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15 Dec 1986

Volume 60, Issue 12, pp. R161-4344

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A review of frequency measurements of optically pumped lasers from 0.1 to 8 THz

M. Inguscio, G. Moruzzi, K. M. Evenson, and D. A. Jennings

J. Appl. Phys. 60, R161 (1986); http://dx.doi.org/10.1063/1.337433 (32 pages) | Cited 49 times

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We present a list of more than 800 far‐infrared laser lines emitted by optically pumped molecular lasers whose frequencies have been measured. For each line, frequency, wavelength, wave number, lasing molecule, CO2 pump line, and, if available, the assignment of the lasing transition, are given. The list is accompanied by a survey of the techniques of frequency measurement in the far infrared. Accuracies and limitations of the various techniques are also discussed.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
33.20.Ea Infrared spectra

Quenching of NF singlet states in a hybrid chemical‐laser system

D. J. Benard, M. A. Chowdhury, and A. T. Pritt

J. Appl. Phys. 60, 4051 (1986); http://dx.doi.org/10.1063/1.337535 (8 pages) | Cited 1 time

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Quenching of NF (a1Δ) and NF (b1Σ) was studied in a subscale upconversion gain medium that was based on energy transfer from NF (b1Σ) to IF. Quenching of NF (b1Σ) by IF was found to occur at gas‐kinetic rates that were large compared to the energy‐transfer rate, indicating low efficiency for the laser. Significant quenching of NF (a1Δ) by IF was also found to occur at a slower rate than was evident for the NF (b1Σ) state.
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42.55.Ks Chemical lasers
78.60.Ps Chemiluminescence
42.55.-f Lasers
34.50.Gb Electronic excitation and ionization of molecules

Direct measurement of the energy spectrum of an intense proton beam

R. J. Leeper, J. R. Lee, L. Kissel, D. J. Johnson, W. A. Stygar, and D. E. Hebron

J. Appl. Phys. 60, 4059 (1986); http://dx.doi.org/10.1063/1.337536 (5 pages) | Cited 18 times

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A time‐resolved magnetic spectrograph was used to measure the energy spectrum of an intense (0.7 TW/cm2) proton beam. A thin gold foil placed at the focus of an ion‐diode Rutherford‐scattered protons by 90° into the spectrograph, reducing the beam intensity to a level suitable for magnetic analysis. The scattered protons were collimated and then deflected in a samarium‐cobalt permanent magnet. The deflected protons were recorded simultaneously on CR‐39 and eight p‐i‐n diodes. A Monte Carlo computer code was used to calculate the sensitivity and resolution of the spectrograph. Data taken on the Proto I accelerator shows a 150–250‐keV‐wide proton‐energy spectrum at each instant in time.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors
29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams

Comparisons of the different configurations of the second‐order reflection grating

Wee Sang Park and S. R. Seshadri

J. Appl. Phys. 60, 4064 (1986); http://dx.doi.org/10.1063/1.337537 (13 pages) | Cited 3 times

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Three canonical equations governing the characteristics of the second‐order reflection grating for the transverse magnetic mode are derived. Based on the solution of the canonical equations, the input coupling efficiency for the Gaussian beam is deduced. The characteristics of the four different operating schemes of the reflection grating are compared with reference to such applications as the frequency selective filter, the output coupler, and the input coupler.
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42.79.Dj Gratings
42.79.Gn Optical waveguides and couplers

Upconversion‐pumped infrared erbium laser

S. A. Pollack, D. B. Chang, and N. L. Moise

J. Appl. Phys. 60, 4077 (1986); http://dx.doi.org/10.1063/1.337486 (10 pages) | Cited 59 times

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A study of upconversion processes in Er3+ ions in CaF2 has led to an unambiguous demonstration of IR lasing produced by upconversion pumping alone. The study has shown: (1) strong upconversion lines originating from the 4I11/2 state; (2) the existence of both two‐photon and three‐photon upconversion processes; (3) an optimum concentration of 5–10 mol % for Er3+; and (4) upconversion efficiencies for the visible bands as high as 10% at 77 K and 1% at 300 K. Measurements of lasing between the 4I11/2 and 4I13/2 levels show that even though the lifetime of the upper (4I11/2) state is only half that of the lower state, self‐quenching does not occur. Upconversion is implicated for this transition both by the nonpersistence of a ‘‘red shift’’ during a lasing pulse, and by the opposite dependence on concentration of laser threshold energy and upconversion‐produced fluorescent intensity. A simple theoretical model shows that a 2.8‐μm laser operating between the 4I11/2 and 4I13/2 levels can be pumped solely by upconversion of ions in the excited 4I13/2 state produced by absorption of a 1.54‐μm pulse. In addition, (1) a minimum of 1.54‐μm pump energy is required; (2) lasing occurs with a delay inversely proportional to the pump energy; and (3) lasing can persist for as long as the lifetime of the lower (4I13/2) state. These predictions have been experimentally verified. The lasing experiments give a lower limit for the upconversion coefficient of α=10−16 cm3 s−1.
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42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.-f Lasers

