Epitaxial InSb Research Articles

Formation of epitaxial InSb films on semi-insulating GaAs(100) by explosive thermal evaporation: their structure and electrical properties

In the present work, the influence of the deposition temperature of InSb films on semi-insulating GaAs(100) on their phase composition, crystal perfection and electrical properties was investigated. The InSb films of various extent of crystal perfection are formed by means of explosive thermal deposition of InSb on semi-insulating GaAs(100) substrates in the temperature range of 375–460 °C. X-ray diffraction analysis established that the films are heteroepitaxial. It is shown that an increase in the deposition temperature of InSb films from 375 to 460 °C leads to a change in the film surface roughness (Ra) from 3.4 to 19.1 nm. The Hall voltage sensitivity to the magnetic field of InSb films varies in the range of 500–1500 mV/T. The electron concentration (n) and mobility (μ) changes in the range of 2 ⋅ 1016 – 6 ⋅ 1016 cm–3, 10 ⋅ 103 – 21 ⋅ 103 cm2/(V ⋅ s). The formed InSb films on semi-insulating GaAs(100) substrate are of practical interest for the manufacture of highly sensitive miniature Hall devices.

Selective-Area Superconductor Epitaxy to Ballistic Semiconductor Nanowires.

Semiconductor nanowires such as InAs and InSb are promising materials for studying Majorana zero modes and demonstrating non-Abelian particle exchange relevant for topological quantum computing. While evidence for Majorana bound states in nanowires has been shown, the majority of these experiments are marked by significant disorder. In particular, the interfacial inhomogeneity between the superconductor and nanowire is strongly believed to be the main culprit for disorder and the resulting "soft superconducting gap" ubiquitous in tunneling studies of hybrid semiconductor-superconductor systems. Additionally, a lack of ballistic transport in nanowire systems can create bound states that mimic Majorana signatures. We resolve these problems through the development of selective-area epitaxy of Al to InSb nanowires, a technique applicable to other nanowires and superconductors. Epitaxial InSb-Al devices generically possess a hard superconducting gap and demonstrate ballistic 1D superconductivity and near-perfect transmission of supercurrents in the single mode regime, requisites for engineering and controlling 1D topological superconductivity. Additionally, we demonstrate that epitaxial InSb-Al superconducting island devices, the building blocks for Majorana-based quantum computing applications, prepared using selective-area epitaxy can achieve micron-scale ballistic 1D transport. Our results pave the way for the development of networks of ballistic superconducting electronics for quantum device applications.

Observation of Conductance Quantization in InSb Nanowire Networks

Majorana zero modes (MZMs) are prime candidates for robust topological quantum bits, holding a great promise for quantum computing. Semiconducting nanowires with strong spin orbit coupling offer a promising platform to harness one-dimensional electron transport for Majorana physics. Demonstrating the topological nature of MZMs relies on braiding, accomplished by moving MZMs around each other in a certain sequence. Most of the proposed Majorana braiding circuits require nanowire networks with minimal disorder. Here, the electronic transport across a junction between two merged InSb nanowires is studied to investigate how disordered these nanowire networks are. Conductance quantization plateaus are observed in most of the contact pairs of the epitaxial InSb nanowire networks: the hallmark of ballistic transport behavior.

MBE-grown InSb photodetector arrays

The MBE method has been applied to grow InSb layers on InSb substrates. These layers have served as a basis for fabricating mid-wave IR photodetector arrays. The characteristics of photodetector arrays on epitaxial InSb layers have been compared with those of series-produced single-crystal InSb arrays.

Structural and morphological features of ultrathin epitaxial InSb films in AlAs matrix

This work presents results of the investigation of structural and morphological features of epitaxial InSb layers in the AlAs matrix. Our research group used transmission electron microscopy (TEM). The specimens were grown by molecular beam epitaxy and prepared in the cross section (110) and plan view foils (100). We found a formation of the embedded epitaxial layer of solid solution InxAl1-xSbyAs1-y in the AlAs matrix during precipitation of In and Sb on the AlAs surface. The embedded layer had continuous area (wetting layer) and islands. The study revealed two types of islands in the epitaxial layer the first having coherent interfacing with the matrix lattice and the second a relaxed island. We estimated concentration of In, Sb in the solid solution by the indirect method. We used the method of geometric phase to analyze the distribution of misfit dislocation cores on the interface. Every misfit dislocation was formed by two close 600-dislocations with the Burgers vectors like a /2 <110>. The sum Burgers vector of the dislocation pair was in the plane of the interface.

