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8 Oct 1990

Volume 57, Issue 15, pp. 1479-1585

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Miniaturized total‐reflection ferroelectric liquid‐crystal electro‐optic switch

S. S. Bawa, A. M. Biradar, K. Saxena, and Subhas Chandra

Appl. Phys. Lett. 57, 1479 (1990); http://dx.doi.org/10.1063/1.103369 (3 pages) | Cited 6 times

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A total internal reflection (TIR) ferroelectric liquid‐crystal optical switch has been described using a larger value of birefringence and higher extraordinary refractive index (ne) of FLC than the refractive index (ng) of glass. The off‐axis orientations of voltage selected optic axes directions provide a convenient matching of transmission and reflection characteristics. This enables one to decrease the critical angle for TIR. The electro‐optic switch can be miniaturized and a large switch array (1×4; 4×4) architecture is feasible.
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78.20.Jq Electro-optical effects
77.80.B- Phase transitions and Curie point
84.32.Dd Connectors, relays, and switches

Spontaneous recombination current in InGaAs/GaAs quantum well lasers

P. Blood, E. D. Fletcher, K. Woodbridge, and M. Vening

Appl. Phys. Lett. 57, 1482 (1990); http://dx.doi.org/10.1063/1.103370 (3 pages) | Cited 3 times

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We have studied the intrinsic factors which determine the threshold current and its temperature dependence in 160‐Å‐wide In0.2Ga0.8As single well quantum lasers with GaAs barriers, grown by molecular beam epitaxy on GaAs substrates. By measuring the relative temperature dependence of the spontaneous emission intensity at threshold we show that radiative transitions between higher order (n=2,3) electron and heavy hole subbands make a significant contribution to the threshold current and its temperature sensitivity, even in devices where the laser transitions are between n=1 subbands. These higher transitions will also influence the dependence of threshold current and its temperature sensitivity on well width.
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42.55.Px Semiconductor lasers; laser diodes
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Detection of a stimulated emission process as an inverse thermal lens signal

Masahide Terazima and Tohru Azumi

Appl. Phys. Lett. 57, 1485 (1990); http://dx.doi.org/10.1063/1.103371 (3 pages) | Cited 3 times

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A stimulated emission process is detected by applying the transient thermal lens (TL) technique developed recently. The observed inverse TL signal compared with the conventional TL signal indicates that a convex thermal lens is created in the solution by the stimulated‐emission process. The sensitivity and the advantages of this method are discussed.
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42.55.Mv Dye lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation

Measurement of nonlinear properties in Ag‐ion exchange waveguides using degenerate four‐wave mixing

Paul R. Ashley, Mark J. Bloemer, and Jack H. Davis

Appl. Phys. Lett. 57, 1488 (1990); http://dx.doi.org/10.1063/1.103372 (3 pages) | Cited 5 times

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Degenerate four‐wave mixing was used to evaluate third‐order nonlinearities in Ag‐Na exchange waveguides. Guided wave linear absorption analysis was used to correlate metallic Ag content with nonlinear properties. Measured conjugate reflectivities approached 4%.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.87.-d Optical testing techniques
42.79.Gn Optical waveguides and couplers

Optimization of modulation ratio and insertion loss in reflective electroabsorption modulators

B. Pezeshki, D. Thomas, and J. S. Harris

Appl. Phys. Lett. 57, 1491 (1990); http://dx.doi.org/10.1063/1.103373 (2 pages) | Cited 31 times

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We show theoretically that the maximum modulation ratio in Fabry–Perot reflective electroabsorption modulators for a given insertion loss is solely a function of the ratio of the maximum to minimum absorption. We increase this ratio by using thinner quantum wells than are conventionally used and obtain significantly improved performance. We obtain an insertion loss of 1.2 dB and a modulation ratio of 7.5 with a 5 V operating bias.
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42.79.Hp Optical processors, correlators, and modulators
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.30.Lr Modulation and optical transfer functions
78.20.Jq Electro-optical effects

