Structure Of InAs Research Articles

Local density of states of a three-dimensional conductor in the extreme quantum limit.

The electronic structure of the narrow gap semiconductor InAs is investigated by scanning tunneling spectroscopy and magnetotransport measurements in the extreme quantum limit. The well-known oscillations of the Hall coefficient are reproduced and the last, most pronounced oscillation is shown to be correlated with the appearance of corrugations in the local density of states. While the increasing part of the Hall constant corresponds to the existence of isolated patterns indicating magnetic field induced localization, the decreasing part correlates with the development of a network which most likely consists of one-dimensional channels. We conclude that the decrease of the Hall constant in the extreme quantum limit is caused by a transition from a purely three-dimensional to a partly one-dimensional transport regime.

Sb-terminated InAs(001)-(2×4) and (2×8) studied using scanning tunneling microscopy and ab initio density functional theory

AbstractWe have studied the structure of MBE-grown InAs(001)-(2×4) surfaces exposed to low Sb2 fluxes by scanning tunneling microscopy (STM) and ab initio density functional theory (DFT). Experimentally, we observe an Sb-terminated α2(2×4) phase over a wide range of temperatures (400–510 °C) for low Sb2 flux (<0.1 ML/s), whereas temperature and As2 flux must be carefully controlled to achieve the same As-terminated surface structure. At lower temperatures, we observe indications of an Sb-terminated (2×8) symmetry surface phase, and we report briefly on its proposed structure and stability, as well as its possible role in subsequent formation of the Sb-terminated (1×3) phase found at typical Sb2 fluxes used during heterostructure growth.

Electronic structure of InAs–GaAs self-assembled quantum dots studied by perturbation spectroscopy

In spite of the intense interest in the last few years in InAs–GaAs self-assembled quantum dots, relatively little direct experimental information has been available on the electronic structure and the forms of the electron–hole wave functions. The present paper reviews the results of recent experiments in which the external perturbations of electric field, hydrostatic pressure and magnetic fields enable key information on the electronic structure of the QDs to be obtained. Some of this information is particularly surprising and contrary to the predictions of recent theories. These findings are expected to provide important guides to future theoretical modelling of the electronic structure of InAs QDs

Luminescence properties of InAs layers and p-n structures grown by metallorganic chemical vapor deposition

The luminescence properties of p-and n-type InAs layers grown by gas-phase epitaxy from metallorganic compounds at atmospheric pressure are investigated. Acceptor levels in InAs are identified with energies 350, 372, 387, and 397 meV. Optimal conditions are determined for the growth of InAs layers in a reactor of planetary type. At a growth temperature of 565 °C, InAs structures were obtained with abrupt p-n junctions. The structures grown were used to make light-emitting diodes operating at wavelengths of 3.1 µm (T=77 K) and 3.7 µm (T=300 K).

InAs-doped silica films for saturable absorber applications

InAs-doped thin silica films having saturable absorption properties were fabricated using rf sputtering. The films contain semiconductor nanoparticles preserving the zincblende crystal structure of bulk InAs. We have investigated the linear and nonlinear optical as well as structural properties of the films. Rapid thermal annealing in nitrogen was successfully used to tailor the optical absorption saturation dynamics. The films having saturable absorber properties were applied to Kerr lens mode locking initiation in a Ti:Al2O3 laser resulting in self-starting mode locking operation with pulses as short as 25 fs.

Surface electronic structure of InAs(100)1 x2/1 x4-Pb

Upon deposition and annealing of one Pb monolayer on the clean, In-terminatedInAs(100)-4 x2/c(8 x2) surface we have obtained a sharp1 x2/1 x4 superstructure. We have investigated its electronic structure by angle-resolved photoemission using synchrotron radiation. From valence-band spectra measured at normal emission as well as along the¯Γ-¯J and¯Γ-¯J′ directions of the surface Brillouin zone, two surface induced states were identified and mapped out.

Bulk and surface electronic structure of InAs(110)

The InAs(110) cleavage surface has been investigated by angle-resolved photoelectron spectroscopy. A separation between the In 4d( 5 2 ) bulk component and the valence band maximum of 16.8 eV is found to be consistent with normal emission spectra. Experimental energy band dispersions, E i( k), for the four bulk valence bands are established along the Σ-line of the bulk Brillouin zone. A bulk band structure calculation utilizing the augmented plane-wave method is made. The experimental and calculated E i( k) dispersions are found to be in good agreement with each other. E i( k ∥) dispersions for two surface-related structures are established along the lines I - M and Y - M of the surface Brillouin zone.