Photodiode properties of molecular beam epitaxial InSb on a heavily doped substrate

Photodiodes of InSb were fabricated on an epitaxial layer grown using molecular beam epitaxy (MBE). Thermal cleaning of the InSb (001) substrate surface, 2° towards the (111) B plane, was performed to remove the oxide. Photodiode properties of МВЕ-formed epitaxial InSb were demonstrated. Zero-bias resistance area product (R0A) measurements were taken at 80K under room temperature background for a pixel size of 100μm×100μm. Values were as high as 4.36×104Ω/cm2, and the average value of R0A was 1.66×104Ω/cm2. The peak response was 2.44(A/W). The epitaxial InSb photodiodes were fabricated using the same process as bulk crystal InSb diodes with the exception of the junction formation method. These values are comparable to the properties of bulk crystal InSb photodiodes.

InSb Mid-Infrared Photon Detector for Room-Temperature Operation

We developed a small InSb mid-infrared (2–7 µm wavelength range) photon detector that operates at room temperature. The photodiode was made from (hetero epitaxial) InSb layers that were grown on a semi-insulating GaAs substrate by molecular beam epitaxy. To suppress the effects of the diffusion current of the p–i–n photodiode, we used an AlInSb barrier layer that raises the resistance of the photodiode. We also optimized the device's doping concentration and the infrared incidence window structure. These optimization steps realized high photoelectric current output in a room-temperature environment. We also increased the signal-to-noise ratio of the detector by connecting multiple photodiodes in series. The size of this detector is 1.9×2.7×0.4 mm3 and the detectivity is 2.8×108 cm Hz1/2/W at 300 K. This is a practical IR detector that can be used in general signal amplification ICs.

Reflection absorption infrared spectroscopy analysis of the evolution of ErSb on InSb

We discuss an ex-situ monitoring technique based on glancing-angle infrared-absorption used to determine small amounts of erbium antimonide (ErSb) deposited on an indium antimonide (InSb) layer epitaxially grown on an InSb (100) substrate by low pressure metal organic chemical vapor deposition (MOCVD). Infrared absorption from the indium–hydrogen (InH) stretching mode at 1754.5cm−1 associated with a top most surface of an epitaxial InSb layer was used to compare varying levels of surface coverage with ErSb. Among four samples of varying coverage of ErSb deposition (7.2 to 21.5 monolayers), detected infrared absorption peaks distinct to InH weakened as ErSb surface coverage increased. In the early stage of ErSb deposition, our study suggests that outermost indium atoms in the InSb buffer layer are replaced by Er resulting in increase in absorption associated with the InH mode. Using this simple ex-situ technique, we show that it is possible to calibrate the amount of ErSb deposited atop each individual InSb substrate for depositions of few to tens of monolayers.

Crystal structure control in Au-free self-seeded InSb wire growth

In this work we demonstrate experimentally the dependence of InSb crystal structure onthe ratio of Sb to In atoms at the growth front. Epitaxial InSb wires are grownby a self-seeded particle assisted growth technique on several different III–Vsubstrates. Detailed investigations of growth parameters and post-growth energydispersive x-ray spectroscopy indicate that the seed particles initially consist ofIn and incorporate up to 20 at.% Sb during growth. By applying this techniquewe demonstrate the formation of zinc-blende, 4H and wurtzite structure in theInSb wires (identified by transmission electron microscopy and synchrotron x-raydiffraction), and correlate this sequential change in crystal structure to the increasingSb/In ratio at the particle–wire interface. The low ionicity of InSb and the large diameter of thewire structures studied in this work are entirely outside the parameters for which polytypeformation is predicted by current models of particle seeded wire growth, suggesting that theV/III ratio at the interface determines crystal structure in a manner well beyond currentunderstanding. These results therefore provide important insight into the relationshipbetween the particle composition and the crystal structure, and demonstrate the potentialto selectively tune the crystal structure in other III–V compound materials as well.

Au-assisted Growth of Indium Antimonide Nanowires by Chemical Vapor Deposition: Temperature and Growth Duration Effects

ABSTRACTIn this paper, we investigate the morphology variation of Au-assisted epitaxial InSb nanowires (NWs) dependence on growth temperature and growth duration by chemical vapor deposition (CVD). The NW length and tapering factor correlated to the NW morphology are determined as a function of growth temperature (300°C-480°C). Higher density and longer NWs were observed on the substrate as proportional to the growth duration. The growth direction of the NWs is &lt;110&gt; by Transmission Electron Microscopy (TEM) studies. The aim of this study is to gain better understanding of the III-V NWs growth mechanism and achieve control over the growth of InSb NWs.

