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12 Jun 1989

Volume 54, Issue 24, pp. 2389-2492

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Surface‐emitting GaAs/AlGaAs lasers with dry‐etched 45° total reflection mirrors

N. Hamao, M. Sugimoto, N. Takado, Y. Tashiro, H. Iwata, T. Yuasa, and K. Asakawa

Appl. Phys. Lett. 54, 2389 (1989); http://dx.doi.org/10.1063/1.101087 (3 pages) | Cited 5 times

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Surface‐emitting GaAs/AlGaAs lasers with 45° total reflection mirrors have been successfully produced using a 45° tilted reactive ion beam etching technique. The ratio of surface‐emitted light output power to edge‐emitted light output power was obtained at values as high as 77%. The total reflection mirror was formed within 1° of the desired precise 45° angle. This type of surface‐emitting laser is promising for optoelectronic integrated circuits because of the simplicity of its structure and fabrication.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Laser‐induced photothermal reflectance investigation of silicon damaged by arsenic ion implantation: A temperature study

I. Alex Vitkin, Constantinos Christofides, and Andreas Mandelis

Appl. Phys. Lett. 54, 2392 (1989); http://dx.doi.org/10.1063/1.101088 (3 pages) | Cited 15 times

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Laser‐induced photothermal reflectance (PTR) measurements of arsenic‐implanted silicon are reported. The photothermal signals as a function of temperature are presented for both annealed and as‐implanted silicon films. The ability to monitor the dependence of signal on doping and on the temperature suggests a novel nondestructive means for characterization of implanted layers. The latter dependence has been qualitatively explained in terms of the temperature variation of the thermal wave effect.
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82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
61.80.Jh Ion radiation effects
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Optical notch filter using thermotropic liquid crystalline polymers

M. L. Tsai, S. H. Chen, and S. D. Jacobs

Appl. Phys. Lett. 54, 2395 (1989); http://dx.doi.org/10.1063/1.101533 (3 pages) | Cited 20 times

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Poly(γ‐benzyl L‐glutamate), partially transesterified with 1‐dodecanol, and polysiloxane were employed to fabricate a right‐ and left‐handed optical element, respectively. The wavelength of selective reflection was tuned via physical blending or annealing at a proper temperature. An optical notch filter comprising elements with each handedness showed an optical density of 2.0 within the rejection band and 73 to 83% transmission outside the band, suggesting liquid crystalline polymers as promising materials for the construction of environmentally robust optical notch filters.
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42.79.Ci Filters, zone plates, and polarizers
42.70.-a Optical materials
78.20.-e Optical properties of bulk materials and thin films
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials

Observation of transient absorption by using the thermal lens method

Masahide Terazima and Tohru Azumi

Appl. Phys. Lett. 54, 2398 (1989); http://dx.doi.org/10.1063/1.101365 (2 pages) | Cited 5 times

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The application of thermal lens spectroscopy to the absorption measurement of the transient species is demonstrated. The unique advantages of this method are discussed.
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78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
07.60.Hv Refractometers and reflectometers
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Rd Visible and ultraviolet spectrometers

Observation of chemical laser oscillation in the visible range

S. Yoshida, K. Shimizu, T. Sawano, T. Tokuda, and T. Fujioka

Appl. Phys. Lett. 54, 2400 (1989); http://dx.doi.org/10.1063/1.101089 (2 pages) | Cited 14 times

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A new visible chemical laser analogous to excimer lasers in lasing principle has been studied. Laser oscillation has been observed in the red spectral range. To our knowledge this is the first demonstration of chemical laser oscillation in the visible spectral range.
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42.55.Ks Chemical lasers
33.20.Kf Visible spectra

Autodoping of GaAs grown by organometallic vapor phase epitaxy on silicon substrates

R. Azoulay, N. Draidia, Y. Gao, L. Dugrand, and G. Leroux

Appl. Phys. Lett. 54, 2402 (1989); http://dx.doi.org/10.1063/1.101090 (3 pages) | Cited 9 times

