Dr Paul Kinsler.
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<> Copyright 1997, Institute for Scientific Information Inc.
<>
<> Database: Science Citation Index
<>
<>
<> (1) TI: Narrow-channel GaInP/InGaAs/GaAs MODFET's for high-frequency
<> and power applications
<> AU: Pereiaslavets_B, Martin_GH, Eastman_LF, Yanka_RW, Ballingall_JM,
<> Braunstein_J, Bachem_KH, Ridley_BK
<> NA: CORNELL UNIV,SCH ELECT ENGN,PHILLIPS HALL,ITHACA,NY,14853
<> SANDERS,CTR MICROELECT,NASHUA,NH,03061
<> NOVELLUS SYST,SANTA CLARA,CA,95050
<> FRAUNHOFER INST APPL SOLID STATE PHYS,FRAUNHOFER SOC,D-79108
<> FREIBURG,GERMANY
<> UNIV ESSEX,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> JN: IEEE TRANSACTIONS ON ELECTRON DEVICES, 1997, Vol.44, No.9,
<> pp.1341-1348
<> IS: 0018-9383
<> AB: We have developed a new concept of narrow (50-80 Angstrom)
<> channel MODFET's, It is shown theoretically and experimentally
<> that only the ground energy level is populated in the narrow-
<> channel device, A new technique to measure mobility at the
<> highest energies of the two-dimensional electron gas (2-DEG)
<> was introduced, With the help of this technique it is shown
<> that, in wide wells, electrons in the excited energy levels
<> have low mobility and consequently degrade device performance,
<> It is shown theoretically and experimentally that the narrow-
<> channel device has a higher electron sheet density and mobility
<> and consequently better performance than a conventional wide-
<> channel MODFET, Excellent quality GaxIn1-xP/InyGa1-yAs/GaAs
<> MODFET's with a pseudomorphic barrier and a pseudomorphic
<> channel were grown by MBE and OMVPE, Higher than 3.4 . 10(12)
<> cm(-2) electron sheet densities for single-side-doped MODFET's
<> on GaAs substrate were measured, One-tenth micron gate length
<> MODFET's achieved f(T)'s over 100 GHz and f(max)'s over 180
<> GHz, These results are comparable to the previously reported
<> results for GaInP MODFET with graded barriers, however the
<> device structure is much simpler.
<>
<> (2) TI: The effect of quantum wells on the mobility of electrons in
<> vertical transport
<> AU: Daniels_ME, Bishop_PJ, Ridley_BK
<> NA: UNIV ESSEX,DEPT PHYS,WIVENHOE PK,COLCHESTER CO4
<> 3SQ,ESSEX,ENGLAND
<> JN: SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 1997, Vol.12, No.4,
<> pp.375-379
<> IS: 0268-1242
<> AB: The mobility of electrons drifting in AlGaAs across GaAs
<> quantum wells has been measured using the geometrical
<> magnetoresistance (GMR) technique over the temperature range 77
<> to 300 K. The mobility is shown to be an oscillating function
<> of well width and to reduce with decreasing period (barrier
<> width plus well width). A theory of these effects is presented
<> and is shown to give a good account of the phenomena.
<> KP: CONDUCTION-BAND STRUCTURE, GA1-XALXAS ALLOYS, DEEP LEVELS
<>
<> (3) TI: Theory of optical-phonon limited hot-electron transport in
<> quantum wires
<> AU: Zakhleniuk_NA, Bennett_CR, Constantinou_NC, Ridley_BK,
<> Babiker_M
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> JN: PHYSICAL REVIEW B-CONDENSED MATTER, 1996, Vol.54, No.24,
<> pp.17838-17849
<> IS: 0163-1829
<> AB: We present a kinetic theory of a nonequilibrium electron gas in
<> a one-dimensional circular quantum wire interacting with
<> acoustic and polar optical phonons. Besides these scattering
<> mechanisms we also include an elastic interaction with
<> interface roughness for the electron momentum relaxation. We
<> have solved the Boltzmann kinetic equation analytically and
<> obtained different distribution functions for a one-dimensional
<> electron gas. A detailed kinetic analysis of the limiting case
<> of the electron gas interacting solely with optical phonons is
<> undertaken and the distribution function is found when this
<> system can be described in a self-consistent way. Our
<> analytical results are in good agreement with previous
<> numerical studies of a similar system using Monte Carlo
<> techniques. As an application of the developed theory we have
<> calculated the electric-field dependences of electron mobility
<> and average energy for different parameters of the quantum
<> wire. It is shown that at high lattice temperature the electron
<> mobility is a nonmonotonous function of the applied electric
<> field and has its maximum value at intermediate electric fields
<> when the transition from acoustic-phonon-limited to optical-
<> phonon-limited transport takes place.
