Showing papers on "Band offset published in 1991"
TL;DR: In this paper, estimates of valence-band and conduction-band offsets for lattice-matched and pseudomorphic strained heterostructures of six technologically important III-V quaternary alloys are presented.
Abstract: Estimates of valence-band and conduction-band offsets for lattice-matched and pseudomorphic strained heterostructures of six technologically important III-V quaternary alloys are presented. Valence-band offsets are obtained via interpolation of the theory-based results of Van de Walle's 'model-solid' approach for the binary constituents. Estimates for band gap differences are obtained via interpolation of the experimental band gap energies of the ternary constituents. Adding the valence-band offset and band gap difference gives an estimate of the conduction-band offset. Band-edge effective masses at Gamma are determined from a linear interpolation of the effective masses of the binary constituents, obtained from self-consistent ab initio band structure calculations. Results are shown to agree well with the outcome of experiments.
399 citations
TL;DR: In this paper, low-temperature photoluminescence spectra of an In0.48Ga0.52P alloy and a p-type GaAs/In0.5P multiple quantum well, both grown by molecular beam epitaxy, were obtained under hydrostatic pressures from 0 to 6 GPa.
Abstract: Low‐temperature photoluminescence spectra of an In0.48Ga0.52P alloy and a p‐type GaAs/In0.48Ga0.52P multiple quantum well, both grown by molecular beam epitaxy, have been obtained under hydrostatic pressures from 0 to 6 GPa. The zero‐pressure extrapolation of the InGaP(X) to GaAs(Γ) transitions yields a 0.40±0.02 valence‐band offset, and hence only a small, 0.06 ± 0.02 eV, conduction‐band offset. These offset values are in agreement with measured values of the confinement energy versus well width.
97 citations
TL;DR: TheEnergy of formation of the 1+1 superlattices, which is effectively a 50% mixed compoud, is calculated and used to make a crude estimate of the energy of formation and the maximum miscibility-gap temperature of the solid solutions.
Abstract: The (110) interfaces SiC/AlN and SiC/BP between the cubic (sphalerite) crystals of these semiconductors are studied within the local-density-functional framework using the linear muffin-tin orbital method and the supercell approach. The preferred bonding configurations are found to be Si-N and C-Al for the former and Si-B and C-P for the latter. Both correspond to cation-anion bonding when the anomalous ion character of BP is taken into account. The latter is independently confirmed by our calculations. The interface energies are calculated as the limits of half the superlattice energies of formation and are found to be 0.45 and 0.50 eV for SiC/AlN and SiC/BP, respectively. Combined with a simple bond-breaking model for the surface energies they are used to estimate the adhesion energies, which are shown to be comparable in magnitude to the surface energies of the individual materials. The energy of formation of the 1+1 superlattices, which is effectively a 50% mixed compoud, is calculated and used to make a crude estimate of the energy of formation and the maximum miscibility-gap temperature of the solid solutions. The band structures of the bulk compounds are presented, including an approximate correction of the band gap. The band alignment is found to be of type I for SiC/AlN and of type II for SiC/BP with the higher valence-band maximum in BP. Strain effects in the case of SiC/BP are briefly discussed. The interface electronic structures including interface states and resonances are analyzed in terms of the local densities of states.
94 citations
TL;DR: Etude theorique de la modification des discontinuites de bande par depot d'intracouches Si and Ge aux homojonctions GaAs et AlAs et aux heterojonction GaAs/AlAs.
Abstract: Etude theorique de la modification des discontinuites de bande par depot d'intracouches Si et Ge aux homojonctions GaAs et AlAs et aux heterojonctions GaAs/AlAs. La discontinuite se revele tres sensible au recouvrement et a l'aspect abrupt de l'intracouche
76 citations
TL;DR: In this paper, first principles calculations of the valence-band offsets at the lattice matched In0.53Ga0.47As/In0.52Al0.48As/inP(001) heterointerfaces, including interface strain, are presented.