Detection of a Micron-Sized Magnetic Particle Using InSb Hall Sensor

We present our results on the realization of ultra-sensitive and non-invasive magnetic sensors based on double-cross InSb Hall bars with dimensions down to 1.5 mum. Hall sensors were patterned from an epitaxial InSb film characterized by the carrier concentration of 3.9 times 1016 cm-3 and high carrier mobility of 1.3 m 2/Vs. We study noise characteristics and magnetotransport properties of Hall sensors as well as their performance with respect to the lateral dimensions of devices. The adjacent crosses are characterized by very similar transport properties, which make them suitable for single magnetic particle detection. The high Hall coefficient, RH les 1000 V/AT, was measured for all devices. The white noise spectral density is of the order of 80 nV/radic Hz providing room-temperature magnetic field sensitivity better than 0.5 muT/ radic Hz. We demonstrate that micron-sized InSb Hall sensors can be successfully used for detection of a single paramagnetic bead with the diameter of 1 mu m. We also model the response of the Hall sensor to an inhomogeneous magnetic field caused by the presence of a magnetic bead.

A silicon metal-oxide-semiconductor field-effect transistor Hall bar for scanning Hall probe microscopy

We demonstrate successful operation of a scanning Hall probe microscope with a few micron-size resolution by using a silicon metal-oxide semiconductor field-effect transistor (Si-MOSFET) Hall bar, which is designed to improve not only the mechanical strength but also the temperature stability. The Si-MOSFET micro-Hall probe is cheaper than the current micro-Hall probes and is found to be as sensitive as a micro-Hall probe with GaAs/AlGaAs heterostructure or an epitaxial InSb two-dimensional electron gas. This was used to magnetically image the surface of a Sm(2)Co(17) permanent magnet during the magnetization reversal process as a function of an external magnetic field below 1.5 T. This revealed firm evidence of the presence of the inverse magnetic seed as theoretically predicted earlier. Magnetically pinned centers, with a typical size 80 mum, are observed to persist even under a high magnetic field, clearly indicating the robustness of the Si Hall probe against the field application as well as the repetition of the measurement.

Growth of high quality, epitaxial InSb nanowires

The growth of InSb nanowires on an InSb(1 1 1) substrate in a closed system is described. A high density InSb nanowires was grown by the use of InSb substrates in a torch sealed quartz tube at a temperature of 400 °C, using a 60 nm size gold colloid catalyst. The typical diameter of the InSb nanowires was 80–200 nm and they consisted of nearly equal atomic percent of In and Sb. Transmission electron microscopy showed the wires to be single crystal, with a growth direction of 〈1 1 0〉.

Molecular beam epitaxial growth of indium antimonide and its characterization

Indium antimonide (InSb) is a promising material for mid- and long-wavelength infrared device applications. However, because of material’s small band gap and low melting point, reproducibility of high quality epitaxial InSb is difficult to obtain. This article reports growth experimentations for determining suitable conditions for growing InSb on InSb(100) substrate using solid source molecular beam epitaxy. The effects of growth temperature and antimony/indium (Sb∕In) flux ratio on epilayer structure, surface roughness, and electronic properties were investigated. The process of oxide desorption observed from reflection high energy electron diffraction pattern is reported. A three-layer model was used to extract the electronic properties of the epilayer, taking into account the effect of parallel conduction. Process conditions for good structural and electronic properties of the InSb epilayer, which includes substrate temperature and flux ratio, have been established in this study and reported herein.

Molecular beam epitaxy grown In1−xAlxSb∕InSb structures for infrared detectors

The core of SCD’s present day focal plane array (FPA) technology is a two-dimensional array of InSb photodiodes. It is produced by ion implantation and is attached to a silicon focal plane processor by indium bumps. We have extended this technology with In1−xAlxSb (0&amp;lt;x&amp;lt;0.03) alloys grown by molecular beam epitaxy on InSb substrates, utilizing a p-i-n structure. The advantages of the grown structures over those fabricated by implantation are already demonstrated in 320×256 element FPAs based on epitaxial InSb mesa diodes. These FPAs have dark currents at 100K comparable to those of implanted FPAs at 77K, with an operability (fraction of working diodes) in excess of 99.5%, and with a residual non-uniformity (RNU) at 100K of less than 0.03% (standard deviation/dynamic range) after a two-point non-uniformity correction (NUC). The RNU remains very low (&amp;lt;0.1%) even when the FPA temperature is shifted by as much as 10K from the NUC temperature. The average dark current at 100K and also the width of its distribution are further reduced by increasing the Al concentration in the FPAs by up to 3%, in accordance with the increase in the alloy energy gap. This has enabled us to achieve high quality thermal images at even higher temperatures than in the binary InSb FPAs. A key issue in achieving highly uniform FPAs is the degree of control of the InAlSb composition, misfit strain relaxation, and defect density. A series of In1−xAlxSb layers with x up to 6% was grown in order to study the effect of the growth conditions on these features. We discuss our results in terms of the misfit strain relaxation mechanisms in the In1−xAlxSb structures including dislocations, tilt, microcracks, and morphological crosshatch patterns.