<> KP: SCATTERING, MOBILITY
<>
<> (4) TI: HOT-ELECTRONS UNDER QUANTIZATION CONDITIONS .1. KINEMATICS
<> AU: RIDLEY_BK, ZAKHLENIUK_NA
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> INST SEMICOND PHYS,UA-252650 KIEV,UKRAINE
<> JN: JOURNAL OF PHYSICS-CONDENSED MATTER, 1996, Vol.8, No.44,
<> pp.8525-8537
<> IS: 0953-8984
<> AB: A detailed analysis of the kinematic peculiarities of the
<> interaction of bulk acoustic phonons with confined electrons in
<> a quantum wire is peformed for intra- and inter-sub-band
<> transitions. Due to quantization of the electron motion in a
<> quasi-one-dimensional wire a new parameter epsilon(c) =
<> (chi(0)m*s(2)W(0))(1/2) appears in the kinetic theory (m* is
<> the electron effective mass, s is the sound velocity, W-0 is
<> the quantum energy of the ground state and Xo is some numerical
<> constant which depends upon the shape of the quantizing
<> potential), characterizing the electron-acoustic-phonon
<> interaction. At low lattice temperatures T-0, when T-0 <
<> epsilon(c), the intra-sub-band interaction has a strong
<> inelastic character for the majority of electrons (assuming
<> that the mean electron energy is also less than epsilon(c)). In
<> the opposite case of high lattice temperatures, T-0 >
<> epsilon(c), this interaction is always quasi-elastic for the
<> majority of electrons because the mean electron energy exceeds
<> epsilon(c). Inter-sub-band scattering, on the other hand, is
<> quasi-elastic at arbitrary lattice temperatures. These
<> kinematic peculiarities of the electron-acoustic-phonon
<> interaction are universal and, in general, do not depend on the
<> physical nature of the quantizing held. It can be an external
<> quantizing magnetic field or size-quantizing electrostatic
<> potential, resulting in the confinement of electrons in a two-
<> dimensional sheet or in a quantum wire, or confinement can be
<> realized due to both electrostatic and magnetic potentials
<> combined. The discussed peculiarities manifest themselves in
<> novel kinetic properties of low-dimensional electron systems.
<> KP: PHONON-SCATTERING, RELAXATION, ENERGY, WIRE
<>
<> (5) TI: HOT-ELECTRONS UNDER QUANTIZATION CONDITIONS .2. THE BOLTZMANN-
<> EQUATION
<> AU: RIDLEY_BK, ZAKHLENIUK_NA
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> INST SEMICOND PHYS,UA-252650 KIEV,UKRAINE
<> JN: JOURNAL OF PHYSICS-CONDENSED MATTER, 1996, Vol.8, No.44,
<> pp.8539-8552
<> IS: 0953-8984
<> AB: A general analysis of the Boltzmann equation is undertaken for
<> the non-degenerate electrons in low-dimensional system
<> interacting with bulk acoustic phonons. We derive expressions
<> for symmetric and antisymmetric collision operators for
<> electrons confined by an arbitrary quantizing potential. These
<> expressions are universal and can be applied to three-, two- or
<> one-dimensional electron gases. As was shown in our previous
<> paper (part I) the kinetics of the low-dimensional electron
<> system is qualitatively different at low and high lattice
<> temperatures due to the kinematic peculiarities of the
<> electron-acoustic-phonon interaction. Here we present the
<> Boltzmann equation to describe the non-equilibrium electron
<> distribution in low-dimensional electron systems under
<> different external conditions which are of physical interest
<> and which will be investigated in the following paper, part
<> III.
<>
<> (6) TI: HOT-ELECTRONS UNDER QUANTIZATION CONDITIONS .3. ANALYTICAL
<> RESULTS AND NEW NONLINEAR REGIMES
<> AU: RIDLEY_BK, ZAKHLENIUK_NA
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> INST SEMICOND PHYS,UA-252650 KIEV,UKRAINE
<> JN: JOURNAL OF PHYSICS-CONDENSED MATTER, 1996, Vol.8, No.44,
<> pp.8553-8581
<> IS: 0953-8984
<> AB: It is shown that the kinetic behaviour of a one-dimensional
<> electron system is qualitatively different at low and high
<> lattice temperatures. At low lattice temperatures the
<> interaction has a strong inelastic character for the majority
<> of electrons. As a result the electron distribution function is
<> to be found from the integro-differential equation. This
<> equation was solved analytically and we obtain the new
<> distribution functions. We have shown that the current-voltage
<> characteristic obeys a sublinear behaviour for warm and hot
<> electrons. Within a wide range of the external electric field E
<> the distribution function for the hot electrons has a sharp
<> anisotropic shape corresponding to the electron streaming
<> regime. The electric-field-dependences of the hot-electron
<> mobility and the mean energy are E-(5/6) and E(1/2),
<> respectively. With increasing E the electron-acoustic-phonon
<> interaction becomes quasi-elastic an the electron distribution
<> function, which is quasi-isotropic, is described by a
<> differential equation of the Fokker-Planck type. No runaway
<> effect arises in strong electric fields, the electron mobility
<> does not depend on E (the 'second ohmic regime') and the mean
<> energy increases as E(4). In the opposite case of high lattice
<> temperatures the electron-acoustic-phonon interaction is always
<> quasi-elastic for a majority of the electrons. The scattering
<> rate decreases when the energy of the electron increases. This
<> results in a runaway effect for hot electrons in a quantum wire
<> and superlinear behaviour of the current-voltage
<> characteristic. To stabilize the one-dimensional electron
<> system it is necessary to take into account the transition of
<> electrons to the continuous energy spectrum for thick quantum
<> wires or interaction with optical phonons for thin quantum
<> wires. We have derived general expressions for the distribution
<> functions under different conditions which are of experimental
<> interest. The theory we have developed can be generalized for a
<> two- or three-dimensional electron gas subjected to an
<> arbitrary quantizing potential, as well as to incorporate other
<> scattering mechanisms.
