InSb Epilayers Research Articles

Direct growth of InSb nanowires on CdTe (0 0 1) substrates by molecular beam epitaxy

The molecular beam epitaxial growth of InSb on CdTe (001) substrates has been performed with a specific growth condition, that results in elongated wire morphology. Atomic force microscopy (AFM) and field emission scanning electron microscopy are performed for characterizing the surface morphology. The AFM images of free-standing InSb/CdTe samples reveal the InSb nanowires (NWs) elongation along the [110] direction of the substrate. We speculate the growth mechanism of NWs by attempting to investigate the intrinsic strain by X-ray diffraction (XRD) analysis. The XRD reveals the compressive strain in InSb epilayer and it could be the origin of NW formation. Phonon scatterings from CdTe, InSb and intermixed compounds are probed by Raman spectroscopy. Optical properties of the lateral NWs on CdTe are revealed by photoluminescence measurements.

High-Quality InSb Grown on Semi-Insulting GaAs Substrates by Metalorganic Chemical Vapor Deposition for Hall Sensor Application**Supported by the Hundred Talents Program of Chinese Academy of Sciences, the CAS Interdisciplinary Innovation Team, the National Natural Science Foundation of China under Grant Nos 61874179, 61804161 and 61605236, and the Key Frontier Scientific Research Program of Chinese Academy of Sciences under Grant No

High-quality InSb epilayers are grown on semi-insulting GaAs substrates by metalorganic chemical vapor deposition using an indium pre-deposition technique. The influence of V/III ratio and indium pre-deposition time on the surface morphology, crystalline quality and electrical properties of the InSb epilayer is systematically investigated using Nomarski microscopy, atomic force microscopy, high-resolution x-ray diffraction, Hall measurement and contactless sheet resistance measurement. It is found that a 2--thick InSb epilayer grown at 450°C with a V/III ratio of 5 and an indium pre-deposition time of 2.5 s exhibits the optimum material quality, with a root-mean-square surface roughness of only 1.2 nm, an XRD rocking curve with full width at half maximum of 358 arcsec and a room-temperature electron mobility of 4.6 × 104 cm2/. These values are comparable with those grown by molecular beam epitaxy. Hall sensors are fabricated utilizing a 600-nm-thick InSb epilayer. The output Hall voltages of these sensors exceed 10mV with the input voltage of 1V at 9.3mT and the electron mobility of 3.2 × 104 cm2/ is determined, which indicates a strong potential for Hall applications.

Bandgap engineering of InSb by N incorporation by metal-organic chemical vapor deposition

Bandgap engineering is necessary for the application of InSb in long wavelength infrared photodetection. InSbN alloys hetero-epitaxially were therefore deposited on GaAs substrate by metal-organic chemical vapor deposition (MOCVD), expecting a large band gap reduction by N incorporation for long wavelength infrared photodetection. The effects of post annealing treatment on the structural and optical properties of the grown InSbN alloy have been well studied. Photoluminescence measurement (PL) indicated that the longest PL wavelength obtained at 10 K is ∼7.2 μm for the InSbN alloys, which manifests an extension of PL wavelength as large as ∼ 1.8 μm in comparison to the undoped InSb epilayers, suggesting a successful band gap reduction by the N incorporation. X-ray photoelectron spectroscopy (XPS) measurements show that three kinds of nitrogen bonds co-exist in the alloys and their percentages vary with annealing conditions. This observation can explain the peak shifts of X-ray diffraction (XRD) and PL spectra. The comparison to our previous works reveals that the InSbN alloys grown on GaAs substrate can achieve more nitrogen incorporation and band gap reduction than the alloys grown on InSb and GaSb substrates.

High electron mobility in InSb epilayers and quantum wells grown with AlSb nucleation on Ge-on-insulator substrates

InSb epilayers and InSb/Al0.20In0.80Sb quantum wells (QWs) were grown on 4°-off-axis Ge-on-insulator (GeOI) substrates by molecular beam epitaxy. An initial AlSb nucleation was found to be important for achieving good crystalline quality. For a 4.0-μm-thick InSb epilayer and 25-nm-thick InSb QW, the room-temperature (RT) electron mobility was increased by 25% and 60% [58 000 cm2/(V-s) for the epilayer and 24 000 cm2/(V-s) for the QW], respectively, by using an off-axis GeOI substrate instead of an on-axis GeOI (001) substrate. This significant improvement may be attributed to the reduction of antiphase domains, microtwins, and threading dislocations. A modified QW structure on a 4°-off-axis GeOI substrate showed a further 25% improvement in RT electron mobility with a value 32 000 cm2/(V-s). This is the highest RT electron mobility in an InSb QW grown on a Ge-based substrate to date.