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We have grown GaAs on silicon substrates by organometallic chemical vapor deposition and we have studied the autodoping of the GaAs layers by silicon during the growth. The epitaxies were performed on GaAs wafers and on GaAs/Si wafers side by side during the same run. By measuring the atomic silicon concentration on the grown layers, we show that a contamination of silicon occurs during the growth process via SiH4 formation and diffusion from the substrate. We propose a model to explain the contamination of the GaAs layers by the silicon substrate.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.Fx Diffusion; interface formation

Characterization of γ‐Fe2O3 homogeneity in magnetic recording media by photoacoustics

S. B. Peralta and A. W. Williams

Appl. Phys. Lett. 54, 2405 (1989); http://dx.doi.org/10.1063/1.101534 (3 pages) | Cited 3 times

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The degree of homogeneity of ferric oxide in magnetic tapes has been characterized using photoacoustic techniques. The method is based on excitation of the sample by a modulated laser beam and subsequent detection of its acoustic response via a condenser microphone. The acoustic response is dependent on the local thermal variations in the sample, and is a direct measurement of the distribution uniformity of the particulate metal oxide in the sample. Results of this study provide a potential means for the rapid evaluation of the quality of magnetic recording media.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)

Characterization of very thin Si oxynitride films produced by rapid thermal processing

N. Novkovski, I. Aizenberg, E. Goin, E. Fullin, and M. Dutoit

Appl. Phys. Lett. 54, 2408 (1989); http://dx.doi.org/10.1063/1.101535 (3 pages) | Cited 3 times

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The electrical properties of thin films of SiO2 can be improved by nitridation and reoxidation. They are very sensitive to the nitrogen profile, as well as to other impurities, such as hydrogen or water, for example, which makes it necessary to carefully adjust processing parameters. The purpose of this work is to characterize very thin oxynitride films produced by rapid thermal processing (RTP) and to optimize their electrical properties in view of applying them in electrically erasable programmable read‐only memories (EEPROMs). We propose a novel etch‐back and test oxidation technique that is very sensitive to traces of nitrogen at the oxynitride/Si interface. We show a strong correlation between the oxidation resistance of the interface and the electrical properties of metal‐oxide‐silicon (MOS) capacitors fabricated with these films. Nitridation conditions that give a maximal resistance to oxidation (for example, 4 s at 1100 °C) also provide the lowest values of interface charges and traps after reoxidation. Using these processing parameters, we achieve a significant increase in charge to breakdown.
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73.61.Ng Insulators
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.40.Rs Electrical and magnetic properties related to treatment conditions
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Activation of Zn and Cd acceptors in InP grown by metalorganic vapor phase epitaxy

M. Glade, D. Grützmacher, R. Meyer, E. G. Woelk, and P. Balk

Appl. Phys. Lett. 54, 2411 (1989); http://dx.doi.org/10.1063/1.101091 (3 pages) | Cited 18 times

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We have investigated the activation by post‐deposition annealing of Zn and Cd acceptors incorporated in InP during epitaxial growth using metalorganic vapor phase epitaxy. Growth was carried out at 20 mbar and atmospheric pressure for Zn‐ and Cd‐doped samples, respectively, using TMI, PH3, DEZn, and DMCd as sources. Post‐epitaxial annealing in a N2 atmosphere at temperatures in the range of 370–470 °C leads to complete activation of the acceptors. This process is strongly temperature dependent and a distinct effect of a GaInAs overlayer was observed. The activation energy is the same for Zn‐ and Cd‐doped samples. It is suggested that the diffusion of vacancies plays a determining role in activating the dopant.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Kk Vapor phase epitaxy; growth from vapor phase
66.30.J- Diffusion of impurities
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Suppression of acoustic phonon scattering in two‐dimensional electron gas on (InAs)1(GaAs)1/InP heterointerfaces

