Showing papers on "Band offset published in 1998"
TL;DR: This review presents a theoretical approach to the band-line-up problem and discusses its application to prototypical systems, with emphasis on ab initio computations and on theoretical models derived from first-principles numerical experiments.
Abstract: Understanding the mechanisms which determine the band offsets and Schottky barriers at semiconductor contacts and engineering them for specific device applications are important theoretical and technological challenges. In this review, we present a theoretical approach to the band-line-up problem and discuss its application to prototypical systems. The emphasis is on ab initio computations and on theoretical models derived from first-principles numerical experiments. An approach based on linear-response-theory concepts allows a general description of the band alignment for various classes of semiconductor contacts and predicts the effects of various bulk and interfacial perturbations on the band discontinuities.
256 citations
TL;DR: In this article, Shubnikov-de Haas measurements on nongated and gated Hall bars were performed to determine the spin-orbit coupling constant of conduction band electrons in In053Ga047As/In077Ga023As/inP heterostructures.
Abstract: Spin splitting of conduction band electrons in In053Ga047As/In077Ga023As/InP heterostructures due to spin-orbit coupling is studied by performing Shubnikov–de Haas measurements on nongated and gated Hall bars From an analysis of the beating pattern in the Shubnikov–de Haas oscillations, the spin-orbit coupling constant is determined For a symmetric sample no beating pattern and thus no spin splitting is observed This demonstrates that the k3 contribution to the spin-orbit coupling constant can be neglected By applying an envelope function theory it is shown that the major contribution to the Rashba spin-orbit coupling originates from the band offset at the interface of the quantum well Using gated Hall bar structures it is possible to alter the spin-orbit coupling by application of an appropriate gate voltage A more negative gate voltage leads to a more pronounced asymmetry of the quantum well, which gives rise to a stronger spin-orbit coupling
245 citations
TL;DR: In this paper, a nitrogen radical beam source was used to incorporate N into GaInAs layers and high resolution x-ray rocking curves measurements indicate that the N composition in GaInNAs layer was increased from 0.009 to 0.03 with increasing N2 flow rate.
Abstract: GaInNAs/GaAs multiple quantum wells (MQWs) with different N composition were successfully grown on semi-insulating GaAs substrate by gas-source molecular beam epitaxy. A nitrogen radical beam source was used to incorporate N into GaInAs layers. High resolution x-ray rocking curves measurements indicate that the N composition in GaInNAs layer was increased from 0.009 to 0.03 with increasing N2 flow rate. Photoluminescence (PL) measurements show that the PL wavelength red shifts with increasing N composition in GaInNAs layer. For a 7-period Ga0.7In0.3N0.02As0.98/GaAs MQW, a PL peak at 1.3 μm wavelength at room temperature has been successfully obtained. The band offset ΔEc for Ga0.7In0.3NxAs1−x/GaAs enlarges quickly from 0.26 eV to 0.56 eV with increasing N concentration from 0% to 3%.
191 citations
TL;DR: In this article, the use of low molecular weight, oligomeric and polymeric heterocyclics as electron transport/hole-blocking layers in organic light-emitting diodes is reviewed.
Abstract: The use of low molecular weight, oligomeric and polymeric heterocyclics as electron transport/hole-blocking layers in organic light-emitting diodes is reviewed. The most widely applied materials are π-electron deficient heterocyclics carrying imine nitrogen atoms in the aromatic ring, such as 1,3,4-oxadiazoles, 1,2,4-triazoles, 1,3,5-triazines, and 1,4-quinoxalines. Properties such as redox potentials, ionization potential, electron affinity and charge transport mobility of the materials, if known, are taken into consideration to support the electron injection/transport and hole-blocking effectiveness. It can be generalized that heterocyclic moieties with high reduction potential reduce the interface barriers caused by the band offset between organic material and cathode and are most suitable materials for electron injection in organic electroluminescent devices. These materials are generally characterized by high ionization potential values that contribute towards the hole-blocking property. A general comparison of devices and materials is only possible with limitations owing to the variations in device structure, fabrication, electrode materials, emitter materials, etc. © 1998 John Wiley & Sons, Ltd.