Effect of substrate miscut on the electron mobility in InSb(001) structures on Ge and Ge-on-insulator substrates

InSb epilayers and InSb/Al0.20In0.80Sb quantum wells were grown on Ge(001) substrates and Ge-on-insulator (GeOI)-on-Si(001) substrates by molecular beam epitaxy. Growth on both on-axis and 4°-off-axis substrate orientations was studied. Anti-phase domains were formed when InSb films were grown on on-axis substrates, but suppressed significantly by the use of 4°-off-axis substrates. Such off-axis substrates also reduced the densities of micro-twin defects and threading dislocations. The defect reduction resulted in an increase in the room-temperature electron mobility from 37,000 to 59,000 cm2/Vs in 4.0-μm-thick InSb epilayers and from 10,000 to 20,000 cm2/Vs in 25-nm-thick InSb quantum wells on Ge(001) and GeOI-on-Si(001) substrates.

Improved electron mobility in InSb epilayers and quantum wells on off-axis Ge (001) substrates

Two types of InSb structures, epilayers and quantum wells (QWs), have been grown on on-axis and 6°-off-axis Ge (001) substrates and examined by reflection high-energy electron diffraction, transmission electron microscopy, X-ray diffraction, atomic force microscopy, and the van der Pauw and Hall effect techniques. Anti-phase domain defects, which prevail in these InSb structures when grown on on-axis Ge (001) substrates, are significantly decreased by the use of 6° off-axis Ge (001) substrates. Such off-axis substrates also lead to reductions in the densities of micro-twins and threading dislocations. Room-temperature electron mobilities in 4.0-μm-thick InSb epilayers and 25-nm-thick InSb QWs grown on 6°-off-axis Ge (001) substrates are 59 000 and 14 000 cm2/(V s), respectively, which are ∼1.5 times higher than their counterparts grown on on-axis Ge (001) substrates. These improved mobilities are the highest among the reported values for each type of structure grown on Ge (001) substrates.

Sb antisite defects in InSb epilayers prepared by metalorganic chemical vapor deposition

High quality InSb epilayers were grown epitaxially on InSb (100) by metalorganic chemical vapor deposition. Different growth temperatures and V/III ratios were employed in the growth and their effects on the quality of the grown films were studied. Low temperature photoluminescence spectra of the samples revealed that in addition to the main band-to-band emission around 5.4μm, an emission peak around 5.87μm was also be observed. Our results indicate that the low energy emission peak was originated from the antisite SbIn defects which can be removed by reducing the V/III ratio.

Strong dependence of spin dynamics on the orientation of an external magnetic field for InSb and InAs

Electron spin relaxation times have been measured in InSb and InAs epilayers in a moderate (<4 T) external magnetic field. A strong and opposite field dependence of the spin lifetime was observed for longitudinal (Faraday) and transverse (Voigt) configuration. In the Faraday configuration the spin lifetime increases because the D’yakonov–Perel’ dephasing process is suppressed. At the high field limit the Elliot–Yafet spin flip relaxation process dominates, enabling its direct determination. Conversely, as predicted theoretically for narrow band gap semiconductors, an additional efficient spin dephasing mechanism dominates in the Voigt configuration significantly decreasing the electron spin lifetime with increasing field.

Doping tunable resonance: Toward electrically tunable mid-infrared metamaterials

We demonstrate metamaterials at the mid-infrared (mid-IR) wavelengths (8–12 μm) that can be widely tuned by doping in adjacent semiconductor epilayers. The metamaterials are based on metallic split ring resonators (SRRs) fabricated on doped indium antimonide (InSb). Finite integral time-domain simulation results and measured transmission data show that the resonance blueshifts when the semiconductor electron carrier concentration is increased while keeping the split ring geometry constant. A resonant wavelength shift of 1.15 μm is achieved by varying the carrier concentration of underlying InSb epilayer from 1×1016 to 2×1018 cm−3. This work represents the first step toward active tunable metamaterials in the mid-IR where the resonance can be tuned in real time by applying an electric bias voltage to control the effective carrier density.