Abstract: First principles calculations of the valence‐band offsets at the lattice‐matched In0.53Ga0.47As/ In0.52Al0.48As/InP(001) heterointerfaces, including interface strain, exhibit transitivity to within 0.01 eV. The theory is in good agreement with the experimental data and together they suggest the values ΔEv=0.35–0.41 eV for In0.53Ga0.47As/InP and 0.15–0.20 eV for In0.53Ga0.47As/In0.52Al0.48As. The theory gives ΔEv=0.25 eV for In0.52Al0.48As/InP, in general agreement with experiment for this less studied interface.
65 citations
TL;DR: In this paper, the photoreflectance spectra of a strained layer (001) In0.21Ga0.79As/GaAs single quantum as well as a function of temperature in the range 10 K
Abstract: We have measured the photoreflectance spectra of a strained layer (001) In0.21Ga0.79As/GaAs single quantum well as a function of temperature in the range 10 K
51 citations
TL;DR: In this article, the optical emission characteristics of biaxially compressed InAs x P1− x /InP strained single quantum well (QW) structures, with nominal compositionx=0.67, have been investigated using photoluminescence (PL) and photoline excitation (PLE) spectroscopies.
Abstract: The optical emission characteristics of biaxially compressed InAs x P1− x /InP strained single quantum well (QW) structures, with nominal compositionx=0.67, have been investigated using photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. The highly strained QWs exhibit intense and narrow PL in the 0.9–1.5 μm wavelength range, similar to the lattice-matched InGaAs(P)/InP system. The 20 K PLE spectra exhibit well-resolved features attributed ton=1 heavy hole (E1H1) and light hole (E1L1) transitions in the 1.0–1.5 μm wavelength range. In addition, features attributed to transitions betweenn=2 electrons and heavy holes (E2H2), and betweenn=1 electrons and unconfined holes (E1Hf), were observed. The energy splitting between the heavy-hole and light-hole bands was found to be a sensitive measure of the band offsets in the system. The best prediction of this splitting was obtained for a valence band offset of δE V ∼0.25δE G . This value of band offset was in agreement with the energy position of the E1Hf transition. The observed transition energies were also compared with the results of a finite square well model, taking into account the effects of strain, and the results offer further support for the band offset assignment. This study indicates that the InAsP system may be advantageous for application in strained-layer optoelectronic devices operating in the 1.3–1.6 μm wavelength range.
50 citations
TL;DR: In this paper, the authors used X-ray photoemission spectroscopy (XPS) to measure the valence-band offset ΔEv for the lattice matched InP/In0.53Ga0.47As and In0.52Al0.48As heterojunction interfaces.
Abstract: X‐ray photoemission spectroscopy (XPS) has been used to measure the valence‐band offset ΔEv for the lattice‐matched InP/ In0.53Ga0.47As and In0.53Ga0.47As/ In0.52Al0.48As heterojunction interfaces. The heterojunctions were formed by molecular‐beam epitaxy. We obtain values of ΔEv (InP/In0.53Ga0.47As) =0.34 eV (ΔEc/ ΔEv=43/57) and ΔEv (In0.53Ga0.47As/ In0.52Al0.48As) =0.22 eV (ΔEc/ ΔEv =68/32) for the respective interfaces. By combining these measurements with available XPS ΔEv (InP/ In0.52Al0.48As) data we find that band offset transitivity is satisfied. Accordingly, the band offsets for heterojunction pairs formed from InP, In0.53Ga0.47As, and In0.52Al0.48As are not influenced by interface specific effects.
50 citations
TL;DR: The optical emission characteristics of highly strained InAs/InP single quantum wells prepared using atmospheric pressure organometallic vapor phase epitaxy have been studied in this paper, where the photoluminescence (PL) spectra exhibited intense emission in the energy range 1.15-1.3 eV, with typical full width at half maximum of 8-14 meV.
Abstract: The optical emission characteristics of highly strained InAs/InP single quantum wells prepared using atmospheric‐pressure organometallic vapor‐phase epitaxy have been studied. For well thicknesses of one to three monolayers (ML), the photoluminescence (PL) spectra exhibited intense emission in the energy range 1.15–1.3 eV, with typical full width at half maximum of 8–14 meV. The dependence of PL emission energy on well thickness for 1–5‐ML‐thick wells was compared with the results of a finite‐well calculation, taking into account the effects of strain on the band structure. Good agreement between experiment and theory was obtained for a valence‐band offset of 270 meV, consistent with recent reports for the InAs/InP system.