<> KP: QUANTUM WIRES
<>
<> (7) TI: REMOTE-IMPURITY SCATTERING IN ALINAS/GAINAS FETS
<> AU: RIDLEY_BK
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO34 3SQ,ESSEX,ENGLAND
<> JN: SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 1996, Vol.11, No.9,
<> pp.1339-1345
<> IS: 0268-1242
<> AB: Theoretical models of remote-impurity, polar-optical phonon and
<> alloy scattering have been applied to an FET structure
<> consisting of AlInAs barriers and GaInAs well lattice-matched
<> to InP, and their predictions of room-temperature mobilities
<> for two occupied subbands compared with experimental data.
<> Three models of remote-impurity scattering were considered.
<> These were the normal model, in which each donor is deemed to
<> scatter independently of the others, the statistical-screening
<> model, in which the interaction is limited to the nearest
<> impurity, and the dipole model, in which only dipole-like
<> fluctuations from a regular array cause scattering. All models
<> predict low mobilities for the electrons in the second subband.
<> The statistical-screening model satisfactorily accounts for the
<> variation of Hall mobility with spacer thickness. The
<> mobilities predicted for polar-optical and alloy scattering
<> were much higher than those observed. It was concluded that the
<> room-temperature mobility was determined by charged-impurity
<> scattering and by interface-roughness scattering.
<> KP: INVERSION LAYERS, HETEROSTRUCTURES, MOBILITY
<>
<> (8) TI: THE LO PHONON LIFETIME IN GAN
<> AU: RIDLEY_BK
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> JN: JOURNAL OF PHYSICS-CONDENSED MATTER, 1996, Vol.8, No.37, pp.L
<> 511-L 513
<> IS: 0953-8984
<> DT: Letter
<> AB: The disparity in the masses of the atomic constituents of GaN
<> means that the usually-assumed mode of decay of a long-
<> wavelength LO mode into two LA modes is forbidden. However,
<> given the available information about the phonon spectrum, it
<> appears that a possible decay route is provided by the emission
<> of a TO and an LA phonon.
<> KP: RAMAN-SPECTROSCOPY, OPTICAL PHONONS
<>
<> (9) TI: THE EFFECT OF QUANTUM-WELLS ON ELECTRON-TRANSPORT ACROSS
<> GAAS/ALGAAS GRADED BARRIER STRUCTURES
<> AU: BISHOP_PJ, DANIELS_ME, RIDLEY_BK, ROBERTS_JS, HILL_G
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> UNIV SHEFFIELD,DEPT ELECTR & ELECT ENGN,EPSRC CENT FACIL III V
<> SEMICOND,SHEFFIELD S1 3JD,S YORKSHIRE,ENGLAND
<> JN: SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 1996, Vol.11, No.6,
<> pp.873-882
<> IS: 0268-1242
<> AB: Electron transport over short n(+) GaAs/AlxGa1-xAs/n(+) GaAs
<> barrier structures containing doped GaAs quantum wells has been
<> investigated. The barriers had graded interfaces at the
<> contacts which inhibited tunnelling at low electric fields. It
<> was found that the presence of wells pinned the Fermi level,
<> eliminating the increase in the barrier height caused by
<> background space charge seen in AlGaAs barriers. The wells also
<> had the effect of magnifying any injected space charge, which
<> meant that the electric field was non-uniform across the
<> sample. Hence the three regions, graded interface/central
<> region with wells/graded interface, functioned like three
<> resistors in series and this behaviour has been modelled
<> successfully using drift-diffusion theory. Increasing the
<> density of wells, which allows tunnelling to occur at lower
<> fields and higher temperatures, limits the range over which the
<> thermionic current dominates.
<> KP: INFRARED PHOTODETECTORS, DETECTOR, CHARGE
<>
<> (10) TI: INELASTIC ELECTRON-ACOUSTIC-PHONON INTERACTION IN QUANTUM-WELL
<> WIRES
<> AU: RIDLEY_BK, ZAKHLENIUK_NA
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> JN: JETP LETTERS, 1996, Vol.63, No.6, pp.464-470
<> IS: 0021-3640
<> AB: Due to the lack of transverse momentum conservation for the
<> electron-acoustic-phonon interaction in quantum wires this
<> interaction becomes strongly inelastic within a wide range of
<> electron energies. As a result the electron distribution
<> function has to be found from an integrodifferential equation.