Yutaka Kodaira, Hiroshi Kuwano, and Kotaro Tsubaki

Appl. Phys. Lett. 54, 2414 (1989); http://dx.doi.org/10.1063/1.101092 (3 pages) | Cited 3 times

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Acoustic phonon scattering of two‐dimensional electron gas on (InAs)1(GaAs)1/InP heterointerfaces is observed by measuring electron energy loss rate, and is compared with that on GaInAs/InP heterointerfaces. The energy loss rate and effective mass of (InAs)1(GaAs)1/InP are obtained by analyzing Shubnikov–de Haas oscillation amplitude as a parameter of the electron temperature and lattice temperature. The resulting suppression of acoustic phonon scattering is due to the smaller deformation potential.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
63.20.K- Phonon interactions
62.65.+k Acoustical properties of solids
72.20.Dp General theory, scattering mechanisms

Monolayer to bilayer transition in reflection high‐energy electron diffraction intensity oscillations during Si(001) molecular beam epitaxy

S. Clarke, M. R. Wilby, D. D. Vvedensky, T. Kawamura, and T. Sakamoto

Appl. Phys. Lett. 54, 2417 (1989); http://dx.doi.org/10.1063/1.101093 (2 pages) | Cited 16 times

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We report the observation of a thermally driven monolayer to bilayer transition in the period of reflection high‐energy electron diffraction oscillations during molecular beam epitaxy on Si(001). This behavior is reproduced in a Monte Carlo growth simulation, from which we infer the origin of the transition results from the competition between incorporation and diffusion kinetics.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
68.55.-a Thin film structure and morphology

Improvements of electrical and optical properties of GaAs by substrate bias application during electron‐cyclotron‐resonance plasma‐excited molecular beam epitaxy

Naoto Kondo and Yasushi Nanishi

Appl. Phys. Lett. 54, 2419 (1989); http://dx.doi.org/10.1063/1.101094 (3 pages) | Cited 3 times

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Electrical and optical properties of GaAs layers are improved by applying substrate bias during electron‐cyclotron‐resonance plasma‐excited molecular beam epitaxy (ECR‐MBE). The highest mobility obtained without substrate bias is 4500 cm2 V−1 s−1. By applying positive bias, the mobility of the grown layer is increased to as high as 6800 cm2 V−1 s−1. Intense photoluminescence spectra comparable to that of a high quality MBE‐grown layer are also observed. The suppression of high‐energy ion impingement on the growing surface plays an important role in obtaining high quality crystal.
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73.61.Ey III-V semiconductors
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Cr III-V semiconductors

AlGaSb avalanche photodiode exhibiting a very low excess noise factor

S. Miura, T. Mikawa, H. Kuwatsuka, N. Yasuoka, T. Tanahashi, and O. Wada

Appl. Phys. Lett. 54, 2422 (1989); http://dx.doi.org/10.1063/1.101095 (2 pages) | Cited 11 times

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An Al0.053Ga0.947Sb avalanche photodiode (APD) has been fabricated and tested. First, measurement of an excess noise factor as well as an ionization rate ratio has been demonstrated. A low excess noise factor of 3.8, which is 1.2 dB lower than the conventional GaInAs APD, has been obtained. From this excess noise factor, the effective value of the hole‐to‐electron ionization rate ratio (keff) has been determined as high as 5, being in good agreement with the hole‐to‐electron ionization rate ratio (β/α) given by the multiplication data. This keff value is the highest ever reported for long‐wavelength III‐V APDs.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Sz Optical communication systems, multiplexers, and demultiplexers

Carrier lifetimes in ion‐damaged GaAs

M. B. Johnson, T. C. McGill, and N. G. Paulter

Appl. Phys. Lett. 54, 2424 (1989); http://dx.doi.org/10.1063/1.101096 (3 pages) | Cited 34 times

