InSb Films Research Articles

Study on the dependence of electrical properties on dislocation levels in InSb films vacuum deposited on glass

The absorption coefficient, as a function of photon energy, of vacuum-deposited indium antimonide (InSb) films on a glass substrate produced by varying the evaporation source material temperature and flash evaporation time interval was determined with Kramers–Kronig analysis developed by Roessler [D. M. Roessler, Br. J. Appl. Phys. 16, 1119 (1965)]. The absorption coefficients can be determined by the analysis without restriction due to a glass substrate which is opaque to below around 0.31 eV of infrared rays (InSb band gap around 0.2 eV is in this opaque region) because the analysis can determine the coefficients from only reflectance data without transmittance data of the film. Therefore, the analysis was conducted with measured reflectance of the films at room temperature. Results of the analysis showed that dislocation levels, which are in good agreement with both the Read and Broudy models for In and Sb dislocations, exist in the films. The Hall coefficient and Hall mobility of the films at room temperature decrease with an increase of the number of transitions between levels, such as transitions from the valence band to a dislocation level, from a dislocation level to any other dislocation level, and from a dislocation level to the conduction band. Deposition conditions for producing high-quality InSb film should be given so that the generation of dislocation levels is suppressed or eliminated from the results. From the above analytical results, the analysis may give more detailed information, such as peaks that correspond to the energy of carrier transitions in the absorption coefficient as a function of photon energy, in comparison with a method of straight determination of the transition energies from only reflectance or transmittance data. Other wide applications of this analytical method are expected.

Effect of substrate temperature on the growth rate and surface morphology of heteroepitaxial indium antimonide layers grown on (100) GaAs by metalorganic magnetron sputtering

The effect of substrate temperature and III/V ratio on the growth rate and surface morphology of heteroepitaxial InSb films grown on GaAs(100) using metalorganic magnetron sputtering has been studied. The surface morphology showed a strong dependence on growth temperature and III/V ratio. Films with ‘‘mirrorlike’’ surfaces could be routinely obtained for deposition temperatures near 400 °C. For films grown above 300 °C, the growth rate increased with increasing trimethylindium flow, at constant antimony sputter power, and exhibited a peak near 400 °C. In this region the growth rate was thermally activated with an observed activation energy of 0.24 eV. Above 400 °C the growth rate decreased with increasing temperature. The surface morphology of these higher-temperature layers indicated a selective etching process as the mechanism for growth rate reduction. Cross-sectional transmission electron microscopy studies indicated a defect density in excess of 1011 cm−2 at the InSb/GaAs interface which decreased to 4.0×109 cm−2 at a distance of 0.3 μm from the interface.

Raman Characterization of InSb/GaAs Grown by Metalorganic Magnetron Sputtering

AbstractThe new technique of metalorganic magnetron sputtering (MOMS) produces high-quality (100) epitaxial InSb films on (100) GaAs substrates, despite the large 14.6% lattice mismatch between InSb and GaAs. We have used Raman scattering to examine MOMS-grown InSb films of thicknesses 0.17 - 2.67 µm, and commercial bulk InSb. We observe the longitudinal optical (LO) phonon peak, and the second order 2LO peak, which is enhanced by outgoing resonance with the E1 + Δ1, gap of InSb. The half-widths and intensities of these bands are related to sample quality as a function of film thickness and to the role of biaxial stress in the InSb film.

An estimation of the impurities causing n- to p-type inversion of conduction in thin InSb films on mica substrates

The 0.1–0.9-μm-thick thin InSb films were prepared on mica substrates by evaporation of InSb to obtain highly sensitive magnetoresistance elements. It was observed that films thinner than 0.15 μm show p-type conduction while films thicker than 0.2 μm show n-type conduction in the extrinsic temperature range. It was also observed that the film, thinned from 0.3 to 0.1 μm by etching from the surface side, showed p-type conduction. The cause of these phenomena was investigated using a secondary ion mass spectroscopy in-depth analysis. It was observed that K, Al, Si and O atoms, constituents of mica substrates, diffused into InSb films from mica substrates. In these atoms, it was estimated that K, Al, and Si atoms could act as acceptors in an InSb crystal contributing to the inversion of conduction type.

