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Abstract: We have investigated the effect of an AlInSb interlayer on dislocation filtering, aiming at a further improvement in the performance of InSb quantum well devices that are often grown on a largely lattice-mismatched substrate, such as Si and GaAs, via an AlInSb buffer layer. Transmission electron microscopy (TEM) analyses under high-tilt bright-field (HTBF) and high-tilt dark-filed (HTDF) conditions provide the capabilities of (A) analyzing the reaction between threading dislocations (TDs) and misfit dislocations (MDs) and (B) measuring local TD and MD densities around an interface which is embedded deep into an epilayer. An HTBF-TEM analysis shows that 50% of TDs are eliminated at an (001) Al0.25In0.75Sb/Al0.10In0.90Sb interlayer interface where the TD density was originally 8.6×109 /cm2. Twenty three percent of the mechanical strain at such an interface was relaxed by a MD density of 1.6×105 /cm. In this study, the detailed practical procedures of HTBF- and HTDF-TEM analyses are also discussed. [ABSTRACT FROM AUTHOR]

Abstract: We investigate the low temperature spin and phase coherence lengths in quasi-one dimensional wires fabricated from a high mobility InSb/InAlSb two dimensional electron system. Spin and phase coherence lengths as a function of wire width and temperature are obtained by fitting the magnetoconductance to an antilocalization theory modified to account for ballistic transport through the wires. Extracted spin coherence lengths are found to be inversely proportional to wire width and display a weak dependence on temperature. Results for the phase coherence length suggest that mechanisms originating in the two dimensional electron system are responsible for phase decoherence. [Copyright &y& Elsevier]

Abstract: The shape dependence of electronic structure, electron g factors in the presence of the external magnetic field of InSb quantum ellipsoids are investigated in the framework of eight-band effective-mass approximation. It is found that as the increasing aspect ratio e, the electron states with P character split into three doublets for the different physical interaction and the light-hole states with S character come up to the top of valence bands at in comparison with the heavy-hole states. In the presence of the external magnetic field, the energy splits of electron states are different for their wave function distribution direction, and the hole ground state remain optical active for a suitable aspect ratio. The electron g factors of InSb spheres decrease with increasing radius, and have the value of about two for the smallest radius, about for sufficiently larger radius, similar to the bulk material case. Actually, the electron g factors decrease as any one of the three dimensions increase. The more dimensions increase, the more g factors decrease. The dimensions perpendicular to the direction of the magnetic field affect the g factors more than the other dimensions. [Copyright &y& Elsevier]

Abstract: We report transverse electron focusing in a symmetrically doped, InSb-based two-dimensional electron system. In a focusing device, the application of a perpendicular magnetic field steers the electron current from an injecting quantum point contact into a collector quantum point contact whenever the diameter of the cyclotron orbit corresponds to an integer fraction of the injector to collector spatial separation. In low-temperature measurements of in-plane gated devices, we observe peaks in the collector voltage at magnetic fields where focusing is expected. The first peak displays substructure which is preserved at temperatures as high as 10K and under a variety of gating conditions. We speculate that this substructure originates from spatially distinct paths for electrons with different spin polarizations arising from the large Dresselhaus effect expected for InSb-based electron systems. [Copyright &y& Elsevier]

Abstract: Two different device geometries are fabricated to investigate ballistic transport of electrons in low-dimensional InSb structures. Negative bend resistance is observed in four-terminal devices of channel widths ranging from 0.2 to 0.65μm. We also report the observation of conductance quantization in quantum point contacts fabricated using in-plane gates. The one-dimensional subbands depopulate with increasing transverse magnetic field up to 3T. Zeeman splitting is resolved at magnetic fields above ∼0.9T. [Copyright &y& Elsevier]

The first FIRM-PL measurements in InSb/GaSb quantum dots have been performed. At low power densities the FIR absorption causes a transfer of carriers between dots and effectively cools the system, preferentially populating large, low energy dots and increasing the photoluminescence (PL) intensity. At higher powers the carrier temperature increases and the PL intensity falls. The spectral dependence of the FIRM-PL signal measures the energy spectrum of the quantum dots, showing a peak at 14.5 meV corresponding to transitions between the first two energy levels of the quantum dot distribution. [Copyright &y& Elsevier]

Ballistic transport is observed in 0.5 μm long four-terminal square structures fabricated from InSb quantum wells with AlxIn1−xSb barriers. Negative bend resistance is observed at temperatures between ∼1.5 and ∼200 K. The disappearance of negative bend resistance at higher temperatures is accompanied by evidence of parallel conducting paths. [Copyright &y& Elsevier]

