InSb Substrates Research Articles

Dirac Cone with Helical Spin Polarization in Ultrathinα-Sn(001) Films

Spin-split two-dimensional electronic states have been observed on ultrathin Sn(001) films grown on InSb(001) substrates. Angle-resolved photoelectron spectroscopy (ARPES) performed on these films revealed Dirac-cone-like linear dispersion around the Γ¯ point of the surface Brillouin zone, suggesting nearly massless electrons belonging to 2D surface states. The states disperse across a band gap between bulklike quantum well states in the films. Moreover, both circular dichroism of ARPES and spin-resolved ARPES studies show helical spin polarization of the Dirac-cone-like surface states, suggesting a topologically protected character as in a bulk topological insulator (TI). These results indicate that a quasi-3D TI phase can be realized in ultrathin films of zero-gap semiconductors.

Effects of TMSb overpressure on InSb surface morphology for InSb epitaxial growth using low pressure metalorganic chemical vapor deposition

We investigated the effects of antimony (Sb) overpressure during thermal cleaning (TC) on the surface morphology of InSb substrates using low pressure metalorganic chemical vapor deposition (LP-MOCVD). During the TC process under H2 ambient, indium (In) droplets were observed inside etch pits on InSb(001) surfaces due to the Sb evaporation from InSb substrates. On the other hand, when InSb substrates were thermally cleaned under trimethylantimony (TMSb) ambient, the formation of In droplets and the etch pits were suppressed, resulting in the smooth InSb surface. The surface morphology of InSb was dependent on TC temperature. Rough surface morphology was observed at low TC temperature of 435°C and it became smoother with increasing TC temperature. The improvement of surface morphology was caused by the surface stabilization with increasing Sb flux and the increase of adatom migration. The dependence of TMSb flow rate on the surface morphology was also investigated. The TMSb overpressure during the TC of InSb must be maintained to grow high quality InSb epitaxial layers with smooth surface using MOCVD.

Growth, steady-state, and time-resolved photoluminescence study of CdTe/MgCdTe double heterostructures on InSb substrates using molecular beam epitaxy

CdTe/MgCdTe double heterostructures (DHs) are grown on InSb substrates using molecular beam epitaxy and reveal strong photoluminescence with over double the intensity of a GaAs/AlGaAs DH with an identical layer structure design grown on GaAs. Time-resolved photoluminescence of the CdTe/MgCdTe DH gives a Shockley-Read-Hall recombination lifetime of 86 ns, which is more than one order of magnitude longer than that of typical polycrystalline CdTe films. These findings indicate that monocrystalline CdTe/MgCdTe DHs effectively reduce surface recombination, have limited nonradiative interface recombination, and are promising for solar cells that could reach power conversion efficiencies similar to that of GaAs.

Chemical passivation of InSb (100) substrates in aqueous solutions of sodium sulfide

The elemental composition and electronic structure of both native-oxide-covered InSb (100) substrates and substrates treated in aqueous solutions of sodium sulfide are analyzed by X-ray photoelectron spectroscopy. It is found that, as a result of treatment in a 1 M aqueous solution of Na2S and subsequent annealing in vacuum at 150°C, the surface layer consisting of complex antimony and indium oxides of nonstoichiometric composition is removed completely with the formation of a continuous layer of chemisorbed sulfur atoms coherently bound to indium atoms. According to atomic-force microscopy data, no etching of the host substrate material occurs during sulfide passivation. A shift (by 0.37 eV) of the In-Sb bulk photoemission towards higher binding energies is found, which indicates that the surface Fermi level shifts deeper into the conduction band.

Reflection absorption infrared spectroscopy analysis of the evolution of ErSb on InSb

We discuss an ex-situ monitoring technique based on glancing-angle infrared-absorption used to determine small amounts of erbium antimonide (ErSb) deposited on an indium antimonide (InSb) layer epitaxially grown on an InSb (100) substrate by low pressure metal organic chemical vapor deposition (MOCVD). Infrared absorption from the indium–hydrogen (InH) stretching mode at 1754.5cm−1 associated with a top most surface of an epitaxial InSb layer was used to compare varying levels of surface coverage with ErSb. Among four samples of varying coverage of ErSb deposition (7.2 to 21.5 monolayers), detected infrared absorption peaks distinct to InH weakened as ErSb surface coverage increased. In the early stage of ErSb deposition, our study suggests that outermost indium atoms in the InSb buffer layer are replaced by Er resulting in increase in absorption associated with the InH mode. Using this simple ex-situ technique, we show that it is possible to calibrate the amount of ErSb deposited atop each individual InSb substrate for depositions of few to tens of monolayers.