Continuously graded‐index separate confinement heterostructure multiquantum well Ga1−xInxAs1−yPy/InP ridge waveguide lasers grown by low‐pressure metalorganic chemical vapor deposition with lattice‐matched quaternary wells and barriers

M. J. Ludowise, T. R. Ranganath, and A. Fischer‐Colbrie

Appl. Phys. Lett. 57, 1493 (1990); http://dx.doi.org/10.1063/1.103374 (3 pages) | Cited 1 time

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Continuously graded‐index separate confinement heterostructure multiple quantum well (four wells, Lz ∼50 Å) lasers fabricated in the Ga1−xInxAs1−yPy/InP system with lattice‐matched quaternary wells (bulk emission wavelength λg=1.39 μm) and barriers (λg=1.2 μm) are reported. A 5‐μm‐wide ridge waveguide laser operates with laser threshold current Ith=34 mA at room temperature (λ∼1286 nm) with an external differential quantum efficiency of ∼19% per facet and a temperature coefficient T0 ∼40 K. Large‐area threshold current density is measured at 1.1 kA/cm2 on a 40×300 μm2 device.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Novel relaxation process in strained Si/Ge superlattices grown on Ge (001)

W. Wegscheider, K. Eberl, G. Abstreiter, H. Cerva, and H. Oppolzer

Appl. Phys. Lett. 57, 1496 (1990); http://dx.doi.org/10.1063/1.103375 (3 pages) | Cited 28 times

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A new mode of misfit defect formation has been observed for the first time in high quality Si/Ge strained‐layer superlattices grown by molecular beam epitaxy on Ge(001). In order to investigate the transition from coherent to incoherent growth we have studied a set of samples with a varying number of superlattice periods by transmission electron microscopy. High‐resolution lattice imaging reveals that strain relaxation occurs through successive glide of 90° (a/6)〈211〉 Shockley partial dislocations on adjacent {111} planes. The resulting microtwins represent the only relaxation mechanism we observed in the samples.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
61.72.Mm Grain and twin boundaries

In situ time‐resolved reflectivity measurements of Al under excimer laser planarization conditions

Paul G. Carey, Bertram J. Woratschek, and Friedrich Bachmann

Appl. Phys. Lett. 57, 1499 (1990); http://dx.doi.org/10.1063/1.103376 (3 pages) | Cited 5 times

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In situ time‐resolved reflectivity (TRR) measurements have been made on unpatterned 800 nm pure Al films located on top of different underlying layers (e.g., substrate, diffusion barrier, or oxide) under XeCl (λ=308 nm, pulse width 40 ns) excimer laser planarization conditions. The reflectivity change observed when using a HeNe (λ=632.8 nm) probe beam is assumed to indicate layer melting. Results show that Al melt durations increase with laser energy fluence, oxide thickness, and substrate temperature. In addition, under certain processing conditions Al areas with a thick underlying oxide remain molten for over 1000 ns while no Al melting is observed where it directly contacts the silicon substrate. This work explains why substrate heating during excimer laser planarization is necessary in order to completely fill high aspect ratio contact holes.
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85.40.Hp Lithography, masks and pattern transfer
85.40.Ls Metallization, contacts, interconnects; device isolation
79.20.Ds Laser-beam impact phenomena
78.47.-p Spectroscopy of solid state dynamics

Interdiffusion and strain relaxation in (SimGen)p superlattices

J.‐M. Baribeau, R. Pascual, and S. Saimoto

Appl. Phys. Lett. 57, 1502 (1990); http://dx.doi.org/10.1063/1.103377 (3 pages) | Cited 49 times