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Photoluminescence excitation correlation spectroscopy has been used to measure the dependence of carrier lifetime on the H+ ion implantation dose in GaAs. For doses greater than 1×1012 cm−2 the carrier lifetime is inversely proportional to the ion dose. The minimum lifetime measured was 0.6±0.2 ps for a dose of 1×1014 cm−2. Most important, there is no sign of saturation of carrier lifetime with ion dose down to this lifetime, thus still shorter lifetimes should be achievable with increased ion dose.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
78.47.-p Spectroscopy of solid state dynamics
61.80.Jh Ion radiation effects
78.55.Cr III-V semiconductors

Reduction in interfacial recombination velocity by superlattice buffer layers in GaAs/AlGaAs quantum well structures

H. Iwata, H. Yokoyama, M. Sugimoto, N. Hamao, and K. Onabe

Appl. Phys. Lett. 54, 2427 (1989); http://dx.doi.org/10.1063/1.101097 (2 pages) | Cited 13 times

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The values of interfacial recombination velocities in GaAs/AlGaAs double heterostructures and quantum wells grown by molecular beam epitaxy with and without superlattice cladding layers are obtained with photoluminescence time‐decay measurements. The authors show that superlattice layers reduce the interfacial recombination velocity from 330 cm/s, the value for double heterostructures with alloy cladding layers, to 40 cm/s, and that they have small effect on the GaAs bulk lifetime.
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68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
78.55.Cr III-V semiconductors

Leakage mechanism for tungsten/chromium metallized silicon p/n junctions

P. Giordano, J. P. Gonchond, J. C. Oberlin, P. Normandon, R. Basset, and A. Chantre

Appl. Phys. Lett. 54, 2429 (1989); http://dx.doi.org/10.1063/1.101098 (3 pages)

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The thermal stability of tungsten/chromium metallized silicon p/n junctions has been studied using several analytical techniques. A direct correlation has thus been established between junction leakage and structure. The main cause of leakage current observed after annealing at above 400 °C was found to be the generation of film‐edge‐induced dislocations associated with chromium disilicide formation.
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73.40.Ns Metal-nonmetal contacts
68.60.Dv Thermal stability; thermal effects
81.40.Rs Electrical and magnetic properties related to treatment conditions
85.30.De Semiconductor-device characterization, design, and modeling

Novel low‐power optical nonlinearity in semiconductor quantum well electro‐optic effect devices

Ch. Weber, K.‐H. Schlaad, C. Klingshirn, C. v. Hoof, G. Borghs, G. Weimann, W. Schlapp, and H. Nickel

Appl. Phys. Lett. 54, 2432 (1989); http://dx.doi.org/10.1063/1.101099 (3 pages) | Cited 2 times

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We report a new type of GaAs/AlGaAs electro‐optic effect device which offers a built‐in optical nonlinearity at extremely low power operation working in the pW to μW regime. The device consists of semitransparent metal electrodes evaporated directly onto the undoped AlGaAs cladding layers of a multiple quantum well structure. We briefly characterize the optical nonlinearity which is based on the quantum‐confined Stark effect and discuss the underlying physical mechanism which relies on the suppression of the internal electric fields of the biased sample. The use of such structures is proposed especially for applications as possible low‐power and low‐cost optical bistable switch.
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78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors
85.60.-q Optoelectronic devices
85.30.De Semiconductor-device characterization, design, and modeling
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks

Electronic structure of [110] Si‐Ge thin‐layer superlattices

Sverre Froyen, D. M. Wood, and Alex Zunger

Appl. Phys. Lett. 54, 2435 (1989); http://dx.doi.org/10.1063/1.101100 (3 pages) | Cited 15 times

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First‐principles electronic structure calculations for SinGen superlattices ( for n=4, 6, and 8) grown epitaxially on a (110) Si substrate reveal a nearly direct band gap (to within ≊0.04 eV for n=4) despite the pronounced indirectness of its constituents. This is unlike superlattices grown in the [001] direction which are indirect when grown on Si and quasi‐direct only on substrates with larger lattice constants, e.g., Ge. Transition dipole matrix elements for the lowest energy direct transition vanish for all repeat periods n but are finite for several other new low‐energy transitions.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.61.Ey III-V semiconductors
73.20.Fz Weak or Anderson localization