High-mobility InSb epitaxial films grown on a GaAs (001) substrate using liquid-phase epitaxy

The growth of epitaxial InSb layers on highly lattice-mismatched semi-insulating GaAs substrates has been achieved via traditional liquid-phase epitaxy. Scanning and transmission electron microscopy show sharp interfaces even at 35 nm resolution. High-resolution x-ray diffraction studies reveal reflections even up to 2θ=153° with distinct layer and substrate peaks, indicating structural coherence. The films grown were n type and the highest electron mobility obtained was 3.96×104 cm2/V s at room temperature. The band gap varies from 0.17 to 0.23 eV in the temperature range of 300–10 K and is consistent with the expected variation. These results indicate that the films grown are comparable to those grown by other sophisticated techniques in terms of structural, optical and electrical properties.

Growth of InSb epitaxial layers on GaAs (0 0 1) substrates by LPE and their characterizations

The growth of epitaxial InSb layers on highly lattice mismatched GaAs substrates has been successfully achieved via the traditional liquid phase epitaxy. Details about nucleation, growth and optimization have been dealt with. High-resolution X-ray diffraction studies on the epilayers reveal all reflections with distinct layer and substrate peaks even up to a highest scattering angle of 153°. However, the layer peaks are considerably broader, indicating extensive dislocations. The average dislocation density was estimated from the Full-width at half-maximum of symmetric reflection. The grown films were n-type and the typical value of the sheet carrier density at 80 K obtained for these samples was 6.12×10 15/cm 2. The Hall mobility at 80 K was 7.058×10 3 cm 2/ Vs . The room-temperature band gap was determined to be 0.198 eV. Raman scattering measurements have also been performed to characterize the grown epilayers.

Twinned InSb molecular layer on Si([formula omitted]) substrate

We studied the formation of a twinned InSb molecular layer on Si(111) substrate (epitaxial relation InSb[112]∥Si[110]) by depositing 1-ML Sb on Si(111)–In(4×1) reconstruction at 210°C, using reflection high-energy electron diffraction, X-ray photoelectron spectroscopy and Auger electron spectroscopy. Sb adsorption replaces Si–In bonds in the In(4×1) reconstruction and forms Si–Sb bonds. Codeposition of In and Sb on the Si(111)-7×7 surface results in the formation of an InSb film with no twin (epitaxial relation InSb[110]∥Si[110]). Annealing this twinned InSb layer above 350°C resulted in the formation of Si(111)–Sb(3×3) structure, and the coalescence of most of the In. However, direct Sb deposition on Si(111)-7×7 at 350°C results in only disordered phase. Softening of the Si/Sb interface by the Si–In and In–Sb reactions is proposed to be responsible for the formation of the InSb twinned layer (at 210°C) and 3×3 structure by Sb (at 350°C).

Sb adsorption on Si(1 1 1)–In(4 × 1) surface phase

We studied the formation of first InSb molecular layer on the Si(111) substrate by depositing about 1ml of Sb on In(4×1) reconstruction in the temperature range 170–350°C, using reflection high-energy electron diffraction (RHEED) and auger electron spectroscopy (AES). The element Sb deposition at 210°C resulted in the formation of an epitaxial InSb molecular layer (not psudomorphic). This surface showed a weak 1×1 RHEED pattern with a ‘dramatic rotation’ of the surface layer with respect to the Si substrate. At this temperature, the deposited Sb atoms do not replace the Si–In bonds. However, Sb deposition above 250°C resulted in the replacement of In-layer by Sb atoms. Subsequently Sb formed various well-ordered reconstructions, which are highly sensitive to the deposition conditions. 1ml Sb deposition on In(4×1) reconstruction at 260, 300 and 350°C formed 2×1, 2×2 and √3×√3 structures, respectively. All these surface phases produced very sharp RHEED patterns indicating the long-range order. For Sb depositions above 300°C, AES results showed negligible In presence on the Si surface, suggesting the coalescence of In reconstruction by the adsorbed Sb. This replacement reaction drastically changes the bonding nature of the Si surface, which explains the role played by the In(4×1) reconstruction for the InSb growth on Si(111) substrate.

Carbon doping of InSb using CBr4 during growth by gas-source molecular beam epitaxy

Carbon doping of epitaxial InSb films grown by gas-source molecular beam epitaxy was studied using carbon tetrabromide as the carbon dopant source. Carbon was found to be a p-type dopant in InSb, yielding the highest as-grown acceptor concentrations to date, up to mid 1020 cm−3 as deposited. Room temperature mobilities ranged from 35 to 90 cm2/V s depending upon doping level. The hole concentration was found to be relatively insensitive to growth temperature between 325 and 400 °C. Higher growth temperatures required higher Sb fluxes in order to maintain a constant hole concentration. Hole concentration increased linearly with increasing CBr4 up to 5×1020 cm−3. Further increase in the dopant flow reduced the hole concentration and mobility and produced polycrystalline material.