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13 Mar 1995

Volume 66, Issue 11, pp. 1301-1434

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Microcavity effects in a spin‐coated polymer two‐layer system

U. Lemmer, R. Hennig, W. Guss, A. Ochse, J. Pommerehne, R. Sander, A. Greiner, R. F. Mahrt, H. Bässler, J. Feldmann, and E. O. Göbel

Appl. Phys. Lett. 66, 1301 (1995); http://dx.doi.org/10.1063/1.113222 (3 pages) | Cited 55 times

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We report on the design and the optical properties of a spin‐coated multilayer organic microcavity. Tri(stilbene)amine blended with polysulfone as the first layer and an oxadiazole derivative (BPBD) blended with polystyrene as the second layer are sandwiched between two planar mirrors. Enhancement of the luminescence and spectrally narrow emission are observed. By means of time resolved luminescence spectroscopy we show that the spontaneous emission rate is increased in the cavity. © 1995 American Institute of Physics.
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78.66.Qn Polymers; organic compounds
78.60.Fi Electroluminescence
78.47.-p Spectroscopy of solid state dynamics

Enhanced mass‐transport smoothing of f/0.7 GaP microlenses by use of sealed ampoules

J. S. Swenson, R. A. Fields, and M. H. Abraham

Appl. Phys. Lett. 66, 1304 (1995); http://dx.doi.org/10.1063/1.113223 (3 pages) | Cited 5 times

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A variety of GaP lens arrays have been routinely produced (array dimensions up to 1.5×1.0 cm, 30×50 elements) with high yield, uniformly good finish, and low transmission loss for 0.8 μm<λ<2.5 μm. Microlenses up to 300 μm in diameter with f numbers as low as 0.7 have been fabricated by a new sealed ampoule mass‐transport technique. The mesa‐step spacing was increased from 10 to 15 μm, with mass‐transport smoothing time‐at‐temperature as short as 8 h, representing a transport‐rate 10–40 times higher than previously reported. By additional chemistry control, smoothing of 30 μm spacings has been demonstrated. Only small pieces of phosphorus are required (no phosphine or hydrogen), consequently little safety burden is incurred. Smoothing in the fused quartz ampoules is shown to be self‐terminated by wafer oxidation, which is sufficiently delayed by loose‐fitting aluminum oxide shielding. © 1995 American Institute of Physics.
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42.79.Bh Lenses, prisms and mirrors
42.82.Cr Fabrication techniques; lithography, pattern transfer

Photoluminescence study of excess carrier spillover in 1.3 μm wavelength strained multi‐quantum‐well InGaAsP/InP laser structures

D. Garbuzov, G.‐J. Shiau, V. Bulovic, M. Boroditsky, C.‐P. Chao, and S. R. Forrest

Appl. Phys. Lett. 66, 1307 (1995); http://dx.doi.org/10.1063/1.113224 (3 pages) | Cited 6 times

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Photoluminescence of 1.3 μm wavelength strained multiple quantum well InGaAsP/InP laser structures has been used to understand the excess carrier redistribution between the quantum well and waveguide regions at a high level of excitation. A model is developed to describe the experimental results. The model suggests that space charge barriers play a significant role in the electron confinement in quantum wells at the high excitation range typical of laser diode operation. © 1995 American Institute of Physics.
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42.55.Px Semiconductor lasers; laser diodes
78.66.Fd III-V semiconductors
78.55.Cr III-V semiconductors

Picosecond all‐optical switching in a Fabry–Perot cavity containing polydiacetylene

R. Quintero‐Torres and M. Thakur

Appl. Phys. Lett. 66, 1310 (1995); http://dx.doi.org/10.1063/1.113225 (3 pages) | Cited 9 times

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Off‐resonant nonlinear optical measurements have been made in a Fabry–Perot cavity containing a polydiacetylene (PTS) single crystal. The cavity length was controlled to select specific bias points on the Fabry‐Perot fringe and the measurements were made by a pump‐probe technique using 90 ps pulses at 1.06 μm wavelength. The changes in transmission at selected bias points were measured as a function of time delay between the pump and the probe. The measured response time was found to be pulse‐width limited and the maximum changes in transmission were as large as 50% at low optical intensities (∼10 MW/cm2). The sign of n2 was determined from the direction of the fringe shift and was found to be negative. All‐optical switching (82 MHz) at a picosecond time scale is demonstrated for an organic material. © 1995 American Institute of Physics.  
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42.70.Jk Polymers and organics
42.65.Pc Optical bistability, multistability, and switching, including local field effects
78.47.-p Spectroscopy of solid state dynamics

Coherent exciton lasing in ZnSe/ZnCdSe quantum wells?

