Showing papers on "Band offset published in 2005"
TL;DR: In this paper, the authors studied the band alignment of HfSiO and hfSiON films by soft x-ray photoemission, oxygen K-edge xray absorption, and spectroscopic ellipsometry.
Abstract: Nitridation of HfSiO films improves certain physical and electrical properties—when using gate stack layers—such as their crystallization temperature and their resistance to interdiffusion. We have studied the band alignment of HfSiO and HfSiON films by soft x-ray photoemission, oxygen K-edge x-ray absorption, and spectroscopic ellipsometry. Nitridation of HfSiO reduced the band gap by 1.50eV±0.05eV, and the valence- and conduction-band offsets by 1.2eV±0.1eV and 0.33eV±0.05eV, respectively. Although the band-gap reduction should lead to increased leakage, the barrier heights are still sufficient for proposed near-future complementary metal-oxide-semiconductor applications.
618 citations
TL;DR: In this article, the characteristics of a ZnO light-emitting diode (LED) comprised of a heterostructure of p-ZnO/n-GaN were reported.
Abstract: We report on the characteristics of a ZnO light-emitting diode (LED) comprised of a heterostructure of p-ZnO/n-GaN The LED structure consisted of a phosphorus doped p-ZnO film with a hole concentration of 668×1017cm−3 and a Si-doped n-GaN film with an electron concentration of 11×1018cm−3 The I–V of the LED showed a threshold voltage of 54 V and an electroluminescence (EL) emission of 409 nm at room temperature The EL emission peak at 409 nm was attributed to the band gap of p-ZnO which was reduced as the result of the band offset at the interface of p-ZnO and n-GaN
332 citations
TL;DR: In this paper, the electronic structure and transmission coefficients of Si nanowires were calculated in a sp/sup 3/d/sup 5/s/sup model, and the effect of wire thickness on the bandgap, conduction valley splitting, hole band splitting, effective masses, and transmission was demonstrated.
Abstract: The electronic structure and transmission coefficients of Si nanowires are calculated in a sp/sup 3/d/sup 5/s/sup */ model. The effect of wire thickness on the bandgap, conduction valley splitting, hole band splitting, effective masses, and transmission is demonstrated. Results from the sp/sup 3/d/sup 5/s/sup */ model are compared to those from a single-band effective mass model to assess the validity of the single-band effective mass model in narrow Si nanowires. The one-dimensional Brillouin zone of a Si nanowire is direct gap. The conduction band minimum can split into a quartet of energies although often two of the energies are degenerate. Conduction band valley splitting reduces the averaged mobility mass along the axis of the wire, but quantum confinement increases the transverse mass of the conduction band edge. Quantum confinement results in a large increase in the hole masses of the two highest valence bands. A single-band model performs reasonably well at calculating the effective band edges for wires as small as 1.54-nm square. A wire-substrate interface can be viewed as a heterojunction with band offsets resulting in reflection in the transmission.
196 citations
TL;DR: In this article, the energy levels of the oxygen vacancy and oxygen interstitial defects in HfO2 using methods not needing a band gap correction were calculated. But they did not consider the effect of band offsets.
92 citations
TL;DR: In this article, the conduction and valence band offsets of thin-film solar cells on a stainless steel substrate were investigated using photoelectron spectroscopy and inverse photoemission.
Abstract: The band alignment at the CdS∕Cu(In,Ga)S2 interface in thin-film solar cells on a stainless steel substrate was investigated using photoelectron spectroscopy and inverse photoemission. By combining both techniques, the conduction and valence band offsets were independently determined. We find an unfavorable conduction band offset of −0.45 (±0.15) eV, accounting for the generally observed low open-circuit voltage and indicating the great importance of the buffer∕absorber conduction band offset for such devices. The surface band gap of the Cu(In,Ga)S2 absorber is 1.76 (±0.15) eV, being increased with respect to the expected bulk value by a copper depletion near the surface.
91 citations
TL;DR: In this paper, the relationship between the exciton binding energy to the band offset in determining the device characteristic of a particular type II heterojunction material was explored for photovoltaic and light-emitting diode applications.