We investigated double-buffer structure which could enable us to grow a high-quality InSb active structure on GaAs (0 0 1). With thick AlSb and InAlSb step-graded buffer layers, we succeeded to obtain InSb films of very high mobility at room temperature. Using transmission electron microscopy, we confirmed attenuation of threading dislocations by the buffer layer. Surface roughness and its power spectral density were analyzed by atomic force microscopy. Furthermore, strain relaxation and mosaicity were investigated by high-resolution X-ray diffraction measurements. [Copyright &y& Elsevier]

Coupled nanostructures have been developed in the InAs/InSb/GaSb materials system in order to extend the emission wavelength further into the infrared, beyond 2 μm. The samples studied consist of a single narrow InAs quantum well grown below a layer of InSb quantum dots in a GaSb matrix, in which the coupling has been altered by changing the thickness of a GaSb spacer layer. The overall transition energy of the combined dot–well system is generally reduced with respect to the dots and well only but the dependence on spacer thickness is more complex than that expected from a simple envelope function model. [Copyright &y& Elsevier]

Infrared LEDs and negative luminescent devices, where less light is emitted than in equilibrium, have been attracting an increasing amount of interest recently. They have a variety of applications, including as a ‘source’ of IR radiation for gas sensing; radiation shielding for, and non-uniformity correction of, high sensitivity staring infrared detectors; and dynamic infrared scene projection. Similarly, infrared (IR) detectors are used in arrays for thermal imaging and, discretely, in applications such as gas sensing. Multi-layer heterostructure epitaxy enables the growth of both types of device using designs in which the electronic processes can be precisely controlled and techniques such as carrier exclusion and extraction can be implemented. This enables detectors to be made which offer good performance at higher than normal operating temperatures, and efficient negative luminescent devices to be made which simulate a range of effective temperatures whilst operating uncooled. In both cases, however, additional performance benefits can be achieved by integrating optical concentrators around the diodes to reduce the volume of semiconductor material, and so minimise the thermally activated generation-recombination processes which compete with radiative mechanisms. The integrated concentrators are in the form of Winston cones, which can be formed using an iterative dry etch process involving methane/hydrogen and oxygen. We present results on negative luminescence in the mid- and long-IR wavebands, from devices made from indium antimonide and mercury cadmium telluride, where the aim is sizes greater than 1 cm×1 cm. We also discuss progress on, and the potential for, operating temperature and/or sensitivity improvement of detectors, where very high-performance imaging is anticipated from systems which require no mechanical cooling. [Copyright &y& Elsevier]

We briefly review the growth and structural properties of InAsxSb1−x (x⩽0.05) bulk single crystals and InAsxSb1−x (x⩽0.06) epitaxial films grown on semi-insulating GaAs substrates. Temperature-dependent transport measurements on these samples are then correlated with the information obtained from structural (XRD, TEM, SEM) and optical (FTIR absorption) investigations. The temperature dependence of mobility and the Hall coefficient are theoretically modelled by exactly solving the linearized Boltzmann transport equation by inversion of the collision matrix and the relative role of various scattering mechanisms in limiting the low temperature and 300 K mobility is estimated. Finally, the first observation of Shubnikov oscillations in InAsSb is discussed. [Copyright &y& Elsevier]

Both magneto-resistive sensors and spintronic hybrid semiconductor devices require thin epitaxial layers of high-mobility InSb. Here we study unintentionally doped InSb epilayers grown on semi-insulating GaAs(100) substrates by molecular-beam epitaxy. We have introduced an initial low-temperature growth step extending the work that the NTT group reported in 2000. We find significant improvement in the room temperature mobility for epilayer thickness between 60 and 300 nm. The importance of the initial growth step to the epilayer mobility performance is discussed. [Copyright &y& Elsevier]

The properties of InSb quantum dots grown by metal organic vapour phase epitaxy are summarised as deduced from photoluminescence, magneto-photoluminescence, and far-infrared modulated photoluminescence experiments. A technique is described for shifting the emission of these dots to lower energy by coupling them with a narrow InAs quantum well, leading to the demonstration of electroluminescence at ∼2.3 μm. [Copyright &y& Elsevier]

Energy loss rates of two-dimensional electron gas in GaInAs/AlInAs, InSb/AlInSb and GaSb/AlGaAsSb heterostructures are theoretically investigated over a wide range of temperature based on the electron–one-phonon and electron–two-phonon interactions. Calculations are presented for electron acoustic one-phonon interaction via deformation potential and piezoelectric coupling and electron–LO phonon interaction with hot phonon effect. In addition, energy loss rate due to electron-two-zone edge transverse acoustic (TA) phonons is also presented. A very good agreement is obtained between the calculations and experimental data in GaInAs/AlInAs structure with the inclusion of electron–two-zone edge TA phonon interaction. In all these three structures energy loss is dominated by (i) acoustic one-phonon scattering at low temperatures, (ii) two-TA zone edge phonons at intermediate temperatures and (iii) LO phonons at high temperatures. It is observed that, hot phonon effect reduces the energy loss rate considerably in these structures. [Copyright &y& Elsevier]