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We report an x‐ray diffraction study of interdiffusion and strain relaxation in (SimGen)p short‐period superlattices. An interdiffusion coefficient Dλ was determined by monitoring, as a function of time, the decay upon annealing of the first order 000 satellite peak arising from the compositional modulation of the superlattice. Strain relaxation was obtained from the shift of the 400 superlattice peak on annealing. In the early stage of annealing the low angle satellite exhibited a rapid nonexponential decay after which a slower exponential decay was observed indicating a larger initial interdiffusion coefficient. This enhancement was correlated with the presence of strain and it disappeared upon relaxation. Diffusion was faster in structures alternating thin Si and thick Ge layers suggesting that migration of Si into Ge is the dominant diffusion process.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.35.Fx Diffusion; interface formation
66.30.J- Diffusion of impurities
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Epitaxial growth of ferroelectric bismuth titanate thin films by pulsed laser deposition

R. Ramesh, K. Luther, B. Wilkens, D. L. Hart, E. Wang, J. M. Tarascon, A. Inam, X. D. Wu, and T. Venkatesan

Appl. Phys. Lett. 57, 1505 (1990); http://dx.doi.org/10.1063/1.104128 (3 pages) | Cited 65 times

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Epitaxial thin films of ferroelectric bismuth titanate Bi4Ti3O12 have been grown by pulsed laser deposition on single‐crystal [100] SrTiO3 substrates. Bismuth titanate has a high Curie temperature (675 °C) and saturation polarization values of 4 and 50 μC/cm2 along the c and b axis, respectively. Its a,b lattice parameters allow thin‐film growth on substrates such as SrTiO3, LaAlO3, MgO, etc. These single crystalline films exhibit good quality as evidenced by x‐ray diffraction, Rutherford backscattering, and transmission electron microscopy. Applications for these films include memory devices and optical displays.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
77.80.B- Phase transitions and Curie point

Picosecond time‐resolved surface‐lattice temperature probe

H. E. Elsayed‐Ali and J. W. Herman

Appl. Phys. Lett. 57, 1508 (1990); http://dx.doi.org/10.1063/1.103378 (3 pages) | Cited 30 times

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Picosecond reflection high‐energy electron diffraction is used as a time‐resolved surface‐lattice temperature probe. A picosecond laser pulse is split into two beams. The first interacts with the sample. The second activates the cathode of an electron gun creating a collimated and focused electron pulse that is well synchronized with the heating laser pulse. The electron pulse is used to generate a reflection high‐energy electron diffraction pattern of the sample. Since heating results in an intensity reduction of the elastically scattered electrons (Debye–Waller effect), the diffraction pattern provides information on the surface temperature as well as structure. Time‐resolved measurements of the picosecond laser‐heated surface show general agreement with a heat diffusion model.
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61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
68.35.Ja Surface and interface dynamics and vibrations
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Optical determination of oxygen outdiffusion in epitaxial silicon grown on n‐type Czochralski substrates

M. Geddo, B. Pivac, A. Borghesi, A. Stella, and M. Pedrotti

Appl. Phys. Lett. 57, 1511 (1990); http://dx.doi.org/10.1063/1.103379 (3 pages) | Cited 8 times

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Oxygen solid‐state outdiffusion from the substrate to the epitaxial layer was investigated by using micro‐Fourier transform infrared measurements in a transversal wafer cross‐section configuration. Interstitial oxygen concentration, obtained by analyzing the 1107 cm−1absorption band, indicated that an oxygen content, clearly detectable by the infrared technique, is present in the epitaxial layer near the interface. To our knowledge this is the first evidence of oxygen outdiffusion from the substrate into the epitaxial layer.
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66.30.J- Diffusion of impurities
68.35.Fx Diffusion; interface formation
78.30.-j Infrared and Raman spectra
78.40.Fy Semiconductors

Rapid thermal annealing of Ge‐implanted InP

P. Kringhøj, V. V. Gribkovskii, and A. Nylandsted Larsen

Appl. Phys. Lett. 57, 1514 (1990); http://dx.doi.org/10.1063/1.103380 (3 pages) | Cited 15 times