Abstract: In this paper we consider the essential electronic excited states in parallel chains of semiconducting polymers that are currently being explored for photovoltaic and light-emitting diode applications. In particular, we focus upon various type II donor-acceptor heterojunctions and explore the relation between the exciton binding energy to the band offset in determining the device characteristic of a particular type II heterojunction material. As a general rule, when the exciton binding energy is greater than the band offset at the heterojunction, the exciton will remain the lowest-energy excited state and the junction will make an efficient light-emitting diode. On the other hand, if the offset is greater than the exciton binding energy, either the electron or hole can be transferred from one chain to the other. Here we use a two-band exciton to predict the vibronic absorption and emission spectra of model polymer heterojunctions. Our results underscore the role of vibrational relaxation and suggest that intersystem crossings may play some part in the formation of charge-transfer states following photoexcitation in certain cases.
60 citations
TL;DR: In this paper, the strain mode and interface structure effects on band offset were investigated and it was shown that the band offsets were strongly dependent on the strain modes and interface structures and that the chemical environment should be well controlled to get reproducible band offsets.
Abstract: First-principles calculations for $\mathrm{Zr}{\mathrm{O}}_{2}∕\mathrm{Si}$ interfaces are presented. Various model interfaces satisfying the general bonding rules were considered. The interface formation energies were evaluated as a function of oxygen potential, which shows the possibility of atomic control of the interface structure by altering the chemical environment. The strain mode and interface structure effects on band offset were investigated. The band offsets were found strongly dependent on the strain modes and interface structures. These results suggest that in epitaxial growth of $\mathrm{Zr}{\mathrm{O}}_{2}$ on Si for gate dielectric applications, the chemical environment should be well controlled to get reproducible band offsets.
56 citations
TL;DR: In this article, the dc drain current characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) at high temperatures have been studied by numerical simulation from the self-consistent solution of Schrodinger's and Poisson's equations.
Abstract: The dc drain current characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) at high temperatures have been studied by numerical simulation from the self-consistent solution of Schrodinger's and Poisson's equations. The effects of temperature on the polarization and conduction band offset in the heterojunction have been considered. Our simulation results of the drain current at high temperature agree very well with reported experimental data. There is a significant reduction of saturation drain current when the temperature increases, and it is concluded that this is caused by both the decrease of saturation carrier velocity and two-dimensional electron density in the HEMT.
52 citations
TL;DR: In this article, the energy discontinuity in the valence band (ΔEv) of Zn0.95Cd0.05O was measured using X-ray photoelectron spectroscopy.
Abstract: X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence band (ΔEv) of Zn0.95Cd0.05O∕ZnO heterostructures grown by rf plasma-enhanced molecular-beam epitaxy. A value of ΔEv=0.17±0.03eV was obtained by using the Zn 2p energy level as a reference. Given the experimental band gap of 2.9 eV for the Zn0.95Cd0.05O, this would indicate a conduction band offset ΔEC of 0.30 eV in this system.
51 citations
Patent•
03 Mar 2005TL;DR: In this paper, the authors propose a SONOS type memory, which includes a semiconductor substrate, first and second impurity regions in the semiconductor substrates doped with impurity ions of a predetermined conductivity, separated a predetermined distance from each other, and a data storage type stack on the semiconductors substrate between the first and the second impurate regions.
Abstract: A SONOS type memory includes a semiconductor substrate, first and second impurity regions in the semiconductor substrate doped with impurity ions of a predetermined conductivity, separated a predetermined distance from each other, a channel region between the first and second impurity regions, and a data storage type stack on the semiconductor substrate between the first and second impurity regions. The data storage type stack includes a tunneling oxide layer, a memory node layer for storing data, a blocking oxide layer, and an electrode layer, which are sequentially formed. A dielectric constant of the memory node layer is higher than dielectric constants of the tunneling and the blocking oxide layers, and a band offset of the memory node layer is lower than band offsets of the tunneling and the blocking oxide layers. The tunneling oxide layer and the blocking oxide layer are high dielectric insulating layers.
33 citations
TL;DR: In this article, the conduction band offset ΔEc increased slowly from 0.82±0.05eV at room temperature to 1.28± 0.05 eV at 850 °C.
Abstract: Band alignment in Hf–Al–O thin films, grown on Si(100) by atomic layer deposition, was determined via x-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. The changes in conduction band offset, valence band offset, and bandgap were obtained as a function of annealing temperature. The bandgap Eg was found to be 5.7±0.05eV for as-deposited Hf–Al–O. After annealing at 600 °C, the increase in Eg was 0.2 eV, and then nearly unchanged up to 850 °C. The conduction band offset ΔEc increased slowly from 0.82±0.05eV at room temperature to 1.28±0.05eV at 850 °C. Even though the band profile of Hf–Al–O is still asymmetric with respect to HfO2, it satisfies the minimum requirement for the determination of the carrier barrier height. The band profiles, obtained via reflection electron energy loss spectroscopy, provided us some insight, which is both convenient and at the same time important, into the way to identify high-k dielectric materials, and we also found that the Hf–Al–O is a promi...
