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15 Apr 1991

Volume 58, Issue 15, pp. 1579-1684

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Noncritically phase‐matched second‐harmonic generation and optical parametric amplification in a lithium triborate crystal

J. Y. Huang, Y. R. Shen, Chuangtian Chen, and Bochang Wu

Appl. Phys. Lett. 58, 1579 (1991); http://dx.doi.org/10.1063/1.105156 (3 pages) | Cited 19 times

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We evaluate the potential of lithium triborate (LBO) temperature‐tuned to achieve type‐I noncritical phase matching, for picosecond high‐power second‐harmonic generation (SHG) and tunable optical parametric amplification (OPA). Pumped by 35 ps, 1.064 μm laser pulses, a conversion efficiency of 65% was obtained from SHG. The output of OPA, pumped by 0.532 μm was tunable from 0.75 to 1.8 μm with an efficiency better than 20%.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.70.-a Optical materials
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.20.-e Optical properties of bulk materials and thin films

Transmission of 1 kW‐class CO2 laser light through circular hollow waveguides for material processing

Akihito Hongo, Ken’ichi Morosawa, Tsuneo Shiota, Kenji Suzuki, Souta Iwasaki, and Mitsunobu Miyagi

Appl. Phys. Lett. 58, 1582 (1991); http://dx.doi.org/10.1063/1.105131 (3 pages) | Cited 8 times

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For the purpose of material processing, we have studied transmission characteristics of germanium‐coated silver hollow waveguides with 1.5 mm ϕ×80 cm. The maximum input power was 1 kW and the transmission was 90% under straight condition. Steel plates 1.6 mm thick were cut by CO2 laser light through the hollow waveguide and the authors confirmed that this type of waveguide could deliver sufficient laser energy for material processing.
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42.79.Gn Optical waveguides and couplers
89.20.Bb Industrial and technological research and development

Hybrid optical bistability based on voltage‐controlled changes of persistent spectral holes

N. Hartmannsgruber and Max Maier

Appl. Phys. Lett. 58, 1585 (1991); http://dx.doi.org/10.1063/1.105132 (3 pages) | Cited 1 time

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Electric field induced changes of the absorption in the center of a persistent spectral hole were used to operate a hybrid optical bistable device. The hole was burned in the inhomogeneously broadened S0–S1 transition of perylene in an amorphous polyvinylbutyral matrix. The external feedback was realized by detecting the zero‐phonon fluorescence light of the dye molecules with a photomultiplier and applying the amplified voltage to the sample.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics

Complementary optical tap fabricated in an electro‐optic polymer waveguide

T. E. Van Eck, A. J. Ticknor, R. S. Lytel, and G. F. Lipscomb

Appl. Phys. Lett. 58, 1588 (1991); http://dx.doi.org/10.1063/1.105133 (3 pages) | Cited 30 times

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An active complementary optical tap made in an electro‐optic polymer waveguide is reported for the first time. This device is the critical component of an optical railtap, a system capable of providing many optical interconnects with a single laser source. The device was fabricated by selective photobleaching of a uniformly poled polymer layer, and complementary switching was demonstrated.
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42.82.-m Integrated optics
85.60.-q Optoelectronic devices
42.79.Gn Optical waveguides and couplers

Selective excitation of single‐mode acoustic waves by phase velocity scanning of a laser beam

Kazushi Yamanaka, Yoshihiko Nagata, and Toshio Koda

Appl. Phys. Lett. 58, 1591 (1991); http://dx.doi.org/10.1063/1.105134 (3 pages) | Cited 20 times

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A novel method for selective generation of single‐mode acoustic waves in multimode media has been developed using a laser beam scanned at the phase velocity of a specified mode. In dispersive media, the acoustic frequency can be varied by changing the scanning velocity. The number of carriers in the generated wave packet is proportional to the difference between the phase and the group velocities. These features were experimentally verified in the fundamental symmetric and asymmetric Lamb waves on an aluminum plate generated by a long‐pulse Nd:YAG laser. Applications to anisotropy and thickness measurements are discussed.
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43.35.Cg Ultrasonic velocity, dispersion, scattering, diffraction, and attenuation in solids; elastic constants
43.35.Pt Surface waves in solids and liquids
62.65.+k Acoustical properties of solids