Electrical and Optical Characterization of InSb Grown on GaAs by MBE

AbstractInSb has been grown on semi-insulating GaAs substrates by molecular beam epitaxy. By growing an InSb buffer layer at 300 C prior to the main InSb layer growth at 420 C, the effect of the 14% lattice mismatch between GaAs and InSb was minimized. A typical 5 µrn InSb film had a room temperature carrier concentration and electron Hall mobility of 2 × 1016/cm3 and 6×104 cm2/Vs, respectively. At 77 K these values became 2 × 1015/cm3 and 1.1 ×105 cm2/Vs. Temperature dependent Hall measurements revealed a peak in the mobility at 85 K and 70 K for the 5 and 10 µm samples. Capacitance-voltage measurements using MIS capacitors produced 77 K carrier concentrations in agreement with the low fieldHall measurements. Carrier lifetimes were determined by photoconductive response measurements. Lifetimes of 20 ns and 50 ns were determined for the 5 and 10 µm films. For comparison, the carrier lifetime in bulk n-type InSb was found to be 200 ns. Optical characterization by room temperature IR transmission spectroscopy showed a broad absorption edge, with an absorption coefficient of 1.4 × 103/cm at a wavelength of 6 µm. Epilayer thickness was determined from observed interference fringes. Raman spectroscopy showed that each epitaxial layer had a spectrum equivalent to that of bulk InSb.

High Resolution Electron Microscopy Studies of MBE Grown InSb Layers on GaAs (100)

InSb films grown directly on (100) GaAs substrates by MBE have been examined in the transmission electron microscope. High quality, epitaxial layers were deposited despite the 14.6% lattice mismatch between film and substrate. Nearly all of the misfit strain has been accommodated by a square array of a/2{011} edge-type misfit dislocations spaced on average 29A apart. These defects are proposed to be spontaneously generated in the epitaxial layer almost as soon as it begins to grow, and are favoured over 60° type dislocations because they are more efficient at relieving misfit strain while allowing more coherent interface area to form. The films that have been produced have low defect densities (ie. threading dislocations and microtwins) considering the large lattice mismatch in this system. Antimony precipitates have been noted in some films, but can be totally eliminated by careful control of the In/Sb flux ratio. Finally we have observed that loss of Sb from the specimen surface leads to a gradual degradation of the InSb during TEM observation, leading to the appearance of surface indium or indium oxide.

Characterization of heteroepitaxial InSb films on GaAs prepared by metalorganic magnetron sputtering

Heteroepitaxial films of InSb on GaAs(100) have been grown by metalorganic magnetron sputtering. Cross-sectional transmission electron microscopy studies indicate that twins are the dominant defects occuring at the InSb-GaAs interface. X-ray diffraction measurements on films of different thicknesses, as well as large area electron channeling measurements, have shown that the density of twins decreases with distance away from the interface and appears to approach an equilibrium value for thicknesses greater than 3 μm.

Heteroepitaxy of InSb on silicon by metalorganic magnetron sputtering

Heteroepitaxial films of InSb have been deposited by metalorganic magnetron sputtering (MOMS) on 〈100〉 silicon substrates using molecular beam epitaxy (MBE) GaAs buffer layers. X-ray diffraction and cross-sectional transmission electron microscopy measurements indicate the epilayers to be structurally similar to layers deposited by MOMS and MBE on high quality GaAs substrates, despite the increased defect density of the GaAs buffer layer. Some of the defects within the buffer layer propagate into the InSb epilayer; however, the majority of defects arise from the lattice mismatch at the interfacial region.

