InSb Crystals Research Articles

Changes of the growth morphology in insb crystals pulled under the presence of ultrasonic vibrations

AbstractIn the Czochralski method, the effect of ultrasonic vibrations on the growth of InSb single crystals was investigated by observing the growth morphology. Remarkable changes which ultrasonic vibrations brought about were: (1) the crystal diameter, (2) the width of the facet region and (3) the inclined angle of non‐facet interfaces near the facet region for the (111) plane. After introducing vibrations, the crystal diameter decreased smoothly with growth time. However, both the facet width and the inclined angle reached each minimum value after 5 to 7 min regardless of the magnitude of vibrational output powers from 30 to 90 W, and they were in roughly proportional relation with each other. The change rates of crystal diameter and of facet width increased with vibrational powers. The decrease of crystal diameter was known to result from the rise of the melt temperature, which was brought by both the mixture of the melt and the thermal energy transformation due to ultrasonic vibrations. The change of facet width depended upon the melt flow itself in addition to the temperature rise.

Isotope scattering of large-wave-vector phonons in GaAs and InSb: Deformation-dipole and overlap-shell models

Scatterings of near-zone-boundary phonons by isotopic disorder in diatomic GaAs InSb crystals are studied theoretically. In multiatomic lattices the scattering rate depends importantly on the vibrational amplitudes of constituent atoms. We find that the wave-vector dependences of these amplitudes, which are predicted by some lattice models, show quite dissimilar behaviors as compared to others. The typical examples investigated in this paper are the deformation-dipole model and the overlap-shell model. With the use of these models the frequency dependence of the relaxation time of phonons is calculated. Both models, however, predict the relaxation time of about 0.1 \ensuremath{\mu}sec for 1-THz TA phonons in GaAs, which is at least 1 order of magnitude shorter than the lifetime reported by Ulbrich et al.

Parametric Decay of a High‐Power Helicon Wave in to a Transverse Acoustic and Another Helicon Waves in Longitudinally Magnetised Cubic Piezoelectric Semiconducting Plasmas

AbstractA detailed analytical investigation is made of the parametric decay of a high‐power helicon into another helicon and an acoustic wave in a longitudinally magnetised n‐type cubic piezoelectric semiconducting crystal belonging to the class 43m. The dispersion relation is obtained by using a hydrodynamic model of an homogeneous, piezoelectric,one‐component (electron) semiconducting plasma, and the threshold value of pump electric field and the growth rate of unstable mode well above the threshold are discussed. The analysis is applied to a specific semiconductor, n‐InSb at 77 K duly irradiated by a high‐power heliconwave for numerical estimation. The laser wave intensities used are in the range of 109 to 1012 Wm−2 which is assumed to be less than the damage threshold of the InSb crystal. The order of waveamplitude is feasible presently. The growth rate is found to be of the order of 1010 s−1.

Field dependence of charge carrier mobility in InSb crystals heavily irradiated by neutrons

Field dependence of charge carrier mobility in InSb crystals heavily irradiated by neutrons

Parametric Conversion of an Electromagnetic Wave into an Acoustic Wave in Magnetised Cubic Piezoelectric Semiconducting Plasmas

AbstractA detailed analytical investigation is made of parametric conversion of an electromagnetic wave into an acoustic wave in a magnetoactive n‐type cubic piezoelectric semiconducting crystal belonging to class 43m under a geometrical configuration which can also be employed in analysing the phenomenon under either Voigt or Faraday orientation. The electric vector E0 of an spatially uniform pump electromagnetic wave (applied along the y‐axis) is normal to propagation direction (along the z‐axis) of the generated low‐frequency transverse‐acoustic wave (Ω, k) and the scattered electromagnetic wave (Ω1, k1). The magnetostatic field is applied in the xz plane making an arbitrary angle θ with propagation vectors k, k1 (antiparallel to each other). The dispersion relation is obtained by using a hydrodynamic model of an homogeneous, piezoelectric, one‐component (electron) semiconductor plasma, and the threshold value of pump electric field and the growth rate of unstable acoustic mode well above the threshold are discussed for isotropic (B0 = 0) and magnetoactive (B0 ≠ 0) plasmas. The analysis is applied to a specific semiconductor, n‐InSb at 77 K duly irradiated by a pulsed 10.6 μm CO2 laser for numerical estimation. The laser wave intensities used are in the range of 109 to 1011 W m−2 which is assumed to be less than the damage threshold of the InSb crystal.