<> We derive the new nonequilibrium distribution functions for
<> these conditions and present the electric field dependences for
<> the kinetic coefficients. Our approach can be applied as well
<> for two-dimensional electron systems or for electrons subjected
<> to an external quantizing magnetic field. (C) 1996 American
<> Institute of Physics.
<>
<> (11) TI: METASTABLE PHOTOGENERATED EFFECTS IN LOW-RESISTIVITY GAAS
<> AU: MACHADO_WV, LANDIN_AFS, AMATO_MA, RIDLEY_BK
<> NA: UNIV BRASILIA,DEPT FIS,BR-70910900 BRASILIA,DF,BRAZIL
<> UNIV ESSEX,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> JN: MATERIALS SCIENCE FORUM, 1995, Vol.196-, pp.1049-1054
<> IS: 0255-5476
<> AB: The photo quenching effect (PQ) followed by an anomalous
<> quenching of the dark current after illumination with strong
<> broad and/or monochromatic light in the range 0.1eV to 1.5eV in
<> low resistivity GaAs was observed. The presence of a 0.2eV
<> level below the conduction band which controls the dark
<> conductivity was noticed. After the illumination the control is
<> taken over by a deeper level, which was estimated to be around
<> 0.3eV below the conduction band. The following time constants
<> were studied: (i) the transient decay for the photocurrent
<> while the light was still on, (ii) the decay time after light
<> removal which decayed well below the dark level (iii) the
<> recovery time to reach the dark level again. All of the three
<> time constants exhibited the same activation energy dependence
<> on the temperature, around 0.33eV, but ranging about three
<> orders of magnitude between them in a given temperature. Below
<> 80K the relaxation time from the depleted state back to the
<> normal one, can be as large as 10(10)seconds, therefore the
<> material behaved like a bistable switch. The main property
<> involving the quenching of the dark current, does not seem to
<> be fully reversible via illumination in the studied range of
<> energy. The type of conduction also remained n-type during the
<> quenched state.
<> KP: SEMI-INSULATING GAAS, SLOW-RELAXATION PHENOMENA, ELECTRON TRAPS,
<> PHOTOCONDUCTIVITY
<> WA: GAAS, METASTABILITY, PHOTO-QUENCHING, EL2, EL2O, ELO
<>
<> (12) TI: HOLES INDUCED BY STRONG NEAR BAND-GAP LIGHT IN GAAS-O - EL2
<> RELATED
<> AU: MACHADO_WV, AMATO_MA, LANDIM_AFS, RIDLEY_BK
<> NA: UNIV BRASILIA,DEPT FIS,IC,BR-70910900 BRASILIA,DF,BRAZIL
<> UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> JN: MATERIALS SCIENCE FORUM, 1995, Vol.196-, pp.1043-1048
<> IS: 0255-5476
<> AB: In this work some anomalies in the photoconductivity
<> measurements in GaAs nominally doped with oxygen, when
<> submitted to strong illumination with energies in the range
<> 1.1eV to 1.5eV at temperatures below 150K are reported. We have
<> identified them as being due to a metastable population of
<> holes sitting at levels in the range 0.4eV to 0.7eV above the
<> valence band. The main features observed is the spectral
<> distribution centered at just about the band gap energy with
<> some structure exhibiting evidence of the existence of levels
<> at about 0.57eV, 0.63eV and 0.70eV above the valence band, with
<> photosensitivity possibly assisted by replicas of 0.03eV
<> phonons. The population of holes is sufficient to provoke an
<> exchange from n-type to p-type under extrinsic excitation in
<> the above energy range. It presents a exponential activation of
<> 33.8meV with temperature below 80K and a deactivation of
<> 42.9meV above that temperature. The difference between these
<> values gives 76.7meV which seems to be related to a negative
<> potential barrier to electron recapture into these centers. The
<> photo-Hall data shows an electron level at 0.5eV below the
<> conduction band which in this turn, may take part in the photo
<> quenching phenomena. We therefore, put forward a model based on
<> a level to level transition involving a shallow acceptor level
<> 0.03eV above the valence band. Our data, however, do not allow
<> us to assert whether the Photoquenching phenomena and/or Holes
<> effect are linked or not to the supposed presence of oxygen,
<> nominally introduced into the material.
<> KP: MEMORY, LEVEL
<> WA: GALLIUM ARSENIDE, PHOTOCURRENT, METASTABLE STATE, HOLES
<>
<> (13) TI: THE INTERACTION OF ELECTRONS WITH OPTICAL PHONONS IN EMBEDDED
<> CIRCULAR AND ELLIPTIC GAAS QUANTUM WIRES
<> AU: BENNETT_CR, CONSTANTINOU_NC, BABIKER_M, RIDLEY_BK
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> JN: JOURNAL OF PHYSICS-CONDENSED MATTER, 1995, Vol.7, No.50,
<> pp.9819-9831
<> IS: 0953-8984
<> AB: We consider electronic intrasubband transitions involving the
<> confined and interface optical phonons of circular and
<> elliptical GaAs quantum wires. Detailed treatments are given
<> for a GaAs wire embedded in AIAs where the electrons are
<> confined via an infinite potential barrier. The optical phonons
<> are described using the dielectric continuum (DC) model, which
<> for the GaAs/AIAs system compares favourably with more
<> sophisticated macroscopic models and ab initio microscopic
<> calculations in its prediction for the total scattering rates.
