurements reveal that the suppressed interlayer interaction also results in more localized pz-like orbitals, and these orbitals couple strongly with the in-plane E' and E″ phonons. Finally, we measured a strong photoresponse of 34.7 mA/W and fast response time of 488 μs for a few layered InSe, suggesting that it is a good material for thin film optoElectronic applications.
Yong Seung Kwon - One of the best experts on this subject based on the ideXlab platform.
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thermoelectric properties and anisotropic Electronic Band Structure on the in4se3 x compounds
Applied Physics Letters, 2009Co-Authors: Jongsoo Rhyee, Yong Seung KwonAbstract:We report the high thermoelectric figure-of-merit (ZT) on the Se-deficient polycrystalline compounds of In4Se3−x (0.02≤x≤0.5) and the anisotropic Electronic Band Structure. The Se-deficiency (x) has the effect of decreasing the semiconducting Band gap and increasing the power factor. The Band Structure calculation for In4Se3−x (x=0.25) exhibits localized hole Bands at the Γ-point and Y-S symmetry line, whereas the significant Electronic Band dispersion is observed along the c-axis. Here, we propose that the high ZT values on those compounds are originated from the anisotropic Electronic Band Structure as well as Peierls distortion.
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Thermoelectric properties and anisotropic Electronic Band Structure on the In4Se3−x compounds
Applied Physics Letters, 2009Co-Authors: Jongsoo Rhyee, Yong Seung KwonAbstract:We report the high thermoelectric figure-of-merit (ZT) on the Se-deficient polycrystalline compounds of In4Se3−x (0.02≤x≤0.5) and the anisotropic Electronic Band Structure. The Se-deficiency (x) has the effect of decreasing the semiconducting Band gap and increasing the power factor. The Band Structure calculation for In4Se3−x (x=0.25) exhibits localized hole Bands at the Γ-point and Y-S symmetry line, whereas the significant Electronic Band dispersion is observed along the c-axis. Here, we propose that the high ZT values on those compounds are originated from the anisotropic Electronic Band Structure as well as Peierls distortion.
Dong Won Hwang - One of the best experts on this subject based on the ideXlab platform.
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Electronic Band Structure and photocatalytic activity of ln2ti2o7 ln la pr nd
Journal of Physical Chemistry B, 2003Co-Authors: Dong Won Hwang, Wei Li, Se Hyuk OhAbstract:Photocatalytic activity in the water splitting of Ln2Ti2O7 (Ln = La, Pr, Nd) with a layered Structure was highly dependent on their Electronic Band Structure. The conduction Band of La2Ti2O7 consisted mainly of Ti 3d and La 5d, whereas the valence Band consisted mainly of O 2p and Ti 3d. The empty La 4f level was found to be located ca. 3.6 eV above the bottom of the conduction Band from both the Electronic Band-Structure calculation and the XPS measurement. The occupied and unoccupied Ln 4f level in Ln2Ti2O7 was shifted to lower energy as the number of 4f electrons increased. This shift of the Ln 4f Band made it possible for the Band-gap energy of both Pr2Ti2O7 and Nd2Ti2O7 to be decreased. For Nd2Ti2O7, the unoccupied Nd 4f level located between the conduction Band and the valence Band was found to be detrimental to photocatalytic activity in water splitting because it could act as an electron-trapping site.
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Electronic Band Structure and Photocatalytic Activity of Ln2Ti2O7 (Ln = La, Pr, Nd)
Journal of Physical Chemistry B, 2003Co-Authors: Dong Won Hwang, Wei Li, Hyuk OhAbstract:Photocatalytic activity in the water splitting of Ln2Ti2O7 (Ln = La, Pr, Nd) with a layered Structure was highly dependent on their Electronic Band Structure. The conduction Band of La2Ti2O7 consisted mainly of Ti 3d and La 5d, whereas the valence Band consisted mainly of O 2p and Ti 3d. The empty La 4f level was found to be located ca. 3.6 eV above the bottom of the conduction Band from both the Electronic Band-Structure calculation and the XPS measurement. The occupied and unoccupied Ln 4f level in Ln2Ti2O7 was shifted to lower energy as the number of 4f electrons increased. This shift of the Ln 4f Band made it possible for the Band-gap energy of both Pr2Ti2O7 and Nd2Ti2O7 to be decreased. For Nd2Ti2O7, the unoccupied Nd 4f level located between the conduction Band and the valence Band was found to be detrimental to photocatalytic activity in water splitting because it could act as an electron-trapping site.