Epitaxial InSb Research Articles

Microstructure of Pyramidal Defects in InSb Layers Grown by Atomic Layer Molecular Beam Epitaxy on InP Substrates

We report on the structural characterization of epitaxial Insb films grown on InP substrates by atomic layer molecular beam epitaxy at relatively low temperatures (330 °C < T < 400 °C). Moreover, we study the effect of the introduction of an interme- diate Insb/InP buffer layer grown by molecular beam epitaxy. The studies were carried out by TEM and HRTEM, to investigate the densities and nature of the defects and the accommoda- tion mechanism between the two types of layers which have a large lattice mismatch (10.4%). Results show a high defect density at the interface vicinity whatever the growth method em- ployed, with or without buffer layers, but better quality layers are obtained as growth proceeds. The prevailing type of defects are threading dislocations and stacking faults for both types of samples, but the introduction of the intermediate layers leads to the formation of two types of complex three-dimensional defects, consisting m crystal misorientations, that induce an anoma- lous growth of the Insb layer leading to different growth rates and the formation of pyramidal or truncated pyramidal hillocks on the surface. In this case scanning electron microscopy and Raman analysis were also performed to study the influence of the defects on surface morphology and confirm their structure. Moreover, anisotropy of the stacking fault distribution is noticed in this sample: the density for (l10)-(ill)A slip planes is higher than for the (l10)-(ill)B slip planes. Strain due to large lattice mismatch is relieved m both types of samples by the

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.

Surface Fermi level pinning in epitaxial InSb studied by electric-field-induced Raman scattering

Electric-field-induced Raman scattering by longitudinal optical (LO) phonons has been used to study the surface Fermi level position in InSb layers grown by molecular beam epitaxy on (100) GaAs. From the analysis of a variety of layers it is found that the LO phonon scattering intensity, relative to that of intrinsic two-LO phonon scattering, decreases with increasing optical power density in n-type samples, but remains constant in p-type and undoped layers, which are residual p type. The power dependence of the relative LO phonon intensity for n-type doping is shown to be caused by a surface electric field, the strength of which is reduced upon increasing illumination due to screening by photogenerated carriers. As this effect is only found in n-type layers, we conclude that the surface Fermi level is pinned at the valence band thus giving rise to a sizeable surface electric field in n-type but not in p-type material.

Flash evaporation of InSb on i-GaAs substrates

Preliminary results of the investigations of the use of the flash evaporation method for obtaining epitaxial InSb films on GaAs substrates are presented. The composition of the vapour stream during the evaporations was controlled by a quadrupole mass spectrometer. The quality of the obtained films has been assessed by X-ray and Hall effect investigations. It is shown that the method can effectively be used for the preparation of high quality epitaxial InSb films only if the chemical composition of the vapour stream is carefully controlled. The most uniform vapour stream can be obtained when several InSb grains, being in various vaporization stages, evaporate simultaneously from the source. The evaporation source should be kept at the maximum possible temperature in order to obtain a maximum concentration of monoatomic antimony molecules in the vapour stream.

Samarium doping of molecular-beam epitaxially grown InSb on InP

We report here on the transport properties epitaxial InSb films grown by molecular-beam epitaxy and doped with Sm in the atom density range from 6.1×1016 cm−3 to 3.2×1018 cm−3 at temperatures between 40 and 400 K. Sm is a donor for InSb. The samples were grown at a flux ratio Sb/In=1.07±0.03. For Sm concentrations below 5×1017 cm−3, 25 atoms of Sm give one extrinsic electron. Samples grown with higher Sm concentrations have extrinsic electron densities around 1×1017 cm−3. At low temperatures (T&amp;lt;150 K), the electron mobility increases with doping concentration up to rare-earth densities of 3×1017 cm−3; at higher rare-earth concentrations, the mobility decreases again. At room temperature, the mobility decreases monotonically with increasing Sm concentration. Very similar results are observed on InSb films doped with Er. We point out that impurity charge ordering was invoked to explain similar observations made on HgSe:Fe.

