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Design of practically realizable unipolar HgCdTe nBn photodetectors has been studied in detail by numerical analysis. The simulations reported herein reveal that, by optimization of barrier doping, dark current levels can be reduc...
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Design of practically realizable unipolar HgCdTe nBn photodetectors has been studied in detail by numerical analysis. The simulations reported herein reveal that, by optimization of barrier doping, dark current levels can be reduced and collection efficiency substantially improved. It is shown that p-type doping of the barrier layer can significantly reduce the effective potential barrier arising from the valence band offset between the absorber and barrier regions, thus enabling HgCdTe nBn detector operation under near zero-bias conditions. However, relatively high electric fields in the space charge regions near the barrier/absorber interface result in enhanced trap-assisted Shockley-Read-Hall thermal generation. Our calculations indicate that nBn HgCdTe detectors with barriers engineered by use of HgTe/Hg0.05Cd0.95Te superlattices have, potentially, substantially better valence band alignment without the need for p-type doping.
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The electronic package with lead-free welding processes must be performed at higher temperature whereas the heat induces to mechanical stress. In this letter, we fabricate a low-$k$ SiOC dielectric comb capacitor with dual damasce...
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The electronic package with lead-free welding processes must be performed at higher temperature whereas the heat induces to mechanical stress. In this letter, we fabricate a low-$k$ SiOC dielectric comb capacitor with dual damascene (DD) structures to study the mechanical stress influence on leakage current $I_{rm leak}$ in DD by bending samples. Tensile stress causes increase of the $I_{rm leak}$ because of the decrease of energy band barrier $Phi$ of SiOC dielectric. In contrast, compress stress increases $Phi$ of SiOC and decreases its $I_{rm leak}$. Finally, we conclude that the electron transport in DD is dominated by Schottky emission. We found that the variation of $I_{rm leak}$ is attributed by the change of energy band barrier under mechanical stress.
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This paper presents a novel nanoscale tunnel FET consisting of an Esaki tunneling diode in the source region. A unique part of the source region is replaced by a heavily doped N-type silicon material establishing a tunneling diode...
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This paper presents a novel nanoscale tunnel FET consisting of an Esaki tunneling diode in the source region. A unique part of the source region is replaced by a heavily doped N-type silicon material establishing a tunneling diode inside the source region. Also, the gate metal is deliberately extended into the source region in order to more couple the created tunneling diode inside the source region. In the result of this new configuration, the band energy bending occurs inside the source region and also the potential barrier will be modified in the channel region thus increasing the ratio of I-ON to I-OFF (I-ON/I-OFF) and reducing the leakage current and ambipolar current for the proposed structure. The proposed structure has been compared with the conventional TFET and PNPN-TFET structure in terms of the I-ON/I-OFF, Leakage current, ambipolar current, drain-source conductance, short channel effects, source-drain capacitance and minimum noise figure showing a performance superiority with respect to other structures under the study.
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Despite many decades of research of diodes, which are fundamental components of electronic and photoelectronic devices with p-n or Schottky junctions using bulk or 2D materials, stereotyped architectures and complex technological ...
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Despite many decades of research of diodes, which are fundamental components of electronic and photoelectronic devices with p-n or Schottky junctions using bulk or 2D materials, stereotyped architectures and complex technological processing (doping and multiple material operations) have limited future development. Here, a novel rectification device, an orientation-induced diode, assembled using only few-layered black phosphorus (BP) is investigated. The key to its realization is to utilize the remarkable anisotropy of BP in low dimensions and change the charge-transport conditions abruptly along the different crystal orientations. Rectification ratios of 6.8, 22, and 115 can be achieved in cruciform BP, cross-stacked BP junctions, and BP junctions stacked with vertical orientations, respectively. The underlying physical processes and mechanisms can be explained using "orientation barrier" band theory. The theoretical results are experimentally confirmed using localized scanning photocurrent imaging. These orientation-induced optoelectronic devices open possibilities for 2D anisotropic materials with a new degree of freedom to improve modulation in diodes.
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For a low surface barrier, the energy band, barrier height and width of the space charge region at the surface of relatively large grains of ZnO are presented analytically on condition that the electron distribution obeys the Bolt...
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For a low surface barrier, the energy band, barrier height and width of the space charge region at the surface of relatively large grains of ZnO are presented analytically on condition that the electron distribution obeys the Boltzmann statistics. It is shown that the temperature in the space charge distribution factor has an important effect on the energy band, barrier height and width of the space charge region. The depletion approximation is a model in which the temperature in the space charge distribution factor is zero. Our results are better than the depletion approximation.
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Fermi-level positions at nearly perfect interfaces of epitaxial erbium silicide on silicon are measured by internal photoemission as a function of the thickness and oxygen contamination of the silicide. Thicknesses in excess of 30...
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Fermi-level positions at nearly perfect interfaces of epitaxial erbium silicide on silicon are measured by internal photoemission as a function of the thickness and oxygen contamination of the silicide. Thicknesses in excess of 30 silicide monolayers (about 120 Angstrom) and oxygen concentration lower than 0.3% are necessary to obtain the lowest value of 0.28 eV for the barrier height on n-type Si. For thinner silicide films or higher oxygen contents, the barrier height increases and shifts the Fermi level downwards across 45% of the Si band gap. Such an unpinning of the Fermi level is believed to be the consequence of the simultaneous occurrence of the high structural perfection of these interfaces, of the low electronegativity of the silicide, and of the low density of metal-induced gap states near the Fermi level. [References: 20]
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We present first-principles calculations of ballistic spin injection in Fe/GaAs and Fe/ZnSe junctions with orientations (00 1), (111), and (I 10). We find that the symmetry mismatch of the Fe minority spin states with the semicond...