Growth of InSb epilayers and quantum wells on Ge(001) substrates by molecular beam epitaxy

InSb epilayers and InSb/Al0.20In0.80Sb quantum well structures were grown on Ge(001) substrates by molecular beam epitaxy. Epilayers grown using a two-step process, which involved different temperatures, were characterized in situ using reflection high energy electron diffraction and studied ex situ using high-resolution x-ray diffraction, Nomarski optical microscopy, and Hall-effect measurements. The narrowest x-ray rocking curve width for 2.0- and 5.0-μm-thick InSb epilayers were 250 and 173 arc sec, respectively. Electron mobilities in the 5.0-μm-thick InSb epilayer and the InSb/Al0.20In0.80Sb single quantum well at room temperature were 34 500 and 8600 cm2/V s, respectively, which are the highest values for these films on Ge(001) substrates reported to date.

Characterization of InSb layers on GaAs substrates using infrared reflectance and a modified oscillator formula

InSb epilayers on GaAs substrates are analyzed using infrared reflectance spectroscopy, but employing a modified Drude oscillator formula. The modified formula enables the determination of 13 parameters: six dielectric parameters for both layer and substrate separately, as well as the thickness of the layer. The formula is tested against previously published data, and to characterize layers grown in this laboratory.

Distribution of dislocations in GaSb and InSb epilayers grown on GaAs (001) vicinal substrates

GaSb and InSb epilayers grown on GaAs (001) vicinal substrates misoriented toward (111) plane were studied using high resolution x-ray diffraction. The results show that GaSb and InSb epilayers take on positive crystallographic tilt, and the asymmetric distribution of 60° misfit dislocations in {111} glide planes have an effect on the tilt. In addition, the vicinal substrate influences the distribution of the threading dislocations in {111} glide planes, and the density of dislocation in the (111) plane is higher than in the (1¯1¯1) plane. A model was proposed to interpret the distribution of full width at half maximum, which can help us understand the formation and glide process of the dislocations.

KINETIC MONTE CARLO SIMULATION OF HETEROEPITAXIAL GROWTH OF InSb BUFFER LAYER AND EFFECTS ON InSb/GaAs FILMS

InSb films on GaAs (001) substrates have been grown using a two-step method by molecular beam epitaxy (MBE). The Kinetic Monte Carlo (KMC) method, based on solid-on-solid (SOS) model has been introduced to simulate the Volmer–Weber growth of InSb buffer layer on GaAs substrate. The buffer surface becomes rough obviously and produces an undulating profile during the last coverage of the substrate. The undulating buffer surface would play an adverse role in the surface morphology of the following InSb epilayer. Therefore, the growth of InSb epilayer before the formation of undulating buffer surface would get a better surface, which has been convinced by the results of atomic force microscope (AFM) observations.

Fabrication and electrical characterization of n-InSb on porous Si heterojunctions prepared by liquid phase epitaxy

Thin films of InSb were grown on p-type porous silicon (PSi) (111) substrates by liquid phase epitaxy (LPE) to obtain monocrystalline InSb epilayer on a PSi substrate for low cost device applications. The structural characterization of the devices was carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The X-ray diffraction measurements indicate that InSb monocrystalline epilayer was successfully grown onto PSi. The current–voltage (I–V) characteristics of n-InSb/p-PSi heterojunction devices were measured in the temperature range of 298–398K. The measurements indicate that these heterojunctions have good rectifying characteristics. The estimated zero-bias barrier height ϕBO and the ideality factor η show strong temperature dependence. The conventional Richardson plot exhibits linear behavior in the entire temperature range indicating that the conduction seems to be predominantly due to thermionic emission mechanism. In addition, the capacitance-voltage characteristics are investigated at frequency of 1MHz. The built-in potential of the heterojunction is determined after eliminating the effect of the capacitance effect of the interface state caused by the lattice mismatch.

Thin InSb films on GaAs substrates by Molecular Beam Epitaxy

We optimized the suitable growth conditions for obtaining smooth surface and high-quality InSb epilayer grown on semi-insulating GaAs substrate. The low temperature (LT) buffer layer was introduced into the growth process to improve the surface morphology and interface quality of the epilayers. It was confirmed that high quality InSb epilayer strongly depends on LT InSb buffer layer and growth conditions and parameters. Our typical InSb samples were obtained at the growth temperature of 420–425 °C, with the optimum Sb/In ratio of 1.4:1, and in our experiments, the epilayer thickness was in the range of 1.0 to 2.2 µm. Typically, the room temperature X-ray diffraction (XRD) full width half maximum (FWHM) of 172'' and mobility of 64300 cm2 V-1 S-1 at 77 K were obtained for typical sample of 2.2 µm thickness.