Room‐temperature optically pumped laser oscillation at 2.07 μm from Ga0.85In0.15As0.13Sb0.87/ Al0.4Ga0.6As0.035Sb0.965 double heterostructures grown by molecular‐beam epitaxy on GaSb substrates

J. P. van der Ziel, T. H. Chiu, and W. T. Tsang

J. Appl. Phys. 60, 4087 (1986); http://dx.doi.org/10.1063/1.337487 (3 pages) | Cited 5 times

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The growth by molecular‐beam epitaxy of high‐quality Ga0.85In0.15As0.13Sb0.87 active layers with Al0.4Ga0.6As0.035Sb0.965 cladding layers on GaSb substrates by molecular‐beam epitaxy is reported. The lattice match of the active layer to the substrate is Δa/a ∼4 ×10−3. Optically pumped laser oscillation was observed from 80 to 300 K with T0=55 K for T<225 K and T0=32 K for 225<T<300 K.
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42.55.Px Semiconductor lasers; laser diodes
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Scalar scattering characteristics of a periodic, impenetrable surface: Effect of surface modeling errors

Akhlesh Lakhtakia, Vijay K. Varadan, and Vasundara V. Varadan

J. Appl. Phys. 60, 4090 (1986); http://dx.doi.org/10.1063/1.337488 (5 pages) | Cited 2 times

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Use is made of the T‐matrix method to examine the effect of surface profile modeling errors in studying the scalar scattering responses of impenetrable, periodic surfaces. It is shown that even small errors can alter the maximum surface slope significantly, thereby taxing the resources of numerical procedures and severely limiting their scopes of applicability. However, it is possible that the power diffraction coefficients are not very different when calculations are made with and without these errors. Possible implications for using such methods in order to understand the scattering behavior of fractal surfaces are discussed.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
11.80.-m Relativistic scattering theory
42.25.Fx Diffraction and scattering

Propagation of intense ion beams across a plasma‐filled magnetic cusp

K. O. Busby, J. B. Greenly, D. A. Hammer, Y. Nakagawa, and P. D. Pedrow

J. Appl. Phys. 60, 4095 (1986); http://dx.doi.org/10.1063/1.337794 (7 pages) | Cited 5 times

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Preionized plasma has been compared with vacuum and with neutral gas as a medium for the propagation of intense ion beams across magnetic fields. Two cusp‐injection ion ring experiments have been used to study the effectiveness of these three cusp‐fill media for space‐charge neutralization, as shown by the subsequent spreading of the injected rings. In the ion ring experiment a ≲100‐ns ion beam was injected into ∼20‐eV plasma fills of ≲1012/cm3, giving much better propagation than vacuum, but not as good as 100‐mTorr H2 gas. In the long‐pulse ion ring experiment with ≳200‐ns beam rise time, plasma fill and vacuum gave similar propagation. The results suggest that for complete neutralization of space charge in ion beams propagating across magnetic fields, background media must be provided to meet certain minimum requirements of conductivity and collisionality which depend upon the beam current and rise time.
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52.40.Mj Particle beam interactions in plasmas
52.55.Lf Field-reversed configurations, rotamaks, astrons, ion rings, magnetized target fusion, and cusps
52.59.Mv High-voltage diodes
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams

Laser‐induced fluorescence study of silicon etching process: Detection of SiF2 and CF2 radicals

Yutaka Matsumi, Satoru Toyoda, Toshio Hayashi, Masao Miyamura, Hideshi Yoshikawa, and Souji Komiya

