InSb Films Research Articles

Molecular-beam epitaxial growth of InSb on GaAs and Si for infrared detector applications

InSb epitaxial films were grown on GaAs and Si substrates by molecular-beam epitaxy using an intermediate AlSb buffer layer. The use of an AlSb intermediate buffer layer greatly facilitates the overgrowth of InSb on significantly lattice-mismatched foreign substrates, such as GaAs and Si. Hall mobility, x-ray rocking curve, and infrared absorption measurements were performed to characterize the samples. Using a 300 nm AlSb buffer layer, 3 μm thick InSb films on GaAs and Si substrates with room-temperature electron mobilities as high as 55 000 cm2 V−1 s−1 were routinely achieved. X-ray rocking curve linewidths of 199 arcsec for InSb on GaAs and 230 arcsec for InSb on Si have been achieved, which represent the best results to date. Our results indicate that AlSb is a very effective buffer layer for InSb devices grown on GaAs and Si substrates.

Growth and characterization of MBE-grown thin films of InSb on Si

Thin (< 1000 Å) InSb single crystalline films with a 〈111〉 orientation have been successfully grown by molecular beam epitaxy (MBE) on Si wafers. A sandwich-type buffer structure, BaF 2/InSb/BaF 2, was used to make this high quality material for semiconductor-on-insulator (SOI) high-speed devices. Both the interdiffusion between adjacent layers and the atomic composition in each layer were examined by Auger electron spectroscopy. The InSb film on the sandwich-type buffer was characterized by X-ray and Hall mobility measurements. The X-ray diffraction patterns indicated the crystallinity and the strain of different structures. The mobility temperature dependences were related not only to impurity and lattice scattering but also to dislocation scattering.

Magnetophotoluminescence of MBE-grown InSb and InAs

The magnetophotoluminescence from thin InSb layers grown by molecular beam epitaxy (MBE) on InSb and GaAs substrates and from MBE InAs on GaAs substrates is studied at low temperatures. With undoped homoepitaxial InSb, the photoluminescence (PL) spectrum contains up to five emission bands. From the observed magnetic field and excitation level dependence of the bands it is inferred that their origin is related to radiative recombination of an exciton-impurity complex, to direct recombination of a free electron with an uncharged acceptor, to recombination at an A+ centre and at deep defects. By comparison with PL from the substrate alone it is shown that two of the defects responsible are unique to the epilayer. The PL spectrum of epitaxial layers of InSb on GaAs shows a single broad band due to band-to-band radiative recombination in the InSb film. The PL of high-mobility InAs layers grown heteroepitaxially at 490 degrees C on GaAs shows a single emission line. Samples grown at lower temperature, resulting in lower mobility, show a second line due to direct recombination of a free electron with an uncharged shallow acceptor, suggesting a correlation between the reduction of mobility and the presence of this acceptor.

InSb thin films prepared by a multilayer vacuum deposition method

Thin films of InSb with a thickness of about 0.8 μm were prepared by employing a thermal evaporation technique of the Sb In metallic sandwich layers followed by a heat-treatment procedure. From X-ray diffraction studies, polycrystalline structures were found for the films treated at temperatures between 400 and 530°C. A room-temperature electron mobility of 1.7 × 10 4 cm 2/V s was observed for the films treated at 500°C.

Narrow-gap semiconductor magnetic-field sensors and applications

Narrow-gap semiconductors have been used for decades in the fabrication of magnetic field sensors, such as magnetoresistors and Hall sensors. Magnetic field sensors are, in turn, used in conjunction with permanent magnets to make contactless potentiometers and rotary encoders. This sensing technology offers the most reliable way to convert a mechanical movement into an electrical signal, and is widespread in automotive applications. Recent developments in the growth of thin epitaxial layers of InAs and InSb on semiinsulating GaAs or InP substrates have resulted in the development of magnetoresistors with excellent sensitivity and operating temperatures up to 285 degrees C. Magnetoresistors and Hall sensors require a very thin active semiconductor region, a high carrier density and a high room-temperature mobility. The best materials are narrow-gap III-V compounds. 2DEG layers in InSb and InAs would be ideally suited for these devices. The accumulation layer at the surface of InAs has been used to make magnetoresistors, Hall sensors and magnetotransistors. n-type doped thin InSb films are used to make magnetoresistors that outperform Si-based Hall sensors, even with integrated amplification. The authors describe device design criteria, materials requirements and a direct comparison of the three types of galvanomagnetic devices, magnetoresistors, Hall sensors and magnetotransistors, made from the same material. They compare the output of different magnetic field sensing technologies, such as Si and GaAs Hall sensors, and NiFe-based magnetoresistors, with InSb magnetoresistors.