Optical properties of InSb films deposited on sapphire substrates by rf sputtering

We have deposited InSb films by rf sputtering on sapphire substrates of various surface orientations [(0001), (112̄0), (011̄2), and (011̄0)]. The epitaxial InSb(111) films are grown only on (0001) sapphire substrates at substrate temperatures 280–320 °C, while the films deposited on (112̄0), (011̄2), and (011̄0) sapphires show that they have polycrystalline structures even when they were deposited at high substrate temperatures. Optical properties of these films are investigated by using spectroscopic ellipsometry. A linear regression analysis and a Bruggeman effective-medium approximation reveal that the epitaxial film has a few void networks in the film. Polycrystalline InSb films, on the other hand, contain a large number of void networks deep in the film medium. Both epitaxial and polycrystalline films have rough-surface overlayers of a few tens of Å.

Resonance Raman scattering from epitaxial InSb films grown by metalorganic magnetron sputtering

We have examined epitaxial InSb films by Raman scattering for the first time. The films, 0.17–2.67 μm thick, were grown on (100) GaAs substrates by the new technique of metalorganic magnetron sputtering. We observe the first and second order longitudinal optical phonon peaks, the latter enhanced by outgoing resonance with the E1+Δ1 gap of InSb, and an upshift of this gap due to compressive biaxial stress. We also observe an anomalous dependence of stress on film thickness. The Raman data indicate good sample quality despite the large lattice mismatch between InSb and GaAs.

Epitaxial growth of InSb on GaAs by metalorganic chemical vapor deposition {au}R. M. ,Biefeld and

InSb epitaxial layers have been grown on GaAs substrates by metalorganic chemical vapor deposition using trimethylindium and triethyl- or trimethylantimony as sources of In and Sb. Transmission electron microscopy revealed the existence of a large number of misfit dislocations at the substrate-epitaxial layer interface and, in some samples, misoriented grains. The quality of the layers improved with thickness as indicated by transmission electron microscopy, x-ray rocking curve widths, and Hall mobilities. The mobility was correlated with surface roughness, x-ray rocking curve width, and the Sb/In ratio. Hall mobilities up to 60 900 and 27 000 cm2/V s were obtained at 300 and 77 K, respectively, on a 2.9-μm-thick epitaxial InSb layer grown using a two-step growth procedure.

OMVPE Growth of Epitaxial InSb Thin Films Using a Novel Group V Source Compound

ABSTRACTTo date, OMVPE has failed to grow epitaxial InSb at temperatures below about 400 °C. Therefore, we have studied InSb deposition using the novel group V source triisopropylantimony (TIPSb) with trimethylindium (TMIn), comparing this with results in the same reactor using trimethylantimony (TMSb). We have grown InSb on both GaAs and on high-resistivity p-type InSb substrates, exploring the effects of temperature, substrate, V/ill ratio, and thickness on film properties. Our best results with TMSb and TMIn were obtained using a V/ill ratio of 8 and growth temperature of 450 °C. The unintentionally doped films exhibited good crystallinity and were n-type about lx1015 cm-3 down to 5 K, with 77 K mobilities of 90,000 and 253,00°Cm2/V-sec for InSb on GaAs and on InSb, respectively. These results are comparable to the best published MBE data. While InSb films could not be grown well at temperatures below 425 °C using TMSb, specular epilayers were obtained with TIPSb at temperatures as low as 300 °C, though with a low deposition rate. Our best conditions with TIPSb were with a Vill ratio of about 12 and a substrate temperature of 350 °C. The results of variable temperature and variable magnetic field Hall, double crystal x-ray diffractometry, Nomarski microscopy, Auger electron spectroscopy and scanning electron microscopy will be presented.

On the microstructure and interfacial structure of InSb layers grown on GaAs(100) by molecular beam epitaxy

Abstract InSb films grown directly on GaAs(100) substrates by molecular beam epitaxy have been examined by transmission electron microscopy (TEM). High-quality epitaxial InSb layers were deposited despite the 14-6% lattice mismatch between film and substrate. Almost all the misfit strain was accommodated by a square array of (a/2){011} edge-type misfit dislocations, spaced on average 29 A apart. A model for the formation of these dislocation arrays is presented. Pure edge-type dislocations are favoured over 60°-type dislocation arrays because they are more efficient at relieving misfit strain and consequently allow more coherent interface area to form. Several types of growth defect, namely Sb inclusions, microtwins and dislocation tangles, were observed in the InSb layers. Various methods for reducing the overall defect density are discussed. Finally, results on the extent of electron beam damage of InSb layers occurring during TEM observation are presented.

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.

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.