Damage effects in insb by an alternate beam channelling technique

Abstract Alternate channelled beams of protons and 4He ions have been used both to introduce and monitor damage in InSb crystals. The studies were facilitated by a simple method which enabled the beams to be alternated easily and quickly. InSb was found to be structurally sensitive to MeV ions, the sensitivity being much greater for He-ion than for proton bombardment. Since proton channelling was found to be more sensitive to damage than He channelling it is suggested the disorder took the form of localized lattice strain probably associated with dislocations.

Direct Determination of Indium Antimonide Energy Band Parameters from Diamagnetic Exciton Spectra

AbstractDiamagnetic exciton spectra of InSb crystals derived from transmission measurements carried out on thin unstressed samples at 1.8 K and in magnetic fields up to 80 kOe are used for a direct determination of parameters of the c‐ and v‐bands. Detailed identification and precise binding energy calculations permit one to derive the cyclotron frequencies of the electron and the holes, and the spin splittings. The m(ϵc) and g(ϵc) relationships thus obtained exhibit good agreement with Kane's model up to energies close to ϵc ϵg. Light holes also reveal a strong nonparabolicity characterized in the linear‐in‐k4 approximation by the coefficient p1h = 0.47 meV−1. An analysis of the splitting of two light‐hole long‐wavelength transitions including the diamagnetic exciton binding energies and the data on the c‐band obtained permits one to calculate the v‐band parameter set.

Diamagnetic excitons and the indium antimonide energy band parameters

AbstractThe oscillatory absorption edge spectrum of InSb crystals exhibiting the discrete structure of the Wannier‐Mott exciton at H  0 is studied at 1.8 K in magnetic fields of up to 80 kOe. The experimental data obtained are analyzed with a computer taking into account the excitonic nature of the phenomenon and the effect on the Landau levels of the nonlocality of potential resulting from the electron—electron exchange interaction. A set of band parameters is presented which provides a minimum discrepancy between the theoretical and experimental spectra of not more than 0.65 meV per datum point: Ep  23.42 eV, F  − 1.18, N1  − 0.33, γ2  36.41, γ2   15.95, γ3  16.99, k  15.22, q  0.31, χ0  17.9. The possible contribution of the higher bands and the reasons for disagreement with other avialable parameters are discussed.

Growth of highly homogeneous InSb single crystals

A characteristic detect, shaped like the letter “Y”, could be found in the [111] pulled InSb crystal. The carrier concentration in the defect is higher than in other parts, which is detrimental in MOS monolithic IR imaging devices. A high quality InSb single crystal for IR imaging devices was found to be grown by a pulling method using a seed inclined 5–10° from the [111] to the [110] direction. The growth conditions for homogeneous InSb single crystals were discussed.

Indium antimonide energy band parameters derived from diamagnetic exciton spectra

The oscillatory absorption edge spectrum of thin InSb crystals in which the discrete structure of the Wannier-Mott exciton had been revealed at H=0 for the first time has been studied at 1.8 K in magnetic fields of up to 80 kOe. The experimental data were analyzed with a computer taking into account the exciton nature of the phenomenon and the effect on the Landu levels of the nonlocality of potential resulting from the electron-electron exchange interaction. A set of band parameters has been obtained providing a minimum discrepancy between the theoretical and experimental spectra by not more than 0.65 meV per point: E p = 23.42 eV, F = -1.18, N 1 = -0.33, r 1 = 36.41, r 2 = 15.95, r 3 = 16.99, r = 15.22, q = 0.31 for h = 17.9 . The reasons for and the extent of discrepancy between the InSb parameters derived by other authors from interband magnetoabsorption experiments are discussed.