Ultrahigh vacuum i n s i t u transmission electron microscopy observations of molecular-beam epitaxially grown InSb(111)

Ultrahigh vacuum in situ transmission electron microscopy has been used to investigate homoepitaxial growth processes and a 2×2 surface reconstruction of InSb(111) by molecular-beam epitaxy. When the incident fluxes (1:1) of Sb4 and In1 are impinged onto the substrate, the respective molecules form homoepitaxially grown InSb films, leaving an excess molecule Sb* which does not contribute to the formation of the InSb films. As a result, there exists a critical temperature (Th) for the condensation of Sb* molecules. Below Th, the surface concentration of Sb* (nSb*) becomes higher than a critical concentration for the condensation (ncSb*), so that two phases (InSb+Sb) grow in a polycrystalline state. However, above Th as nSb* becomes lower than ncSb*, InSb films grow with the 2×2 reconstructed surfaces. This critical temperature is defined as a homoepitaxial temperature. Quantitative interpretations of Th are discussed.

Enhancement of low temperature thermopower in high-resistivity films

We present measurements and calculations of the thermopower of amorphous Tl-Te and In-Sb films. The observed thermopower (even for films near the metal-semiconductor transition) shows a temperature-dependent enhancement in good agreement with the theoretical electron-phonon enhancement, which we calculate for Tl 90Te 10 and In 80Sb 20 using the Eliashberg function obtained from superconductivity data.

Materials developments for write-once and erasable phase-change optical recording

Stoichiometric amorphous films of InSb or GaSb are found to have very short (< 15 ns) crystallization times when heated to temperatures close to their melting point. They can be used for write-once amorphous to crystalline optical recording. By adding Te to InSb the crystallization time can be tuned so that erasable crystalline to amorphous optical recording is feasible with a 1-microm sized circular erase spot. Carrier-to-noise ratios of more than 50 dB are achievable at compact disk (CD) recording conditions. The erasable medium allows for CD - type run - length - !imited encoding at user bit densities of < 0.6 pm/bit.

Rapid crystallization of thin solid films

Laser-beam-controlled heating appears to be an excellent technique for driving isothermal transformations in a thin solid film on a thick substrate. The transformation is detected by the change in optical properties of the film as it evolves from the initial to the final state. Results are presented for the amorphous-to-crystalline transition in 100 nm thick films of InSb and of some Te alloys on thick glass substrates. Discrimination between interface growth and homogeneous crystallization can be made from the data. The crystallization of InSb films can be desribed by an Avrami equation with a single activation energy of 154 ± 6 kJ/mol over the full range of measured crystallization times between 100μs and 1000s. For low temperatures the results are consistent with differential scanning calorimetry (DSC) measurements. For Te-alloy films, the large temperature interval covered by the experimental method enables clear observation of the curvature of the temperature-time-transmission (T–t–t) plot.

Measurement of the Sound Velocity in AlAs by Picosecond Ultrasonics

AbstractPicosecond ultrasonics have been used to measure the sound velocity and index of refraction in a thin film of AlAs. The AlAs layer was grown by molecular-beam epitaxy on a buffer layer of GaAs which was deposited on a semi-insulating GaAs wafer. The AlAs film was capped by a thin layer of GaAs, and a very thin film of InSb. To generate a sound wave effectively a picosecond light pulse was absorbed in the InSb film. As the sound wave propagates through the microstructure it changes the optical properties in the various films, and this produces a change in the optical reflectivity, which is measured. From the round trip time of the acoustic wave we have determined the sound velocity in the AlAs film.

Microstructures of The Electron-Beam Evaporated InSb Thin Films

AbstractPolycrystalline InSb thin films have been prepared by the two-source electron-beam evaporation method. The InSb films have been grown on both pure Si (100) substrate and on Si (100) substrate which has been thermally oxidized to form a thin amorphous SiOx overlayer. The as-grown thin films have been heat treated under N2 atmosphere which is slightly mixed with air. A thin InOx layer is formed on the top surface of the thin film.After heat treatment, the InSb films grown on the oxidized Si substrate shows a preferred (111) orientation. While the films grown on Si substrate do not show such preferred orientation as evidenced by the X-ray diffraction patterns.The TEM cross sectional morphologies of the InSb film grown on oxidized Si substrate shows an ordered arrangement of the grains. While the film grown on the pure Si substrate shows a random arrangement of the grains. The film grown on the oxidized Si substrate also shows the existence of the twin boundary and an ordered arrangement of the precipitation of the second phase.

