Photosensitive Sb-n-InSb Schottky barrier diodes

The current–voltage and capacitance–voltage characteristics of Sb-n-InSb metal-semiconductor contacts with a Schottky barrier fabricated by pulsed laser deposition and subsequent thermal annealing were measured at 77 K. By comparing with the general theory for such contacts that takes into account the presence of a tunnel-transparent dielectric interfacial layer and surface states, all contact parameters were determined. The structures demonstrated large photosensitivity in the 3–5 μm spectral region and thus can be used for efficient, broadband, and fast photodetection in the mid-IR range.

Source:IOPscience

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PTCDA molecules on a KBr/InSb system: a low temperature STM study

We have used scanning tunnelling microscopy (STM) at 77 K to investigate 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) molecules adsorbed on an ultrathin (1–2 monolayer (ML)) film of KBr grown on a c(8 × 2)InSb(001) substrate. The molecules are stabilized both at the KBr steps and on the terraces. On the 1 ML film the PTCDA molecules appear predominantly as single entities, whereas on the 2 ML film formation of molecular clusters is preferred. Differences in the adsorption configurations indicate that the interaction between the molecules and the surface differs significantly for the cases of 1 and 2 ML films. We present images of the molecules obtained with sub-molecular resolution for both filled and empty state sampling modes. We argue that the highest occupied molecular orbital (the lowest unoccupied molecular orbital) is responsible for intramolecular contrast in filled (empty) state images of the molecules, even though they are deformed due to strong interaction with the substrate.

Source:IOPscience

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One-dimensional electron transport and thermopower in an individual InSb nanowire

We have measured the electrical conductance and thermopower of a single InSb nanowire in the temperature range from 5 to 340 K. Below temperature (T) 220 K, the conductance (G) shows a power-law dependence on T and the current (I)–voltage (V) curve follows a power-law dependence on V at large bias voltages. These features are the characteristics of one-dimensional Luttinger liquid (LL) transport. The thermopower (S) also shows linear temperature dependence for T below 220 K, in agreement with the theoretical prediction based on the LL model. Above 220 K, the power law and linear behaviours respectively in the G–T and S–T curves persist but with different slopes from those at low temperatures. The slope changes can be explained by a transition from a single-mode LL state to a multi-mode LL state.

Source:IOPscience

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Lateral n–i–p junctions formed in an InSb quantum well by bevel etching

We have used a novel, simple technique based on bevel etching, to fabricate samples containing lateral n–i–p junctions in an InSb/InAlSb quantum well. The structure was designed by self-consistent solution of Schrödinger's and Poisson's equations, and grown by molecular beam epitaxy on a SI GaAs substrate. Current/voltage characteristics were measured as a function of temperature between 10 and 80 K, and rectifying characteristics were obtained over the whole temperature range.

Source:IOPscience

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Epitaxial growth and electronic properties of few-layer stanene on InSb (1 1 1)

Stanene has been theoretically predicted to be a 2D topological insulator with a large band gap, potentially hosting quantum spin Hall effect at room temperature. Here, few-layer stanene films have been epitaxially grown on Sb-terminated InSb (1 1 1) surface and their structural and electrical properties are characterized. Scanning tunneling spectrum results reveal a large bulk bandgap in single-layer stanene (over 0.2 eV). Moreover, spectroscopy evidence for a filled edge state near the steps was observed. The gap decreases dramatically with increasing number of layers, and multilayer stanene should become a Dirac semimetal in the bulk limit. The changeover may involve nontrivial topological phase transitions. Clear and reproducible Shubnikov–de Haas oscillations were observed on the single-layer stanene films that were exposed to atmospheric conditions for an extended period of time, showing the possibility for device experiments using nanofabrication and magneto-transport. Our results demonstrate that the single-layer stanene is a promising topological material for exploring fundamental physics and quantum applications.

Source:IOPscience

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Raman Spectroscopy of the Damages Induced by Ar-Ion Beam Etching of InSb(100) Surface

The strong enhancement of forbidden TO mode on Ar ion beam-etched InSb(100) surfaces was examined by Raman spectroscopy. By raising the applied RF power in Ar-ion etching from 50 to 200 W, the integrated area ratio of ITO/ILO increased from 0.05 to 0.23 and the full width at half maximum of LO peak increased from 5.46 to 7.46 cm−1. Such increases are induced by the partly disordered structure deformed by bombarded Ar ions. Raman spectroscopy could investigate the microscopic damages of the crystalline structure leading to break the Raman selection rules.

Source:IOPscience

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Ion irradiation-induced polycrystalline InSb foam

InSb films with various thicknesses were deposited by magnetron sputtering on SiO2/Si substrates and subsequently irradiated with 17 MeV Au+7 ions. The structural and electronic changes induced by ion irradiation were investigated by synchrotron and laboratory based techniques. Ion irradiation of InSb transforms compact films (amorphous and polycrystalline) in open cell solid foams. The initial stages of porosity were investigated by transmission electron microscopy analysis and reveal the porous structure initiates as small spherical voids with approximately 3 nm in diameter. The evolution of porosity was investigated by scanning electron microscopy images, which show that film thickness increases up to 16 times with increasing irradiation fluence. Here we show that amorphous InSb films become polycrystalline foams upon irradiation with 17 MeV Au+7 ions at fluences above 1014 cm−2. The films attain a zincblende phase, with crystallites randomly oriented, similarly to the polycrystalline structure attained by thermal annealing of unirradiated films.