J. Appl. Phys. 60, 4102 (1986); http://dx.doi.org/10.1063/1.337489 (7 pages) | Cited 36 times

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Using a laser‐induced fluorescence (LIF) technique, SiF2 and CF2 radicals are detected during the downstream etching of silicon with a discharge of CF4 gas. It is confirmed that SiF2 radical is desorbed from the surface in the etching of silicon by fluorine atom. Addition of O2 gas to the CF4 discharge enhances the LIF intensity of SiF2 radical and extinguishes that of CF2. Mechanism of the increase of etching rate of silicon by addition of O2 is discussed on the basis of the results of LIF measurements. The etching rate of silicon is proportional to the LIF intensity of SiF2, when the microwave power of the discharge is changed. The relationship between the intensity of chemiluminescent continuum and the concentration of SiF2 is revealed, which suggests that the chemiluminescence is attributed to the emission of SiF@B|3 which is produced by the reaction between SiF2 and fluorine atoms in the gas phase. There is no signal of SiF2 during the etching of either SiO2 or SiNx.
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81.65.-b Surface treatments
78.60.Ps Chemiluminescence
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Some characteristics of the hollow anode glow

Vujo I. Miljević

J. Appl. Phys. 60, 4109 (1986); http://dx.doi.org/10.1063/1.337490 (4 pages) | Cited 12 times

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A new type of discharge realized in a diode consisting of a cathode and a special type of hollow anode is presented. The distinctive arrangement of dark and luminous regions between the cathode and anode with a characteristic hollow anode glow has been observed in the discharge. The optical spectrum strongly depends on the discharge current, and can be practically a spark or arc spectrum without any lines of anode or cathode material.
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52.80.Hc Glow; corona
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

A model of radio frequency planar discharges

A. M. Pointu

J. Appl. Phys. 60, 4113 (1986); http://dx.doi.org/10.1063/1.337491 (6 pages) | Cited 32 times

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A simple model, using an asymmetrical double probe theory, is presented to describe a rf planar glow discharge. It reasonably agrees with available experimental results for a capacitively coupled excitation electrode and frequencies of about 100 kHz.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.40.Hf Plasma-material interactions; boundary layer effects
52.75.-d Plasma devices

Propagation of a mildly relativistic electron beam at sub‐Torr pressures

J. R. Smith, R. F. Schneider, M. J. Rhee, H. S. Uhm, and W. Namkung

J. Appl. Phys. 60, 4119 (1986); http://dx.doi.org/10.1063/1.337492 (8 pages) | Cited 26 times

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This report presents observations on propagation of a mildly relativistic electron beam (γ=2.4) in several different gases (air, He, N2, and Ar) at low pressure (10–320 mTorr). At such low pressures, and with beam currents of several kiloamperes, beam‐induced ionization may result in self‐focusing of an electron beam. Beams propagating under this condition are said to be in the ion‐focusing regime of propagation. The injected beam has an rms radius of 0.7 cm and a transverse temperature of 35 keV. Beam transport efficiency was measured for He, N2, and Ar. A simple calculation was performed to determine the space‐charge neutralization fraction as a function of time. Using the results of this calculation, the charge‐transport efficiency is found and compared with the experimentally measured quantity.
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52.40.Mj Particle beam interactions in plasmas
52.27.Ny Relativistic plasmas
51.50.+v Electrical properties (ionization, breakdown, electron and ion mobility, etc.)
41.75.Ht Relativistic electron and positron beams

Anode discharge mode and cathodic plasma state in high‐current vacuum arcs

H. Toya, Y. Uchida, T. Hayashi, and Y. Murai

J. Appl. Phys. 60, 4127 (1986); http://dx.doi.org/10.1063/1.337493 (6 pages) | Cited 8 times

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Anode surface states and traces of the cathode spots after arcing of various anode discharge modes in vacuum have been studied in the current range of 5–20 kA. Spectroscopic measurements of the radial electron temperature profile in the cathode region, which is related to the distribution of the current density, have also been performed to investigate the cathodic plasma state of the arcs in the various anode modes. The arc of a half‐wave sinusoidal current of 60 Hz was burned between a 60‐mm‐diam anode and a 30‐mm‐diam cathode spaced 4 mm apart. The electrodes were made of oxygen‐free, high‐conductivity copper. The cathode spots spread uniformly over the entire cathode and a uniform current density profile was obtained in the diffuse‐arc mode. It was found, however, that the cathode spots bunch together and the current density profiles peak at the center of the discharge in the anode‐spot mode. The cathode‐spot bunching and the nonuniformity in the current density profile become significant with a sufficient increase in arc current to cause severe erosion of the anode. Another finding was that the cathode spots spread almost uniformly over the cathode while a nonuniform current density profile appears in the diffuse arc associated with the presences of the arc‐voltage fluctuation and a slight anode melting, i.e., in which the transition to the foot‐point mode has begun. The occurrence of current constriction in the arc without cathode‐spot bunching will be briefly discussed.
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52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.80.Vp Discharge in vacuum
52.75.Kq Plasma switches (e.g., spark gaps)