STUDY OF VERTICALLY ALIGNING GROWTH OF SELF-ASSEMBLED InAs/GaAs QUANTUM DOTS

We have grown two-layer InAs structures spaced by 6.5nm GaAs. Self-assembled InAs quantum dots (QDs) occur in the first layer with 2.5ML InAs coverage due to S-K growth mode. The second layer changes from 2D to 3D growth when the thickness of InAs is 1.5ML, which is obviously smaller than the critical thickness (1.7ML) of single InAs layer structures. Transmission electron microscopy shows that two-layer QDs with different heights have been obtained according to the mechanism of a vertically correlated arrangement. But only one photoluminescence peak related with large QD ensemble has been observed as a result of strong electronic coupling in InAs QD pairs.

Effect of infrared laser radiation on the structure and electrophysical properties of undoped single-crystal InAs

Substantial changes have been found in the electrical properties and structural parameters of single-crystal InAs after exposure to infrared laser radiation with photon energy less than the energy gap of InAs and power density W<50 W/cm2. The changes are due to the transformation and redistribution of intrinsic point defects in the field of the laser electromagnetic field.

Atomic force microscopy study of morphology and dislocation structure of InAs and GaSb grown on highly mismatched substrates

We have studied the surface morphology and dislocation structure of InAs grown on GaAs or InP substrates and of GaSb grown on GaAs substrates by metalorganic chemical vapour deposition (MOCVD). Atomic force microscopy (AFM) has been used to determine quantitative threading dislocation densities by observing singularities in the atomic terrace structure. All layers were grown using a thin ∼ 100 nm low temperature buffer layer grown at 400°C, which was found to greatly improve surface morphology for all materials combinations studied. The lowest dislocation densities were found for thick GaSb layers on GaAs, with around 1 × 10 6 cm −2 for a 5 μm layer. While somewhat higher levels were observed for InAs (5 × 10 6 cm −2 ), the surface roughness for these films was significantly lower. In all samples the limiting factor for surface roughness is observed to be the formation of hillocks consisting of growth spirals centred on dislocations. We suggest ways in which these data may be used to calculate some fundamental MOCVD crystal growth parameters such as the critical radius for nucleation.

Electronic structure of InAs(1-bar 1-bar 1-bar)2 x 2 and InSb(1-bar 1-bar 1-bar)2 x 2 studied by angle-resolved photoelectron spectroscopy.

The electronic structure of molecular-beam-epitaxy-grown InAs(1\ifmmode\bar\else\textasciimacron\fi{} 1\ifmmode\bar\else\textasciimacron\fi{} 1\ifmmode\bar\else\textasciimacron\fi{})2\ifmmode\times\else\texttimes\fi{}2 and InSb(1\ifmmode\bar\else\textasciimacron\fi{} 1\ifmmode\bar\else\textasciimacron\fi{} 1\ifmmode\bar\else\textasciimacron\fi{})2\ifmmode\times\else\texttimes\fi{}2 surfaces is investigated by angle-resolved photoelectron spectroscopy. Valence-band spectra, and dispersions of five surface-related structures, are presented. The qualitative similarities of data from the two surfaces indicate that they are very similar, with respect to atomic and electronic structure. Comparisons with other (111) surfaces support the identification of the surface-related structures. \textcopyright{} 1996 The American Physical Society.

Photoluminescence Studies of Single Submonolayer InAs Structures Grown on GaAs (001) Matrix

We report a detailed analysis of optical properties of single submonolayer InAs structures grown on GaAs (001) matrix. It is shown that the formation of InAs dots with 1 monolayer (ML) height leads to localization of exciton under certain submonolayer InAs coverage, which play a key role in the highly improved luminescence efficiency of the submonolayer InAs/GaAs structures.

Photoluminescence studies of single submonolayer InAs structures grown on GaAs (001) matrix

Optical properties of single submonolayer InAs structures grown on GaAs (001) matrix are systematically investigated by means of photoluminescence and time-resolved photoluminescence. It is shown that the formation of InAs dots with 1 ML height leads to localization of excitons under certain submonolayer InAs coverages, which play a key role in the highly improved luminescence efficiency of the submonolayer InAs/GaAs structures.