Source:IOPscience

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Electron transport lifetimes in InSb/Al1-x In x Sb quantum well 2DEGs

We report magnetotransport measurements of InSb/Al1-x In x Sb modulation doped quantum well (QW) structures and the extracted transport  and quantum  lifetime of carriers at low temperature  We consider conventional transport lifetimes over a range of samples with different doping levels and carrier densities, and deduce different transport regimes dependent on QW state filling calculated from self-consistent Schrödinger–Poisson modelling. For samples where only the lowest QW subband is occupied at electron densities of  cm−2 and  cm−2quantum lifetimes of  ps, and  ps are extracted from Shubnikov–de Haas oscillations below a magnetic field of  T. The extracted ratios of transport to quantum lifetimes,  and are similar to values reported in other binary QW two-dimensional electron gas systems, but are inconsistent with predictions from transport modelling which assumes that remote ionized donors are the dominant scattering mechanism. We find the low  ratio and the variation in transport mobility with carrier density cannot be explained by reasonable levels of background impurities or well width fluctuations. Thus, there is at least one additional scattering mechanism unaccounted for, most likely arising from structural defects.

Source:IOPscience

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Deep level transient spectroscopy measurements on heterostructure InSb/InAlSb diodes

Deep level transient spectroscopy (DLTS) measurements have been conducted on MBE-grown heterostructure InSb/In1−xAlxSb diodes. The measurements were conducted in the temperature range 10–130 K and two majority carrier (electron) traps, labelled E1 and E2, have been observed. A trap signature has been produced from the DLTS spectra for both traps. The activation energies determined from Arrhenius plots of the peak temperatures as a function of rate window for E1 and E2 were 17 meV and 79 meV, respectively. The apparent capture cross-sections and concentrations for E1 and E2 have also been measured.

Source:IOPscience

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PTCDA molecules on an InSb(001) surface studied with atomic force microscopy

PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) molecular structures assembled on an InSb(001) c(8 × 2) reconstructed surface have been studied using frequency modulated atomic force microscopy. The high-resolution imaging of the structures is possible through repulsive interactions, using the constant height scanning mode. During initial stages of growth the [110] diffusion channel dominates as indicated by formation of long PTCDA molecular chains parallel to the [110] crystallographic direction on the InSb surface. For a single monolayer coverage a wetting layer of PTCDA is formed. Finally it is shown that the PTCDA/InSb is a promising system for building molecular nanostructures by manipulation of single molecules with the AFM tip.

Source:IOPscience

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Gas mixture influence on the reactive ion etching of InSb in an inductively coupled methane-hydrogen plasma

In this paper, inductively coupled plasma etching of InSb material has been investigated using methane–hydrogen chemistry. Plasma conditions were first studied in terms of bias autopolarization, partial methane quantity in a CH4/H2 mixture and chamber pressure. The surface morphology of the etched samples was analyzed using an atomic force microscope, scanning electron microscope and x-ray photoelectron spectrometry (XPS) measurements. The results highlight the difficulties in removing etching products related to In, and the surface roughness is mainly correlated with the methane ratio in the mixture. The best surface stoichiometry, with a surface roughness of 7 nm and an etch rate of 110 nm min−1, was obtained with the addition of argon. To evaluate the feasibility of high performance infrared photodiodes, InSb monopixels were fabricated by dry etching, electrically characterized under illumination and compared with devices obtained by wet etching.

Source:IOPscience

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Strain energy of (111) and ([111 over bar]) surfaces of InSb

The strain energies per unit area of polished (0.1 μm powder) surfaces of InSb have been computed from the observed curvature of thin wafers polished on one side and etched on the other, as being of order 1 erg cm-2. These values are much larger than those computed by others from InSb wafers treated similarly on both sides and are ascribed only indirectly to surface bonding configurations.

Source:IOPscience

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Characterization of Al2O3/InSb/Si MOS diodes having various InSb thicknesses grown on Si(1 1 1) substrates

This paper discusses the capacitance–voltage (C–V) characteristics of Al2O3/InSb/Si (1 1 1) MOS diodes grown using MBE via InSb bi-layer with special care to the surface reconstruction. This growth technique is based on our finding that the InSb layer grown on a Si (1 1 1) substrate is rotated by 30° with respect to the substrate under certain initial conditions. This rotation drastically reduces the lattice mismatch from 19.3% to 3.3%, and improves the crystal quality of an InSb layer. To investigate the possibilities of InSb MOSFETs on Si substrates, we fabricated MOS diodes having an Al2O3 insulator film deposited by atomic layer deposition. C–V characteristics were measured both at RT and 77 K. It was found that the InSb grown on Si shows a degraded C–V curve compared to the InSb substrate, even though the mobility of the grown layer is quite high. We also investigated the effects of InSb thickness on the C–V characteristics of the MOSFETs. It was found that the quality of MOS diodes first degrades when decreasing the InSb thickness from 1 μm to 50 nm; further reduction of the InSb thickness improves it again. It was demonstrated that the MOS diode having a 10 nm InSb layer shows a good C–V curve, which is comparable to that of the InSb substrate. Finally, we discussed the possibility of the InSb/Si pseudomorphic MOSFETs.

Source:IOPscience

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Strain energy of (111) and ([111 over bar]) surfaces of InSb

The strain energies per unit area of polished (0.1 μm powder) surfaces of InSb have been computed from the observed curvature of thin wafers polished on one side and etched on the other, as being of order 1 erg cm-2. These values are much larger than those computed by others from InSb wafers treated similarly on both sides and are ascribed only indirectly to surface bonding configurations.

Source:IOPscience

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