Horizontal Zone-Melting of Indium Antimonide in Vacuum. II. Characterization by Galvanomagnetic Measurements at 77 K

Magnetoresistance and transverse magnetophonon resonance data at 77 K for n-type InSb crystals (prepared by the method described in Part I) are given, with the aim of detecting residual impurities and inhomogeneities. The importance of 1) using boat material not wetted by InSb and 2) low-temperature annealing (at 200°C for one week) are shown experimentally. The concentration of residual impurities is estimated to be 2×1014/cm3, and three kinds of impurity are found. Furthermore, dislocations and non-uniform distribution of the compensating acceptor impurities are identified as the source of inhomogeneities. It is concluded that the carrier concentration of less than 1014/cm3 is due to the compensation effect and that the reliable maximum mobility at 77 K is 8×105cm2/V·s.

Brillouin instability inn-type piezoelectric semiconductors

The paper aims at the detailed analytical investigation of Brillouin instability in a magnetoactive $n$-type cubic piezoelectric semiconducting crystal belonging to class $\overline{4}3m$ under a geometrical configuration which can also be employed in analyzing the phenomenon under either Voigt or Faraday orientation. The electric vector ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{E}}}_{0}$ of the spatially uniform pump electromagnetic wave (applied along the $y$ axis) is normal to the magnetostatic field ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{B}}}_{0}$ (along the $z$ axis) as well as to the plane of propagation $x\ensuremath{-}z$ plane) of the internally generated low-frequency transverse-acoustic wave ($\ensuremath{\omega},\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}$) and the scattered electromagnetic wave (${\ensuremath{\omega}}_{1},{\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}_{1}$). The propagation vectors $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}$, ${\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}}_{1}$ (antiparallel to each other) are in the $x\ensuremath{-}z$ plane making an angle $\ensuremath{\theta}$ with the $x$ axis. The dispersion relation has been obtained by using a hydrodynamic model of the homogeneous, piezoelectric, one-component (electron) semiconductor plasma, and the critical value of the pump electric field (necessary to achieve physically reasonable growth of an unstable wave) and the growth rate of the unstable Brillouin mode well above the critical field have been obtained for isotropic (${B}_{0}=0$) and magnetoactive (${B}_{0}\ensuremath{\ne}0$) plasmas. We have applied our analysis to a specific semiconductor, $n$-InSb at 77 K duly irradiated by a pulsed 10.6-\ensuremath{\mu}m C${\mathrm{O}}_{2}$ laser for numerical estimation. Qualitative agreement between the analytical results and the numerical analysis has been noticed. The laser wave intensities used here are in the range of ${10}^{9}$ to ${10}^{12}$ W ${\mathrm{m}}^{\ensuremath{-}2}$ which is assumed to be less than the damage threshold of the InSb crystal. The phase velocity of the growing unstable mode is found to be constant over the whole range of system parameters and equal to the acoustic velocity in the crystal. The magnitude of the critical field decreases with increasing magnetostatic field and decreasing $\ensuremath{\theta}$. The growth rate increases and attains a maximum value at a certain value of the pump intensity, magnetostatic field, and $\ensuremath{\theta}$, and if these are raised further, growth rate starts decreasing. The magnitude of the growth rate is found to be \ensuremath{\sim} ${10}^{8}$ ${\mathrm{sec}}^{\ensuremath{-}1}$ at laser intensities of the order of ${10}^{10}$ W ${\mathrm{m}}^{\ensuremath{-}2}$. When the analysis is extended to Voigt and Faraday configurations, the results are not very encouraging.

