InSb Films Research Articles

Annealing effect of vacuum evaporated InSb thin films

A method of single-source vacuum evaporation for preparing InSb thin films, having high electron mobilities onto glass substrates is studied. Electron mobilities of 6500 cm 2 /Vs in the 1.7μm thick InSb film is obtained by single-source vacuum evaporation followed by capped annealing. The effects of the source temperature, the substrate temperature and the post annealing conditions on electrical and crystal properties of the deposited films are discussed.

Photoconductivity of InSb/GaAs heterostructures at low temperature

We have studied the low-temperature coplanar photoconductivity under pulsed and continuous illumination of n-InSb/GaAs heterostructures grown by metalorganic magnetron sputtering. The large lattice mismatch and the large difference in band gaps give rise respectively to a highly defective region at the interface and a high built-in field. The effect of these factors on the photoconductivity is then a function of the InSb film thickness. For photon energies above the InSb band gap, up to about 0.4 eV, we observe positive photoconductivity due to an increase in the electron density coupled with trapping of the excess minority carriers. As the film thickness is decreased from 2 to 0.2 μm, the photoconductivity gain per absorbed photon decreases and the decay time increases, indicating the presence of trapping or recombination centers near the interface. Illumination with photons of energy greater than 0.4 eV leads to the coexistence of a positive photoconductivity and a very slow transient negative photoconductivity which gives rise to high gains at low modulation frequencies. The negative photoconductivity increases with increasing photon energy and decreasing film thickness. Illumination at 0.9 eV from both sides of the heterostructure shows that the effect is related to diffusion and trapping of hot electrons at the interface. The onset of the saturation of the effect indicates a concentration of electron traps of about 1014 cm−2 at the interface, a value similar to the concentration of edge-type dislocations that predominantly accommodate the lattice mismatch in this heterostructure.

Incoherent transmissivity and reflectivity of an absorbing-plane plate or layer with linear variations in thickness

The normal-incidence transmissivity and reflectivities (front and back) for the incoherent case are calculated for an absorbing-plane sample with linear variation of the thickness. Closed-form expressions for the direct determination of the energy (intensity) coefficients of a free-standing sample and of a film on a transparent substrate are given. The results are illustrated with the simulated infrared spectra of semiconductor InSb films of different thicknesses.

Optical Characterization and Mapping of Four INCH InSb Epitaxial thin Films Grown on GaAs by Turbo Disk Metalorganic Chemical Vapor Deposition

ABSTRACTA large number of 4 inch (100 mm) diameter 1–2 μm thick InSb films have been grown on GaAs by low pressure metalorganic chemical vapor deposition (MOCVD) turbo disk technology. Raman scattering microscopy was used to study the effects of III-V source ratios on the film crystalline quality and to optimize the growth parameters. Multi-point Raman measurements over the entire 4” wafer were performed to exhibit the uniformity distribution of the film crystalline quality. A FTIR reflectance mapping system has been established to map the film thickness distribution. Good uniformity of the film thickness and crystalline perfection was obtained. Raman and FTIR are showing useful tools for non-destructive characterization of large area wafers for industrial mass production.

Ellipsometric and thermoreflectance spectra of epitaxial InSb films.

We have measured spectroscopic-ellipsometry (SE) and thermoreflectance (TR) spectra of epitaxial InSb film sputter-deposited on a (0001) sapphire substrate in the 1.5--5.5-eV photon-energy range at room temperature. These data are analyzed on the basis of a simplified model of the interband transitions. Results are in satisfactory agreement with the experimental data over the entire range of photon energies. The finding definitely links the temperature-induced change in the dielectric function (TR) to the first derivative of the unperturbed dielectric function (SE). The importance of the fractional coefficients \ensuremath{\alpha} and \ensuremath{\beta} has also been demonstrated for a reliable interpretation of the observed TR line shapes.