45 citations
TL;DR: In this article, the first calculation of transport in InAs/GaSb/AlSb-based interband tunnel structures using a realistic band structure model is presented, and the results are compared with calculations using a two-band model which includes only the lowest conduction band and the lighthole band.
Abstract: We report on the first calculation of transport in InAs/GaSb/AlSb‐based interband tunnel structures which uses a realistic band structure model. The results are compared with calculations using a two‐band model which includes only the lowest conduction band and the light‐hole band. It is found that heavy‐hole states can introduce substantial hole‐mixing effects in device structures containing GaSb quantum wells, and should have a significant influence on current‐voltage characteristics interband devices.
36 citations
TL;DR: In this paper, the authors demonstrate that the effective band discontinuity at an n-isotype heterojunction interface can be significantly modified by introducing p-type δ doping close to the interface during molecular beam epitaxy growth.
Abstract: We demonstrate that the effective band discontinuity at an n‐isotype heterojunction interface can be significantly modified by introducing p‐type δ doping close to the interface during molecular beam epitaxy growth. This is shown for the case of the relaxed InAs‐GaAs interface where the band discontinuities with and without δ doping have been measured by the I‐V technique coupled with appropriate numerical modeling of the interface.
TL;DR: An extremely small, in-plane effective-mass hole ground state was observed, thus proving that the hole quantum well is located in the biaxially compressed, InSb layer.
Abstract: Long-wavelength magnetotransmission and photoluminescence measurements were performed on InAs{sub 0.13}Sb{sub 0.87}/InSb strained-layer superlattices (SLS's). The energies and reduced effective masses of several interband optical transitions were obtained from these experiments. SLS's with different layer thicknesses produced self-consistent results. With these data, the type-II band offset and band-edge strain-shift parameters were accurately determined. Consistent with a type-II offset, an extremely small, in-plane effective-mass hole ground state was observed, thus proving that the hole quantum well is located in the biaxially compressed, InSb layer. Nonparabolicity, suggesting valence-band anticrossing, was also observed.
TL;DR: In this paper, a simulation technique based on the dynamical theory of x-ray diffraction in concert with TEM measurements was used to extract the In composition in the quantum well as well as the thicknesses can be directly extracted.
Abstract: Single and multiple quantum well samples have been grown by atmospheric pressure metalorganic chemical vapor deposition at In compositions from 9 to 28% and layer thicknesses ranging from 15 to 140 A, depending upon the composition. Selected samples containing three quantum wells of a given composition but with different thicknesses were characterized by x‐ray double‐crystal diffractometry, low‐temperature photoluminescence, and transmission electron microscopy (TEM). Using a simulation technique based on the dynamical theory of x‐ray diffraction in concert with TEM measurements, the In composition in the quantum well as well as the thicknesses can be directly extracted. The peak positions of the photoluminescence are used to determine the strained and unstrained energy gap and the conduction band offsets associated with InxGa1−xAs of a given composition. We have found the discontinuities to be 60% of the difference in the energy gap of GaAs and strained InxGa1−xAs.
TL;DR: In this article, the effect of valence band discontinuity at the collector base heterojunction on the current gain and base charge storage is modeled and the results discussed here are applicable to Si/SiGe double-heterojunction bipolar transistors.
Abstract: The effect of valence‐band discontinuity at the collector base heterojunction on the current gain and base charge storage is modeled. It is shown that the onset of the Kirk effect is accompanied by a sharp drop in the current gain and ft due to the formation of a potential barrier. The variation of barrier height with collector current density is determined and its effect on current gain and base transit time described. The results discussed here are applicable to Si/SiGe double‐heterojunction bipolar transistors.
TL;DR: In this article, the authors used deep level transient spectroscopy to determine the band offset of a GaAs/GaInAs/GAAs single quantum well and proposed an original model which takes into account the fact that the emission rate of electrons depends on the charge density in the well, and thus varies continuously during the emission process.