Performance and application of a double crystal monochromator in the energy region [formula omitted] eV

The performance and application of an ultrahigh vacuum compatible constant-deviation double-crystal monochromator (JUMBO) in operation at SSRL is demonstrated. The monochromator can be operated with any of four pairs of crystals interchangeable in situ. An electronic maximum search feedback loop optimizes the intensity of the spatially fixed outgoing beam as the photon energy is scanned. The monochromatic beam is focused (∼1.5 mm × 5 mm) onto the sample by a toroidal mirror. Monochromator crystals of beryl(10 1 0), InSb(111) and Ge(111) have been tested in the energy regions 800−1540 eV, 1690–4000 eV and 1930–4500 eV, respectively. The performance of these crystals with regard to the resolution, the intensity, the level of scattered light, and the contribution of higher orders have been determined. Various effects arising from a radiation-induced temperature gradient in the monochromator crystals are discussed. Novel studies of bulk and surface properties of materials by angle-resolved photoemission, X-ray induced Auger spectroscopy, photon-stimulated ion desorption, bulk and surface extended X-ray absorption fine structure (EXAFS and SEXAFS) measurements in this previously inaccessible energy region of the electromagnetic spectrum are also discussed.

Raman instability inn-type piezoelectric semiconductors

Raman instability of the Stokes component of the scattered electromagnetic wave has been investigated in an $n$-type piezoelectric semiconductor in the presence of a large transverse magnetostatic field. The general dispersion relation has been obtained following the coupled-mode theory and considering that the scatte$\stackrel{\mathrm{\ifmmode \dot{}\else \.{}\fi{}}}{\mathrm{r}}$ing results not only from the molecular vibrations produced owing to the pump wave at a frequency equal to that of the transverse-optical phonons but also from the electron plasma wave. The analysis has been applied to both cases of isotropic (${B}_{0}=0$) and magnetoactive (${B}_{0}\ensuremath{\ne}0$) plasmas. The threshold value of the pump amplitude necessary for the onset of instability and the growth rate of the unstable mode well above the threshold have been obtained analytically for ${B}_{0}=0$ and ${B}_{0}\ensuremath{\ne}0$. It is observed that a large transverse magnetostatic field can reduce the threshold value of the pump amplitude and increase the growth rate of the unstable Raman mode at an electric field amplitude greater than the threshold value. Numerical estimates have been made for $n$-InSb crystal at 77 K. The crystal has been irradiated with a pulsed 10.6-\ensuremath{\mu}m C${\mathrm{O}}_{2}$ laser to obtain the necessary electric field. The analytical as well as the numerical results have been compared with those of Sen while studying Brillouin instability in $n$-type magnetoactive piezoelectric semiconductors.

High-frequency dielectric properties of covalent semiconductors within the nearly-free-electron approximation. I. The one-plasmon-band model

The macroscopic dielectric response function ${\ensuremath{\epsilon}}_{M}(\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}, \ensuremath{\omega})$ is calculated analytically for covalent semiconductors in the high-frequency limit. The effects of the periodic crystal potential are included by second-order perturbation theory within the self-consistent-field approximation. A study of the plasmon line shape, i.e., of the energy-loss function $\mathrm{Im}[\ensuremath{-}\frac{1}{{\ensuremath{\epsilon}}_{M}}(0, \ensuremath{\omega})]$ and of the optical absorption $\mathrm{Im}{\ensuremath{\epsilon}}_{M}(0, \ensuremath{\omega})$ demonstrates the importance of local-field corrections in covalent semiconductors. In the long-wavelength limit, the theory predicts that the unknown effective pseudopotential form factors ${U}_{\stackrel{\ensuremath{\rightarrow}}{\mathrm{G}}}$ for reciprocal-lattice vectors with $|\stackrel{\ensuremath{\rightarrow}}{\mathrm{G}}|\ensuremath{\ge}|{\stackrel{\ensuremath{\rightarrow}}{\mathrm{G}}}_{400}|$ may be obtained successively for increasing $|\stackrel{\ensuremath{\rightarrow}}{\mathrm{G}}|$ and increasing excitation energies $\ensuremath{\hbar}\ensuremath{\omega}$ from energy-loss experiments or optical measurements. Available experimental data in two cases (Si and Ge) show absorption edges near the predicted energies associated with particular ${U}_{\stackrel{\ensuremath{\rightarrow}}{\mathrm{G}}}$. For the first time, the anisotropic plasmon dispersion has been calculated for semiconductors and is compared with recent loss experiments on single crystals of Si, GaAs, and InSb. Owing to the similarity of the crystal potential in these compounds, the theory predicts the same trends for all three materials, namely: ${\ensuremath{\omega}}_{p}^{[100]}(\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}})>{\ensuremath{\omega}}_{p}^{[110]}(\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}})>{\ensuremath{\omega}}_{p}^{[111]}(\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}})$. For Si and GaAs this is in agreement with experiment whereas unexpectedly the experiment shows that ${\ensuremath{\omega}}_{p}^{[110]}(\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}})>{\ensuremath{\omega}}_{p}^{[100]}(\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}})>{\ensuremath{\omega}}_{p}^{[111]}(\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}})$ for InSb.