Laser Induced Phase Transformations in Thin Insb Films

ABSTRACTThin In46Sb54 films have been prepared on glass substrates by flash evaporation. Films of 1000 Å were deposited at room temperature. After 7 mins' thermal annealing at 450ºC, an average grain size increased from 20 nm to 200 nm. Under exposure to a Fraunhofer diffracted pulsed Nd-YAG laser beam, the films showed different microstructures for different applied laser power. In general, five regions are identified: 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 unchanged region. The previous five regions are counted from the center of the exposed area outward. The pulse duration is 16 ns. In this paper, an atomic migration mechanism is proposed to explain the power dependent microstructures changes. Transmission electron microscopy was mainly used to characterize the films. The application of this type of phase transformations in the phase change optical storage is also discussed.

Uniform growth of InSb on GaAs in a rotating disk reactor by LP-MOVPE

Uniform films of InSb on GaAs substrates have been grown in a vertical, high-speed rotating disk reactor by low pressure MOVPE. Highly uniform and specular films were obtained over a 50 mm diameter wafer placed at the center of a 5 inch diameter wafer platter. Characterization of thickness, sheet resistance, mobility, and surface morphology was performed by SEM, sheet resistance mapping, Hall effect measurements, and Nomarski microscopy. Thickness uniformity, measured at 10 points radially across the wafer with a 3 mm edge exclusion, is as low as 1.84% with an average uniformity over several runs of only 2.8%. Results obtained from Hall mobility measurements taken by a 7 point cross-pattern show an average mobility of 41,030 cm 2/V · s with a coefficient of variation of 7.1% at 300 K. The sheet resistance uniformity, as determined by a 55 point, contactless, eddy current technique, shows a coefficient of variation as low as 1.37% with an average uniformity over 22 consecutive growth runs of only 3.1%. The effects of growth temperature and V/III ratio on the surface morphology and electronic properties were also studied, resulting in high quality epitaxial layers. With a growth temperature of 475°C and a V/III ratio of 18, Hall mobilities as high as 45,000 cm 2/V · s at 300 K and 31,500 cm 2/V · s at 77 K were measured on a 2 μm thick InSb layer. The corresponding carrier concentrations were 2.05×10 16 and 4.57×10 15 cm −3.

A possible mechanism for the recrystallization of InSb film on mica substrates

The recrystallization of InSb films while growing through the melting–solidification process was investigated in detail. A great fluctuation of the film temperature was seen in some cases of the growing film, especially in the early stage of the evaporation process. This fluctuation of the film temperature gives rise to the melting–solidification process. In this work, two distinct types of temperature fluctuations were observed. It was found that the shape of the temperature fluctuation curves can be reasonably explained by the variation of deposition rate in such a way that a higher deposition rate at the early stage of evaporation yields higher temperature fluctuations. The deposition rate was also found to depend on the preheating time of source, hence the optimum deposition rate was easily obtained by varying this time. The optimum substrate temperature and preheating time for high quality InSb films were 260 °C and 180 s, respectively. The present method greatly improves the reproducibility of preparing high quality InSb thin film.

Hydrogen-assisted reactive evaporation of quasi-stoichiometric polycrystalline InSb films

We report here a new technique for evaporating polycrystalline InSb films, using hydrogen beams as carriers for each elemental source. The films obtained show X-ray diffraction patterns before annealing that are totally exempt from impurity peaks, unlike those other workers have previously reported for evaporated InSb.

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.

Analysis of Optical Constants for Sputter-Deposited InSb Films Based on the Interband-Transition Model

The dielectric-function spectra for InSb films rf-sputter-deposited on (0001) and (011̄0) sapphire substrates have been analyzed by using a simplified interband transition model. The film deposited on (0001) sapphire is epitaxial, while the film on (011̄0) sapphire is polycrystalline in structural properties. The model based on the Kramers-Kronig transformation includes the E0, E0+Δ0, E1, E1+Δ1, E0′, E0′+Δ0′, E2, E1′ gaps and indirect gap (EgL) as the main dispersion mechanisms. The analysis suggests that the sputter-deposited InSb films include a small and a large number of void networks in the film medium for epitaxial and polycrystalline films, respectively. Dielectric-function-related optical constants, such as the refractive index and extinction coefficient, of the InSb films are also presented and analyzed.

Fabrication Process and Properties of Nb-InSb-Nb Planar Junction

A Nb-InSb-Nb planar junction with a normal layer of InSb thin film was fabricated by a new process. In this report, the details of the fabrication process and properties of the junction are discussed. The Nb-InSb-Nb junction fabricated using the new process showed a supercurrent. This means that there is no notable barrier, such as the Schottky barrier at the interface between Nb and InSb. The InSb film has a mobility of 500∼700 cm2/V·s, which is 17∼23 times larger than that of Si. This makes it possible to realize the superconductor-semiconductor-superconductor junction with a low carrier density of 1017 cm-3.