Emitter tests in an open thermionic converter with vapor injection through the collector

Susen Wriedt, Kenneth Möller, and Leif Holmlid

J. Appl. Phys. 60, 4133 (1986); http://dx.doi.org/10.1063/1.337494 (3 pages) | Cited 1 time

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Mo and Pt emitters and a Ni collector with 400 laser‐bored holes were used in an ‘‘open’’ thermionic converter. The alkali vapor was introduced into the converter through the array of holes in the collector from an adjacent alkali metal reservoir with separately controlled temperature. The overall results from the open thermionic converter are comparable to results from enclosed converters. The results found with a Cs plasma are encouraging, with barrier indices down to below 1.8 eV, at emitter temperatures around 1500 K in the case of a Mo emitter. The output power density was around 3.5 W cm−2. In the case of a Pt emitter, both Cs and K plasmas were used, with power densities up to 5.7 and 1.8 W cm−2, respectively close to 1800 K. The structure of the laser‐bored collector may have contributed to these results, as well as the efficient removal of impurities in the ‘‘open’’ converter.
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52.75.Fk Magnetohydrodynamic generators and thermionic convertors; plasma diodes
79.40.+z Thermionic emission

High‐temperature hardness of Ga1−xInxAs

S. Guruswamy, J. P. Hirth, and K. T. Faber

J. Appl. Phys. 60, 4136 (1986); http://dx.doi.org/10.1063/1.337495 (5 pages) | Cited 19 times

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Substantial solid‐solution strengthening of GaAs by In acting as InAs4 units has recently been predicted for an intermediate‐temperature plateau region. This strengthening could account, in part, for the reduction of dislocation density in GaAs single crystals grown from the melt. Hardness measurements at high temperatures up to 900 °C have been carried out on (100) GaAs, Ga0.9975In0.0025As, and Ga0.99In0.01As wafers, all of which contain small amounts of boron. Results show a significant strengthening effect in In‐doped GaAs. A nominally temperature‐independent flow‐stress region is observed for all three alloys. The In‐doped GaAs shows a higher plateau stress level with increasing In content. The results are consistent with the solid‐solution strengthening model. The magnitude of the solid‐solution hardening is sufficient to explain the reduction in dislocation density with In addition.
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62.20.Qp Friction, tribology, and hardness
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
61.72.sd Impurity concentration
61.72.sh Impurity distribution
61.72.sm Impurity gradients
61.72.Yx Interaction between different crystal defects; gettering effect

Effect of thermal relaxation and low‐temperature irradiation on the chemical short‐range order of amorphous Zr‐Fe alloys

J. Wecker, H. C. Freyhardt, H. Adrian, and S. Klaumünzer

J. Appl. Phys. 60, 4141 (1986); http://dx.doi.org/10.1063/1.337496 (9 pages)

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Amorphous Zr100‐xFex ribbons have been produced by melt spinning in the composition range 20≤x≤43. The superconducting transition temperature Tc is used as a probe for studying structural changes in the zirconium‐rich alloys. Modifications of the short‐range order are controlled by sample composition, by annealing at temperatures below the crystallization temperature (relaxation), and by low‐temperature irradiation with heavy ions. In contrast to amorphous Zr‐(Cu, Ni, Co) alloys, the critical temperature Tc in the Zr‐Fe system increases with increasing annealing temperature. Low‐temperature irradiations, on the other hand, lead to a decrease in Tc, which levels off at a value identical for as‐quenched and relaxed samples. The results are discussed on the basis of an association model. In the amorphous state, the iron‐poor alloy decomposes into iron‐rich associates (possibly with Zr2Fe stoichiometry) embedded in a superconducting matrix, slightly improverished in iron, which is described as a regular solution of the components. The composition dependence of the electrical resistivity and the Vickers hardness, as well as previous Mössbauer experiments, indicate the existence of two different associates for x>30, with concentrations of approximately 33 and 50 at. % Fe, respectively.
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61.80.Jh Ion radiation effects
81.40.Rs Electrical and magnetic properties related to treatment conditions
65.20.-w Thermal properties of liquids
65.40.gd Entropy
61.43.Fs Glasses
61.43.-j Disordered solids

