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20 Mar 1989

Volume 54, Issue 12, pp. 1077-1185

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High‐power and high‐speed semi‐insulating blocked V‐grooved inner‐stripe lasers at 1.3 μm wavelength fabricated on p‐InP substrates

H. Horikawa, H. Wada, Y. Matsui, T. Yamada, Y. Ogawa, and Y. Kawai

Appl. Phys. Lett. 54, 1077 (1989); http://dx.doi.org/10.1063/1.100762 (3 pages) | Cited 7 times

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A maximum cw power of 90 mW at 25 °C was obtained for a GaInAsP/InP laser with a semi‐insulating InP current blocking layer grown by metalorganic vapor phase epitaxy on a p‐type InP substrate, a 700‐μm‐long cavity, and an antireflection coating on the front facet. The 3 dB bandwidth was in excess of 6 GHz with a low parasitic capacitance of 15 pF despite the long cavity. The semi‐insulating layer with the resistivity of 5×107 Ω cm was formed by doping only Fe. The current blocking characteristics of the blocking layer with the same configuration as the lasers were examined under various temperatures.
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42.55.Px Semiconductor lasers; laser diodes
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Guided‐wave optical wavelength demultiplexer using an asymmetric Y junction

T. Negami, H. Haga, and S. Yamamoto

Appl. Phys. Lett. 54, 1080 (1989); http://dx.doi.org/10.1063/1.100763 (3 pages) | Cited 15 times

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An optical wavelength demultiplexer using an asymmetric Y junction is numerically analyzed and the experimental results are reported. This demultiplexer utilizes both the mode splitting characteristic of an asymmetric Y junction and the waveguide dispersion of channel waveguides. Analysis shows that the device with step‐index profile has more than 20 dB isolation for wavelengths with 6.5% separation from the center wavelength. The fabricated device composed of two‐step ion exchanged soda‐lime glass waveguides coated asymmetrically with Corning 7059 glass thin film separated the lights of 0.63 and 0.84 μm wavelengths.
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42.79.Gn Optical waveguides and couplers
42.79.Ci Filters, zone plates, and polarizers
42.82.-m Integrated optics
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Absorption edges of mixed silver‐halide crystals and polycrystalline optical fibers

N. Barkay, F. Moser, D. Kowal, and A. Katzir

Appl. Phys. Lett. 54, 1083 (1989); http://dx.doi.org/10.1063/1.100764 (3 pages) | Cited 8 times

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Optical absorption edges of mixed AgClxBr1−x (0≤x≤1) crystals and polycrystalline fibers were investigated as a function of composition. Both visible edge, resulting from electronic transitions, and infrared edge due to multiphonon processes behave as the one‐mode (amalgamation) type of mixed crystals, shifting continuously with composition. Quantitative expressions were used to discuss the results. Polycrystalline extruded fibers preserve this spectral window of silver‐halide crystals, except for slight deviations which are explained by the small‐grain structure of the fibers.
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78.40.Ha Other nonmetallic inorganics
78.30.Hv Other nonmetallic inorganics
42.81.Gs Birefringence, polarization

Enhancement of second‐harmonic generation in optical fibers by a hydrogen and heat treatment

François Ouellette, Kenneth O. Hill, and Derwyn C. Johnson

Appl. Phys. Lett. 54, 1086 (1989); http://dx.doi.org/10.1063/1.100765 (3 pages) | Cited 9 times

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Optical fiber exposed to high‐pressure hydrogen gas for 3–4 days, and subsequently heated in air at temperatures in the range 250–500 °C for 8–24 h, shows an enhanced second‐harmonic conversion efficiency after seeding with 1.06 μm and 532 nm light, when compared with untreated fiber seeded under similar conditions. Up to now, an enhancement by as much as a factor of 4.4 has been observed. Some possible correlations between this enhancement and the change in the defect content of the fiber due to the H2 ‐heat treatment are pointed out.
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81.40.Tv Optical and dielectric properties related to treatment conditions
42.81.Gs Birefringence, polarization
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Cavity length dependence of threshold current for quantum well lasers