Comment on ‘‘Optical characterization of submonolayer and monolayer InAs structures grown in a GaAs matrix on (100) and high-index surfaces’’ [Appl. Phys. Lett. 64, 1526 (1994)

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Response to Comment: ‘‘Comment on ‘Optical characterization of submonolayer and monolayer InAs structures grown in a GaAs matrix on (100) and high-index surfaces’ ’’ [Appl. Phys. Lett. 66, 111 (1995)

Response to Comment: ‘‘Comment on ‘Optical characterization of submonolayer and monolayer InAs structures grown in a GaAs matrix on (100) and high-index surfaces’ ’’ [Appl. Phys. Lett. <b>66</b>, 111 (1995)

Initial growth stage and optical properties of a three-dimensional InAs structure on GaAs

A few mololayers of InAs is heteroepitaxially grown on GaAs substrate by molecular-beam epitaxy. Structure and optical properties are investigated. Reflection high-energy electron-diffraction observation reveals that an InAs layer forms a three-dimensional structure with specific facets after two-dimensional growth. The transmission electron microscope observation shows that these structures have structural anisotropy in the growth plane. Photoluminescense spectroscopy shows that the luminescence from the InAs structures exhibits the polarization property caused by the quantum dot effect of the structural anisotropy.

Lateral piezoelectric fields—a universal feature of strained III–V and II–VI semiconductor heterostructures

Strained II–VI and III–V semiconductor heterostructures in general are expected to have a piezoelectric polarization with a non-zero component in the plane of the interfaces which generates lateral piezoelectric fields. We use InAs structures synthesized on vicinal (110)-GaAs surfaces as a model system to study such fields for the first time. These lateral fields manifest themselves in strong blueshifts of the photoluminescence peaks and an energy dependence of the radiative lifetime. Our experiments unambiguously prove the existence of these electric fields and furthermore demonstrate their tremendous impact on the electronic and optical properties of our InAs/GaAs-samples.

Optical characterization of submonolayer and monolayer InAs structures grown in a GaAs matrix on (100) and high-index surfaces

We studied the optical properties of InAs/GaAs heterostructures with InAs average layer thickness ranging from 1 Å [one-third of a monolayer (ML)] to 4 ML grown on (100) and (311) surfaces. Extremely high optical quality was revealed for the structures with ultrasmall InAs coverage. We attribute the improvements to the first stage of InAs growth on the GaAs surface which we refer to as submonolayer epitaxy. Optical anisotropy found in photoluminescence (PL), as well as in PL excitation spectra indicates a highly anisotropic growth mode for InAs molecules on the GaAs (100) surface. An InAs/GaAs superlattice composed of submonolayer InAs exhibits greatly improved luminescence efficiency at room temperature and much better nonequilibrium carrier capture compared to either the (In,Ga)As alloy or an InAs/GaAs superlattice composed of monolayer-thick InAs layers with the same average In composition.

Investigation of InAs submonolayer and monolayer structures on GaAs(100) and (311) substrates

We demonstrate a new route to the synthesis of InAs monolayer structures in GaAs by bridging the fundamental gap between the requirement of the lowest possible substrate temperatures to suppress In segregation and the necessity to maintain sufficiently high temperatures for the growth of low-defect density material. This mediation between opposing aspects of the molecular beam epitaxy of these InAs structures is achieved by a modulation of the substrate temperature and by a minimization of the amount of GaAs cap material grown at low temperature. High-resolution x-ray diffraction and high-resolution electron microscopy combined with photoluminescence (PL) and PL excitation spectroscopies reveal excellent structural properties for our series of (311) and (100) oriented submonolayer and monolayer structures. A comparison of our PL results with already published data proves our In concentration profiles to be very sharp and from a numerical analysis we deduce an upper limit of 0.2 for the In segregation probability in these structures. In addition we obtain as upper limits for the conduction band offsets Q(100)c≤0.4 and Q(311)c≤0.55 for (100) and (311) orientations, respectively.

Local structure about Mn atoms in In1-xMnxAs diluted magnetic semiconductors.

X-ray-absorption fine-structure measurements were performed at the Mn [ital K] edge on In[sub 0.88]Mn[sub 0.12]As diluted magnetic semiconductors prepared by molecular-beam epitaxy. It has been found that in the high-growth-temperature samples ([ital T][sub [ital s]]=280 [degree]C), Mn atoms are primarily incorporated in the form of MnAs clusters with NiAs structure. No significant disorder is observed. In the low-growth-temperature samples ([ital T][sub [ital s]]=210 [degree]C), the majority of Mn atoms form small ([ital r][similar to]3 A), disordered, sixfold-coordinated centers with As. The presence of disorder in MnAs centers for the latter case is established using the method of cumulants. Only a very small fraction of Mn atoms may substitute for In in the zinc-blende InAs structure. Effective valency and coordination of Mn atoms deduced from the near-edge structure are the same for both the high- and low-growth-temperature In[sub 1[minus][ital x]]Mn[sub [ital x]]As films. The formal valency is lower than +3. The local structures established in the present work are consistent with the observed difference in magnetic behavior for samples prepared at different substrate temperatures.