Disordering of AlAs‐GaAs superlattices by Si and S implantation at different implant temperatures

E. A. Dobisz, B. Tell, H. G. Craighead, and M. C. Tamargo

J. Appl. Phys. 60, 4150 (1986); http://dx.doi.org/10.1063/1.337497 (4 pages) | Cited 31 times

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We have investigated by transmission electron microscopy the enhanced disordering of GaAs‐AlAs superlattices due to Si and S implantation with subsquent annealing. The implants were performed at 77 K, room temperature, and 210 °C at a dose of 2.5×1014 cm−2 with energy of 100 keV. The greatest enhancement occurs, after annealing, for Si implants performed at 77 K. We find no enhancement due to S implants. The apparent damage due to implantation prior to annealing is strikingly less for superlattices compared with bulk GaAs.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
61.80.Jh Ion radiation effects
66.30.J- Diffusion of impurities
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Vacancy self‐diffusion in a screw dislocation in a simple cubic lattice

J. P. Stark

J. Appl. Phys. 60, 4154 (1986); http://dx.doi.org/10.1063/1.337498 (6 pages) | Cited 2 times

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Correlated self‐diffusion in a screw dislocation in a simple cubic crystal is treated with a vacancy mechanism. First and second neighbor jumps are considered within the dislocation core and matrix functions are generated which permit the limit of an infinite dislocation length to be examined for the tight binding approximation. The correlation factor f for positive vacancy binding to the dislocation is found in the range of 0.73≥f ≥0.52 as the binding energy increases without bounds. Previous calculations for an edge dislocation showed that the correlation factor was bound by the limits 0.75≥f ≥0. Comparable calculations of the diffusion coefficient suggest that the diffusivity becomes infinitely large in the same limit in a manner similar with what happens in an edge dislocation. Namely, as the binding energy of the vacancy increases without bounds, the number of available vacancies for diffusion increases indefinitely as a result of the length of dislocation acting as a source.
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66.30.-h Diffusion in solids
61.72.Lk Linear defects: dislocations, disclinations
61.72.jd Vacancies
61.72.jj Interstitials

Theory of thin‐film orientation by ion bombardment during deposition

R. Mark Bradley, James M. E. Harper, and David A. Smith

J. Appl. Phys. 60, 4160 (1986); http://dx.doi.org/10.1063/1.337499 (5 pages) | Cited 110 times

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We study the development of orientational order in thin films grown with off‐normal incidence ion bombardment during deposition. The overall orientational order in our model results from the dependence of the sputtering yield on grain orientation. We demonstrate that the degree of orientational order at the surface of a thick film grows slowly with increasing ion flux until, at a critical value of the flux, it begins to rise more steeply and then saturates at its maximum value. The time needed to approach the thick‐film limit displays a peak as the ion flux is varied. We compare our work with the experimental results of Yu et al. [Appl. Phys. Lett. 47, 932 (1985)] and use our results to show how the deposition technique can be optimized.
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68.55.-a Thin film structure and morphology
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
81.15.Jj Ion and electron beam-assisted deposition; ion plating

The occurrence of cross hatch during GaAs homoepitaxy

J. E. Cunningham, T. H. Chiu, A. Ourmazd, J. Shah, and W. T. Tsang

J. Appl. Phys. 60, 4165 (1986); http://dx.doi.org/10.1063/1.337500 (4 pages) | Cited 5 times

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We report on the observation of a morphological defect structure, ‘‘cross‐hatch’’ and the experimental circumstances that lead to its occurence during GaAs homoepitaxy. Photoluminescence, x‐ray diffraction and transmission electron miscroscopy (TEM) results obtained on cross‐hatched samples are presented and discussed in regards to the nature and origin of the defect structure.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Influence of substrate structure on the growth of hydrogenated amorphous silicon studied by in situ ellipsometry

R. W. Collins and J. M. Cavese

J. Appl. Phys. 60, 4169 (1986); http://dx.doi.org/10.1063/1.337501 (8 pages) | Cited 3 times

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Using in situ ellipsometry as a probe, the effect of substrate microstructure on the growth habit of high‐quality hydrogenated amorphous silicon (a‐Si:H) has been studied. An understanding of the growth process is important when combining a‐Si:H with other materials in thin‐film multilayer devices. The present study concentrates on cases where a‐Si:H of different microstructure, microcrystalline Si:H (μc‐Si:H), and single‐crystal Si are used as substrates. The a‐Si:H top film is grown under identical conditions on each substrate material and pseudo‐dielectric‐function trajectories are collected during growth. These trajectories have been applied to characterize the bulk and interface structure and the evolution of surface roughness layers during growth. For the same deposition conditions, a range of growth patterns is observed, depending on the structure of the substrate.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.35.Gy Mechanical properties; surface strains
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.55.-a Thin film structure and morphology