Competition between fundamental and second‐harmonic operations in a submillimeter wave gyrotron

T. Idehara, T. Tatsukawa, I. Ogawa, T. Mori, H. Tanabe, S. Wada, G. F. Brand, and M. H. Brennan

Appl. Phys. Lett. 58, 1594 (1991); http://dx.doi.org/10.1063/1.105135 (3 pages) | Cited 14 times

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Competition between electron cyclotron fundamental (f=fc) and second‐harmonic (f=2fc) operation in a submillimeter wave gyrotron is described. Even when the magnetic field intensity is adjusted to the optimum value for second‐harmonic operation, we can get a pure mode only for small beam currents. As the beam current is increased, excitation of the fundamental appears and eventually suppresses the second harmonic. The observed competition between the fundamental and second harmonic is compared with a computer simulation.
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84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
52.50.Gj Plasma heating by particle beams
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Dynamics of excimer laser‐ablated aluminum neutral atom plume measured by dye laser resonance absorption photography

Ronald M. Gilgenbach and Peter L. G. Ventzek

Appl. Phys. Lett. 58, 1597 (1991); http://dx.doi.org/10.1063/1.105136 (3 pages) | Cited 48 times

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We report the first dye laser resonance absorption photographs of a single species of aluminum ground‐state neutral atoms in the plume ablated from solid aluminum by KrF excimer laser radiation. Aluminum ground‐state neutral atoms were diagnosed by illuminating the ablated plume with a dye laser tuned to the 32P1/2–42S1/2 transition at 394.4 nm. Measurements have been performed in vacuum as well as in argon and air environments. Streaming velocities measured for neutral aluminum atoms in vacuum ranged from 0.5×106 cm/s at low excimer laser fluences of 1–2 J/cm2 to 3.4×106 cm/s at high fluences of 7 J/cm2. Dye laser resonance absorption photography measurements of ablated aluminum in argon and air showed slower expansion at 50 and 200 Torr, while observations at 760 Torr indicate turbulent mixing of aluminum neutrals near the surface. Differences between data in argon and air may be due to oxidation of neutral aluminum atoms.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
89.20.Bb Industrial and technological research and development

Enhanced silicon etching in nitrogen‐containing SF6‐O2 plasma

V. Premachandran

Appl. Phys. Lett. 58, 1600 (1991); http://dx.doi.org/10.1063/1.105137 (2 pages) | Cited 1 time

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The effect of addition of small amounts of nitrogen into SF6‐O2 plasma has been studied in terms of atomic fluorine concentration and the silicon etch rate. A factor of seven increase in the atomic fluorine concentration is observed when O2 along with 1% N2 is introduced into the SF6 plasma. With oxygen alone in the feed, the increase was less than a factor of 3. Consequently, an enhanced silicon etch rate is achieved in a SF6‐O2‐N2 plasma.
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81.65.-b Surface treatments
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

X‐ray scattering study of lattice relaxation in ErAs epitaxial layers on GaAs

P. F. Miceli, C. J. Palmstrøm, and K. W. Moyers

Appl. Phys. Lett. 58, 1602 (1991); http://dx.doi.org/10.1063/1.105138 (3 pages) | Cited 26 times

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We present the results of a high‐resolution x‐ray scattering study of the lattice relaxation in [001]ErAs epitaxial layers grown on [001]GaAs. Three thickness regimes are found. ErAs is pseudomorphic on GaAs for thicknesses below 70 Å and between 70 and 300 Å lattice relaxation is observed concomitant with an increase of the in‐plane mosaic due to the formation of misfit dislocations. Above 300 Å, the out‐of‐plane transverse scattering from the ErAs lattice planes is no longer specular and further relaxation appears to be related to the out‐of‐plane mosaic. The ratio of elastic constants, C12/C11, is measured to be 0.126. Thin‐film interference oscillations are observed and modeled, finding that for 140 Å of ErAs the interface fluctuations are ∼2.5 monolayers. ErAs/GaAs is an ideal system for x‐ray scattering studies of lattice relaxation and structure in epitaxial layers.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.

