InSb Films Research Articles

Evidence for dislocation-related amphoteric behaviour of Si dopant in high-mobility InSb thin films

Silicon-doped InSb films of 100 nm thickness were grown by molecular-beam epitaxy on undoped low-temperature InSb buffer layers on GaAs(100) substrates. For a set of samples grown with the same Si flux, the free carrier concentration also increased with buffer thickness, and an analysis which included an estimate of the donor-doping properties of the dislocations suggests that a fraction of the silicon may also be trapped at the dislocations, where it acts as an acceptor. Hall effect measurements, corrected for the effects of parallel conduction in the buffer layer, and surface depletion in the doped region, showed that the mobility of the Si-doped region improved as the buffer layer thickness increased, and reached corrected values as high as 15 000 cm2 V−1 s−1, approaching that of lightly compensated material. These mobility dependences are quantitatively consistent with the incorporation model.

Optical and transport properties of InSb thin films grown on GaAs by metalorganic chemical vapor deposition

Optical and transport properties of InSb thin films grown on GaAs by metalorganic chemical vapor deposition (MOCVD) have been investigated by far-infrared (FIR) reflectance spectroscopy. The lattice vibration behaviors of a series of MOCVD InSb/GaAs(100) materials grown under different growth conditions were studied. Effects of III–V source ratios on the films crystalline quality were examined. Two additional weak modes in the wavenumber regions of 210–240 cm − 1 were observed and they appeared more prominent at low temperatures. Interference fringe effects modify the FIR reflectance band of the GaAs substrate, which are related to the uniformity of film thickness and crystalline perfection. The dielectric constant, phonon modes and other optical parameters, as well as transport properties including carrier concentration, mobility, effective mass were calculated theoretically and compared with experimental results. The obtained distribution values of the InSb LO phonon mode frequency, line width, relative integrated intensity ratio between the forbidden and defect-related TO phonon and the allowed LO mode are adopted as figures of merit for the quality of the InSb films. The electrical transport properties of carrier concentration, mobility, and effective mass as well as the dielectric constant of these films have been determined by optical method non-destructively.

III-V족 화합물 반도체 InSb 나노와이어의 전기화학적 합성 및 특성 평가

본 연구에서는 그동안 전기화학적으로 합성되지 못했던 III-V족 화합물 반도체 InSb를 구연산 용액으로부터 합성하였으며 자체 제조한 AAO를 나노템플릿으로 이용하여 정전압 도금을 실시하여 InSb 나노와이어를 제조하였다 제조된 InSb나노와이어는 X선 회절분석 결과 단결정의 나노와이어는 아니었으나 정확하게 화학양론을 만족시키는 화합물임을 확인하였고, 평판 박막 상태의 InSb와는 달리 나노와이어의 길이방향으로 (220) 방향의 결정이 주로 성장하는 우선결정방위를 가지고 있음을 알 수 있었다. 또한 집합적으로 배열된 상태에서 측정된 I-V특성 곡선에서는 n형 반도체의 특성을 보이되 밴드갭이 좁고, 전자이동도가 큰 InSb고유의 특성상 반금속과 유사한 전기적 특성을 보유하고 있음을 확인하였다. To the best knowledge, the formation and characterization of InSb nanowires have not been reported yet in spite of its good characteristics as a III-V compound semiconductor. The nanowire arrays were potentiostatically electrodeposited in a mixing solution of indium chloride, antimony chloride, citric acid, and potassium citrate according to our previous work on the electrodeposition of the stoichiometric InSb films. The electrical properties of nanowire arrays were measured by semiconductor parameter analyzer, and the microstructural analysis of the nanowires was conducted by employing XRD. Our experimental results indicate that the InSb nanowires have a highly preferred orientation of (220) direction and also exhibit electrical characteristics of n-type semiconductors which we, however, similar to semi-metals mainly due to their narrow band-gap and high electron mobility.

Study of structural and optical properties of InSb-doped SiO 2 thin films

The non-linear absorption and the structure of rf-cosputtered SiO 2:InSb films were investigated after different heat-treatments at temperatures ranging from 200 to 900 °C. The heat-treatment was 1 min or 4 h in an atmosphere of nitrogen or under vacuum, respectively. After annealing at a temperature higher than 200 °C, the presence of nanocrystallites in the layers was detected by transmission electron microscopy (TEM) and Raman spectroscopy. The growth of either Sb or InSb nanocrystals essentially depends on both the annealing temperature and the heat-treatment time. Particularly, it was shown that a rapid thermal annealing (RTA) is necessary to obtain crystals of InSb with size estimated to be about 15 nm. The largest positive non-linear coefficient β, as measured by the Z-scan method at 1064 nm in a nanosecond regime, was found to be equal to 1.8 × 10 −3 cm/W when the films contain InSb particles of larger size (up to 100 nm). However, when increasing the incident irradiance on the sample, the non-linear effect does not increase and seems to saturate, which can explain the discrepancies observed with previous works on similar materials. This disagreement may also be due to different response times of the non-linearities related to thermal effects in the continuous wave (CW) open-aperture Z-scan configuration.