Galvanomagnetic properties of annealed InSb single crystals

p-type InSb crystals have been obtained by annealing n-type InSb crystals at 350 °C in vacuum (10−5 Torr) for different durations. The dc Hall effect and conductivity studies have shown that the inversion temperature increases with increase in annealing time, whereas the Hall mobility decreases. The ratio of electron to hole mobility b is calculated from the log RH -vs-1/T curve and also from electron and hole concentrations. The ratio b is also calculated theoretically from electron and hole mobilities. The value b obtained from experiments is found to differ from the b calculated theoretically. This discrepancy has been attributed to the scattering of charge carriers by dislocations produced during annealing. Using the Dexter and Seitz mechanism [Phy. Rev. 86, 964 (1952)] the dislocation densities have been estimated in the annealed samples.

Investigation of convection in melts and crystal growth under large inertial accelerations

A centrifuge arrangement is described which was used to investigate density-gradient driven convection in melts (In, InSb) and crystal growth (InSb). The melts were heated in a cylindrical tube by aid of a gradient furnace with axis parallel to centrifugal force. We studied the onset of unsteady convection in the melts (acceleration equal to 1–20 times earth gravity), as well as the effects of the different hydrodynamic states on a growing InSb crystal as a function of variable gravity level (1–3 times earth gravity). It is demonstrated that all results of temperature measurement in the melts and the occurrence of doping striations in the grown crystal can be explained by defining a common Rayleigh number with a variable acceleration instead of constant earth gravity 9.81 m/s 2.

Ionized impurity scattering of electrons in single crystals of n-type InSb

Ionized impurity scattering of electrons in single crystals of n-type InSb

Photoconductivity from Free Carrier Absorption in Mercury-Cadmium-Telluride

We report the development of the first hot-electron photoconductive detector using crystals of the alloy-semiconductor mercury-cadmium-telluride, [Hg1-x, Cdx]Te. When the detector is irradiated with near-millimeter wave radiation, sensitivity is observed spanning the wavelength region from 0.12 to 4.4 mm. At a temperature of 4.2 K and a wavelength of 2.5 mm, the noise equivalent power is observed to be 9.7×10-11 W/√Hz with a response time less than 40 ns. The voltage responsivity decreases by approximately 50-percent for each 5 K increase in temperature above 4.2 K. Comparative performance measurements are reported for various InSb crystals.

A low-noise InSb thin film hall element: Fabrication, device modeling, and audio application

Low-noise InSb thin film Hall elements have been developed as magnetic sensors for audio tape playback. Approximately 1.4-μm thick Hall elements are fabricated by vacuum deposition followed by microzone melting, film thinning, and subsequent heat treatment. After film thinning, electron mobility at room temperature is 6 m2/V . s showing the 1-ppm level impurity concentration. After heat treatment, noise is at the 0.5-μV level for frequencies in the 102-104Hz range and signal-to-noise ratio of the Hall elements is 82 dB in a 1-mT (10-G) magnetic flux density. The device characteristics as functions of dc bias current is successfully computer-simulated, where element Joule heating is taken into account. The calculated results agree quantitatively with the experimental results. For this device modeling, electrical transport properties in InSb crystals are calculated and related to element temperature and ionized-impurity concentrations. In order to apply the Hall elements to audio magnetic heads for cassette tape playing, the head design principle and the head signal-to-noise ratio are clarified for the first time. The advantages of the Hall effect magnetic heads are also discussed.