Reversible Eu2+↔Eu3+ transitions at Eu‐Si interfaces

W. A. Henle, M. G. Ramsey, F. P. Netzer, and K. Horn

Appl. Phys. Lett. 58, 1605 (1991); http://dx.doi.org/10.1063/1.105139 (3 pages) | Cited 3 times

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Valence switching at Eu‐Si interfaces is demonstrated by resonant photoemission during repeated oxidation‐reduction cycles performed by room‐temperature O2 exposure and mild heating. The Eu2+↔Eu3+ transitions are accompanied by Fermi level switching associated with changes in the stoichiometry of the surface heterostructure. The ability to cycle between two well‐defined magnetic states at a surface may be attractive in technological applications.
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75.20.Hr Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.-b Surface treatments

Novel reflectance modulator employing an InGaAs/AlGaAs strained‐layer superlattice Fabry–Perot cavity with unstrained InGaAs/InAlAs mirrors

I. J. Fritz, D. R. Myers, G. A. Vawter, T. M. Brennan, and B. E. Hammons

Appl. Phys. Lett. 58, 1608 (1991); http://dx.doi.org/10.1063/1.105140 (3 pages) | Cited 17 times

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We present a novel approach to optoelectronic devices by combining mechanically stable strained and unstrained epitaxial multilayers. We illustrate our approach with an optical reflectance modulator based on an asymmetric Fabry–Perot resonator designed to operate near 1.06 μm. The resonator is grown on a mechanically relaxed buffer of In0.11Ga0.89As deposited on a GaAs substrate. For mirrors, quarter‐wave stacks of In0.11Ga0.89As and In0.1Al0.9As, lattice matched to the buffer, are used. The Fabry–Perot cavity consists of an In0.23Ga0.77As/Al0.35Ga0.65As strained‐layer superlattice whose planar lattice constant also matches the buffer. Our first device operates at 1.04–1.05 μm depending on lateral position across the wafer. The insertion loss at resonance is less than 2 db and a fractional modulation of over 60% has been achieved with a 4 V bias swing.
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85.60.-q Optoelectronic devices
42.79.Hp Optical processors, correlators, and modulators
78.20.Jq Electro-optical effects

Molecular beam epitaxy of ZnSe1−xTex ternary alloys

F. S. Turco‐Sandroff, R. E. Nahory, M. J. S. P. Brazil, R. J. Martin, and H. L. Gilchrist

Appl. Phys. Lett. 58, 1611 (1991); http://dx.doi.org/10.1063/1.105141 (3 pages) | Cited 13 times

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ZnSe1−xTex ternary alloy has been grown over the entire range of composition by molecular beam epitaxy on GaAs and InP substrates. A precise control of the composition is achieved by growing this material under Zn‐rich conditions. For low Te concentrations, However, significant Te surface segregation is observed, which may be due to surface energy minimization. The band‐gap energy has been measured over the entire range of composition and presents a very strong bowing with a minimum energy of 2.05 eV for a Te concentration of 0.65.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Md Surface thermodynamics, surface energies
78.55.Et II-VI semiconductors

Effect of structural parameters on transport characteristics of GaInAs/AlInAs two‐dimensional electron gases grown by molecular beam epitaxy

M. A. Tischler and B. D. Parker

Appl. Phys. Lett. 58, 1614 (1991); http://dx.doi.org/10.1063/1.105142 (3 pages) | Cited 8 times

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The effect of structural parameters on the transport characteristics from 15 to 300 K of molecular beam epitaxy grown GaInAs/AlInAs two‐dimensional electron gas structures lattice matched to InP is determined. The AlInAs buffer layer thickness was varied from 1000 to 10 000 Å. One sample also incorporated a GaInAs/AlInAs superlattice. The AlInAs spacer layer was varied from 25 to 200 Å. The buffer layer thickness and structure has almost no effect on the mobility or sheet density. Increases in the AlInAs spacer thickness resulted in a monotonically decreasing sheet density and a peak in the mobility at 100 Å. The highest 77 K mobility was 66 700 cm2/V s with ND=1.20×1012 cm−2 in the structure with the 100 Å spacer. The effect of illumination and temperature on the sheet concentration in these structures as well as on ‘‘bulk’’ AlInAs:Si is much smaller than in AlGaAs/GaAs structures or ‘‘bulk’’ AlGaAs, indicating that devices based on this material system will not be characterized by freeze‐out and persistent photoconductivity.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.30.De Semiconductor-device characterization, design, and modeling
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Ey III-V semiconductors