Characterization of p-type In–Sb thin films prepared by vacuum evaporation

Thin films of InSb have been prepared onto well-cleaned glass substrates at different substrate temperatures (303, 473 and 523 K) by vacuum evaporation. The elemental composition of the deposited InSb films was evaluated by Auger electron spectroscopy (AES) and it was found to be 24% (In) and 76% (Sb). X-ray diffraction patterns indicated the polycrystalline nature of the InSb films with preferential orientation along (1 1 1) plane. Particle size ( D), dislocation density ( δ ) and strain ( ε ) were determined from the XRD patterns. The particle size increases with the increase of substrate temperature, which was found to be in the range from 8.31 to 24.95 nm. In Laser Raman study, the presence of longitudinal mode (LO) confirms that the deposited films were having crystalline nature. Hall measurements indicate that the films were p-type, having carrier concentration ≅ 10 16 cm −3 and mobility (1.1–6.5)×10 3 cm 2/V s.

Effect of hetero‐interface on weak localization in InSb thin film layers

Magnetoresistance (MR) effects caused by the quantum interference have been investigated in the InSb thin films grown on GaAs(100) substrates by MBE. The positive MR arising from the weak anti-localization (WAL) found in the accumulation layer at the InSb/GaAs interface for a 0.1 µm thick undoped film has been explained by taking account of the spin-Zeeman effect on spin-orbit interaction (SOI) caused by the asymmetric potential at the hetero interface (Rashba term) with SO scattering rate τso–1 ∼ 1.7 × 1012 s–1 from the fits of MR. In Sn-doped films, the negative MR found in extremely weak magnetic fields crossovers to the positive MR with decreasing the film thickness from d = 1 µm to 0.1 µm. These results have been analyzed using a two-layer model for the films; the SO scattering rate in the intrinsic InSb film due to the bulk inversion asymmetry (Dresselhaus term) has been found to be as small as τso–1 ≤ 2 × 109 s–1 and when the interface is approached in the film the WL crossovers to the WAL with the increase of SOI in the layers caused by the increased influence of the Rashba electric field. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of substrate temperature on the properties of vacuum evaporated InSb films

AbstractIndium Antimonide (InSb) thin films were grown onto well cleaned glass substrates at different substrate temperatures (303, 373 and 473 K) by vacuum evaporation. The elemental composition of the deposited InSb film was found to be 52.9% (In) and 47.1% (Sb). X‐ray diffraction studies confirm the polycrystallinity of the films and the films show preferential orientation along the (111) plane. The particle size (D), dislocation density (δ) and strain (ε) were evaluated. The particle size increases with the increase of substrate temperature, which was found to be in the range from 22.36 to 32.59 nm. In Laser Raman study, the presence of longitudinal mode (LO) confirms that the deposited films were having the crystalline nature. Raman peak located at 191.26 cm–1 shift towards the lower frequencies and narrows with increase in deposition temperature. This indicates that the crystallinity is improved in the films deposited at higher substrate temperatures. Hall measurements indicate that the films were p‐type, having carrier concentration ≅1016 cm–3 and mobility (4–7.7) ×103 cm2/Vs. It is observed that the carrier concentration (N) decreases and the Hall mobility (μ) increases with the increase of substrate temperature. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of buffer layers on the structural and electronic properties of InSb films

We have investigated the effects of various buffer layers on the structural and electronic properties of n-doped InSb films. We find a significant decrease in room-temperature electron mobility of InSb films grown on low-misfit GaSb buffers, and a significant increase in room-temperature electron mobility of InSb films grown on high-misfit InAlSb or step-graded GaSb+InAlSb buffers, in comparison with those grown directly on GaAs. Plan-view transmission electron microscopy (TEM) indicates a significant increase in threading dislocation density for InSb films grown on the low-misfit buffers, and a significant decrease in threading dislocation density for InSb films grown on high-misfit or step-graded buffers, in comparison with those grown directly on GaAs. Cross-sectional TEM reveals the role of the film/buffer interfaces in the nucleation (filtering) of threading dislocations for the low-misfit (high-misfit and step-graded) buffers. A quantitative analysis of electron mobility and carrier-concentration dependence on threading dislocation density suggests that electron scattering from the lattice dilation associated with threading dislocations has a stronger effect on electron mobility than electron scattering from the depletion potential surrounding the dislocations. Furthermore, while lattice dilation is the predominant mobility-limiting factor in these n-doped InSb films, ionized impurity scattering associated with dopants also plays a role in limiting the electron mobility.