Liquid phase epitaxial growth of lattice mismatched InSb, GaInAs and GaInAsSb on GaAs substrates using a quaternary melt

Abstract We have developed and established a unique technique for growing highly lattice mismatched ternary and quaternary compounds on binary substrates using a quaternary melt thermo-chemistry. In this technique, growth is initiated from a pseudo-quaternary melt on compatible substrates. Growth of GaInAs, InAsSb, GaInAsSb and InSb epilayers on GaAs has been achieved using In–Ga–As–Sb melts. The grown epilayers have a uniform composition and are very thick ( > 100 μ m ) . Between the GaAs substrate and the uniform composition epilayer, there exists a graded composition quaternary which is found to be extremely beneficial in relieving misfit. No specific efforts were made to change growth conditions (during epi-growth) to compositionally grade the buffer layers. Hence, this growth scheme is extremely simple to implement and can be used for the growth of a variety of alloy semiconductors by appropriately selecting the growth temperature and melt composition. One of the key highlights of this work is the growth of In x Ga 1 - x As y Sb 1 - y epilayers with cut-off wavelength of 10 μ m on GaAs substrates. This paper will discuss the melt thermo-chemistries and the process for this new epilayer growth method.

Molecular beam epitaxial growth of indium antimonide and its characterization

Indium antimonide (InSb) is a promising material for mid- and long-wavelength infrared device applications. However, because of material’s small band gap and low melting point, reproducibility of high quality epitaxial InSb is difficult to obtain. This article reports growth experimentations for determining suitable conditions for growing InSb on InSb(100) substrate using solid source molecular beam epitaxy. The effects of growth temperature and antimony/indium (Sb∕In) flux ratio on epilayer structure, surface roughness, and electronic properties were investigated. The process of oxide desorption observed from reflection high energy electron diffraction pattern is reported. A three-layer model was used to extract the electronic properties of the epilayer, taking into account the effect of parallel conduction. Process conditions for good structural and electronic properties of the InSb epilayer, which includes substrate temperature and flux ratio, have been established in this study and reported herein.

Tuning the inherent magnetoresistance of InSb thin films

We have investigated the 300 K inherent magnetoresistance of undoped InSb epilayers grown on GaAs(001) by molecular-beam epitaxy. The magnetoresistance of these films can be described well using a simplified model that incorporates gradation of properties away from the InSb/GaAs interface and the interplay between conduction and impurity bands. Although there is no significant intrinsic contribution in InSb bulk crystalline (001) materials due to its isotropic Fermi surface and mobility tensor, the linear and quadratic terms in the magnetoresistance as well as the overall magnitude can be tuned by varying the film thickness from 100 to 2000 nm.

Geometric manipulation of the high-field linear magnetoresistance in InSb epilayers on GaAs (001)

We address the inherent high-field magnetoresistance (MR) of indium antimonide epilayers on GaAs (001), studying the modification of the MR when processed into a set of geometries. The changes produced by the geometries are quite subtle. The extraordinary MR geometry produces the highest low-field MR while the Corbino geometry produces the largest high-field magnetoresistance. We demonstrate that any material with an unsaturating linear intrinsic MR, will also have an unsaturating linear Corbino MR, and that the ideal material for linear MR sensors in conventional geometries would have a high mobility and a small, linear intrinsic MR.

Effect of the low-temperature buffer thickness on quality of InSb grown on GaAs substrate by molecular beam epitaxy

The effect of initial low-temperature grown buffer (LT buffer) layer thickness on quality of InSb grown on GaAs substrate by molecular beam epitaxy (MBE) with the two-step growth method was investigated. The characteristics of InSb layers were analyzed by using Raman scattering, triple-axis crystal X-ray diffraction (XRD) and atomic force microscopy (AFM). It is shown that the crystalline quality and the root-mean-square (RMS) roughness of the InSb layer have close relation to the thickness of initial grown low-temperature buffer layer. With the spatial correlation model, the Raman line shapes of the first-order longitudinal optical phonon mode of InSb epilayer have been analyzed, which well agrees with the experimental results. We found that the optimal LT buffer thickness is about 30 nm suitable for obtaining smooth surface and high-quality InSb epilayer grown on semi-insulated GaAs substrate.