Thermally stable and nonspiking Pd/Sb(Mn) ohmic contact to p‐GaAs

C. C. Han, X. Z. Wang, S. S. Lau, R. M. Potemski, M. A. Tischler, and T. F. Kuech

Appl. Phys. Lett. 58, 1617 (1991); http://dx.doi.org/10.1063/1.105143 (3 pages) | Cited 13 times

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A thermally stable, nonspiking ohmic contact to p‐GaAs has been developed based on the solid‐phase regrowth mechanism. The contact metallization consists of a layered structure of Pd(250 Å)/Sb(100 Å)/Mn(10 Å)/Pd(250 Å)/p‐GaAs. Thermal annealing of the contact between 300 and 600 °C for 10 s yields contact resistivities in the range of low 10−6 Ω cm2 on substrates doped to 2.5×1018 cm−3. A contact resistivity of 4.5×10−7 Ω cm2 can be obtained after annealing at 500 °C on samples with a doping concentration of 4.5×1019 cm−3. The contact metallization remains uniform in thickness and the contact interface is flat after the contact is formed. The consumption of the substrate is limited to less than a hundred angstroms. Contact resistivities are stable at 400 °C.
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73.40.Cg Contact resistance, contact potential

Excitons and light‐induced degradation of amorphous hydrogenated silicon

Martin S. Brandt and Martin Stutzmann

Appl. Phys. Lett. 58, 1620 (1991); http://dx.doi.org/10.1063/1.105144 (3 pages) | Cited 9 times

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Excitonic states involved in electronic transport of undoped amorphous hydrogenated silicon (a‐Si:H) are observed using spin‐dependent photoconductivity (SDPC). Upon light soaking the excitonic signal decreases with regard to the SDPC signal due to recombination via dangling bonds. It has been suggested that excitonic tail‐to‐tail recombination leads to metastable defect creation in a‐Si:H. Our experimental results are shown to be consistent with this model.
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71.35.-y Excitons and related phenomena
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ng Disordered solids
72.40.+w Photoconduction and photovoltaic effects

Subband mixing effect in double‐barrier diodes with a restricted lateral dimension

Seigo Tarucha, Yoshiro Hirayama, and Yasuhiro Tokura

Appl. Phys. Lett. 58, 1623 (1991); http://dx.doi.org/10.1063/1.105145 (3 pages) | Cited 15 times

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Tunneling characteristics of double‐barrier diodes with a restricted lateral dimension are studied. When a large number of closely spaced emitter subbands contribute to the tunneling, the current versus voltage characteristics exhibit a series of peaks separated by the voltages that correspond to subband splittings in the double‐barrier region. When the lowest emitter subband mainly contributes to the tunneling, they exhibit peaks separated by approximately twice the voltages that correspond to the subband splittings in the double‐barrier region. These differences can be explained by the effects of mixing two‐dimensional emitter subbands with one‐dimensional subbands in the double‐barrier region.
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73.40.Gk Tunneling
85.30.Mn Junction breakdown and tunneling devices (including resonance tunneling devices)
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds

Si ultrashallow p+n junctions using low‐energy boron implantation

A. Bousetta, J. A. van den Berg, D. G. Armour, and P. C. Zalm

Appl. Phys. Lett. 58, 1626 (1991); http://dx.doi.org/10.1063/1.105146 (3 pages) | Cited 13 times

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Ultrashallow boron‐doped junctions in silicon have been investigated using secondary‐ion mass spectroscopy and four‐point probe technique. The junctions were obtained by implanting B+ ions into n‐type Si(100) at 200 eV to doses of 1.5×1014 and 6×1014 cm−2 and at substrate temperatures in the range 30–900 °C during B implantation. Both post‐implantation in situ annealing by electron bombardment heating and rapid thermal annealing in a separate system were employed. The results show that sub 20 nm p+n junctions are obtained without the need for further processes such as preamorphization and high‐temperature annealing.
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61.72.uf Ge and Si
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Bb Theories and models of crystal defects