Single crystalline InAsxSb1 − x films with cut-off wavelength of 7–8 μm grown on (1 0 0) InSb substrates by liquid phase epitaxy

InAsxSb1−x single crystalline films with x from 0.02 to 0.05 have been successfully grown on (100) InSb substrates by liquid phase epitaxy without a buffer layer. High-resolution X-ray diffraction (HRXRD) was used to characterize the crystal quality of the films. The full-width at half-maximum (FWHM) of the (400) rocking curve (RC) line ranged from 157.96 to 417.02arcsec, revealing that the films are good single crystals with (100) surface orientation. Composition of the films was analyzed by energy dispersive X-ray analysis (EDXA) and HRXRD using Vegard’s law. The surface microstructures and morphologies of the films were characterized by scanning electronic microscopy (SEM) and optical microscopy. Optical properties were characterized by Fourier transform infrared (FTIR) transmission spectrum. A cut-off wavelength of 8.06μm at x=0.05, indicates the potential applications of the material for long-wavelength infrared detectors.

Comparative analysis of oxide phase formation and its effects on electrical properties of SiO2/InSb metal-oxide-semiconductor structures

We report on the changes in the interfacial phases between SiO2 and InSb caused by various deposition temperatures and heat treatments. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were used to evaluate the relative amount of each phase present at the interface. The effect of interfacial phases on the electrical properties of SiO2/InSb metal-oxide-semiconductor (MOS) structures was investigated by capacitance–voltage (C–V) measurements. The amount of both In and Sb oxides increased with the deposition temperature. The amount of interfacial In oxide was larger for all samples, regardless of the deposition and annealing temperatures and times. In particular, the annealed samples contained less than half the amount of Sb oxide compared with the as-deposited samples, indicating a strong interfacial reaction between Sb oxide and the InSb substrate during annealing. The interface trap density sharply increased for deposition temperatures above 240°C. The C–V measurements and Raman spectroscopy indicated that elemental Sb accumulation due to the interfacial reaction of Sb oxide with InSb substrate was responsible for the increased interfacial trap densities in these SiO2/InSb MOS structures.

Characterization of Al2O3/InSb/Si MOS diodes having various InSb thicknesses grown on Si(1 1 1) substrates

This paper discusses the capacitance–voltage (C–V) characteristics of Al2O3/InSb/Si (1 1 1) MOS diodes grown using MBE via InSb bi-layer with special care to the surface reconstruction. This growth technique is based on our finding that the InSb layer grown on a Si (1 1 1) substrate is rotated by 30° with respect to the substrate under certain initial conditions. This rotation drastically reduces the lattice mismatch from 19.3% to 3.3%, and improves the crystal quality of an InSb layer. To investigate the possibilities of InSb MOSFETs on Si substrates, we fabricated MOS diodes having an Al2O3 insulator film deposited by atomic layer deposition. C–V characteristics were measured both at RT and 77 K. It was found that the InSb grown on Si shows a degraded C–V curve compared to the InSb substrate, even though the mobility of the grown layer is quite high. We also investigated the effects of InSb thickness on the C–V characteristics of the MOSFETs. It was found that the quality of MOS diodes first degrades when decreasing the InSb thickness from 1 μm to 50 nm; further reduction of the InSb thickness improves it again. It was demonstrated that the MOS diode having a 10 nm InSb layer shows a good C–V curve, which is comparable to that of the InSb substrate. Finally, we discussed the possibility of the InSb/Si pseudomorphic MOSFETs.

Structural and luminescent properties of bulk InAsSb

The strong bandgap bowing in the InAsxSb1−x alloy system allows it to potentially be used for infrared photodetection in the middle and long wavelength range. The authors have used compositionally graded metamorphic buffer layers to accommodate the misfit strain between InAsxSb1−x alloys and GaSb and InSb substrates in order to reach the long wave infrared range. In this work, we present the characterization of metamorphically grown InAsxSb1−x films that demonstrate strong photoluminescence in the spectral range from 5 to 9 μm.

Fabrication of High-Quality InSb Nanowire Arrays by Chemical Beam Epitaxy

We present investigations on InSb nanowires grown directly on InSb substrates. A chemical beam epitaxy system was used to synthesize InSb nanowires. Growth at low temperatures (300−400 °C) resulted in extensive parasitic InSb thin film deposition and stacking faults within these nanowires. To circumvent both problems, InSb nanowires were synthesized at temperatures above 410 °C. By further optimizing the growth parameters completely stacking fault-free, free-standing InSb nanowires were obtained. By combining chemical beam epitaxy and laser interference lithography, large areas of ordered InSb nanowires were fabricated. Temperature-dependent electrical measurements on these InSb nanowire arrays showed intrinsic bulklike behavior.