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Results from n‐type doping by Ge implantation at 200 keV into 〈100〉 p‐type InP are reported. The degree of recrystallization and electrical activity after capless annealing by rapid thermal annealing was investigated as a function of dose, implantation, and annealing temperature by a combination of Rutherford backscattering spectrometry/channeling, differential Hall/resistivity, and secondary‐ion mass spectrometry measurements. Room‐temperature implantations resulted in continuous amorphous layers even at a dose of 2×1013cm−2 in contrast to hot implantations at 200 °C where no amorphous layers were created even for a dose as high as 5×1014 cm−2. For the latter dose an activation percentage of 37 and a maximum carrier concentration of 1×1019 cm−3 were achieved after rapid thermal annealing at 830 °C for 1 s.
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61.72.U- Doping and impurity implantation
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
73.61.Ey III-V semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Effect of cathode spacer layer on the current‐voltage characteristics of resonant tunneling diodes

P. Mounaix, O. Vanbesien, and D. Lippens

Appl. Phys. Lett. 57, 1517 (1990); http://dx.doi.org/10.1063/1.103381 (3 pages) | Cited 25 times

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The effect of a lightly doped cathode spacer layer on resonant tunneling of Al0.3Ga0.7As‐GaAs double‐barrier heterostructures is examined. A self‐consistent band‐bending calculation combined with a quantum calculation of current‐voltage characteristics is used to model the experimentally observed I‐V curves. It is found that the I‐V characteristics show additional structures, sensitively dependent upon temperature. These effects result from the formation of a wide barrier by space‐charge reaction in the spacer layer leading to two possible resonant states. The validity of the theoretical approach is supported by the good agreement with experimental results.
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73.40.Gk Tunneling
72.80.Ey III-V and II-VI semiconductors
73.50.Fq High-field and nonlinear effects

Ultrafast optical nonlinearities of type II AlxGa1−xAs/AlAs multiple quantum wells

J. Feldmann, E. Göbel, and K. Ploog

Appl. Phys. Lett. 57, 1520 (1990); http://dx.doi.org/10.1063/1.103382 (3 pages) | Cited 12 times

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We present experimental studies of the transient optical nonlinearities near the direct band gap of type II AlxGa1−xAs/AlAs multiple quantum wells. The response of the optical nonlinearity at the band‐gap excitonic transition is critically dependent on laser photon energy. A complete recovery of the bleached absorption in the lower part of the excitonic resonance with a picosecond time constant at room temperature occurs due to an enhanced collision broadening of the excitonic resonance after the fast spatial Γ–X transfer. Our results demonstrate that the intrinsic response of optical devices based on exciton nonlinearities can be much faster in type II structures as compared to type I structures.<squeeze;2p>
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78.47.-p Spectroscopy of solid state dynamics
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Optical detection of biatomic sheets of silicon in Si/Ge superlattices

J. D. White, G. Fasol, R. A. Ghanbari, M. A. Gell, C. J. Gibbings, and C. G. Tuppen

Appl. Phys. Lett. 57, 1523 (1990); http://dx.doi.org/10.1063/1.104092 (3 pages)

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A distinctive Raman spectrum associated with biatomic sheets of silicon in Si/Ge superlattices has been found in the energy range 370–410 cm−1. This double‐peaked structure was obtained over an order of magnitude of germanium layer thickness, but was not found in the alloy control layers or structures with thicker Si layers. It is proposed that the signal is due to modes that are normally forbidden in this scattering configuration. Strong direct optical transitions have been predicted for certain Si/Ge superlattices incorporating biatomic sheets of Si and this distinctive Raman signal could be used to characterize the biatomic sheets of silicon in these structures.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
78.66.-w Optical properties of specific thin films

Cathodoluminescence study of the damage induced by low‐energy boron implantation using a chemical bevel

A. C. Papadopoulo, C. Dubon‐Chevallier, A. M. Pougnet, and P. Krauz

Appl. Phys. Lett. 57, 1526 (1990); http://dx.doi.org/10.1063/1.103341 (2 pages)