<> The DC model has been applied previously to the circular case,
<> but here we evaluate the rates analytically. It is shown that
<> the behaviour of the electrons and phonons in elliptical wires
<> is both quantitatively and qualitatively different from that in
<> circular wires, especially as regards angular properties.
<> KP: INTERFACE PHONONS, SCATTERING RATES, LO PHONONS, WELLS,
<> HETEROSTRUCTURES, SYSTEMS, ALAS
<>
<> (14) TI: OPTICAL PHONONS IN A QUANTUM-WELL CONTAINING MONOLAYERS
<> AU: RIDLEY_BK
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> CORNELL UNIV,SCH ELECT ENGN,ITHACA,NY,14853
<> JN: APPLIED PHYSICS LETTERS, 1995, Vol.66, No.26, pp.3633-3635
<> IS: 0003-6951
<> KP: SUPERLATTICES, MODES
<>
<> (15) TI: NONLINEAR SPATIOTEMPORAL DYNAMICS IN P-N-JUNCTIONS
<> INCORPORATING QUANTUM-WELLS - LONGITUDINAL TRANSPORT
<> AU: STRAW_A, DACUNHA_A, GUPTA_R, BALKAN_N, RIDLEY_BK
<> NA: UNIV ESSEX,DEPT PHYS,WIVENHOE PK,COLCHESTER CO4
<> 3SQ,ESSEX,ENGLAND
<> JN: SUPERLATTICES AND MICROSTRUCTURES, 1994, Vol.16, No.2, pp.173-
<> 177
<> IS: 0749-6036
<> AB: A novel light emitting device is proposed and demonstrated
<> experimentally. The device consists of a GaAs quantum well
<> placed on the n-side of the depletion region of a Ga1-xAlxAs p-
<> n junction. Electric fields are applied parallel to the layers
<> between two point contacts. The operation of the device is
<> based upon the accumulation, in the quantum well, of excess hot
<> electrons injected from the n region of the barrier via
<> tunnelling and thermionic emission. Negative charge
<> accumulation in the depletion region changes the potential
<> profile, and therefore leads to a decrease in the depletion
<> width and the potential barrier in the p-side of the junction.
<> Hot holes then diffuse into the quantum well to recombine with
<> the electrons. Emitted light intensity is independent of the
<> polarity of the applied voltage. Theoretical modelling of the
<> device is carried out by solving Schrodinger's and Poisson's
<> equations self-consistently by incorporating tunnelling, and
<> diffusion dynamics of the hot carriers.
<> KP: ELECTRIC-FIELD
<>
<> (16) TI: CONTINUUM MODEL OF THE OPTICAL MODES OF VIBRATION OF AN IONIC-
<> CRYSTAL SLAB
<> AU: RIDLEY_BK, ALDOSSARY_O, CONSTANTINOU_NC, BABIKER_M
<> NA: UNIV ESSEX,DEPT PHYS,WIVENHOE PK,COLCHESTER CO4
<> 3SQ,ESSEX,ENGLAND
<> JN: PHYSICAL REVIEW B-CONDENSED MATTER, 1994, Vol.50, No.16,
<> pp.11701-11709
<> IS: 0163-1829
<> AB: Optical vibrations of a thin ionic slab are described by a
<> macroscopic theory involving the hybridization of LO, TO, and
<> interface-polariton modes. The resultant modes are triple
<> hybrids, which satisfy both elastic and electromagnetic
<> boundary conditions at the two surfaces. Analytic expressions
<> are derived for the relative ionic displacements and related
<> electric fields, and for the dispersion relations, assuming
<> elastic isotropy and neglecting retardation effects. Comparison
<> of mode patterns with those obtained by Fuchs and Kliewer, who
<> used electromagnetic boundary conditions only, show that Fuchs-
<> Kliewer modes are a good approximation to the system of the
<> triple-hybrid modes our theory describes.