Monte Carlo analysis of high‐field hole diffusion coefficients in nondegenerate GaAs

R. Joshi and R. O. Grondin

Appl. Phys. Lett. 54, 2438 (1989); http://dx.doi.org/10.1063/1.101101 (2 pages) | Cited 3 times

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We examine the field dependence of the carrier diffusion coefficients in GaAs using an ensemble Monte Carlo technique. An analysis for the field dependence of the hole diffusivity is presented for the first time. Unlike for the electrons, no significant interband transfer effects are observed. The hole diffusivity is seen to decrease monotonically with increasing field.
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72.20.Ht High-field and nonlinear effects
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Dp General theory, scattering mechanisms
85.30.De Semiconductor-device characterization, design, and modeling

Laser‐assisted metalorganic chemical vapor deposition of zinc selenide epitaxial films

G. B. Shinn, P. M. Gillespie, W. L. Wilson, and W. M. Duncan

Appl. Phys. Lett. 54, 2440 (1989); http://dx.doi.org/10.1063/1.101084 (3 pages) | Cited 8 times

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Laser‐assisted metalorganic chemical vapor deposition has been used to grow epitaxial zinc selenide at temperatures as low as 200 °C. The metalorganic sources, dimethylzinc (DMZ) and diethylselenide (DESe), were photodissociated with radiation from a 193 nm ArF excimer laser passing parallel to a (100) GaAs substrate. A two‐stage purge scheme prevented deposition on the windows while minimizing disturbances of the gas flow in the growth region. The temperature dependence for both thermal and laser‐assisted film growth rates was examined. The reactor pressure was maintained at 100 Torr with a 10:1 DESe to DMZ ratio and 0.12 Torr partial pressure of DMZ. The laser was operated at a repetition rate of 20 Hz with pulse energies of 50 mJ. The laser‐assisted growth rate of ZnSe remained approximately constant at 1 μm/h over the temperature range 200–400 °C. At higher temperatures the thermally driven process begins to become important. Photoluminescence analysis indicates that the material grown at 400 °C by the laser‐assisted process is of better quality than films grown by either method at other temperatures.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Cr III-V semiconductors
68.55.-a Thin film structure and morphology

Electromigration in Al/SiO2 films prepared by a partially ionized beam deposition technique

P. Li, A. S. Yapsir, K. Rajan, and T.‐M. Lu

Appl. Phys. Lett. 54, 2443 (1989); http://dx.doi.org/10.1063/1.101085 (3 pages) | Cited 7 times

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It has been found that the electromigration resistance of pure Al/SiO2 thin films prepared by the partially ionized beam (PIB) deposition technique can be improved significantly as compared to those deposited by the conventional means. The PIB contained 0.8–1.2% of Al self‐ions and a bias potential of 2–5 kV was applied to the substrate during deposition. The enhancement of the electromigration resistance of the Al films is believed to be associated with the strong preferred orientation (in the [111] direction) that these films have. Surprisingly the preferred orientation effect is not accompanied by an enlargement of the Al grain size. This combination of preferred orientation and small grain size may find important applications in future very large scale integrated metallization.
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66.30.Qa Electromigration
66.30.Lw Diffusion of other defects
73.61.At Metal and metallic alloys
68.35.Fx Diffusion; interface formation

Photopumped phonon‐assisted laser operation (77 K) of In0.5(AlxGa1−x)0.5P quantum well heterostructures

D. W. Nam, N. Holonyak, K. C. Hsieh, C. P. Kuo, R. M. Fletcher, T. D. Osentowski, and M. G. Craford

Appl. Phys. Lett. 54, 2446 (1989); http://dx.doi.org/10.1063/1.101067 (3 pages) | Cited 4 times