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Boron implantation is used in AlGaAs/GaAs heterojunction bipolar transistor fabrication technology in order to eliminate the lateral diode between the n+‐GaAs emitter contact layer and the p+‐GaAs implanted well. The cathodoluminescence intensities measured on a bevel before and after the implantation have been investigated to evaluate the amount of damage induced by low‐energy implantation in the underlying AlGaAs emitter layer.
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78.60.Hk Cathodoluminescence, ionoluminescence
61.72.U- Doping and impurity implantation
85.30.Pq Bipolar transistors
81.40.Tv Optical and dielectric properties related to treatment conditions

Light‐induced defect studies in hydrogenated amorphous silicon by exoelectron emission

R. S. Bhide, V. Manorama, S. K. Pawar, Suvarna Babras, S. V. Bhoraskar, and V. G. Bhide

Appl. Phys. Lett. 57, 1528 (1990); http://dx.doi.org/10.1063/1.103342 (3 pages) | Cited 7 times

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Exoelectron emission was observed from previously light soaked, glow discharge prepared a‐Si:H films by thermal stimulation. The energy analysis of exoelectrons was incorporated by a 127° cylindrical deflection analyzer (CDA). Observed energies of exoelectrons (4–8 eV) suggest that the delocalized electron gains energy during emission either from the Coulomb potential or from the exchange of energy from dangling bond annihilation. Several models of dangling bond creation are discussed; however, the actual mechanism appears to be more complex.
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79.75.+g Exoelectron emission
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Formation of arsenic precipitates in GaAs buffer layers grown by molecular beam epitaxy at low substrate temperatures

M. R. Melloch, N. Otsuka, J. M. Woodall, A. C. Warren, and J. L. Freeouf

Appl. Phys. Lett. 57, 1531 (1990); http://dx.doi.org/10.1063/1.103343 (3 pages) | Cited 170 times

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We have grown film structures by molecular beam epitaxy which include GaAs buffer layers grown at low substrate temperatures (250 °C). The film structures have been examined using transmission electron microscopy. The layers grown at normal temperatures (600 °C) were free of defects or clusters. In contrast, the layer which was grown at low substrate temperatures contained precipitates which have been identified as hexagonal arsenic. The density of the arsenic precipitates is found to be very sensitive to the substrate temperature during growth.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.30.Mh Solid-phase precipitation
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Improved contacts to semi‐insulating GaAs photoconductive switches using a graded layer of InGaAs

D. Kuchta, J. R. Whinnery, J. S. Smith, J. M. Woodall, and D. Pettit

Appl. Phys. Lett. 57, 1534 (1990); http://dx.doi.org/10.1063/1.103344 (3 pages)

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High performance photoconductive switches are demonstrated using a molecular beam epitaxy grown graded layer of InxGa1−xAs to make an ohmic contact to semi‐insultating GaAs. It is found that the graded layer results in a peak signal amplitude that is more than a factor of 2 larger than what is obtained using conventional alloyed AuGeNi contacts.
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85.60.Dw Photodiodes; phototransistors; photoresistors
73.40.Cg Contact resistance, contact potential
73.40.Sx Metal-semiconductor-metal structures

Nonalloyed ohmic contacts on low‐temperature molecular beam epitaxial GaAs: Influence of deep donor band

H. Yamamoto, Z‐Q. Fang, and D. C. Look

Appl. Phys. Lett. 57, 1537 (1990); http://dx.doi.org/10.1063/1.103345 (3 pages) | Cited 34 times