<> KP: ELECTRON-PHONON INTERACTION, GAAS-ALAS SUPERLATTICES, QUANTUM-
<> WELLS, DOUBLE HETEROSTRUCTURES, FROHLICH INTERACTION,
<> DISPERSION, SCATTERING
<>
<> (17) TI: PHONON-SCATTERING SUPPRESSION IN SHORT PERIODIC ALAS/GAAS
<> MULTIPLE-QUANTUM-WELL STRUCTURES
<> AU: LETRAN_TT, SCHAFF_WJ, RIDLEY_BK, CHEN_YP, CLARK_A, EASTMAN_LF
<> NA: CORNELL UNIV,SCH ELECT ENGN,PHILLIPS HALL,ITHACA,NY,14853
<> JN: JOURNAL OF APPLIED PHYSICS, 1994, Vol.75, No.7, pp.3491-3499
<> IS: 0021-8979
<> AB: The suppression of longitudinally polarized optical-phonon
<> (LOP) electron scattering in multiple quantum wells (MQWs) was
<> sought in short periodic AlAs/GaAs with well widths of 12, 15,
<> and 20 monolayers and AlAs barrier widths of 2 and 4
<> monolayers, based on a study of electron mobility in the plane
<> of the MQW. Two-dimensional electron-gas structures with MQWs
<> of up to eight wells in their channel were grown. Their
<> mobilities at room temperature were slightly reduced, as
<> compared to samples without MQW channel, due to interaction
<> with interface polaritons from AlAs barriers, while mobility at
<> temperatures < 50 K improved due to reduction of remote ionized
<> impurity scattering. The theoretical analysis of the results
<> based on the model of hybridon-electron interaction in an
<> infinite superlattice is presented. The reduction of room-
<> temperature mobility in the MQWs is believed to be caused by
<> the interaction of electrons with both barrier interface-
<> polariton (IP) -like modes and the well LOP-IP hybrids. An
<> alternative explanation of the results of a similar experiment
<> done elsewhere is offered denying the evidence of strong
<> suppression of LOP scattering there.
<> KP: OPTICAL PHONONS, SUPERLATTICES, MOBILITY
<>
<> (18) TI: SPACE-CHARGE-MEDIATED CAPTURE OF ELECTRONS AND HOLES IN A
<> QUANTUM-WELL
<> AU: RIDLEY_BK
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> CORNELL UNIV,SCH ELECT ENGN,ITHACA,NY,14853
<> JN: PHYSICAL REVIEW B-CONDENSED MATTER, 1994, Vol.50, No.3,
<> pp.1717-1724
<> IS: 0163-1829
<> AB: Unequal quantum-well capture rates of electrons and holes give
<> rise to the accumulation of space charge which accelerates the
<> capture of electrons and retards the capture of holes. This
<> case is analyzed for the GaAs/Ga0.7In0.3As single-quantum-well
<> system using two optical-phonon spectra: (a) bulk spectrum in
<> both barrier and well, and (b) bulk spectrum in the barrier,
<> confined hybrids in the well. Phonon confinement reduces the
<> capture rate significantly. Equilibrated resonant capture times
<> for a 50-angstrom well obtained are for bulk modes and for bulk
<> and/or confined modes.
<> KP: CARRIER CAPTURE, OPTICAL PHONONS, SUPERLATTICES
<>
<> (19) TI: OPTICAL-PHONON TUNNELING
<> AU: RIDLEY_BK
<> NA: UNIV ESSEX,DEPT PHYS,WIVENHOE PK,COLCHESTER CO4
<> 3SQ,ESSEX,ENGLAND
<> JN: PHYSICAL REVIEW B-CONDENSED MATTER, 1994, Vol.49, No.24,
<> pp.17253-17258
<> IS: 0163-1829
<> AB: LO phonons in polar material can tunnel resonantly through a
<> rigid barrier provided that they can excite an interface
<> polariton. A theory of phonon tunneling based on a macroscopic
<> continuum model is presented. The ability of LO phonons to be
<> transmitted is shown to be dependent upon there being
<> sufficient dispersion for the LO frequency band to overlap
<> significantly the ''classical'' dispersion of interface modes.
<> The interaction with electrons in the barrier is discussed. It
<> is also shown that interface modes appear in their own right
<> only in the frequency range below the LO band but above
<> omega(TO).
<> KP: GAAS-ALAS SUPERLATTICES, LATTICE-DYNAMICS, QUANTUM-WELL, MODES,
<> HETEROSTRUCTURES, VIBRATIONS, SYSTEMS
<>
<> (20) TI: EFFECT OF BULK DISPERSION ON THE ELECTRON OPTICAL-PHONON
<> INTERACTION IN A SINGLE-QUANTUM-WELL
<> AU: CONSTANTINOU_NC, RIDLEY_BK
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> JN: PHYSICAL REVIEW B-CONDENSED MATTER, 1994, Vol.49, No.24,
<> pp.17065-17071
<> IS: 0163-1829
<> AB: The interaction of electrons with GaAs optical phonons is
<> investigated for a single GaAs/AlAs quantum well using the
<> hybrid model of optical phonons, which incorporates bulk-mode
<> dispersion. We predict resonances in the individual hybrid
<> scattering rates as a function of well width corresponding to
<> wave vectors where the modes anticross. Nevertheless, although
<> the physics is quite different, we find that the total
<> scattering rate is insensitive to the value of the bulk
<> dispersion, and is given to an excellent approximation by the
<> dielectric continuum model, for both intrasubband and
<> intersubband scattering processes. We conclude, in accord with
<> recent results of lattice dynamics, that for the evaluation of
<> scattering rates, the dielectric continuum model provides a
<> very good approximation.