Abstract: Using deep level transient spectroscopy, we have determined the band offset of a GaAs/GaInAs/GaAs single quantum well. To interpret the data, we propose an original model which takes into account the fact that the emission rate of electrons depends on the charge density in the well, and thus varies continuously during the emission process, contrary to previous models. The validity of the analysis is tested with success by using capacitance‐voltage measurement to determine the band offset.
TL;DR: In this article, GexSi1-x/Si internal-photo-emission infrared detectors with cutoff wavelengths up to 25 micrometers have been fabricated with the objective of obtaining high free-carrier absorption.
Abstract: Heterojunction GexSi1-x/Si internal-photoemission infrared detectors exhibiting nearly ideal thermionic-emission dark-current characteristics have been fabricated with cutoff wavelengths out to 25 micrometers . Heteroepitaxial p-GexSi1-x layers, degenerately doped with boron to concentrations exceeding 1020 cm-3 in order to obtain high free-carrier absorption, are grown in Si substrates by molecular beam epitaxy. The detector cutoff wavelength, which is determined to first order by the valence- band offset, is tailored by varying the composition of the GexSi1-x layer and can be fine tuned by adjusting such parameters as the doping concentration and growth temperature. High-quality imaging without uniformity correction has been demonstrated in the long-wavelength infrared spectral band for 400 X 400- and 320 X 244-element focal plane arrays consisting of GexSi1-x/Si detectors, which have cutoff wavelengths of 9.3 and 10.5 micrometers , respectively, and monolithic CCD readout circuitry.
TL;DR: In this paper, the authors examined two wide-gap DMS quantum well systems in which the band alignment is dominated by the DMS spin splitting rather than by the more commonly observed effects of differences in bandgap, natural band offset, and strain.
Abstract: Heterostructures containing diluted magnetic semiconductor (DMS) layers offer the possibility of magnetically tuning the heterojunction band alignment due to the extraordinarily large spin‐splitting of the DMS bands (large effective g‐factor). This field‐dependent band alignment has significant consequences for spin‐dependent carrier confinement as evidenced in magnetooptic or magneto‐transport experiments. We have examined two wide‐gap DMS quantum well systems in which the band alignment is dominated by the DMS spin‐splitting rather than by the more commonly observed effects of differences in bandgap, natural band offset, and strain. Quantum well structures with (Zn,Fe)Se or (Zn,Mn)Se barriers and ZnSe wells have been grown to investigate magnetically tuned, spin‐dependent quantum confinement. In these systems, the band offset appears almost entirely in the conduction band, so that the electrons are confined to the ZnSe wells. However, the hole confinement is continuously tunable by an external magnetic ...
TL;DR: In this paper, the growth of Zn1−yCdySe1−xTex alloys by molecular beam epitaxy on GaAs substrates has been investigated and the optical properties and the band structure of this new material have been investigated.
Abstract: We report the growth of Zn1−yCdySe1−xTex alloys by molecular beam epitaxy on GaAs substrates. The optical properties and the band structure of this new material have been investigated. The compositional dependence of the quaternary band gap was studied using photoconductivity measurements and is well described by a third degree function of x and y. Photoluminescence spectra at low temperature show a single broad band, which narrows with increasing Te composition. We discuss the applicability of this new material for ZnSe/ZnCdSeTe heterostructures and predict a region of optimal band offsets for useful confinement of both electrons and holes.
TL;DR: In this article, the authors studied the pressure range where the emissions quench and take on the characteristics of the X-minima in the InGaAs/GaAs structures, these transitions display an unexpected pressure coefficient, -2.6 meV/kbar, twice that of theX minima in GaAs.