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The photopumped phonon‐assisted laser operation (612 nm, 77 K) of a high‐gap In1−y(AlxGa1−x)yP quantum well heterostructure (QWH) lattice matched to GaAs (y≊0.5) is identified using a single rectangular sample that is shifted in its heat sinking from (a) low Q when clamped onto Au (bare edges) to (b) high Q when further compressed into Au with all four edges reflecting. For the low‐Q QWH sample photopumped in a spot (partially photopumped), phonon‐assisted laser operation (abrupt threshold, narrow spectrum) is observed on closely spaced end‐to‐end laser modes ΔE=ℏωLO≊45–47 meV below the lowest confined‐particle transitions. For the same sample shifted to high Q, edge‐to‐edge laser operation across the sample on confined‐particle transitions is ‘‘turned on’’ also, thus providing an unambiguous experimental reference (ℏωLO≊45–47 meV) for the phonon sideband.
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42.55.Px Semiconductor lasers; laser diodes
63.20.K- Phonon interactions
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
78.55.Cr III-V semiconductors

Single‐crystal germanium grown on (1102) sapphire by molecular beam epitaxy

D. J. Godbey, S. B. Qadri, M. E. Twigg, and E. D. Richmond

Appl. Phys. Lett. 54, 2449 (1989); http://dx.doi.org/10.1063/1.101068 (3 pages) | Cited 4 times

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Crystalline germanium films have been successfully grown on the (1102) sapphire surface using molecular beam epitaxy. Growth at temperatures above 700 °C and after preannealing the sapphire substrates above 1100 °C resulted in germanium films with a (110) orientation. A 500 nm germanium film grown at 800 °C after preannealing the sapphire substrate at 1400 °C gave an x‐ray rocking curve width that measured 317 arcsec at half maximum for the (220) reflection.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology

Current‐controlled negative differential resistance in four‐terminal heterostructure devices

A. Kastalsky, M. Milshtein, L. G. Shantharama, J. Harbison, and L. Florez

Appl. Phys. Lett. 54, 2452 (1989); http://dx.doi.org/10.1063/1.101069 (3 pages) | Cited 2 times

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We demonstrate new effects of the current‐controlled (S‐shaped) negative differential resistance (NDR) in different circuit configurations of four‐terminal modulation‐doped AlGaAs/GaAs heterostructure devices, with the magnitude of the voltage drop varied by external electrodes. We observe two S‐shaped instabilities having different physical origins. One effect arises due to an avalanche in the top AlGaAs layer underneath the reverse‐biased gate region. Another phenomenon relies on the creation, during the avalanche, of nonequilibrium hot electrons at the conducting channel (quantum well). This dramatically enhances electron flow over the heterostructure barriers and gives rise to a strongly pronounced current‐controlled NDR with a peak‐to‐valley ratio of ∼10.
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85.30.De Semiconductor-device characterization, design, and modeling
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Thin‐film deposition by a new laser ablation and plasma hybrid technique

J. Krishnaswamy, A. Rengan, J. Narayan, K. Vedam, and C. J. McHargue

Appl. Phys. Lett. 54, 2455 (1989); http://dx.doi.org/10.1063/1.101070 (3 pages) | Cited 78 times

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We have developed a new laser ablation and plasma hybrid technique for depositing thin diamond‐like carbon (DLC) films on Si〈100〉 substrates at room temperature and at 110 °C with improved optical and mechanical properties. The technique involves coupling of laser energy (λ=0.308 μm, pulse duration=40 ns, and power 125 MW/cm2) to a graphite target and superimposing capacitively stored energy (2–3 J at 3 kV) to the laser ablated spot. The laser‐ and plasma‐deposited diamond‐like carbon films were analyzed by spectroscopic ellipsometry and microhardness measurements. These films showed considerable improvements in both uniformity and homogeneity. Optical properties and hardness of the films deposited by this technique closely match the DLC films. We discuss possible causes of improvements in the above properties of these films.
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81.15.Rs Spray coating techniques
68.60.Bs Mechanical and acoustical properties
78.66.-w Optical properties of specific thin films
79.20.Ds Laser-beam impact phenomena
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