Structural and Electrical Characteristics of the Thermally Evaporated InSb Thin Films

AbstractPolycrystalline InSb thin films have been prepared by the two-source thermal co-evaporation method. The InSb films have been grown on both pure Si (100) substrate and on Si (100) substrate which has been thermally oxidized to form a thin amorphous SiOx overlayer. The as-grown films have been heat treated under N2 atmosphere at different temperatures ranged from 520 to 535 C. Both as-grown films have (220) diffraction as the main peak. The heat treated films which have high mobility values show the (111) preferred orientation. For the heat treated film on oxidized Si substrate, the TEM cross sectional morphologies show the existence of the precipitaion of the second phase and the interface diffusion of InSb into the SiOx layer.

The preparation of epitaxial InSb films by magnetron sputtering

InSb, with its narrow bandgap, has found application in a wide variety of infrared detector applications, ranging from infrared astronomy on the Galileo satellite to tactical weapon guidance systems. However, InSb also demonstrates an extremely high electron mobility, up to 1 000 000 cm2∙V−1∙s−1 at 77 K, which makes it of particular interest for very high-speed circuit applications. In the past, most multilayer InSb structures have been prepared by conventional crystal-growth techniques, including liquid-phase epitaxy, metalorganic chemical vapour deposition, and molecular-beam epitaxy. In this presentation, the preparation of thin epitaxial films of InSb by magnetron sputtering will be discussed. Using this technique, we have deposited good quality epitaxial InSb films on [Formula: see text] InSb and [Formula: see text] GaAs. In this study, the effects of substrate temperature and sputter pressure on film morphology, composition, and growth rate are examined. As well, preliminary measurement of the electrical characteristics of these layers and their crystal quality as determined by X-ray diffraction and large-area electron-channelling pattern analysis are presented.

Pulsed flash evaporation of InSb films

Pulsed flash evaporation of InSb films

The metal-semiconductor transition in amorphous InSb films

The metal-semiconductor transition takes place with the change of the substrate temperature T s in amorphous InSb films which is formed by the vapour deposition. Amorphous InSb behave as metallic behaviours for T s < 120 K, as semiconductive for T s > 120 K, superconductivity on one side of the metal was researched.

Photolytic Deposition of Insb Films

ABSTRACTFilms of InSb were deposited on GaAs &lt;100&gt; substrates at room temperature by excimer laser photolysis at 193 or 248 m of a mixture of trimethylindium (TMIn) and trimethylantimony (TMSb) in a hydrogen carrier medium. These films were compared to thermally grown MOCVD InSb films by optical microscopy and x-ray analysis and found to be stoichiometric polycrystalline, InSb. In situ UV absorption spectroscopy has been used for the first time on an MOCVD system to monitor and control the partial pressures of the metalorganic reactants during deposition. This latter diagnostic was found to be critically important since parasitic reactions cause depletion of TMIn during transport from the source bubbler to the growth chamber.

The structural and compositional characterization of InSb films prepared by metalorganic magnetron sputtering

Metalorganic magnetron sputtering has been used to deposit polycrystalline and homoepitaxial films of indium antimonide. In this technique a metal antimony target is magnetron sputtered in a reactive vapor of trimethylindium (TMI). Stoichiometric layers of indium antimonide could be deposited for all growth temperatures studied (20–370 °C). However, below 250 °C the films were either amorphous or composed of very small crystallites. Above 290 °C the layers were epitaxial as determined from the electron channeling patterns observed. For these layers the growth rate was controlled by the TMI flow with the excess antimony flux acting to stabilize the surface. The surface morphology was excellent with ‘‘mirrorlike’’ surfaces except at high TMI flows where indium surface droplets were formed.