Reflection Absorption Infrared Spectroscopy Study on the Spontaneous Formation of Erbium Monoantimonide Nanoparticles on Indium Antimonide Surfaces

ABSTRACTWe describe an ex-situ monitoring technique for a small amount (∼30 mono-layers) of erbium monoantimonide (ErSb) deposited on an indium antimonide (InSb) epitaxial layer prepared on InSb(100) substrates by metal organic chemical vapor deposition (MOCVD). Our objective is to improve thermoelectric properties of nanocomposites that employ nanometer size semi-metallic ErSb particles (ErSb nanoparticles) embedded in ternary group III-V compound semiconductor host materials such as indium gallium antimonide (InGaSb) and indium antimonide arsenide (InSbAs). The formation of ErSb nanoparticles embedded in a host material is spontaneous and needs to be carefully controlled to tune the size and volume density of the ErSb nanoparticles. We used an ex-situ monitoring technique based on glancing-angle infrared-absorption, reflection absorption infra-red spectroscopy (RAIRS), to study the formation of ErSb nanoparticles to correlate the amount of delivered ErSb and surface morphology of the surface of InSb covered with ErSb.

Binary Data Transmission Performance of Sub-20 nm Indium Antimonide Nanowires

ABSTRACTWe investigated the data transmission performance of indium antimonide (InSb) nanowires (NWs) synthesized on InSb (100) substrate using chemical vapor deposition (CVD) having diameters of 20 nm and below. The results indicate that the data transmission performance of NWs suffer from low mobility values on the order of 10-to-15 cm2V-1s-1 because of the scattering due to their small diameters, crystal defects and oxidation occurs during growth and cooling. The 20 nm NWs can sustain data rates up to 5 mega bits per second (Mbps) without any impedance matching and de-embedding of the parasitic parameters coming from the measurement system with a bit error rate (BER) level of 10-8. The data rate is directly proportional to the diameter of the NWs.

The effects of growth parameters on the RF-MBE growth of dilute InNSb films

A series of InNSb films have been grown on InSb (0 0 1) substrates under various growth conditions by plasma-assisted molecular beam epitaxy (MBE). The InNSb films were characterized by high-resolution x-ray diffraction, atomic force microscopy and Raman spectra. High quality single crystal InNSb films with N compositions up to 1.34% (from x-ray diffraction) were grown. It was found that the N composition of the films can be increased by increasing the In/Sb flux ratio and radio frequency (RF) power or by decreasing the growth temperature. The effects of growth parameters on the crystalline quality of the InNSb films were also discussed in detail.

Characterization of photodiodes, made from a p-type epitaxial layer grown on n-type InSb by LPE method

In this article the performance of photodiodes made from epitaxially grown layers of p-InSb on n-type InSb substrates is reported. The effect of increasing Cd atomic weight percent on p-type carrier concentration and mobility at 77 K is also discussed. In our epitaxial growth method, a ramp cooling technique was used. Finally by improving growth parameters such as growth temperature, prior cleaning of B face (Sb) n-InSb substrates and cooling rate, adequate epitaxial layers of p-InSb on n-InSb <1 1 1> and consequently highly sensitive photodiodes have been obtained. A high detectivity photodiodes fabricated for p-InSb on n-InSb substrate by liquid phase epitaxy (LPE) was measured using optoelectronic tests and the detectivity of the diodes was compared with n-InSb on p-InSb. Several other tests such as Hall effect, thickness measurements, I– V and X-ray diffraction (XRD) were also performed and morphology images will be presented in this paper.

Chemical vapor deposition and electrical characterization of sub-10 nm diameter InSb nanowires and field-effect transistors

Synthesis of InSb nanowires using a chemical vapor deposition technique, as a function of growth temperature and time, was investigated. High aspect ratio InSb nanowires, having a diameter of about 5–10 nm, were grown at 400 °C for 1 h on InSb (1 1 1) substrate onto which 60 nm Au particle was used as a metal catalyst. The synthesized InSb nanowires had zinc blend single crystal structure without any stacking faults, and they were covered with a thin (∼1 nm thick) amorphous layer. Electrical characterization of InSb nanowires was conducted utilizing a back-gated SNWFET. Device characterization demonstrated that NWs were n-type and exhibited a high I on/ I off ratio of 10 6 and device resistance of 250 kΩ.