Transport properties of InSb and InAs thin films on GaAs substrates

The heterointerfaces in InAs and InSb thin films grown on GaAs were found to affect the temperature dependence of the film's electrical properties such as electron mobility, electron density, and resistivity. The InAs and InSb surfaces of the films, which act as heterointerfaces with air, were found to similarly affect the electrical properties. It was found that the electron mobility of both InAs and InSb films grown on GaAs substrates has a three-layer structure.

半導体薄膜ホール素子の現状とその応用分野の展開

The recent status of research, application, production and the characteristics of InSb and InAs thin film Hall elements are reviewed. Hall elements are now major application area for thin film technology such as vacuum deposition and MBE. Highly sensitive InSb thin filmHall elements formed by vacuum deposition are often applied as magnetic sensors for DC brushless motors used in electronic equipment such as Videotape recorders(VTRs) and personal computers(PCs). InAs thin film and InAs deep quantum well(DQW) Hall elements with high sensitivity and stability over a wide temperature range have been developed by molecular beam epitaxy (MBE). The temperature dependence of InSb single crystal thin films grown on GaAs substrate by MBE were reduced dramatically to very small value by Sn doping as donor impurity. The Hall elements fabricated from the Sn doped InSb single crystal thin films show the very small temperature dependence.They have potential for the present and future applications as magnetic sensors required by many electronic systems.

The role of impurity band conduction in the low temperature characteristics of thin InSb films grown by molecular beam epitaxy

We report on the temperature-dependent electrical properties of high-quality undoped InSb layers of various thicknesses grown on GaAs(100) substrates by molecular beam epitaxy. The layers are found to be n-type in the measured temperature range (77–297 K). A differential Hall approach was employed to characterize the depth dependence of the electrical properties of the InSb films. The temperature variations of these data were then modelled with the inclusion of conduction through an impurity band, formed by the overlap of the wavefunctions of the dislocation-related donors. These analyses suggest that the contribution of the impurity band is dominant close to the interface even at room temperature, but its effect falls with increasing thickness, until at ∼1000 nm, its contribution is only comparable to that of the conduction band at low temperatures. The dislocation donor densities deduced from this modelling follow an approximately reciprocal trend with increasing distance from the interface.

Effect of surface composition on melting of thin InSb films

We demonstrate the possibility of melting thin (0.1–0.5 µm) InSb films directly in atmosphere under the protective layer of native oxides to obtain high mobility of majority carriers (up to 25 000 cm2/V s). The features of the film synthesis process based on thermal pulsed evaporation of InSb powder in vacuum are studied experimentally. Such a technique makes it possible to provide necessary compositional inhomogeneity of the deposited film for subsequent melting in air.

Fabrication and properties of InSb films with ion-beam sputtering for use in the amplification of magneto-surface-acoustic waves

The magnetic surface acoustic wave (MSAW) device can be manipulated by an external magnetic field. However the MSAW is attenuated largely at high frequencies above MHz. Therefore, we proposed a MSAW device having a hybrid structure consisting of FeB amorphous thin film/InSb semiconductor thin film/LiNbO 3 substrate. This device is utilized for amplification of surface acoustic waves by the interaction between surface acoustic waves and the carriers in the InSb semiconductor. We prepared (111) InSb thin films by ion beam sputtering. We obtained InSb thin films having Hall mobilities of about 2000 cm2/Vs by subsequent annealing. This showed the possibility of MSAW amplification by low voltages.

High-mobility thin InSb films grown by molecular beam epitaxy

The problem of preparing high-mobility thin InSb films is revisited for magnetoresistive and spintronic sensor applications. We introduce a growth process that significantly improves the electrical properties of thin unintentionally doped InSb layers (60–300 nm) epitaxially grown on GaAs(100) substrates by reducing the density of dislocations within the interfacial layer. The epilayer properties are well described by a differential two-layer model. This model confirms that the contribution of the interface can only be donor-like. Moreover, the electrical properties of the InSb layers change continuously away from the interface up to sample thickness of the order of 1 μm.