110 citations
TL;DR: In this article, the minimum thickness of SiO 2 on Si substrate at which a proper barrier height between Si 2 and Si holds was evaluated by studying the band offset between SiO and Si as a function of Si 2 thickness.
62 citations
TL;DR: An analytical theory of intervalley mixing at semiconductor heterojunctions is presented in this paper, where Burt's envelope function representation is used to analyze a pseudopotential Hamiltonian.
Abstract: An analytical theory of intervalley mixing at semiconductor heterojunctions is presented Burt's envelope-function representation is used to analyze a pseudopotential Hamiltonian, yielding a simple $\ensuremath{\delta}$-function mixing between $\ensuremath{\Gamma}$ and $X$ electrons and light and heavy holes This coupling exists even for media differing only by a constant band offset (ie, with no difference in Bloch functions)
60 citations
TL;DR: In this article, an estimation for the band offsets and the fundamental band gap was presented for Si1−x−yGexCy alloys tensile or compressive strained on Si(001).
Abstract: An estimation for the band offsets and the fundamental band gap will be presented for Si1−x−yGexCy alloys tensile or compressive strained on Si(001). This estimation considers both the band lineup at the interface of two different materials as well as the strain effects. Unknown material parameters have been adjusted to obtain the best agreement with experimental results for tensile strained Si1−yCy layers. The obtained results agree very well with the first experimental data for the effect of C on band-structure properties in Si1−x−yGexCy. For a completely strain-compensated (cubic) Si1−x−yGexCy layer, we predict significant “Ge effects” (smaller gap than Si, valence-band offset to Si) with values depending on the Ge content.
51 citations
TL;DR: In this paper, the growth of InAs nanocrystals is initiated with formation of In islands followed by diffusion of As atoms into the In dots, and the band discontinuity of the InAs/Si interface has been evaluated using the results of synchrotron radiation photoelectron spectroscopy (SRPES).
36 citations
Patent•
21 Jul 1998
TL;DR: In this article, a thin oxide region is introduced to a surface of a GaN layer prior to contact meal evaporation by carefully controlling the oxidation of the surface, which results in the normally present surface states to be smothered and thus a low band offset is observed in an ohmic contact.
Abstract: A thin oxide region is introduced to a surface of a GaN layer prior to contact meal evaporation by carefully controlling the oxidation of the surface. This results in the normally present surface states to be smothered and thus a low band offset is observed in an ohmic contact comprising the contact metal and the GaN layer. The thickness of the oxide region preferably is about 8 Å to 25 Å. Other elements such as S, Se, Te, As, P and Hf can be used as an alternative to O. Devices using the thin region in the ohmic contact may include semiconductor laser devices, light emitting diodes, and III-V based transistors.
35 citations
TL;DR: In this paper, angle resolved x-ray photoemission spectroscopy (XPS) was used to study the interface between Ga0.5In 0.5P and GaAs grown by gas source molecular beam epitaxy, showing that the interface is abrupt for a growth temperature of 400°C and indium segregation is effective at 500°C but less than that in GaInAs at the same temperature.
Abstract: We have studied by angle resolved x-ray photoemission spectroscopy (XPS) the interface between Ga0.5In0.5P and GaAs grown by gas source molecular beam epitaxy. For cations, we show that the interface is abrupt for a growth temperature of 400 °C and that indium segregation is effective at 500 °C but less than that in GaInAs at the same temperature. For anions, growth of the two layers in rapid succession results in the incorporation of an excess of arsenic in the GaInP epilayers and a diffuse interface. As soon as these predominant experimental effects are suppressed, the abruptness of the interface is limited by a weak arsenic surface segregation. For this quasi-abrupt interface, we report a valence band offset of ≈0.3 eV as determined by XPS.
25 citations
TL;DR: In this article, the exciton transition in InSb/AlxIn1−xSb multi-quantum well samples was observed and identified with the use of a simple quantum well model.