M. E. Flatté, E. Runge, and H. Ehrenreich

Appl. Phys. Lett. 66, 1313 (1995); http://dx.doi.org/10.1063/1.113226 (3 pages) | Cited 9 times

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A new mechanism for exciton lasing in ZnSe/ZnCdSe quantum wells is proposed. Lasing, occurring below the lowest exciton line, may be associated with a BCS‐like condensed (coherent) exciton state. This state is most stable at low temperatures for densities in the transition region separating the exciton Bose gas and the coherent exciton state. Calculations show the gain region to lie below the exciton line and to be separated from the absorption regime by a transparency region of width, for example, about 80 meV for a 90 Å ZnSe/Zn0.75Cd0.25Se quantum well. Experimental observation of the transparency region using differential spectroscopy would confirm this picture. © 1995 American Institute of Physics.
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78.45.+h Stimulated emission
78.66.Hf II-VI semiconductors
42.55.Px Semiconductor lasers; laser diodes

Electroluminescence from CdSe quantum‐dot/polymer composites

B. O. Dabbousi, M. G. Bawendi, O. Onitsuka, and M. F. Rubner

Appl. Phys. Lett. 66, 1316 (1995); http://dx.doi.org/10.1063/1.113227 (3 pages) | Cited 367 times

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Electroluminescence is obtained from nearly monodisperse CdSe nanocrystallites (quantum dots) incorporated into thin films (1000 Å) of polyvinylcarbazole (PVK) and an oxadiazole derivative (t‐Bu‐PBD) and sandwiched between ITO and Al electrodes. The electroluminescence and photoluminescence spectra (bandwidths ≤40 nm) are nearly identical at room temperature and are tunable from ∼530 to ∼650 nm by varying the size of the dots. Voltage studies at 77 K indicate that while only the dots electroluminesce at the lower voltages, both the dots and the PVK matrix electroluminesce at higher applied voltages. Variable temperature studies indicate that the electroluminescence efficiency increases substantially as the films are cooled down to cryogenic temperatures. © 1995 American Institute of Physics.
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78.60.Fi Electroluminescence
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Helium bubbles in silicon: Structure and optical properties

R. Siegele, G. C. Weatherly, H. K. Haugen, D. J. Lockwood, and L. M. Howe

Appl. Phys. Lett. 66, 1319 (1995); http://dx.doi.org/10.1063/1.113228 (3 pages) | Cited 22 times

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Silicon samples were implanted with 20 keV He at various temperatures. The damage and the size of the He bubbles created during the implantation were measured with Raman spectroscopy and transmission electron microscopy. Room temperature implantation with 2.5×1017 He atoms/ cm2 produced an amorphized layer with a high density of small voids (∼5 nm). After annealing at 923 K the amorphous layer was recrystallized, but still contained extended defects. The He bubbles coalesced forming large bubbles in the implanted region. Implantation at 723 K left the Si essentially crystalline, but with a large number of defects. The He bubbles created at this temperature were larger than after room temperature implantation. Light emitting properties of this porous material are briefly discussed. © 1995 American Institute of Physics.
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61.80.Jh Ion radiation effects
61.72.Qq Microscopic defects (voids, inclusions, etc.)