Bismuth-stabilizedc(2×6)reconstruction on a InSb(100) substrate: Violation of the electron counting model

By means of scanning tunneling microscopy/spectroscopy (STM/STS), photoelectron spectroscopy, and first-principles calculations, we have studied the bismuth (Bi) adsorbate-stabilized InSb(100) substrate surface which shows a $c(2\ifmmode\times\else\texttimes\fi{}6)$ low-energy electron diffraction pattern [thus labeled $\text{Bi}/\text{InSb}(100)c(2\ifmmode\times\else\texttimes\fi{}6)$ surface] and which includes areas with metallic STS curves as well as areas with semiconducting STS curves. The first-principles phase diagram of the Bi/InSb(100) surface demonstrates the presence of the Bi-stabilized metallic $c(2\ifmmode\times\else\texttimes\fi{}6)$ reconstruction and semiconducting $(4\ifmmode\times\else\texttimes\fi{}3)$ reconstruction depending on the chemical potentials, in good agreement with STS results. The existence of the metallic $c(2\ifmmode\times\else\texttimes\fi{}6)$ phase, which does not obey the electron counting model, is attributed to the partial prohibition of the relaxation in the direction perpendicular to dimer rows in the competing reconstructions and the peculiar stability of the Bi-stabilized dimer rows. Based on (i) first-principles phase diagram, (ii) STS results, and (iii) comparison of the measured and calculated STM and photoemission data, we show that the measured $\text{Bi}/\text{InSb}(100)c(2\ifmmode\times\else\texttimes\fi{}6)$ surface includes metallic areas with the stable $c(2\ifmmode\times\else\texttimes\fi{}6)$ atomic structure and semiconducting areas with the stable $(4\ifmmode\times\else\texttimes\fi{}3)$ atomic structure.

Growth and properties of Al2O3 and SiO2 nanolayers on III–V semiconductors

We describe atomic layer deposition of silica and alumina layers on GaAs, InAs, and InSb substrates. The conditions for layer-by-layer growth of surface nanostructures are established, and some of their dielectric parameters are evaluated.

Calculation of phase diagrams in Al xIn 1−xAs/InP, As xSb 1−xAl/InP and Al xIn 1−xSb/InSb nano-film systems

The models for calculation of phase diagrams of semiconductor thin films with different substrates were proposed by considering the contributions of strain energy, the self-energy of misfit dislocations and surface energy to Gibbs free energy. The phase diagrams of the Al x In 1− x As and As x Sb 1− x Al thin films grown on the InP (1 0 0) substrate, and the Al x In 1− x Sb thin films grown on the InSb (1 0 0) substrate at various thicknesses were calculated. The calculated results indicate that when the thickness of film is less than 1 μm, the strain-induced zinc-blende phase appears, the region of this phase extends with decreasing of the layer thickness, and there is small effect of surface energies of liquid and solid phases on the phase diagrams.

The production and structure of submicrometer Eu0.75Fe0.25O films on InSb, Si, and GaAs substrates

The conditions for fabrication and the crystal structure of the up-to-350-nm-thick Eu 0.75 Fe 0.25 O lay- ers formed on InSb, Si, and GaAs substrates are studied. For the first time, 100-200 nm films with morpho- logical surface inhomogeneities not exceeding 10 nm in size are produced by flash evaporation of targets close in composition to Eu 0.75 Fe 0.25 O onto InSb(001) substrates. The films exhibit ferromagnetic properties in com- bination with semiconductor properties at room temperatures.

New process results in smoother indium antimonide substrates

The high optical transparency of indium antimonide (InSb) substrates makes them attractive for IR focal-plane arrays (IRFPAs) and detectors, free-space communications, transistors, and integrated optoelectronics.1–3 A large-diameter crystalline InSb surface can accommodate new and bigger advanced IRFPA designs. However, the 150mm diameter of these antimonides poses unique surface-polishing challenges to substrate manufacturers. To improve the resolution and sensitivity of highperformance IRFPA imaging systems in the 1–5.4μm region (77◦K), the substrates’ surface must meet or surpass stringent demands. In particular, for detector-fabrication processes requiring epitaxy growth for the device layer, the starting InSb surface must be ultrasmooth, less than one atomic layer in roughness. It should also desorb the Sb and In surface oxides in an abrupt and fast outgassing process.4 A consistent and easily desorbable surface oxide helps improve advanced-device epilayer yield and performance in Sb-based IRFPA manufacturing. The substrate’s chemomechanical-polish (CMP) history is a primary factor in InSb surface smoothness and oxide desorption. We wanted to consistently produce surfaces suitable for recent epitaxy processes with stringent substrate-surface specifications. To do so, we analyzed the substrate-surface orientation, atomic roughness, oxide desorption, and crystallinity as a function of CMP process. Our resulting CMP process for largerdiameter InSb single-crystal surfaces has produced a smoother InSb starting surface and abrupt oxide-desorption characteristics suitable for device-layer molecular-beam-epitaxy (MBE) material growth.5 We applied a standard semiconductor-grade CMP to two groups of antimonide substrates separated from the same boule. We used a proprietary CMP process for group A. For group Figure 1. Thermal x-ray photoelectron spectroscopy analysis spectra in electron volts (eV) for the antimonide (Sb) 3d (electron orbital) binding-energy peaks of both Group A and B chemomechanical polish surfaces at 400◦C shows the Sb oxide removed for Group B polished surfaces. CMP: Chemomechanical polish.