Abstract: We report the observation of interband exciton transitions in InSb/AlxIn1−xSb multi-quantum-well samples. The exciton peaks are identified with the use of a simple quantum well model. The strain present in the InSb wells alters the spectrum significantly from that for unstrained III–V materials and makes it possible to use the exciton spectrum in determining the band offset.
TL;DR: In this article, the role of interfacial defects in determining the band offset at silicon-oxide/silicon interfaces was studied using the first-principles band-offense evaluation method.
TL;DR: In this paper, the structural and photoluminescence properties of pseudomorphic Si1−yCy and Si 1−x−yGexCy multiple quantum well (QW) structures on (001) Si substrates offer a quantitative characterization of the band gap and band offset shifts caused by C alloying for y < 3%.
Abstract: Studying the structural and photoluminescence properties of pseudomorphic Si1−yCy and Si1−x−yGexCy multiple quantum well (QW) structures on (001) Si substrates offer a quantitative characterization of the band gap and band offset shifts caused by C alloying for y<3% The main features of Si1−yCy alloys, which are a reduced lattice constant and a strong lowering of the conduction band energy, promise that C may serve as a counterpart to Ge in Si heteroepitaxy The photoluminescent properties of Si1−yCy and SiGeC QWs are comparable to SiGe Novel pseudomorphic Si1−yCy/SiGe coupled QW structures and Si1−yCy/Ge quantum dot structures result in a strong enhancement of the photoluminescent efficiency The ternary SiGeC material system offers a higher degree of freedom in strain and band edge engineering of structures We focus on our recent results on Si1−yCy and SiGeC QW layers embedded in Si concerning the growth by solid-source molecular beam epitaxy, structural properties, thermal stability, optical properties, and band offsets The prospects of SiGeC alloys for realization of optoelectronic structures are discussed First characteristics from 075 μm p-channel modulation-doped field-effect transistor devices containing an active SiGeC layer demonstrate good electrical properties
TL;DR: In this article, a tuning region with bandgap wavelength lattice matched to an InP substrate was investigated, where an unstrained InGaAsP/InGaAsSb superlattice with an estimated band offset was used.
Abstract: Type II superlattices as tuning regions in continuously tunable laser diodes are investigated. They are used to create an artificial indirect semiconductor by spatially separating electrons and holes from each other. At a given current the mean electron density is increased and therefore a larger tuning range and efficiency are achieved. The type II superlattice can be prepared in different ways, e.g. by a superlattice consisting of two different semiconductors, by a doping superlattice, by alternately strained layers or by combining these effects. In the case of a tuning region with bandgap wavelength lattice matched to an InP substrate, one may use an unstrained InGaAsP/InGaAsSb superlattice with an estimated band offset of 302 meV. This enhances the tuning by a factor of 160 in the low-current limit. At high tuning currents this factor decreases, but it is still considerable.
TL;DR: In this paper, the band offsets at the Ga0.5P heterojunction lattice matched to (001) GaAs was calculated over the whole range of aluminum composition from x=0.0 to 0.5 using the first-principles pseudopotential method with virtual crystal approximation.
Abstract: In this work, the band offsets at the Ga0.5In0.5P/AlxGa0.5−xIn0.5P heterojunction lattice matched to (001) GaAs was calculated over the whole range of aluminum composition from x=0.0 to 0.5 using the first-principles pseudopotential method with virtual crystal approximation. The valence band offset, VBO, varies with x as VBO=0.433x eV, while the inferred conduction band offset CBO at Γ minimum (band-gap difference minus the valence band offset) varies in x as CBOΓ=0.787x eV. Our results are in good agreement with the experimental data.
TL;DR: In this article, the authors interpreted photoluminescence peak energy shifts under applied uniaxial stress and uniprocessional stress in the framework of a multi-band Kohn-Luttinger model.
Abstract: Photoluminescence peak energy shifts under applied [110] and [100] uniaxial stress are interpreted within the framework of a multi-band Kohn–Luttinger model which takes into account the mixing of heavy, light, and spin-orbit split-off holes within the valence band. Experimental data are presented for 0.5%, 1%, and 1.7% Si1−yCy/Si samples which are best fitted with a conduction band offset of approximately 70%. At this value of the conduction band offset, we show that small amounts of space charge induced band bending are required to explain the experimentally observed results.