<> KP: GAAS-ALAS SUPERLATTICES, SEMICONDUCTOR HETEROSTRUCTURES, RAMAN-
<> SCATTERING, CONFINED LO, MODES, SYSTEMS, REDUCTION
<>
<> (21) TI: TRANSIENT PHOTOCONDUCTIVITY IN A WIDE ALGAAS BARRIER
<> AU: BISHOP_PJ, DANIELS_ME, RIDLEY_BK, RITCHIE_DA, JONES_GAC, HILL_G
<> NA: UNIV ESSEX,DEPT PHYS,WIVENHOE PK,COLCHESTER CO4
<> 3SQ,ESSEX,ENGLAND
<> UNIV CAMBRIDGE,CAVENDISH LAB,CAMBRIDGE CB3 0HE,ENGLAND
<> UNIV SHEFFIELD,DEPT ELECTR & ELECT ENGN,SERC III-V SEMICOND
<> FACIL,SHEFFIELD S1 3JD,S YORKSHIRE,ENGLAND
<> JN: SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 1994, Vol.9, No.5 SS,
<> pp.849-851
<> IS: 0268-1242
<> AB: The transient photocurrent flowing over a wide undoped AlGaAs
<> barrier has been investigated as a function of bias voltage,
<> voltage polarity, laser intensity and sample temperature.
<> Excitation was by pulses of length 100 ps from a Nd:YAG laser.
<> The radiation, which uniformly illuminated the top surface of
<> the mesa, could produce excess carrier densities of the order
<> of 1 X 10(19) cm-3. The time constant of the decay for zero
<> bias was 4 ns at 100 K. It was independent of laser intensity,
<> which suggests that the lifetime was determined by radiative
<> recombination in the contact regions. A trap-limited hole
<> mobility of 2 cm2 V-1 s-1 was deduced from the low-field data.
<> KP: CONDUCTION, TRANSPORT, GAAS
<>
<> (22) TI: HOT-ELECTRON RELAXATION VIA THE EMISSION OF GAAS OPTICAL MODES
<> AND ALAS INTERFACE MODES IN GAAS ALAS MULTIQUANTUM WELLS
<> AU: OZTURK_E, CONSTANTINOU_NC, STRAW_A, BALKAN_N, RIDLEY_BK,
<> RITCHIE_DA, LINFIELD_EH, CHURCHILL_AC, JONES_GAC
<> NA: UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> UNIV CAMBRIDGE,CAVENDISH LAB,CAMBRIDGE CB3 0HE,ENGLAND
<> JN: SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 1994, Vol.9, No.5 SS,
<> pp.782-785
<> IS: 0268-1242
<> AB: We demonstrate via hot-electron photoluminescence and high-
<> temperature mobility measurements the importance of the AlAs
<> interface mode in the energy relaxation of electrons in
<> GaAs/AlAs multi-quantum wells. A corresponding investigation of
<> a similar GaAs/Al0.24Ga0.76As system illustrates that this is
<> not the case for AlGaAs barrier devices where GaAs modes are
<> the dominant energy relaxation process. The importance of the
<> AlAs interface mode is not simply related to its intrinsic
<> scattering rate but also to its shorter lifetime (compared with
<> GaAs modes). Hot-phonon effects are therefore crucial to a full
<> understanding of the experimental data.
<> KP: DOUBLE HETEROSTRUCTURES, PHONON INTERACTIONS, TRANSPORT
<>
<> (23) TI: ENERGY AND MOMENTUM RELAXATION RATES FOR CONFINED AND INTERFACE
<> MODES IN QUANTUM-WELL STRUCTURES
<> AU: GUPTA_R, RIDLEY_BK
<> NA: UNIV ESSEX,DEPT PHYS,WIVENHOE PK,COLCHESTER CO4
<> 3SQ,ESSEX,ENGLAND
<> JN: SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 1994, Vol.9, No.5 SS,
<> pp.753-755
<> IS: 0268-1242
<> AB: In GaAs/AlAs quantum well structures both the confined GaAs
<> optic phonon and the AlAs interface polariton (IP) mode
<> contribute to the energy and momentum relaxation of hot
<> electrons. It has been shown that in real multiple quantum well
<> structures elastic scattering of phonons can lead to a non-
<> drifting population of hot phonons, which results in a
<> suppression of the high-field electron drift velocity. The
<> consequences for device application are obvious. The non-drift
<> of the mode is determined by the relative magnitudes of its
<> energy and momentum relaxation rates.
<> We present a calculation of the lifetime and the elastic
<> scattering rates for confined and interface modes in GaAs/AlAs
<> quantum wells. It is found that the decay rates of the two
<> modes exhibit different well-width dependences, and that
<> scattering from interface roughness is the dominant mechanism
<> for momentum relaxation. The implications for high-field
<> transport are discussed.