Low pressure chemical vapor deposition of InSb using neopentylstibine and trimethylindium

Low pressure chemical vapor deposition of InSb using neo-pentylstibine and trimethylindium has been studied with x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy, Raman spectroscopy, and scanning electron microscopy (SEM). At 600 K, the InSb film with an In:Sb atomic ratio of 1 and a growth rate of ∼2 Å/min was formed on GaAs(110). The binding energies of the In and Sb 3d5/2 XPS peaks are in excellent agreement with those taken from InSb single crystal and amorphous samples. The He(II) ultraviolet photoelectron spectrum also agrees reasonably well with photoemission spectra taken from InSb using different photon beam sources. The corresponding Raman spectrum showed two phonon peaks at 179 (TO) and 190 (LO) cm−1, respectively, which are virtually identical to the Raman data reported for InSb single crystal samples. The XPS measurements suggested a three-dimensional growth mechanism for the InSb film on GaAs(110), which was confirmed by the SEM measurement. However, at ∼800 Å thickness, the SEM picture showed a very smooth InSb film, with the presence of some uncovered holes corresponding to ∼3% of the total surface area. The substrate temperature effect on the film growth was also investigated. At temperatures below 400 K, film growth was very slow and the decomposition of NpSbH2 and TMIn seemed to be incomplete, whereas above 800 K, metal droplets were clearly visible by SEM. The optimal growth temperature lies at approximately 600–700 K.

Thin InSb films—A candidate for multiple recording

Thin In46Sb54 films were prepared on glass substrates via flash evaporation. Films of 1000 Å were deposited at room temperature. After 7 min of thermal annealing at 450 °C, an average grain size increased from 20 to 200 nm. Under exposure to Fraunhofer diffracted pulsed Nd-YAG laser beam, the films exhibited different microstructures for different applied laser powers. Five regions were basically identified, i.e., ablation region, regions with grain sizes less than 20 nm, grain sizes ranging from 400 to 1000 nm, grain sizes ranging from 200 to 400 nm, and an unchanged region. The previous five regions were counted from the center of the exposed area outward. The pulse duration was 16 ns. Also, an atomic migration mechanism was proposed which accounts for the power dependent microstructural changes. Transmission electron microscopy was primarily used in characterizing the films. This type of phase transformation could find potential application in the phase change multiple recording.

Effect of phonon scattering on free-carrier absorption in n-type indium antimonide films

The free-carrier absorption in n-type InSb films has been investigated for carriers confined in quasi-two-dimensional (2D) semiconductors with the nonparabolic energy band of electrons. We discuss the effect of phonon scattering on the free-carrier absorption coefficient (α) for both deformation-potential coupling and piezoelectric coupling. α is found to depend on the photon polarization relative to the direction normal to the quasi-2D structure, the photon frequency, the film thickness, and the temperature. α could be complex due to the interaction between photons, phonons, and electrons. (i) When the acoustic phonon scattering is dominant, α increases with decreasing the film thickness for phonons polarized parallel or perpendicular to the layer plane. It is also shown that α increases with decreasing photon frequency and increasing temperature for photons polarized parallel to the layer plane, while for photons polarized perpendicular to the layer plane the α temperature-dependence is more complicated. (ii) If the piezoelectric scattering is dominant, α is also decreasing with increasing the film thickness for photons polarized parallel or perpendicular to the layer plane. But α decreases with increasing temperature for photons polarized perpendicular to the layer plane. Moreover, numerical results for the parallel polarization are much smaller than those for the perpendicular polarization.

Effect of the Introduction of a MBE Buffer Layer on the Morphology of InSb Almbe Layers Grown on InP Substrates

ABSTRACTIn this paper we report on the morphology of InSb layers grown by atomic layer molecular beam epitaxy (ALMBE) onto InP substrates at low temperatures (330<T<400°C), comparing the nature and densities of defects with those found in ALMBE InSb films grown over InSb/InP buffer layers grown by molecular beam epitaxy (MBE). The main types of defects for ALMBE direct layers are threading dislocations and stacking faults with similar defect densities along both á110ñ directions. The inclusion of the intermediate InSb/InP MBE grown buffer layers leads to lower threading dislocation densities but higher and anisotropic stacking fault distribution. Moreover, different types of three-dimensional defects appear, which are associated with pyramidal or truncated pyramidal hillocks on the surface. These defects, consisting in twins associations are originated at the InSb/InP MBE interface and they are induced by an anomalous growth of InSb layers. In all the cases, the strain caused by the large lattice mismatch is accommodated by means of a pure edge-type misfit dislocation network placed at the interface.