Role of hydrogen ions in plasma‐enhanced chemical vapor deposition of hydrocarbon films, investigated by in situ ellipsometry

A. von Keudell, W. Jacob, and W. Fukarek

Appl. Phys. Lett. 66, 1322 (1995); http://dx.doi.org/10.1063/1.113229 (3 pages) | Cited 24 times

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Ion bombardment during plasma‐enhanced chemical vapor deposition of hydrocarbon films mainly governs the properties of the films. The range of this ion‐induced modification of the optical properties of hydrocarbon films was determined in situ by monochromatic ellipsometry. The hydrocarbon films were deposited by an electron cyclotron resonance methane plasma onto silicon substrates and additional rf bias was applied to vary the kinetic energy of the impinging ions. The ion‐induced modification of the film properties was investigated by means of a double layer consisting of a polymerlike film with low optical absorption and a hard carbon film with high absorption on top. The deposition of this double layer was monitored in situ by ellipsometry during the growth and during the erosion of this film system in an oxygen plasma at floating potential. From these data it is possible to determine with high accuracy the range of the ion‐induced modification of the optical properties. This layer ranges from 6 Å at 30 V dc self‐bias to 40 Å at 100 V dc self‐bias, which is consistent with TRIM.SP calculations for the bombardment of polymerlike films by hydrogen ions. © 1995 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.80.Jh Ion radiation effects
78.66.Nk Insulators

Fabrication of metallic nanowires with a scanning tunneling microscope

N. Kramer, H. Birk, J. Jorritsma, and C. Schönenberger

Appl. Phys. Lett. 66, 1325 (1995); http://dx.doi.org/10.1063/1.113230 (3 pages) | Cited 34 times

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A procedure to pattern thin metal films on a nanometer scale with a scanning tunneling microscope (STM) operating in air is reported. A 30 nm film of hydrogenated amorphous silicon (a‐Si:H) is deposited on a 10 nm film of TaIr. Applying a negative voltage between the STM tip and the a‐Si:H film causes the local oxidation of a‐Si:H. The oxide which is formed is used as a mask to wet etch the not‐oxidized a‐Si:H and subsequently, the remaining pattern is transferred into the metal film by Ar ion milling. Metal wires as narrow as 40 nm have been fabricated. Since a‐Si:H can be deposited in very thin layers on almost any substrate, the presented procedure can be applied to structure all kind of thin films on a nanometer scale. © 1995 American Institute of Physics.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices
85.40.Hp Lithography, masks and pattern transfer

Transmission electron microscopy observation of interfacial reactions in high‐temperature sputtered Al alloy/TiN system

M. Okihara, N. Hirashita, K. Hashimoto, and H. Onoda

Appl. Phys. Lett. 66, 1328 (1995); http://dx.doi.org/10.1063/1.113231 (3 pages) | Cited 7 times

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Transmission electron microscopy was used to study the interfacial reactions and crystallographic structure in high‐temperature sputtered Al alloy/TiN system. An intermediate layer and semispherical precipitates were observed as the reaction products during high‐temperature sputtering at 500 °C. Electron diffraction analysis indicated that the intermediate layer consisted of hexagonal AlN and cubic TiN. Semispherical precipitates were also found to consist of tetragonal Al3Ti. Additional energy dispersive x‐ray spectrometer analysis suggested that the intermediate layer was formed by the diffusion of Al atoms into the TiN film. © 1995 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.15.Cd Deposition by sputtering

Heteroepitaxial growth of BaTiO3 films on Si by pulsed laser deposition

Myung‐Bok Lee, Masashi Kawasaki, Mamoru Yoshimoto, and Hideomi Koinuma

Appl. Phys. Lett. 66, 1331 (1995); http://dx.doi.org/10.1063/1.113232 (3 pages) | Cited 28 times

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Dielectric BaTiO3 films were heteroepitaxially grown on Si (100) substrates in cube‐on‐cube manner by employing a conductive TiN buffer layer. An epitaxial TiN film was grown by KrF pulsed excimer laser deposition. BaTiO3 film was grown epitaxially on the TiN film at a substrate temperature higher than 600 °C and in an oxygen pressure less than 1 mTorr. This epitaxial BaTiO3/TiN layer on Si was observed to have sharp interfaces and little interdiffusion of constituent atoms by secondary ion mass spectrometry. The surface of the BaTiO3 film had a root‐mean‐square roughness less than 1 nm as observed by atomic force microscopy. A TiN/BaTiO3/TiN trilayer structure was formed and the dielectric property was measured for this metal‐insulator‐metal type capacitor. The BaTiO3 film showed a high relative dielectric constant of 803 at the frequency of 1 MHz and a low leakage current less than 10−8 A/cm2 at 2 V. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Fg Pulsed laser ablation deposition
77.55.-g Dielectric thin films