TL;DR: In this paper, the low temperature growth conditions of mixed Ba0.7Sr0.3O layers on Si100 were investigated using the combination of low energy electron diffraction, x-ray photoemission XPS, and electron energy loss spectroscopy.
Abstract: The low temperature growth conditions of mixed Ba0.7Sr0.3O layers on Si100 were investigated using the combination of low energy electron diffraction, x-ray photoemission XPS, and electron energy loss spectroscopy. With these methods crystallinity, stoichiometry, and electronic structure of both occupied and unoccupied levels were studied as a function of layer thickness. Oxide layers were generated by evaporating the metals in oxygen ambient pressure with the sample at room temperature after determination of the minimum oxygen pressure necessary for full oxidation. Good crystallinity with perfect lattice matching was only obtained starting with preadsorbed metallic layers at a concentration close to one monolayer ML, with best results starting from the Sr5 1. The XPS analysis shows that a sharp interface is formed during oxidation. The chemical species present at the interface are up to 1 ML of mono-oxidized Si and 1 ML of a mixed Sr –O–S i species. No silicide and silicate species or SiO2 formation at the interface after oxidation were found. Both interface and mixed oxide layers turned out to be stable to temperatures up to at least 600 ° C. Starting already at 1M L of Ba 0.7Sr0.3O, the band gap was found to be 4.3 eV, independent of layer thickness. We determined the valence band offset with respect to n-Si to be �2.2 eV, resulting in a conduction band offset of +1.0 eV.
TL;DR: In this paper, band discontinuities and band bending at the epitaxial SrTiO3∕GaAs(001) interface were investigated using x-ray and ultraviolet photoelectron spectroscopy.
Abstract: Band discontinuities and band bending at the epitaxial SrTiO3∕GaAs(001) interface were investigated using x-ray and ultraviolet photoelectron spectroscopy. Results showed that the epitaxial SrTiO3∕GaAs(001) formed a type II heterojunction with conduction and valence band offsets being 0.6 and 2.5 eV, respectively, for both n- and p-GaAs(001) substrates. The photoemission results further revealed that Fermi level was unpinned at the epitaxial SrTiO3∕GaAs(001) interface.
TL;DR: In this article, the authors quantitatively determined the band offsets of single quantum wells with varying nitrogen and indium content by surface photovoltage measurements, and showed the different effect of nitrogen on the valence and on the conduction band states.
Abstract: The band offsets of InGaAsN single quantum wells with varying nitrogen and indium content were quantitatively determined by surface photovoltage measurements. The experimental data directly show the different effect of nitrogen on the valence and on the conduction band states. While the conduction band offset strongly increases with increasing nitrogen concentration, the valence band offset is only weakly affected. In contrast, indium influences the valence and the conduction band states in the same way: both the valence and conduction band offsets increase with increasing indium content. In particular, the conduction band offset varies with In content as in N-free InGaAs quantum wells.
TL;DR: In this paper, a source-heterojunction-MOS-transistor (SHOT) was proposed for high-speed MOSFETs with relaxed-SiGe/strained-Si heterojunction source structures.
Abstract: We have developed the source-heterojunction-MOS-transistor (SHOT), a novel high-speed MOSFET with relaxed-SiGe/strained-Si heterojunction source structures for quasi-ballistic or full-ballistic transistors. Using the band-offset energy at the source SiGe/strained-Si heterojunction, high velocity electrons can be injected into the strained-Si channel from the SiGe source region. For the first time, we have experimentally demonstrated that the transconductance is enhanced in SHOT for high applied drain voltage, compared to that of strained- and conventional silicon-on-insulator MOSFETs. We have also shown that the transconductance enhancement in SHOT depends on both the gate drive and the drain bias.
28 Apr 2005
TL;DR: In this paper, the authors describe the growth and performance of AlInAsSb/AlSb barriers using a 0.3 mole fraction of Al in the Group III elements.