C. Shieh, R. Engelmann, J. Mantz, K. Alavi, and C. Shu

Appl. Phys. Lett. 54, 1089 (1989); http://dx.doi.org/10.1063/1.100766 (3 pages) | Cited 4 times

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The cavity length dependence of the threshold current for separate confinement quantum well lasers with a single well, three wells, and six wells is studied. Only the single quantum well laser showed the anomalous increase of threshold current at short cavity length. Comparison of the experimental results with theoretical calculations concludes that the polarization enhancement of the oscillator strength in a quantum well has to be taken into account in the gain spectrum calculation of the quantum well laser.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.55.Px Semiconductor lasers; laser diodes

Broadband tunability of gain‐flattened quantum well semiconductor lasers with an external grating

Michael Mittelstein, David Mehuys, Amnon Yariv, Jeffrey E. Ungar, and Rona Sarfaty

Appl. Phys. Lett. 54, 1092 (1989); http://dx.doi.org/10.1063/1.100767 (3 pages) | Cited 14 times

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Quantum well lasers are shown to exhibit flattened broadband gain spectra at a particular pumping condition. The gain requirement for a grating‐tuned external cavity configuration is examined and applied to a semiconductor quantum well laser with an optimized length of gain region. The predicted very broadband tunability of quantum well lasers is confirmed experimentally by grating‐tuning of uncoated lasers over 85 nm, with single longitudinal mode output power exceeding 200 mW.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes
42.79.Dj Gratings
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Nonlinear Bragg reflector based on saturable absorption

B. G. Kim, E. Garmire, Steven G. Hummel, and P. D. Dapkus

Appl. Phys. Lett. 54, 1095 (1989); http://dx.doi.org/10.1063/1.100768 (3 pages) | Cited 10 times

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The first observation of nonlinear reflection from a Bragg reflector composed of Ga0.8 Al0.2As/AlAs layers due to the band filling effect was measured by the pump probe method. The nonlinearity was primarily due to saturable absorption. Optically induced reflectivity changes of as much as 38% were measured.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
42.79.Hp Optical processors, correlators, and modulators
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
07.60.-j Optical instruments and equipment
42.79.-e Optical elements, devices, and systems

Planar waveguide lenses in GaAs by using ion milling

T. Q. Vu, J. A. Norris, and C. S. Tsai

Appl. Phys. Lett. 54, 1098 (1989); http://dx.doi.org/10.1063/1.100769 (3 pages) | Cited 9 times

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We report, for the first time, the fabrication of negative index‐change planar waveguide microlenses in GaAs by using ion milling. The waveguide lenses that have been fabricated and tested include single lenses and lens arrays of analog Fresnel, chirp grating, and hybrid analog Fresnel/chirp grating types. We have obtained small focal spot sizes and good efficiencies in such preliminary components. Ion milling has been shown to be a simple and versatile technique for fabrication of waveguide lenses in GaAs and applicable to any other substrate material. Such ion‐milled waveguide lenses should facilitate realization of a variety of monolithically integrated optic device modules and circuits in GaAs and other related substrates with applications to communications, signal processing, and computing.
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42.82.-m Integrated optics
42.15.Eq Optical system design
42.79.Bh Lenses, prisms and mirrors
42.79.Gn Optical waveguides and couplers

Maker fringes in biaxial crystals and the nonlinear optical coefficients of thiosemicarbazide cadmium chloride monohydrate

S. X. Dou, M. H. Jiang, Z. S. Shao, and X. T. Tao

Appl. Phys. Lett. 54, 1101 (1989); http://dx.doi.org/10.1063/1.100770 (3 pages) | Cited 8 times

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Precise theoretical results of Maker fringes in biaxial crystals are presented which include such necessary corrections as absorption, finite beamwidth effects, and multiple reflections. Their applications to the new nonlinear optical material, organometallic complex crystal thiosemicarbazide cadmium chloride monohydrate (TSCCC, point group Cs‐m), and the corresponding experimental values of its six independent nonlinear optical coefficients are given.
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78.20.-e Optical properties of bulk materials and thin films
63.10.+a General theory