Comparison of bulk and quantum wire photodetectors

D. L. Crawford, R. L. Nagarajan, and J. E. Bowers

Appl. Phys. Lett. 58, 1629 (1991); http://dx.doi.org/10.1063/1.105147 (3 pages) | Cited 6 times

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A theoretical comparison of the operating characteristics of p‐i‐n GaAs/AlGaAs photodetectors incorporating either bulk or quantum wire absorbing regions is presented in an effort to realistically compare both the bandwidth and the quantum efficiency of these devices. Devices utilizing quantum wire absorbing regions may have enhanced operating characteristics assuming increased absorption and saturated carrier drift velocities can be realized in these quantized structures.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.50.Pz Photoconduction and photovoltaic effects

Structure, properties, and thermal stability of in situ phosphorus‐doped hydrogenated microcrystalline silicon prepared by plasma‐enhanced chemical vapor deposition

S. J. Jeng, D. E. Kotecki, J. Kanicki, C. C. Parks, and J. Tien

Appl. Phys. Lett. 58, 1632 (1991); http://dx.doi.org/10.1063/1.105148 (3 pages) | Cited 3 times

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The correlations between structural, chemical, electrical, optical properties of in situ phosphorus‐doped hydrogenated microcrystalline silicon prepared by plasma‐enhanced chemical vapor deposition have been studied by high‐resolution transmission electron microscopy, secondary‐ion mass spectrometry, electrical conductivity, and optical measurements. Microcrystallinity has been observed at a substrate temperature as low as 100 °C with a 1% dilution of (1% PH3/SiH4) in H2. In situ phosphorous‐doped hydrogenated microcrystalline silicon is best grown at 200–300 °C in terms of microstructure, H and P content, and dopant activation. The effects of thermal processing and the use of silicon nitride cap deposited prior to anneal on the structure and properties of phosphorous‐doped hydrogenated microcrystalline silicon are also reported. The use of a silicon nitride capping layer is shown to inhibit recrystallization of hydrogenated microcrystalline silicon during rapid thermal anneal.
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61.43.Fs Glasses
61.43.-j Disordered solids
61.44.Br Quasicrystals
61.72.uf Ge and Si
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Removal of the sulfur passivation overlayer on a (NH4)2Sx‐treated GaAs surface by vacuum‐ultraviolet irradiation

Yuji Takakuwa, Michio Niwano, Shinya Fujita, Yuki Takeda, and Nobuo Miyamoto

Appl. Phys. Lett. 58, 1635 (1991); http://dx.doi.org/10.1063/1.105149 (3 pages) | Cited 7 times

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Effects of photon irradiation on the chemical state of a (NH4)2Sx‐treated GaAs surface have been investigated using photoemission and photon‐stimulated desorption (PSD) spectroscopic techniques with synchrotron radiation (SR). It is shown that a sulfur‐passivation overlayer on the (NH4)2Sx‐treated GaAs surface is readily removed by irradiating SR in the vacuum‐ultraviolet (VUV) region onto the surface, suggesting the possibility of cleaning the sulfur‐passivated GaAs surface by VUV irradiation. The dominant PSD ion product that desorbs from the sulfur‐passivated GaAs surface during VUV irradiation is found to be H+. No desorption of sulfur ions is observed, which suggests that sulfur adatoms desorb as neutral species.
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61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)
81.65.-b Surface treatments
85.40.Ls Metallization, contacts, interconnects; device isolation

Effect of scattering by native defects on electron mobility in modulation‐doped heterostructures

W. Walukiewicz and E. E. Haller

Appl. Phys. Lett. 58, 1638 (1991); http://dx.doi.org/10.1063/1.105150 (3 pages) | Cited 3 times

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The effect of scattering by native defects on carrier mobility in modulation‐doped heterostructures is calculated. The concentration of the defects is determined using the amphoteric native defect model. It is shown that the Fermi level induced reduction of the defect formation energy leads to an increased incorporation of native defects and reduced mobility in AlGaAs/GaAs inverted modulation‐doped heterostructures. This new mechanism explains the experimentally observed difference in the values of electron mobilities in normal and inverted modulation‐doped heterostructures. The effects of native defects on the carrier mobilities in heterostructures based on other semiconductor systems are also discussed.
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72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
73.61.Ey III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Fundamental chemical differences among Pb defects on (111) and (100) silicon