Abstract: For many years, mid-infrared (2-5μm) semiconductor lasers operating at or near room temperature have been sought for use in LADAR, gas sensing, and spectroscopy. Smaller bandgap materials necessary for this range are more susceptible to non-radiative Auger recombination. Further, as laser structures become more complicated, like quantum cascade intersubband and interband lasers, Shockley-Read-Hall losses increase. The simplest structure is Type-I multiple quantum well (MQW), but few QW III-V heterojunction material systems capable of 2-5μm emission have a Type-I offset. One such system with InAsSb wells and AlInAsSb barriers has been unable to exceed 175K under CW operation partially due to poor carrier confinement associated with small valence band offsets. This paper describes the growth and performance of AlInAsSb/InAsSb lasers using a 0.3 mole fraction of Al in the Group III elements. Increased Al content enhances the valence and conduction band offsets, but the AlInAsSb alloy exhibits a miscibility gap above 0.06 Al mole fraction, so a digital alloy technique was used to grow high quality 0.3-2μm thick quaternary films. As Al mole fraction in the barriers was increased from 0.20 to 0.30 an 80-fold increase in photoluminescence (PL) was observed. The corresponding lasers were grown and tested demonstrating lasing at 3.9μm and 50K. Theoretical studies suggest that adding Ga to the barriers, forming an AlGaInAsSb quinary alloy, results in band structures more favorable towards minimizing Auger effects and realizing Type I offset behavior over a wider range of alloy compositions. PL structures were grown and tested, again using a digital alloy technique for the quinary alloy. Preliminary results show promise.
TL;DR: In this article, the chemical bonding state and energy band structure of (La2O3)1−x(SiO2)x(0⩽x⩾1) films grown on sulfur-passivated n-GaAs (001) were investigated.
Abstract: This letter investigates the chemical bonding state and energy band structure of (La2O3)1−x(SiO2)x(0⩽x⩽1) films grown on sulfur-passivated n-GaAs (001). The dielectric bandgap and interfacial band alignment were modified by compounding the La2O3 films with SiO2. A shift in binding energy of the core level was observed by comparing the electronegativities of the second nearest-neighbor element. The controlled parameters of energy band structure were systematically monitored by valence band and absorption spectra. Band offset values were almost linearly related to the concentration of SiO2 when no Fermi level pinning in the midgap of n-GaAs was assumed. The correlation between band parameter and electrical properties, as probed by capacitance and leakage current measurements, is discussed.
TL;DR: In this article, a physics-based single-piece charge model for strained-silicon (s-Si) MOSFETs from accumulation to strong-inversion regions is presented.
Abstract: A physics-based single-piece charge model for strained-silicon (s-Si) MOSFETs from accumulation to strong-inversion regions is presented. The model is formulated from regional solutions of the well-known Pao-Sah equation and unified with interpolation functions while keeping the physics in the derived flat-band voltages that depend on the device material and structural parameters, such as band gaps, conduction and valence band offsets, Ge mole fraction, layer thickness, and doping. The model is validated by comparison with numerical devices for a wide range of Ge mole fractions and s-Si layer thicknesses. It is shown that the model accurately describes the physical behavior of the surface potentials, terminal charges and capacitances, especially charge accumulation/depletion at the s-Si/SiGe interface that gives rise to the observed "plateau" in the capacitance-voltage characteristics.
TL;DR: In this paper, the chemistry and energy band structure of (Gd2O3)1−x(SiO2)x(0⩽x⩾1) films grown on n-GaAs (001) were investigated.
Abstract: This letter investigates the chemistry and energy band structure of (Gd2O3)1−x(SiO2)x(0⩽x⩽1) films grown on n-GaAs (001). Dielectric band gap and interfacial band alignment of Gd2O3 films were modified by compounding with SiO2. Binding energy shift of core level was observed from different electronegativity of second nearest-neighbor element. Controlled parameters of energy band structure were systematically characterized by valence band, absorption, and energy loss spectra. Assuming no Fermi level pinning in the midgap of n-GaAs, band offset values represent almost linear dependency on the concentration of SiO2. The correlation of band offset with the electrical properties, as probed by capacitance and leakage current measurements, was also discussed.
TL;DR: In this article, a growth procedure for short wavelength (λ < 5 μm) GaInAs/AlAsSb-on-InP material system with a conduction band offset of about 1.6 eV was proposed.
TL;DR: In this article, tight binding calculations of the band alignment in InAs/GaSb type II broken-gap superlattices have been carried out with a valence band offset value of 057 eV obtained at root temperature 300 k, in good agreement with experiments.
TL;DR: In this paper, a semi-empirical second nearest neighbor sp 3 tight binding view of heterostructure electronic band structure calculations is presented. And the model can be useful in understanding the effects of electronic structure of heter-structures on charge transport and performance of nanoscale devices.