Preparation of TiN films by photochemical vapor deposition

Seiji Motojima and Hidetoshi Mizutani

Appl. Phys. Lett. 54, 1104 (1989); http://dx.doi.org/10.1063/1.100771 (2 pages) | Cited 2 times

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The TiN films have been prepared by photochemical vapor deposition using a D2 lamp from a gas mixture of TiCl4 ‐NH3 (or N2) ‐H2. The deposition temperature of the TiN films was lowered by 50–100 °C by irradiation with a D2 lamp as compared to that without irradiation. The deposition rate was increased by 35–300% with irradiation.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)

Novel characterization of implant damage in SiO2 by nuclear‐deposited energy

A. Hiraiwa, H. Usui, and K. Yagi

Appl. Phys. Lett. 54, 1106 (1989); http://dx.doi.org/10.1063/1.101429 (3 pages) | Cited 14 times

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Etching enhancement in through‐implanted SiO2 has been characterized by nuclear‐deposited energy independently of implant conditions. An empirical expression has been proposed to describe the etching rate for any implantation. The enhanced etching has been related to the Si‐O vibrational frequency shift. Etching enhancement has been found to reflect the structural change in SiO2, and to be a good measure of degradation. The structural change of SiO2 stops and the etching rate reaches a maximum for an ion dose corresponding to nuclear‐deposited energy larger than 3.4×1023 eV/cm3. This energy is equal to the total SiO bonding energy (3.8 eV) in a unit volume of SiO2.
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61.80.Jh Ion radiation effects
81.05.Kf Glasses (including metallic glasses)
81.65.-b Surface treatments
68.55.-a Thin film structure and morphology
73.61.Ng Insulators

Modeling of laser planarization of thin metal films

Paul F. Marella, David B. Tuckerman, and R. Fabian Pease

Appl. Phys. Lett. 54, 1109 (1989); http://dx.doi.org/10.1063/1.100772 (3 pages) | Cited 7 times

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The differences between excimer (≊30 ns pulse duration) and flashlamp‐pumped dye (≊500 ns pulse duration) laser planarization are examined for 1.5–2 μm thick gold films over SiO2 layers. Test structures containing bar patterns (square waves) of 5000 Å peak‐to‐trough amplitude with spatial periods ranging from 10 to 100 μm were prepared and laser irradiated. A linear model is presented which described the time evolution of the film’s surface topography when melted with a dye laser pulse. Excimer laser planarization is found to be susceptible to evaporative recoil effects which may cause undesired pattern amplification.
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81.05.Bx Metals, semimetals, and alloys
85.40.Ls Metallization, contacts, interconnects; device isolation
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)

Tunnel spectroscopy of the AlGaAs‐GaAs heterostructure interface

H. W. M. Salemink, H. P. Meier, R. Ellialtioglu, J. W. Gerritsen, and P. R. M. Muralt

Appl. Phys. Lett. 54, 1112 (1989); http://dx.doi.org/10.1063/1.100773 (3 pages) | Cited 18 times

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The material interface of a molecular beam epitaxy grown Al0.5Ga0.5As‐GaAs heterostructure is investigated on a cross‐sectional (110) cleavage plane using tunnel spectroscopy. The depleted n‐type region and the electron confinement layer adjacent to the interface are identified with local current‐voltage spectroscopy. The spatial width of these layers is close to 15 nm. The spectroscopy can be interpreted with the valence‐band offset in the interface, and a value of 0.35 eV is found for this quantity.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Suppression of DX centers in GaAlAs‐GaAs heterostructures

J. C. Bourgoin, S. L. Feng, D. Stiévenard, X. Letartre, E. Barbier, and J. P. Hirtz

Appl. Phys. Lett. 54, 1115 (1989); http://dx.doi.org/10.1063/1.100774 (3 pages) | Cited 14 times