J. H. Stathis and L. Dori

Appl. Phys. Lett. 58, 1641 (1991); http://dx.doi.org/10.1063/1.105244 (3 pages) | Cited 34 times

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Using electron spin resonance, a single defect (called Pb0) is observed at the Si(111)/SiO2 interface, whereas two different defects (called Pb0 and Pb1) are observed at the Si(100)/SiO2 interface. While the structure of the Pb center is well established as a silicon dangling bond, the identities of Pb0 and Pb1 are controversial. We have discovered that under processing conditions where the hydrogen passivation reaction Si⋅+H0→Si‐H passivates the Pb center at the Si(111)/SiO2 interface, the Pb1 center is likewise passivated but the Pb0 center is not. We conclude that the structure of Pb1 is a silicon dangling bond similar to the Pb on (111), and that the Pb0 is a fundamentally different defect, in agreement with recent theoretical calculations.
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68.35.Dv Composition, segregation; defects and impurities
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
76.30.Mi Color centers and other defects

Raman microprobe study of narrow InxGa1−xAs stripes on patterned GaAs(100) substrates

W. C. Tang, H. J. Rosen, S. Guha, and A. Madhukar

Appl. Phys. Lett. 58, 1644 (1991); http://dx.doi.org/10.1063/1.105151 (3 pages) | Cited 17 times

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The strain and structural variations across InGaAs ridges (∼1 μm) and valleys (∼3 μm) grown on patterned GaAs(100) substrates are examined via Raman microprobe spectroscopy. High spatial resolution scans across these structures show significant variations in the Raman features (phonon frequency, linewidth, and intensity). Variation in the GaAs‐like longitudinal optical mode frequency suggests a large difference in strain found in the InGaAs on top of the 1 μm ridges and in the valleys. Concomitant measurement of phonon linewidth and Ar+ laser‐induced heating are also indicative of the same. These results, in conjunction with transmission electron microscope studies, demonstrate that Raman microprobe spectroscopy is a powerful tool for probing patterned semiconductor structures on a microscopic scale.
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78.30.Fs III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology

Experimental determination of the effects of degenerate Fermi statistics on heavily p‐doped GaAs

E. S. Harmon, M. R. Melloch, M. S. Lundstrom, and M. L. Lovejoy

Appl. Phys. Lett. 58, 1647 (1991); http://dx.doi.org/10.1063/1.105152 (3 pages) | Cited 2 times

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The effects of degenerate Fermi statistics on electron injection currents for p+‐GaAs grown by molecular beam epitaxy are presented. To achieve Be dopant concentrations of greater than 8×1019 cm−3, the substrate temperature during growth was reduced to approximately 450 °C from the usual 600 °C. In this heavily doped material, we measure unexpectedly large electron injection currents which are interpreted in terms of an effective narrowing of the band gap. At extremely heavy doping densities, the Fermi level pushes into the valence band and degenerate Fermi statistics must be taken into account. For doping concentrations greater than 1×1020 cm−3, effects due to degenerate Fermi statistics oppose the band‐gap shrinkage effects; consequently, a reduction in the electron injection currents is observed. The result is a substantial reduction in gain for AlGaAs/GaAs heterostructure bipolar transistors when the base is doped above 1020 cm−3.
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72.80.Ey III-V and II-VI semiconductors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ey III-V semiconductors

Bloch states of electrons in a corrugated quantum channel in a magnetic field

Craig S. Lent and Manhua Leng

Appl. Phys. Lett. 58, 1650 (1991); http://dx.doi.org/10.1063/1.105153 (3 pages) | Cited 5 times

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We calculate the band structure of a long ballistic channel whose width is modulated periodically in the presence of a perpendicular magnetic field. The channel is narrowed on one side only, the other wall remaining straight. At zero magnetic field, the periodic modulation of the width produces miniband gaps. As the magnetic field is increased, the gaps disappear. The band structure at high fields consists of free‐electron‐like bands associated with magnetic edge states, and flatbands associated with localized Landau levels. The asymmetry in the walls causes electrons moving through the channel in one direction to have a different effective mass from electrons moving in the opposite direction.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.15.-m Methods of electronic structure calculations
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
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