TL;DR: In this article, the critical thickness, lattice constant, strain, and optical transition energies for GaInNAs/GaAs quantum well structures tuned for emission at 1.3 and 1.55 µm were discussed.
Abstract: We report results from theoretical and experimental investigations of GaInNAs/GaAs quantum well structures. Optical transition energies for samples with different In and N concentrations were determined by photoluminescence measurements. The results show that the reduction of the ground-state transition energy by the introduction of N decreases with increasing In concentration. The experimental data are compared with calculations using the effective-mass approximation. Modifications of the band-gap energy due to N incorporation were accounted for using the two-level repulsion model. Proper effective-mass and band offset values, based on recent experimental work, were used. Calculated and measured transition energies show good agreement. The critical thickness, lattice constant, strain, and optical transition energies are discussed for GaInNAs/GaAs quantum well structures tuned for emission at 1.3 and 1.55 µm, in particular. Such a simple model, within the effective-mass approximation, is a very useful guide for device design.
TL;DR: In this article, the electron energy band alignment at the interfaces of Hf-based complex oxides with (100)Si and Au was determined using internal photoemission and photoconductivity measurements.
TL;DR: In this paper, the microstructural properties of the MgxZn1−xO/Si(1.0) interface were investigated using transmission electron microscopy (TEM) and chemical states of the heterostructure were studied by high resolution X-ray photoelectron spectroscopy (XPS).
TL;DR: In this paper, the authors analyzed the electronic properties of the hole gas formed in Ga1−xMnxAs/GaAs/GA1−mnxA/Ga 1−mnsxAs heterostructures and found that there is an exchange coupling between the magnetic layers that oscillates between ferromagnetic and antiferromagnetic as a function of different parameters of the problem.
Abstract: Spin injection in low-dimensional semiconductors have a great potential to be used in magnetoelectronics and spintronics. In our work we analyze the electronic properties of the hole gas formed in Ga1−xMnxAs/GaAs/Ga1−xMnxAs heterostructures. We find that there is an RKKY-type exchange coupling between the magnetic layers that oscillates between ferromagnetic and antiferromagnetic as a function of the different parameters of the problem. As an example we calculate the spin-dependent hole density, the polarization and the coupling energy, using an efficient self-consistent procedure to solve simultaneously the Schrodinger and Poisson equations, taking into account the interaction with Mn magnetic moments. Our results indicate that the coupling energy also oscillates in terms of the band offset Vw which describes the difference in electronegativity between the Mn and GaAs atoms.
TL;DR: In this article, an extension of the HEIWIP concept to wavelengths longer than 110 lm in the GaAs/AlGaAs system requires the use of AlGaAs as the emitter material to reduce the barrier height.
Journal Article•
TL;DR: In this article, the thermal stability and band alignment of HfO2 thin film grown by atomic layer deposition (ALD) were studied by using X-ray photoelectron spectroscopy (XPS) and reflection electron energy loss spectrum (REELS).
Abstract: The thermal stability and band alignment of HfO2 thin film grown by atomic layer deposition (ALD) were studied by using X-ray photoelectron spectroscopy (XPS) and reflection electron energy loss spectroscopy (REELS). Band gaps and valence band offsets for HfO2 thin film were estimated from the onset energy of REELS and valence band spectra of XPS. The changes in conduction band offset, valence band offset and band gap were obtained as a function of annealing temperature. HfO2 thin film is found to have asymmetric barrier for electrons and holes and there is a little increase in band gap values after annealing treatment.
TL;DR: In this article, a SiGe/Si Multiple Quantum Wells (MQWs) structure is proposed for highly sensitive photodetection, and the calculated photoconductive gain for this structure exceeds 2.
TL;DR: In this paper, the authors calculated the entropy associated with the transition of electrons into and out of InAs/GaAs quantum dots (QDs) by considering the temperature dependence of energy eigenvalues due to strain and energy band offset variations.
Abstract: Entropies associated with the transition of electrons into and out of InAs/GaAs quantum dots (QDs) are calculated by considering the temperature dependence of energy eigenvalues due to strain and energy band offset variations. It is found that, for InAs/GaAs quantum dots with base/height dimensions of 20/10 nm, the contribution from the surrounding lattice to entropy is smaller than 4 × 10 - 5 eV / K for the temperature region below 100 K, where most measurements of thermal emission rates are performed. Including the electron degeneracy, the total entropy change has an upper limit of 1 × 10 - 4 eV / K when releasing the first electron from the s-shell, while the second released s-electron is connected with an entropy change not larger than the absolute value of - 2 × 10 - 5 eV / K .