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Using deep level transient spectroscopy we have studied the DX center in a series of periodic GaAs/GaAlAs uniformly Si doped structures. The presence of the DX center is only detected when the structures do not exhibit superlattice behavior. This is understood by the fact that either the DX associated level is resonant in the first conduction miniband (or above it) or that it does not exist because the original band structure of GaAlAs is destroyed by electron delocalization. Examination of the variation of the concentration of DX centers in periodic planar doped GaAlAs structures shows that this disappearance is due to a band structure effect, thus demonstrating that the DX center originates from a shallow‐deep instability of the L‐band effective mass state of the Si impurity due to intervalley mixing.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
71.55.Eq III-V semiconductors

Longitudinal electron drift mobility of hydrogenated amorphous silicon/silicon nitride multilayer structures revealed by time‐of‐flight measurements

R. Hattori and J. Shirafuji

Appl. Phys. Lett. 54, 1118 (1989); http://dx.doi.org/10.1063/1.101478 (3 pages) | Cited 7 times

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Electron drift mobility longitudinal to hydrogenated amorphous silicon/silicon nitride multilayer structures has been measured by the time‐of‐flight method. Transient photocurrent shows a clear kink corresponding to the transit time. The room‐temperature electron mobility in multilayer structures is smaller by three or four orders of magnitude than that observed in bulk a‐Si:H. The room‐temperature electron mobility decreases with decreasing well layer width at constant layer thickness of 13 Å, while the activation energy of the mobility increases. The lifetime of electrons tends to increase when the well layer thickness is reduced.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Dn Low-field transport and mobility; piezoresistance
73.61.Cw Elemental semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
73.61.Ng Insulators

Enhancement of free‐carrier concentration in n‐type AlxGa1−xAs grown by metalorganic vapor phase epitaxy in the temperature range 850–950 °C

P. Basmaji, A. Zaouk, P. Gibart, D. Gauthier, and J. C. Portal

Appl. Phys. Lett. 54, 1121 (1989); http://dx.doi.org/10.1063/1.100775 (3 pages) | Cited 6 times

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AlxGa1−xAs 0.2<x<0.4 epilayers were grown by metalorganic vapor phase epitaxy in the temperature range of 850–950 °C. It has been experimentally shown that epitaxial growth at high temperatures enhances the free‐carrier concentration and causes unusual behavior of deep centers for Sn‐doped AlxGa1−xAs. From the temperature dependence of the Hall carrier density, and assuming multivalley conduction, an activation energy of the donor of 10 meV was deduced. Furthermore, these samples did not exhibit persistent photoconductivity. Besides, when all parameters of the epitaxy were kept constant, the aluminum fraction in the epitaxial layers slightly increases as the growth temperature increases.
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73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.15.Kk Vapor phase epitaxy; growth from vapor phase
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.61.Ey III-V semiconductors

Self‐limiting deposition of Ga on a GaAs surface by thermal decomposition of diethylgalliumchloride observed by x‐ray photoelectron spectroscopy

H. Ohno, H. Ishii, K. Matsuzaki, and H. Hasegawa

Appl. Phys. Lett. 54, 1124 (1989); http://dx.doi.org/10.1063/1.100776 (3 pages) | Cited 8 times

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Clean surfaces of molecular beam epitaxially grown GaAs were exposed to diethylgalliumchloride (DEGaCl) and the resultant change was observed by in situ x‐ray photoelectron spectroscopy. At a substrate temperature of 300 °C, a self‐limiting reaction between DEGaCl and the surface resulted in one monolayer of Ga deposition which is believed to lead to atomic layer epitaxy of GaAs using DEGaCl. No appreciable increase of Cl or C was observed after exposure. Discussion on the mechanism of the self‐limiting reaction is also presented.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Dielectric characteristics of fluorinated ultradry SiO2

Yasushiro Nishioka, Yuzuru Ohji, Kiichiro Mukai, Takuo Sugano, Yu Wang, and T. P. Ma

Appl. Phys. Lett. 54, 1127 (1989); http://dx.doi.org/10.1063/1.101479 (3 pages) | Cited 28 times

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Improvement of dielectric breakdown characteristics and hot‐electron‐induced interface degradation of metal‐oxide‐semiconductor capacitors having fluorinated ultradry oxides has been demonstrated. The fluorine is introduced through HF surface treatment of Si prior to oxidation. Secondary‐ion mass spectrometry data indicate that SiF distribution is peaked both at the surface of the oxide and at the SiO2/Si interface in the fluorinated ultradry oxide. The possible role of fluorine on the improvement of the dielectric characteristics will be discussed.
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85.30.Tv Field effect devices
77.22.Jp Dielectric breakdown and space-charge effects
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