Abstract: InxGa1-xAs quantum wells grown pseudomorphically in GaAs and AlGaAs with values ofx up to 0.25 have been studied by photoluminescence under high hydrostatic pressure. We concentrate here on the pressure range where the emissions quench and take on the characteristics of theX-minima. In the InGaAs/GaAs structures, these transitions display an unexpected pressure coefficient, -2.6 meV/kbar, twice that of theX minima in GaAs. We assign these transitions to theX minima in the wells, and therefore make a direct measurement of the strainedX positions as a function of composition. In the InGaAs/AIGaAs structures the crossovers occur against theX-minima in the barriers and these crossovers yield an accurate value for the band offset ratio for InGaAs/GaAs heterojunctions which is found to be 60:40 (CB:VB).
TL;DR: In this article, the authors determined the valence (or conduction)band offset for GaAs-InGaAs superlattices by comparing the calculated energies with conduction intersubband energies obtained from electronic Raman scattering (ERS).
Abstract: The valence (or conduction)‐band offset for GaAs‐InGaAs superlattices is determined by comparing the calculated energies with conduction intersubband energies obtained from electronic Raman scattering (ERS). A valence‐band offset of 40% is estimated for samples with an In content of about 20%, whereas the offset is found to be 60% for samples with an In content of about 5%.
TL;DR: In this paper, an optimized nearest neighbor tight-binding description of valence bands in strained-layer III-V semiconductors is developed and applied to the calculation of offset at strained heterojunctions, where a single set of universal interatomic matrix elements can be found which, when appropriately scaled for bond length, simultaneously provide near-optimum tightbinding predictions.
Abstract: An optimized nearest‐neighbor tight‐binding description of valence bands in strained‐layer III‐V semiconductors is developed and applied to the calculation of valence‐band offsets at strained heterojunctions It is first shown that a single set of universal interatomic matrix elements can be found which, when appropriately scaled for bond length, simultaneously provide near‐optimum tight‐binding predictions of valence‐band uniaxial deformation potentials, trends in photoelectric thresholds, and valence bandwidths for the common III‐V compounds Application of the optimized tight‐binding model to the calculation of valence‐band offsets at strained heterojunctions is then discussed, and one simple approach is described which combines a fully strain‐dependent version of the optimized tight‐binding model with Tersoff’s quantum‐dipole heterojunction model Offsets calculated using this combined approach are shown to agree with experimental data better than either strain‐dependent natural tight‐binding offsets
TL;DR: In this article, the conduction and valence band offsets in a GaAs/GaAs1-xPx (x=0.15, 0.20, 0., 0.22) strained-layer single quantum well structures have been determined by the combination of the reflectance and photoluminescence measurements.
Abstract: High-quality GaAs/GaAs1-xPx (x=0.15, 0.20, 0.22) strained-layer single quantum well structures have been grown on GaAs1-yPy (y=0.1, 0.2) substrates by metal organic vapor phase epitaxy (MOVPE) and characterized by the combination of the reflectance and photoluminescence measurements. Relying on the strong and highly resolved optical transitions between the energy subbands of electrons and holes (including heavy and light holes) in the spectra, we have accurately determined the conduction and valence band offsets in this strained system. The results obtained clarify for the first time that the band offsets are strongly dependent on elastic strain or composition.
TL;DR: Explicit formulae for superlattice subband energies and effective masses in terms of the effective masses and layer widths of the constituent materials and the band offset are presented in this article.
Abstract: Explicit formulae for superlattice subband energies and effective masses in terms of the effective masses and layer widths of the constituent materials and the band offset are presented.
TL;DR: It was found that the energy difference between In 4d and Ga 3d core levels in InAs/GaAs heterostructures depends only slightly on the in-plane lattice constant, and a large effect of strain on the valence-band offset is shown in this system.
Abstract: We studied heterojunction band offsets at highly strained InAs/GaAs (100) heterointerfaces, using in situ x-ray photoemission spectroscopy with an emphasis on the effects of strain. Two extreme cases are examined: an InAs layer pseudomorphically grown on a GaAs substrate (type I); a GaAs layer grown on an InAs substrate (type II). It was found that the energy difference between In 4d and Ga 3d core levels in InAs/GaAs heterostructures depends only slightly on the in-plane lattice constant: 1.64 eV for type I and 1.60 eV for type II. However, the valence-band offsets \ensuremath{\Delta}${\mathit{E}}_{\mathit{V}}$[==${\mathit{E}}_{\mathit{V}}$(InAs)-${\mathit{E}}_{\mathit{V}}$(GaAs)], which are deduced by theoretically taking into account the effects of strain on the core-level energies relative to the valence-band maxima as well as on a splitting of the valence-band maxima, are very different: 0.53 eV for type I and -0.16 eV for type II. This clearly indicates a large effect of strain on the valence-band offset (\ensuremath{\sim}0.7 eV) in this system.