<> KP: SCATTERING
<>
<> (24) TI: LONGITUDINAL TRANSPORT IN GA1-XALXAS P-N-JUNCTIONS
<> INCORPORATING GAAS QUANTUM-WELLS - HOT-ELECTRON LIGHT EMITTERS
<> AU: DACUNHA_A, GUPTA_R, STRAW_A, BALKAN_N, RIDLEY_BK
<> NA: UNIV ESSEX,DEPT PHYS,WIVENHOE PK,COLCHESTER CO4
<> 3SQ,ESSEX,ENGLAND
<> JN: SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 1994, Vol.9, No.5 SS,
<> pp.677-680
<> IS: 0268-1242
<> AB: Experimental results on hot-electron parallel transport in GaAs
<> quantum wells, situated in the n-side of the depletion region
<> of a Ga1-xAlxAs p-n junction, are presented. In our structures
<> hot electrons are thermionically excited from the n-side of the
<> junction into the quantum wells in the depletion region, by the
<> application of pulsed longitudinal electric fields. The
<> accumulation of the electrons in the depletion region modifies
<> the potential profile of the junction, resulting in a reduction
<> of the potential barrier and the depletion width in the p-side.
<> Thus, hot holes are excited into the valence bands of the
<> quantum wells via thermionic emission or tunnelling to
<> recombine radiatively with the electrons.
<> A simple modelling of the device is carried out by solving the
<> Poisson and Schrodinger equations for the p-n junction
<> incorporating a single quantum well.The results of this
<> modelling describe the experimental observations very well. It
<> is also shown that population inversion in the junction can be
<> achieved at high fields. The device is therefore a very
<> efficient light emitter with the main advantages over the
<> conventional laser diodes being: the emitted light is
<> independent of the polarity of the applied voltage; and only
<> two point contacts are required, thus making it a very simple
<> device to fabricate.
<> KP: DEPENDENCE
<>
<> (25) TI: HOT-ELECTRON TRANSPORT ACROSS A WIDE ALGAAS BARRIER CONTAINING
<> QUANTUM-WELLS
<> AU: DANIELS_ME, BISHOP_PJ, RIDLEY_BK, RITCHIE_DA, GRIMSHAW_M,
<> LINFIELD_EH, JONES_GAC
<> NA: UNIV ESSEX,DEPT PHYS,WIVENHOE PK,COLCHESTER CO4
<> 3SQ,ESSEX,ENGLAND
<> UNIV CAMBRIDGE,CAVENDISH LAB,CAMBRIDGE CB3 0HE,ENGLAND
<> JN: SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 1994, Vol.9, No.5 SS,
<> pp.595-598
<> IS: 0268-1242
<> AB: An experimental and theoretical study has been made of electron
<> transport over a series of wide AlxGa1-xAs barriers with graded
<> interfaces, containing GaAs quantum wells in the central
<> Al0.25Ga0.75As region. Extensive measurements of both the
<> voltage and temperature dependence of the current were made, as
<> well as measurements of magnetoresistance. In these structures
<> tunnelling is expected to be negligible and hence drift-
<> diffusion thermionic emission theory was used to interpret the
<> data. Good agreement between theory and experiment was obtained
<> using a low-field model for electric fields up to 10 kV cm-1.
<> At applied electric fields greater than 10 kV cm- 1 agreement
<> between theory and experiment was obtained to within an order
<> of magnitude when the model was modified to include a saturated
<> drift velocity plus the effect of injected space charge. At
<> high electric fields periodic negative differential resistance
<> (NDR) oscillations were observed. The model usually given to
<> explain these oscillations involves tunnelling and is,
<> therefore, not obviously applicable to these structures. An
<> alternative description of their origin is discussed, based
<> upon the NDR associated with intervalley transfer.
<> KP: SEMICONDUCTOR SUPERLATTICES, ALLOY COMPOSITION, FIELD,
<> CONDUCTION
<>
<> (26) TI: OPTICAL-MODE HYBRIDS IN QUANTUM-WELLS, SUPERLATTICES AND SLABS
<> AU: RIDLEY_BK
<> NA: CORNELL UNIV,SCH ELECT ENGN,PHILLIPS HALL,ITHACA,NY,14853
<> UNIV ESSEX,DEPT PHYS,COLCHESTER CO4 3SQ,ESSEX,ENGLAND
<> JN: PHYSICA SCRIPTA, 1993, Vol.T49B, pp.454-458
<> IS: 0281-1847
<> AB: The presence of interfaces causes the hybridization of LO and
<> TO modes in non-polar material and of LO, TO and interface
<> polaritons (IP) in polar material. Hybridization arises as a
<> consequence of the necessity to satisfy simultaneously
<> electromagnetic and mechanical boundary conditions. Optical
<> mode analogues of surface Rayleigh waves appear in non-polar
<> slabs, and in polar superlattices the involvement of interface
<> polaritons causes significant dispersion and anisotropy.
<> Results from a continuum theory are shown to describe
<> experimental results reasonably well. Hybridization affects the
<> quantum properties due to the coherent mixing of LO, TO and IP,
<> and this, in turn, affects the interaction with electrons.
<> Estimates of the electron-hybridon scattering rate in GaAs
<> quantum wells are presented.
<> KP: PHONON INTERACTIONS, HETEROSTRUCTURES
<>
<> **** End of Data ****
<>
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