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The Ohmic nature of the nonalloyed metal contact on molecular beam epitaxial GaAs grown at 200 °C was studied. The specific contact resistances at room temperature and 120 K were 1.5×10−3 and 7.0×10−1 Ω cm2, respectively. These values are anomalously low considering that the conduction‐band electron concentration in this material is less than 1011 cm−3 at room temperature. The experimental results indicate that the carrier transport at the metal/semiconductor interface is dominated by a dense (∼3×1019 cm−3) EL2‐like deep donor band, rather than the usual conduction band.<squeeze;1.6p>
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73.40.Cg Contact resistance, contact potential
73.40.Ns Metal-nonmetal contacts
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors

Deposition of SiC films by pulsed excimer laser ablation

M. Balooch, R. J. Tench, W. J. Siekhaus, M. J. Allen, A. L. Connor, and D. R. Olander

Appl. Phys. Lett. 57, 1540 (1990); http://dx.doi.org/10.1063/1.103346 (3 pages) | Cited 34 times

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Thin films of β‐SiC were grown on Si substrates by excimer laser pulse ablation of bulk SiC. The films were examined by Auger electron, x‐ray, and photoelectron spectroscopies and laser ionization mass analysis techniques. The film was smooth as monitored by scanning electron microscopy. Scanning electron and scanning tunneling microscopy (STM) showed inclusions in the deposited SiC films, and laser ionization mass analysis detected SiC dimers in the vapor plume emitted from the target.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
79.20.Ds Laser-beam impact phenomena

Subpicosecond photoresponse of carriers in low‐temperature molecular beam epitaxial In0.52Al0.48As/InP

S. Gupta, P. K. Bhattacharya, J. Pamulapati, and G. Mourou

Appl. Phys. Lett. 57, 1543 (1990); http://dx.doi.org/10.1063/1.103347 (3 pages) | Cited 36 times

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Femtosecond time‐resolved reflectivity and photoconductive switching measurements have been made of In0.52Al0.48As grown by molecular beam epitaxy on (100) InP substrates at growth temperatures ranging from 150 to 480 °C. A response/switching time of ∼400 fs is measured in the sample grown at 150 °C. Temperature‐dependent measurements shed light on the nature of the material producing the ultrafast response.
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78.47.-p Spectroscopy of solid state dynamics
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Interband resonant tunneling diode in δ‐doped GaAs

Y. H. Wang

Appl. Phys. Lett. 57, 1546 (1990); http://dx.doi.org/10.1063/1.103348 (2 pages) | Cited 16 times

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Novel negative differential resistance (NDR) diodes, suggesting interband resonant tunneling diodes, in δ‐doped GaAs prepared by molecular beam epitaxy are demonstrated. Two Si and one Be δ‐doped planes were inserted in the GaAs layer, i.e., n+‐δn+‐i‐δp+‐i‐δn+‐n+, to form the required band structure. Electrons are then transported from the conduction band of the n+ layer and resonantly tunnel through the valence band of the δp+ induced quantum well. Symmetric NDR characteristics with a peak‐to‐valley current ratio of 1.7 and a peak current density of 5 kA/cm2 under forward and reverse biases operating at room temperature are observed.
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85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling

Electronic structure and dynamics of thin Ge/GaAs(110) heterostructures

R. Haight and J. A. Silberman

Appl. Phys. Lett. 57, 1548 (1990); http://dx.doi.org/10.1063/1.103349 (3 pages) | Cited 4 times

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Using angle‐resolved picosecond laser photoemission we have investigated both occupied and transiently excited empty states at the surface of Ge grown epitaxially on GaAs(110). We observe a normally unoccupied, Ge layer derived state whose separation from the valence‐band maximum of the system is 700±50 meV at six monolayers Ge coverage. The evolution of the electronic structure is followed as a function of coverage and correlated with low‐energy electron diffraction. The time dependence of the transiently occupied Ge signal is compared with that of the clean GaAs(110) surface and shows that electrons are <me;40p>prevented from diffusing into the GaAs bulk by the conduction‐band offset of 330±40 meV.
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73.25.+i Surface conductivity and carrier phenomena
78.47.-p Spectroscopy of solid state dynamics
81.65.-b Surface treatments
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