TL;DR: In this paper, the energy-band nonparabolicity of both conduction and valence bands was investigated and the required value of the ratio of the conduction-band and the valence-band discontinuities was found to be close to 2/3 in agreement with the value found by other methods.
Abstract: Energy levels in InP/Ga0.47In0.53As quantum wells are calculated after reformulating the energy‐dependent effective mass to be used for taking into account the energy‐band nonparabolicity of both constituents. The required value of the ratio of the conduction‐band and valence‐band discontinuities is found to be close to 2/3, in agreement with the value found by other methods. The value of the nonparabolicity factor is also found to be the same as that used in earlier transport studies.
TL;DR: An overall picture is obtained for the electronic structure of these superlattices with a valence-band offset close to 0.5 eV, which is consistent with the observed spectra.
Abstract: (001) superlattices containing 15 principal layers of AlAs and either one or two of InAs have been grown by atomic-layer molecular-beam epitaxy on undoped (001) GaAs substrates. The samples, between 0.1 and 0.3 \ensuremath{\mu}m thick, have been studied by photoluminescence, electroreflectance, and piezoreflectance and monitored by phonon Raman-scattering spectroscopy and x-ray diffractometry. An empirical tight-binding model, combined with surface Green-function matching, is used to discuss the experimental data. An overall picture is obtained for the electronic structure of these superlattices with a valence-band offset close to 0.5 eV, which is consistent with the observed spectra.
TL;DR: In this paper, the authors used Ga-As dipole intralayers with the Ge valence band edge on the As side of the junction at lower energy to create 0.35-0.45 eV band offsets at Ge homojunctions.
Abstract: We have created 0.35–0.45 eV band offsets at Ge homojunctions using Ga–As dipole intralayers, with the Ge valence band edge on the As side of the junction at lower energy. This is, to our knowledge, the first time that intralayer control of band discontinuities is extended to homojunctions, thereby expanding the potential domain of band gap engineering. Because these offsets occur over just a few atomic spacings, they rival heterojunction band edge discontinuities in breadth. The offsets were measured with synchrotron‐radiation photoemission spectroscopy. Similar band offset magnitudes occur for both ‘‘Ga‐first’’ and ‘‘As‐first’’ growth sequences, consistent with a truly dipolar effect. Both cleaved Ge(111) and thick ≊50 A Ge films deposited on cleaved Ge(111) were used as substrates, obtaining consistent results. The sign and magnitude of the effect is in agreement with a ‘‘theoretical alchemy’’ model. Experimental evidence of microdiffusion is discussed.
TL;DR: In this article, the authors measured interface defect densities and conduction-band offset energies for liquid-phase epitaxially grown n−N isotype In0.53Ga0.47As/InP heterojunctions using capacitance-voltage methods.
Abstract: Interface charge densities and conduction‐band offset energies for liquid‐phase epitaxially grown n‐N isotype In0.53Ga0.47As/InP heterojunctions have been measured using capacitance‐voltage methods. Extremely low interface charge densities have been obtained in some samples, and they are found to be independent of both the measurement temperature and the magnitude of lattice mismatch. Our samples show a clear peak and notch in the apparent free‐carrier concentration profile at temperatures as low as 83 K. This is in contrast to results reported previously where the notch, due to the carrier depletion at the heterojunction, was observed to vanish at low temperature. An electron trap has been identified in one of the samples. The trap is uniformly distributed within the bulk of the In0.53Ga0.47As layer at a density of 5×1014 cm−3. In spite of the presence of this relatively low density defect, the heterojunctions grown for this study apparently have considerably lower interface defect densities than observe...