TL;DR: In this paper, the authors measured the contactless electroreflectance and piezoreflectance spectra at 300 and 20 K from a GaN AlGaN heterojunction structure grown by metalorganic chemical vapor deposition on 6 H -SiC substrate.
TL;DR: In this article, the effect of carbon incorporation on the band alignment of compressively strained Si1−x−yGexCy/Si is investigated, with a negligible effect on the conduction band alignment.
Abstract: Optical absorption measurements have been performed to study the effect of substitutional carbon on the valence band offset of compressively strained p+ Si1−x−yGexCy/(100) p− Si. The compressively strained p+ Si1−x−yGexCy/(100) p− Si heterojunction internal photoemission structures were grown by rapid thermal chemical vapor deposition with substitutional carbon levels up to 2.5%. Carbon decreased the valence band offset by 26±1 meV/% substitutional carbon. Based on previous reports of the effect of carbon on the band gap of Si1−x−yGexCy, our work suggests that the effect of carbon incorporation on the band alignment of compressively strained Si1−x−yGexCy/Si is to reduce the valence band offset, with a negligible effect on the conduction band alignment.
TL;DR: In this article, the conduction-band offset Qc is used as an adjustable parameter to study the band offset in the strained Zn0.79Cd0.21Se/ZnSe double quantum wells, grown by molecular beam epitaxy on (100) GaAs substrates, using contactless electroreflectance (CER) at 15 and 300 K.
Abstract: We have studied various excitonic transitions of strained Zn0.79Cd0.21Se/ZnSe double quantum wells, grown by molecular beam epitaxy on (100) GaAs substrates, using contactless electroreflectance (CER) at 15 and 300 K. A number of intersub-band transitions in the CER spectra from the sample have been observed. An analysis of the CER spectra has led to the identification of various excitonic transitions, mnH(L), between the mth conduction band state and the nth heavy (light)-hole band state. The conduction-band offset Qc is used as an adjustable parameter to study the band offset in the strained Zn0.79Cd0.21Se/ZnSe system. The value of Qc is determined to be 0.67±0.03.
TL;DR: In this paper, the effect of strain on the band structure of In/sub x/Ga/sub 1-x/P-In/sub 0.5/P multiple quantum wells (MQW's) has been investigated from high-pressure and low-temperature photoluminescence measurements.
Abstract: The effect of strain on the band structure of In/sub x/Ga/sub 1-x/P-In/sub 0.5/Al/sub 0.5/P multiple quantum wells (MQW's) has been investigated from high-pressure and low-temperature photoluminescence measurements. The biaxial strain in the wells was varied between +0.6% compressive to -0.85% tensile strain by changing the well composition x from 0.57 to 0.37. Strain increases the valence band offsets in either tensile or compressively strained structures. Whereas relatively insensitive to tensile strain, the valence band offsets showed a strong dependence on the magnitude of the compressive strain. Good agreement is found between the measured valence band offsets and those predicted by the model solid theory, except for the largest compressively strained MQW's, for which the model calculations underestimate the measured valence band offset. Strain and the associated variations in composition also modified the separation among the well states associated with /spl Gamma//sub 1c/, L/sub 1c/, and X/sub 1c/. From these results, the bandgaps of each conduction band extrema were calculated in In/sub x/Ga/sub 1-x/P for 0.37
TL;DR: In this article, a band model is proposed to interpret electron field emission data from diamond-like carbon and diamond is summarised and the model is constructed from existing data on electron affinities and band offsets, within a theory of band offsets.
Abstract: Electron field emission data from diamond-like carbon and diamond is summarised and a band model is proposed to interpret it. The model is constructed from existing data on electron affinities and band offsets, within a theory of band offsets. In diamond, there is a large offset for the conduction band at the back-contact, causing this to be the dominant tunnel barrier for electron emission. Nitrogen and grain boundaries reduce this barrier by forming a depletion layer of ionised donors, which reduces the tunnelling distance. In diamond-like carbon, the conduction band offset at the back-contact is small and the dominant barrier is at the surface. Nitrogen decreases the emission barrier by increasing the bulk Fermi level and decreasing the work function.