High-mobility InSb thin films on GaAs (0 0 1) substrate grown by the two-step growth process

InSb heteroepitaxial thin films were grown on GaAs (0 0 1) substrate by the temperature variation two-step growth process. X-ray rocking curve widths and electrical properties of the InSb films with different thickness were investigated. The best value of a 2-μm thick InSb film had an X-ray rocking curve width of 277 arcsec and room-temperature Hall mobilities, the carrier concentrations obtained were 55,000 cm 2/V s and 1.5×10 16/cm 3, respectively. The enhanced mobilities and reduced carrier concentration of InSb films suggested a low defect density due to confinement of the dislocation in the InSb/GaAs interface.

Textural properties of InSb thin films

The growth of flash-evaporated InSb films on non-oriented substrates between 160°C and 450°C is investigated. For the substrate temperatures T s<400°C the films are textured in the (1 1 0) plane, and their average grain size is of the order of 0.2 μm. At T s⩾400°C the preferred grains orientation becomes a mixture of the (1 1 0) and the (1 1 1), with a predominance of the (1 1 1) orientation at the highest temperatures. The average grain size increases to about 1 μm. The low-temperature texture in the (1 1 0) plane can be explained by the kinetic theory of the nucleation process and grain development, whereas the high-temperature orientation distribution can be explained by the thermodynamic requirements of minimization of the surface energy of the system. The latter consideration assumes that the lowest surface energy planes in InSb are (1 1 0), (1 1 1) A and (1 1 1) B and that the energies have comparable magnitudes.

High-magnetic-field studies of transport properties in Sn-doped InSb thin films on GaAs(1 0 0) substrates

Magnetotransport measurements for Sn-doped InSb thin films with thickness of d=0.3–1.0 μm grown on semi-insulating GaAs(1 0 0) substrates by MBE have been performed under high-magnetic fields up to 53 T using a pulsed magnet at 4.2 K. The Shubnikov–de Haas (S–dH) oscillations including 0 + maximum corresponding to the lowest Landau level ( i=0) as well as the spin-splittings (for i=1 and 2) have been observed for d>0.5 μm on the positive magnetoresistance (MR) ( ρ xx ) in perpendicular magnetic fields. The plateau-like structure of the Hall resistance ( ρ xy ) around the last minimum of ρ xx and the slope of its sublinear dependence on magnetic field becomes clear as decreasing d. The positive MR of ρ xx and the sublinear behavior of ρ xy have been consistently explained for d=1.0 μm by the two-layer model assuming the presence of the accumulation later with low mobility at the InSb/GaAs interface which act as the parallel conduction channel with the high-mobility layer in the InSb film. Moreover, the shoulder corresponding to the zeroth maximum which has remained ambiguous about the appearance in ρ zz for bulk systems has been apparently observed for all measured films.

High-quality highly mismatched InSb films grown on GaAs substrate via thick AlSb and In xAl 1− xSb step-graded buffers

We investigated double-buffer structure which could enable us to grow a high-quality InSb active structure on GaAs (0 0 1). With thick AlSb and InAlSb step-graded buffer layers, we succeeded to obtain InSb films of very high mobility at room temperature. Using transmission electron microscopy, we confirmed attenuation of threading dislocations by the buffer layer. Surface roughness and its power spectral density were analyzed by atomic force microscopy. Furthermore, strain relaxation and mosaicity were investigated by high-resolution X-ray diffraction measurements.

Growth of InSb thin films on GaAs(100) substrates by flash evaporation epitaxy

A two-stage flash-evaporation epitaxy of InSb thin films on GaAs(100) substrates is developed. In the first, low temperature stage, a buffer layer of thickness of about 20 nm is deposited. In the second, high temperature stage the bulk of the film is deposited. Thus obtained InSb films have good structural and electrical properties, comparable with those obtained by MBE. They can be used for practical applications, e.g. for Hall sensors. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of growth parameters on the surface morphology and crystallinity of InSb epilayers grown by liquid phase epitaxy

Unintentionally doped homoepitaxial InSb films have been grown by liquid phase epitaxy employing ramp cooling and step cooling growth modes. The effect of growth temperature, degree of supercooling and growth duration on the surface morphology and crystallinity were investigated. The major surface features of the grown film like terracing, inclusions, meniscus lines, etc are presented step-by-step and a variety of methods devised to overcome such undesirable features are described in sufficient detail. The optimization of growth parameters have led to the growth of smooth and continuous films. From the detailed morphological, X-ray diffraction, scanning electron microscopic and Raman studies, a correlation between the surface morphology and crystallinity has been established.