One‐dimensional subbands and mobility modulation in GaAs/AlGaAs quantum wires

K. Ismail, D. A. Antoniadis, and Henry I. Smith

Appl. Phys. Lett. 54, 1130 (1989); http://dx.doi.org/10.1063/1.100738 (3 pages) | Cited 51 times

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Devices consisting of 100 parallel, modulation‐doped GaAs/AlGaAs wires, each about 40 nm wide, have been fabricated and tested at 4.2 and 77 K. The wires were created by ion milling a shallow grating into the doped AlGaAs layer. The mask for etching the grating was produced by x‐ray nanolithography, and lift‐off of Ti/Au. The grating period was 200 nm and the linewidth about 85 nm. Backgate bias or illumination was used to modulate the charge density in the wires. Conductance measurements at 4.2 K provide clear evidence of quasi‐one‐dimensional density of states. A corresponding modulation of the electron mobility, above and below values in the two‐dimensional system, was observed.
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85.30.Tv Field effect devices
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.55.-a Thin film structure and morphology

Quantum‐confined subband transitions of a GaAs sawtooth doping superlattice

B. Ullrich, C. Zhang, and K. v. Klitzing

Appl. Phys. Lett. 54, 1133 (1989); http://dx.doi.org/10.1063/1.100739 (3 pages) | Cited 20 times

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In this letter we present for the first time the observation of quantum‐confined transitions of a short‐period sawtooth doping superlattice in photocurrent and luminescence. The luminescence was investigated with different laser intensities. Due to the nature of the band modulation of sawtooth doping superlattices, the resonant energies for optical transitions are dependent on the intensity of the laser beam. We present a model, which incorporates both the Kronig–Penney energy dispersion and the self‐consistent intensity‐dependent internal field to explain the observed energy shift. Furthermore, the differences between photocurrent and luminescence measurements are discussed.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.50.Pz Photoconduction and photovoltaic effects
73.61.Ey III-V semiconductors

Submicron‐gate In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As heterojunction metal‐semiconductor field‐effect transistors grown by molecular beam epitaxy

J. B. Kuang, P. J. Tasker, Y. K. Chen, G. W. Wang, L. F. Eastman, O. A. Aina, H. Hier, and A. Fathimulla

Appl. Phys. Lett. 54, 1136 (1989); http://dx.doi.org/10.1063/1.100740 (3 pages) | Cited 2 times

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We report the dc and microwave performance of i‐InAlAs/n+‐InGaAs/i‐InAlAs heterojunction metal‐semiconductor field‐effect transistors (MESFETs) with gate lengths from 0.25 to 0.35 μm. At 10 GHz, an extrinsic transconductance (gm) of 507 mS/mm, a current gain cutoff frequency (ft) of 49.5 GHz, and a power gain cutoff frequency (fmax) of 70.5 GHz were observed for a 0.25 μm gate device. For a 0.3 μm gate device, a gm of 545 mS/mm, an ft of 42 GHz, and an fmax of 114 GHz were measured. Output conductance as low as 7.7 mS/mm was measured. The voltage gain for measured devices is well above 20 for a wide range of bias conditions.
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85.30.Tv Field effect devices

Fabrication of n+/p InP solar cells on silicon substrates

C. J. Keavney, S. M. Vernon, V. E. Haven, S. J. Wojtczuk, and M. M. Al‐Jassim

Appl. Phys. Lett. 54, 1139 (1989); http://dx.doi.org/10.1063/1.100741 (3 pages) | Cited 8 times