TL;DR: In this paper, the surface, interface and valence band structures of ultra-thin silicon oxides at the initial stage of oxidation were reviewed and it was shown that the surface and interface structures are affected by the interface structures.
TL;DR: In this article, room temperature photoreflectance (PR) measurements were performed on five nominally 90 A wide undoped single quantum well (QW) structures in barriers, lattice matched to an InP substrate.
Abstract: Room temperature photoreflectance (PR) has been performed on five nominally 90 A wide undoped single quantum well (QW) structures in barriers, lattice matched to an InP substrate. The nominal QW Ga composition varies between x = 0.47 and x = 0.68, corresponding to tensile strains between zero and 1.47%, respectively. Room temperature photoluminescence measurements are also performed on the same position on the sample as the PR. Allowed and forbidden interband QW transition energies, given by least-squares fitting to the PR, are found to agree well with theoretical predictions based on an effective mass formalism, including excitonic binding energies and quantum-confined Stark effects. In achieving this agreement, values for the QW composition, thickness and band offset are determined by refining their nominal values. The conduction band offsets are found to range from 0.35 to 0.14 for tensile strains between zero and 1.40%. The energies of the ground state light- and heavy-hole QW transitions increase roughly linearly with tensile strain.
TL;DR: In this article, the strain dependence of the band lineups at ZnS/CdS and ZnSe/ZnTe (001) interfaces has been investigated using a first principles pseudopotential planewave technique and the local density approximation for the exchange-correlation potential.
Abstract: The strain dependence of the band lineups at ZnS/CdS and ZnSe/ZnTe (001) interfaces has been investigated using a first principles pseudopotential planewave technique and the local density approximation for the exchange-correlation potential. Similarly, the linear and quadratic deformation potentials (DPs) of the cubic ZnS, ZnSe, ZnTe and CdS have been calculated. It is found that the ZnSe/ZnTe superlattices are of type II, with a valence band offset varying almost linearly between 0.54 and 1.14 eV by going from ZnTe to ZnSe substrates. The ZnS/CdS superlattices have a very small and show a transition from type I to type II by changing the strain state. Moreover, the conduction band offset at the ZnS/CdS interface is found to have a quite strong strain dependence. Our results for linear deformation potentials of the semiconductors considered are in the range of the available experimental data and theoretical results, and strong non-linear effects have been predicted. The quadratic DPs and the relaxation of the semicore d-electrons are found to have small, but not negligible, effects on the calculated band lineups.
TL;DR: In this article, the band offsets are calculated for both the Ga-As and interface bonds within first-principles local density functional theory and it is shown that the band offset is independent of the type of interfacial bond, while the valence band offset, VBO, decreases linearly with x as.
Abstract: The band offsets are calculated for both the Ga-As and interface bonds within first-principles local density functional theory. It is found that the band offsets are independent of the type of interfacial bond, while the valence band offset, VBO, decreases linearly with x as and the inferred conduction band offset CBO (the band-gap difference minus the valence band offset) decreases linearly as for .
TL;DR: In this article, the conduction-band discontinuity ratio of strained InAsP alloys was determined by fitting the well thickness dependence of transition energies in quantum wells, and the obtained Qc value was 0.35, which is relatively small compared to previous reports.
Abstract: The band line-up of InAsP/InP heterojunctions was investigated. The conduction-band discontinuity ratio Qc of strained InAsP alloys was determined by fitting the well thickness dependence of transition energies in InAsP quantum wells. This method does not require precise values of deformation potentials of InAsP, allowing more reliable determination of the band offset. The obtained Qc value was 0.35, which is relatively small compared to previous reports. This value of the band offset is consistent with the predictions from the semi-empirical linear combination of atomic orbitals (LCAO) model.
TL;DR: In this paper, the band discontinuities in ZnSe/AlAs(0 0 1) heterojunctions fabricated by molecular beam epitaxy are found to depend on the local interface composition in a manner reminescent of what was found earlier.