Self-diffusion in polycrystalline InSb films

In the present paper self-diffusion of indium and antimony is studied in polycrystalline InSb films by the neutron activation tracer scanning method. Grain boundary diffusion parameters are evaluated in the temperature range 200 to 400 degrees C. The pre-exponential factor and activation energy for indium self-diffusion are 1.17*10-10 m2 s-1 and 0.84 eV respectively. For antimony self-diffusion these parameters are 1.32*10-8 m2 s-1 and 1.11 eV. Both indium and antimony atoms diffuse via grain boundaries in the temperature range studied. The grain boundary energy and its temperature dependence are also reported.

Spectroscopic-Ellipsometry and Thermoreflectance Spectra of Sputter-Deposited InSb Films

Spectroscopic-ellipsometry (SE) and thermoreflectance (TR) spectra of InSb films sputter-deposited on sapphire substrates are reported. Measurements are made on the same crystal in the 1.5–5.5-eV photon energy range at room temperature. These data are analyzed on the basis of a simplified model of the interband transitions. Results are in satisfactory agreement with the experimental data over the entire range of photon energies. The finding definitely links the temperature-induced change in the dielectric function (TR) to the first derivative of the dielectric function (SE).

Polarity propagation in the InSb/ alpha -Sn/InSb heterostructure.

Films of InSb{111}A,B grown on \ensuremath{\alpha}-Sn(111)/InSb{111}A,B by molecular beam epitaxy behave as if the polarity of their surfaces could receive that of the initial InSb substrates. InSb on \ensuremath{\alpha}-Sn(111)/InSb(111)B alternates the surface polarity with \ensuremath{\alpha}-Sn thickness. Below 5 bilayers (BL) \ensuremath{\alpha}-Sn, the growing InSb exhibits the B type of surface composed of Sb and beyond 5 BL it changes toward the A type. This is due to Sb segregation from the initial InSb(111)B substrate to the \ensuremath{\alpha}-Sn surface. On the other hand, InSb on \ensuremath{\alpha}-Sn(111)/InSb(111)A always grows with the A-type surface via formation of the intermixing layers of (${\mathrm{In}}_{\mathit{x}}$${\mathrm{Sn}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$)Sb, decreasing the value of x with increasing InSb thickness.

InSb films for magnetic sensors

InSb films are prepared by a source-temperature-programmed evaporation method and hot-wire recrystallization method for Hall elements and magnetoresistance (MR) elements, respectively, to reduce imperfections of the crystal structure, and their crystalline and electrical properties are studied. An optimum source-temperature programme is investigated and the films thus prepared are used for Hall elements. An X-ray analysis of the film shows a high degree of stoichiometry. Magnetically sensitive InSb films have been prepared by hot-wire recrystallization. A room-temperature MR value of Δ R/R o = 155 %/T was obtained at 1 T with a length to width ratio ( l/w) = 0.4. Samples have been prepared by sequential deposition of In, InSb, and SiO onto unheated mica substrates.

Growth of high mobility InSb by metalorganic chemical vapor deposition

Thin films of InSb have been grown on insulating GaAs substrates using the metalorganic chemical vapor deposition technique with trimethyl indium and trimethyl antimony as reactants. We find that the mobilities obtained are usually low unless indium is predeposited onto the substrate. This indium predeposition technique greatly improves the yield of InSb films with mobilities of ~50000 crn2V−1S−1 at room temperature and a typical thickness of 2 microns. With this predeposition technique, the electron mobilities of these films become relatively independent of the vapor stroichiometry during growth and of the growth temperature. The electron mobilities are also very uniform across a wafer. These properties are obtained even when the film growth rate exceeds 2 μm/h.

無電解めっきによるインジウム‐アンチモン合金薄膜の形成

The elctroless plating of In-Sb alloy films on an alumina substrate was achieved with a bath using titanium trichloride as the reducing agent. The stoichiometric ratio of indium and antimony in deposits depended mainly on the concentration ratio of the antimony trichloride to the indium trichloride in the bath and on plating conditions, especially the pH.Stoichiometric In-Sb films were produced from a solution containing 0.08M indium trichloride, 0.0002M antimony trichloride, 0.34M trisodium citrate, 0.14M trisodium nitrilotriacetate, 0.04M titanium trichloride, and sodium carbonate for pH control, under the conditions of pH 8.6, 7.8, and 7.2, corresponding to bath temperatures of 50°C, 60°C and 70°C. The resulting deposits were polycrystalline films of InSb (111), (220), and (311), which had Hall mobilities of 2.5∼4.2×103cm2/V·s, which are nearly identical to those of InSb films which have been vacuumdeposited on an alumina substrate.