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InP solar cells were fabricated from films deposited by metalorganic chemical vapor deposition on Si substrates (using a GaAs buffer layer) and on GaAs substrates. Air mass zero efficiencies of 7.1% and 9.4%, respectively, were achieved. Prospects are good for improving the material quality of the InP films, but more work is needed to make the n+‐p‐p+ structure of the InP solar cells compatible with the silicon substrates, which cause n‐type doping of the III‐V films.
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84.60.Jt Photoelectric conversion
73.50.Pz Photoconduction and photovoltaic effects
73.61.Ey III-V semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Monolayer abruptness in highly strained InAsxP1−x/InP quantum well interfaces

R. P. Schneider and B. W. Wessels

Appl. Phys. Lett. 54, 1142 (1989); http://dx.doi.org/10.1063/1.100742 (3 pages) | Cited 25 times

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InAsxP1−x/InP strained quantum well structures have been prepared by atmospheric‐pressure organometallic vapor phase epitaxy (OMVPE). Structures with compositions of x=0.40–0.67 and quantum well thicknesses of 0.8–16 nm were evaluated using photoluminescence spectroscopy. Strain in the pseudomorphic wells ranged from 1.3 to 2.1%. Doublets and multiplets are observed in the photoluminescence spectra and are attributed to luminescence from regions in the wells differing in thickness by a single monolayer, with atomically smooth interfaces over areas greater in lateral extent than the exciton diameter. Typical full widths at half maximum of the photoluminescence from the thinnest wells are 8–14 meV, comparable to the best reported values for thin lattice‐matched quantum wells prepared from the InGaAs(P)/InP system using OMVPE.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.35.Fx Diffusion; interface formation
78.55.Cr III-V semiconductors

Layer intermixing in 1 MeV implanted GaAs/AlGaAs superlattices

S.‐Tong Lee, Samuel Chen, G. Rajeswaran, G. Braunstein, P. Fellinger, and J. Madathil

Appl. Phys. Lett. 54, 1145 (1989); http://dx.doi.org/10.1063/1.100743 (3 pages) | Cited 10 times

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Layer intermixing in MeV Si‐implanted GaAs/AlGaAs superlattices (SLs) with doses between 3×1015 and 1×1016 /cm2 has been examined by transmission electron microscopy and secondary‐ion mass spectrometry. After either rapid thermal annealing at 1050 °C for 10 s or furnace annealing at 850 °C for 3 h, all the SLs showed a highly crystalline, defect‐free zone in the near‐surface region followed by a band of secondary defects, with the maximum density located about 1 μm below the surface. A totally mixed region, within the secondary defect band, occurred only in the SL implanted to 1×1016 Si/cm2 and annealed at 850 °C for 3 h. At lower doses or under rapid thermal annealing, only slight Al/Ga interdiffusion was observed, primarily in the layers that contained the high density of dislocation defects. For either annealing condition, the Si concentration profiles showed only slight broadening and they correlated with the distribution of secondary defects as well as with the depth of the intermixed layer. The effects of dynamic annealing and surface on the implantation energy dependence, i.e., MeV vs keV, of layer intermixing are discussed.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
68.35.Fx Diffusion; interface formation

Photoemission study of the band bending and chemistry of sodium sulfide on GaAs (100)

C. J. Spindt, R. S. Besser, R. Cao, K. Miyano, C. R. Helms, and W. E. Spicer

Appl. Phys. Lett. 54, 1148 (1989); http://dx.doi.org/10.1063/1.100744 (3 pages) | Cited 30 times

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Recently, there has been a great deal of interest in Na2S⋅9H2O as a passivating chemical treatment for GaAs surfaces. It has been shown that it reduces the high surface recombination velocity characteristic of GaAs surfaces, and may offer hope for ‘‘unpinning’’ the surface Fermi level. We have used photoemission spectroscopy to study the band bending and chemistry of these overlayers on n‐type GaAs (100). Identically prepared samples show the characteristic increase in the photoluminescence signal, and have also been characterized using surface conductivity measurements. We find using photoemission that the surface Fermi level of the treated wafer is still near midgap. We also observe the chemistry at the interface, and offer a possible explanation of the photoluminescence and surface conductivity data in terms of it and the advanced unified defect model.
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73.20.At Surface states, band structure, electron density of states
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.65.-b Surface treatments
79.60.Jv Interfaces; heterostructures; nanostructures
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