Erbium doping of molecular-beam epitaxially grown InSb on InP

The transport properties of molecular-beam epitaxially grown InSb films doped with Er (atom densities NEr from 4.3×1016 cm−3 to 3.6×1020 cm−3) are reported at temperatures between 40 and 400 K. Er is a donor in InSb films grown under Sb to In flux ratios smaller than 1.1. At a flux ratio Sb/In=1.06, 25 atoms of Er give one extrinsic electron. The maximum extrinsic electron concentration achievable is ∼1.8×1017 cm−3, obtained for NEr≳4×1018 cm−3. Magnetoresistance measurements at 4.2 K show evidence for spin–disorder scattering of the electrons. The low-temperature (T&amp;lt;150 K) electron mobility increases with doping concentration up to rare-earth densities of 1×1018 cm−3; at higher rare-earth concentrations, the mobility decreases again. At room temperature, the mobility decreases monotonically with increasing Er concentration. We note the analogy between these results and the observations made on HgSe:Fe, a system in which the carrier mobilities might be enhanced by impurity charge ordering.

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.

High-Quality InSb Growth on GaAs and Si by Low-Pressure Metalorganic Chemical Vapor Deposition

ABSTRACTWe report the first InSb film growth on Si by low-pressure metalorganic chemical vapor deposition. High-quality layers of InSb have been grown on Si and GaAs substrates. InSb films displayed mirror-like morphology on both substrates. X-ray full width at half maximum of 171 arcsec on GaAs and 361 arcsec on Si for a InSb layer thickness of 3.1 μm were measured. Room-temperature Hall mobilities of 67,000 and 48,000 cm2/V.s with carrier concentration of 1.5×1016 and 2.3×1016 cm−3 have been achieved for InSb films grown on GaAs and Si substrates, respectively. A 4.8 μ-thick InSb film on GaAs exhibited mobility of 76,200 cm2/Vs at 240 K.

Optical properties of amorphous InSb

We have presented experimental results for the optical constants of amorphous InSb films prepared by rf plasma deposition. The measured data are analyzed on the basis of a simplified model of nondirect optical transitions between the valence and conduction bands. Introducing a phenomenological damping effect into the model, the calculated spectra become structureless, which are typically observed in tetrahedrally bonded amorphous semiconductors. Results are in reasonable agreement with the experimental data over the entire range of photon energy (0.3–5.3 eV).

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.

Inversion of conduction type in thin InSb films prepared on glass substrates

Thin InSb films with average thicknesses of 0.15 and 0.4 μm were prepared on glass substrates by evaporation of In and Sb to obtain homogeneous and In droplets-free films. The substrate-temperature dependence of some properties of the film was investigated between 350 and 470 °C. Highly (111)-oriented 0.15an 450 °C, respectively. It was observed that 0.4-μm-thick films show p-type conduction in the extrinsic temperature range. The cause of these phenomena was investigated using a secondary ion mass spectroscopy in-depth analysis. As a representative in the constituents of glass substrates, the diffusion of Na, K, Mg, Ca, Ba, B, Al, Si, Pb, and O atoms into the InSb films was investigated more precisely. Among these atoms, it was estimated that K, Mg, and Si atoms could act as acceptors in an InSb crystal contributing to the inversion of conduction type.

Use of atomic layer epitaxy buffer for the growth of InSb on GaAs by molecular beam epitaxy

A 300 Å buffer layer of InSb grown by atomic layer epitaxy at a substrate temperature of 300 °C at the GaAs/InSb interface has been employed to grow epitaxial films of InSb having bulk-like properties. The reduction of the defects in the top InSb film has been observed with cross-sectional transmission electron microscopy and channeling Rutherford backscattering spectroscopy. The optimum substrate temperature for the primary InSb layer growth was 420 °C with an atomic flux ratio of Sb to In of 1.4 and a growth rate of 1 μm/h. The best 5-μm-thick InSb layers had x-ray rocking curve widths of 100 s, 77 K n-type carrier concentrations in the low 1015/cm3 range, and 77 K carrier mobilities greater than 105 cm2/V s. Mesa isolated photodiodes had carrier lifetimes of 20 ns, in comparison to 200 ns observed in bulk InSb having a similar carrier concentration. An unexplained, weak free-electron spin resonance transition has been observed in these films.

Growth and properties of InAs xSb 1−x, Al yGa 1−ySb, and InAs xSb 1−x/Al yGa 1−ySb heterostructures

A series of undoped InSb and InAs xSb 1−x layers were grown using tetramer Sb 4 and As 4 sources on (100)-oriented semi-insulating GaAs and InP substrates with different growth parameters. Very high electron mobilities (70,000 and 110,000 cm 2/V⋯s in InSb at 300 and 77 K, respectively) and n-type conductivity are obtained for all alloy compositions. The flux ratio P Sb/ P In played a crucial role in determining the surface morphology and the mobility of InSb films. Barrier heights of A1 p−Al yGa 1−ySb Schottky diodes are measured and are 0.4 eV. A 300 Å Si-doped InAs 0.8Sb 0.2 channel region sandwiched bet ween undoped Al 0.4Ga 0.6Sb buffer and gate barrier regions has μ = 1000 cm 2/ V⋯ s and n s = 5.4×10 12 cm −2 at 300 K. 1 μm ga te FETs made with this heterostructure have shown a maximum extrinsic g m = 160 mS/mm and ƒ T = 5 GHz at 300 K .