TEM Study of MOCVD Grown InSb/GaAs Heterostructures with and without TMIn Predeposited Layers

ABSTRACTHigh quality InSb epilayers were grown on GaAs substrates by metal organic chemical vapor deposition using a two-step growth procedure involving trimethal indium (TMIn) predeposition. From transmission electron microscopy studies, we found that an interdiffusion layer of thickness of 10 Å forms at the interface when the substrate is exposed to TMIn for approximately 6 secs prior to the growth of the InSb filns. Hall mobilities up to σ 52,000 cm2/V-s were obtained at 300 K on a 2.1-μm-thick InSb heteroepitaxial film. In contrast, samples without TMIn predeposition showed polycrystallinity of the InSb films grown on single crystalline GaAs substrates. The effect. of TMNIn predeposition is to minimize the misorientation of the grains, suppress the polycrystallinity, decrease the density of threading dislocations, and increase the electron mobilities in the films. However, we found that too much TMIn predeposition gives rise t.o an intermixing layer at the InSb/GaAs interface which deteriorates the film quality. Details of the effect of the TMIn predeposition on the microstructure of InSb/GaAs with different predeposition times (zero, 6, and 12 secs) are discussed.

Sb as an indium-absorptive barrier in ZnSe/InP(100) heterostructures

Antimony layers, sandwiched between a ZnSe/InP(100) heterostructure interface, can be used as a barrier preventing outdiffusion of In into ZnSe epilayers. Through core level photoemission spectroscopy and reflection high-energy electron diffraction investigations, we found that the Sb layer must be annealed in order to prevent In outdiffusion. Barrier action occurs by means of InSb formation. A single pseudomorphic monolayer was insufficient to prevent In from outdiffusing. A thicker Sb layer greatly reduced In outdiffusion but through misfit dislocation the initially strained InSb film relaxed to its bulk lattice constant and did not allow for subsequent pseudomorphic epitaxy of strained ZnSe overlayers.

Transport properties in n-type InSb films grown by metalorganic chemical vapor deposition

We have measured the temperature and magnetic field dependence of the Hall mobility and transverse magnetoresistance in n-type InSb films epitaxially grown on GaAs substrates by metalorganic chemical vapor deposition. The films show a giant magnetoresistance: e.g., at 240 K the resistivity increases over 20 times at a magnetic field of 5 T; the low field coefficient of resistivity at 77 K is as high as 47.5 μΩ cm/G. The Hall mobility decreases with magnetic field and saturates at higher fields. By taking the interface carrier transport into account, the observed field dependence of the Hall mobility and magnetoresistance may be understood based on a two-layer model.

Growth of In1−xTlxSb, a new infrared material, by low-pressure metalorganic chemical vapor deposition

We report the growth of In1−xTlxSb, a new III-V alloy for long-wavelength infrared detector applications, by low-pressure metalorganic chemical vapor deposition. In1−xTlxSb with good surface morphology was obtained on both GaAs and InSb substrates at a growth temperature of 455 °C. X-ray diffraction measurements showed resolved peaks of In1−xTlxSb and InSb films. Infrared absorption spectrum of In1−xTlxSb showed a shift toward lower energies compared to InSb spectrum. Hall mobility data on In1−xTlxSb/InSb/GaAs structure showed enhanced mobility at low temperatures compared to InSb/GaAs structure.

Temperature fluctuations during the deposition of InSb films

High-quality InSb films must be grown through the melting-solidification process. A fluctuation of the film temperature, especially in the early stages of the evaporation process gives rise to this melting-solidification process. The shape of the temperature fluctuation curves can be explained by the variation of deposition rate during the evaporation process. It was found that the fluctuation of the film temperature was closely related to the maximum value of the deposition rate. The optimum fluctuation curve of film temperature was established by selecting a suitable value of the maximum deposition rate. The maximum deposition rate of around 50 Hz/s gives the optimum fluctuation curve, which causes a large area of black spots. The effectiveness of the sensing position of the substrate temperature on the fluctuation of film temperature is also investigated.