Amorphous diffusion barriers in Al‐Si and Au‐Si contacts

L. S. Hung, E. G. Colgan, and J. W. Mayer

J. Appl. Phys. 60, 4177 (1986); http://dx.doi.org/10.1063/1.337502 (5 pages) | Cited 2 times

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Coevaporated amorphous Co50Ta50 and Co50Mo50 alloys were investigated for applications as diffusion barriers in Al‐Si and Au‐Si metallization. The high‐temperature stability of diffusion barriers has been found to be correlated with the thermodynamical driving forces for chemical reaction between the barrier constituents and their surroundings. Amorphous Co50Ta50 films react with Al overlayers at temperatures around 450 °C, much lower than the crystallization temperature. A TaAl3 layer interposed between the amorphous film and the Al overlayer provides an ideal scheme against degradation during high‐temperature annealing. Amorphous Co50Mo50 alloys possess low mutual solubilities and unfavorable free energies for compound formation with Au; it thus remains intact and prevents the interaction between the Si substrate and an overlay Au film during thermal annealing at 550 °C. Degradation of the layered structure at localized points is observed and attributed to the presence of pinholes and other macroscopic defects in the amorphous film.
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68.35.Fx Diffusion; interface formation
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Doping studies using thermal beams in chemical‐beam epitaxy

W. T. Tsang, B. Tell, J. A. Ditzenberger, and A. H. Dayem

J. Appl. Phys. 60, 4182 (1986); http://dx.doi.org/10.1063/1.337503 (4 pages) | Cited 16 times

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The use of chemical‐beam expitaxy instead of chemical vapor deposition allows the incorporation of thermal atomic beams for doping. Dopant profile measurements by a differential capacitance‐voltage technique and secondary ion mass spectroscopy technique show that there is no surface segregation with Si dopants in InP at all growth temperatures (<600 °C). On the other hand, Sn and to a lesser extent Be show surface segregation which can be reduced by growing the InP at a lower temperature (<550 °C). From this study, it is seen that Si should be preferred as the n‐type dopant in producing InP/InGaAs high electron mobility transistors.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Bulk electron traps in zinc oxide varistors

J. F. Cordaro, Y. Shim, and J. E. May

J. Appl. Phys. 60, 4186 (1986); http://dx.doi.org/10.1063/1.337504 (5 pages) | Cited 24 times

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Three types of commercial zinc oxide varistor materials were examined using admittance spectroscopy between 30 and 350 K. Maxima in the ac conductance at frequencies from 1 to 100 kHz are observed. The maxima are interpreted as arising from electron traps located within the depletion regions of double Schottky barriers at ZnO‐ZnO grain boundaries. Two traps are observed in each material and are likely to be from common origin. The trap energies are found to be 0.17 and 0.33 eV below the conduction‐band edge. The traps are likely to be associated with native defects in ZnO and may influence device characteristics such as voltage overshoot.
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71.55.Ht Other nonmetals
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Investigation of trapping states in a Nb‐doped rutile by admittance spectroscopy

K. Kobayashi, M. Takata, Y. Fujimura, and S. Okamoto

J. Appl. Phys. 60, 4191 (1986); http://dx.doi.org/10.1063/1.337505 (6 pages) | Cited 5 times

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In order to obtain semiconductivity, rutile crystals have been doped with Nb by means of diffusion. The resulting Nb‐doped rutile crystals have an electrical resistivity ≂80 Ω cm at room temperature. Impedance analysis of a Nb‐doped TiO2‐Au diode suggests that the measurement frequency must be lower than 10 kHz to detect the capacitance and conductance of the depletion layer. Thus, an admittance spectroscopic method is used to study traps in the diode of the Nb‐doped TiO2‐Au. Two trap levels, located at 0.24 and 0.37 eV below the bottom of the conduction band, have been detected by this method. The state densities and capture cross sections of these trap levels are also determined.
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71.55.-i Impurity and defect levels
72.80.Ga Transition-metal compounds
73.30.+y Surface double layers, Schottky barriers, and work functions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
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