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We present first-principles calculations of ballistic spin injection in Fe/GaAs and Fe/ZnSe junctions with orientations (00 1), (111), and (I 10). We find that the symmetry mismatch of the Fe minority spin states with the semiconductor conduction states can lead to extremely high spin polarization of the current through the (001) interface for hot and thermal injection processes. Such a symmetry mismatch does not exist for the (I 11) and (I 10) interfaces, where smaller spin injection efficiencies are found. The presence of interface states at the Fermi energy is found to lower the current spin polarization.
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Precise evaluation of the effective work function and the built-in voltage in metal-oxide-metal (MOS) or metal-insulator-metal (MIM) stacks is crucial for attaining the functionality of various oxide-based electron devices. We stu...
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Precise evaluation of the effective work function and the built-in voltage in metal-oxide-metal (MOS) or metal-insulator-metal (MIM) stacks is crucial for attaining the functionality of various oxide-based electron devices. We studied the impact of a low work function (WF) metal interlayer (IL), i.e. Ti, on the electron barrier height between the metal Fermi level and the conduction band of the oxide insulator. The experiments were performed on structures comprised of a layer of thermal SiO_2 or an atomic layer deposited Al_2O_3 on heavily doped p- or n-Si substrates. In order to evaluate the impact of the Ti IL, 3, 6 or 10nm thick Ti films have been deposited prior to TiN_x sputtering. Spectral curves of electron photoemission from the metal layer into the oxide were analyzed in order to determine the energy barrier for electrons between the Fermi level of the metal and the conduction band of the insulator (φ_e). As expected, the insertion of the low WF metal shifts the barrier to lower energies, depending on the IL thickness. However, while a 3-nm thick Ti IL is sufficient to lower the barrier by 0.5 eV in the SiO_2-based stack, it has no measurable impact on the barrier in the Al_2O_3/Ti/TiN_x stack. For the latter structure, both Ti and the Al_2O_3 thicknesses influence the φ_e lowering trend, suggesting that oxygen scavenging from Al_2O_3 by Ti and nitridation of the Ti IL by subsequent TiN deposition may affect the band alignment between the metal and the oxide.
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Nanostructure fabrication or surface processing in general is predominantly kinetics-limited. One of the kinetics factors is surface diffusion, which involves intricate interplay between the diffusing atoms and substrate atoms. On...
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Nanostructure fabrication or surface processing in general is predominantly kinetics-limited. One of the kinetics factors is surface diffusion, which involves intricate interplay between the diffusing atoms and substrate atoms. On Cu{111} surfaces, both adatoms and dimers diffuse very fast. Recent studies have shown that adatoms encounter a large facet-facet barrier, even though their conventional Ehrlich-Schwoebel barriers are small. This work examines the facet-facet diffusion barriers of dimers. Our results show that a dimer prefers diffusion through atom-by-atom mechanism, having a barrier of 0.52 eV from {111} to {111} facet and a barrier of 0.55 eV from {111} to {100} facet. When the two atoms in a dimer diffuse simultaneously, the barrier is 0.97 eV from {111} to {111} facet and 0.62 eV from {111} to {100} facet.
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It is unreliable to evaluate the Schottky barrier height (SBH) in monolayer (ML) 2D material field effect transistors (FETs) with strongly interacted electrode from the work function approximation (WFA) because of existence of the...
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It is unreliable to evaluate the Schottky barrier height (SBH) in monolayer (ML) 2D material field effect transistors (FETs) with strongly interacted electrode from the work function approximation (WFA) because of existence of the Fermi-level pinning. Here, we report the first systematical study of bilayer (BL) phosphorene FETs in contact with a series of metals with a wide work function range (Al, Ag, Cu, Au, Cr, Ti, Ni, and Pd) by using both ab initio electronic band calculations and quantum transport simulation (QTS). Different from only one type of Schottky barrier (SB) identified in the ML phosphorene FETs, two types of SBs are identified in BL phosphorene FETs: the vertical SB between the metallized and the intact phosphorene layer, whose height is determined from the energy band analysis (EBA); the lateral SB between the metallized and the channel BL phosphorene, whose height is determined from the QTS. The vertical SBHs show a better consistency with the lateral SBHs of the ML phosphorene FETs from the QTS compared than that of the popular WFA. Therefore, we develop a better and more general method than the WFA to estimate the lateral SBHs of ML semiconductor transistors with strongly interacted electrodes based on the EBA for its BL counterpart. In terms of the QTS, n-type lateral Schottky contacts are formed between BL phosphorene and Cr, Al, and Cu electrodes with electron SBH of 0.27, 0.31, and 0.32 eV, respectively, while p-type lateral Schottky contacts are formed between BL phosphorene and Pd, Ti, Ni, Ag, and Au electrodes with hole SBH of 0.11, 0.18, 0.19, 0.20, and 0.21 eV, respectively. The theoretical polarity and SBHs are in good agreement with available experiments. Our study provides an insight into the BL phosphorene-metal interfaces that are crucial for designing the BL phosphorene device.
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