Odd–even effects of the polar anchoring strength in nematic liquid crystal on rubbed polyimide Langmuir–Blodgett films with alkyl chain lengths

Dae‐Shik Seo, Shunsuke Kobayashi, Michinori Nishikawa, Jae‐Hyung Kim, and Yoshikazu Yabe

Appl. Phys. Lett. 66, 1334 (1995); http://dx.doi.org/10.1063/1.113233 (3 pages) | Cited 17 times

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The odd–even effect of the alkyl chain length of rubbed polyimide Langmuir–Blodgett (LB) films on the extrapolation length of 5CB has been successfully evaluated by measuring polar anchoring strength. The extrapolation length of 5CB for rubbed PI‐LB films with even numbers is small compared with odd numbers for alkyl chain lengths of greater than 7 carbons. The extrapolation length of 5CB on rubbed PI‐LB films with odd numbers increases gradually as the temperature increases but tends to diverge near the clearing temperature ( Tc=35.3 °C). The extrapolation length diverges because of rapidly decreasing surface order near Tc. It is suggested that the polar anchoring strength on rubbed PI‐LB films with an even number is strong because of relatively high surface ordering caused by more crystalline surfaces. Finally, it is concluded that the odd–even effects of the polar anchoring strength in NLCs are strongly related to the character of the polymer and observed clearly for long alkyl chain lengths. © 1995 American Institute of Physics.
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61.30.Gd Orientational order of liquid crystals; electric and magnetic field effects on order

Imprint and oxygen deficiency in (Pb,La)(Zr,Ti)O3 thin‐film capacitors with La‐Sr‐Co‐O electrodes

J. Lee, R. Ramesh, V. G. Keramidas, W. L. Warren, G. E. Pike, and J. T. Evans

Appl. Phys. Lett. 66, 1337 (1995); http://dx.doi.org/10.1063/1.113234 (3 pages) | Cited 75 times

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La‐Sr‐Co‐O/Pb‐La‐Zr‐Ti‐O/La‐Sr‐Co‐O thin‐film capacitors have been grown in various oxygen ambients by pulsed laser deposition. As the oxygen ambient became more reducing, the capacitors developed more voltage asymmetry in hysteresis loops and a more preferred polarization state directed towards the top electrode. PLZT capacitors cooled in a fully oxidizing atmosphere (i.e., 1 atm oxygen pressure) exhibited nominally symmetric hysteresis loops and also showed little imprint both with and without fully saturating bias fields. We find that ambient oxygen pressure is an important process parameter and the imprint behavior is closely related with ambient oxygen induced effects such as oxygen vacancies, its related defect‐dipole complexes and trapping of free charges. The different imprint behavior under negative and positive bias also suggests that the dipolar‐defect complexes tend to cause imprint in PLZT capacitors. © 1995 American Institute of Physics.  
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
73.40.Rw Metal-insulator-metal structures
77.55.-g Dielectric thin films
81.15.Fg Pulsed laser ablation deposition

Photoemission capacitance transient spectroscopy of n‐type GaN

W. Götz, N. M. Johnson, R. A. Street, H. Amano, and I. Akasaki

Appl. Phys. Lett. 66, 1340 (1995); http://dx.doi.org/10.1063/1.113235 (3 pages) | Cited 69 times

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Electronic defects in n‐type GaN were characterized by photoemission capacitance transient spectroscopy. Conventional deep level transient spectroscopy is of limited use in semiconductors with wide band gaps (e.g., 3.4 eV for GaN at 300 K) because it utilizes thermal energy for charge emission which restricts the accessible range of bandgap energies to within ∼0.9 eV of either band edge, for practical measurement conditions. For electron photoemission to the conduction band, four deep levels were detected at optical threshold energies of approximately 0.87, 0.97, 1.25, and 1.45 eV. It is suggested that the above photodetected deep levels may participate in the 2.2 eV defect luminescence transitions, which are also demonstrated for our material. © 1995 American Institute of Physics.
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71.55.Eq III-V semiconductors

Controlled III–V semiconductor cluster nucleation and epitaxial growth via electron‐beam lithography

J. W. Sleight, R. E. Welser, L. J. Guido, M. Amman, and M. A. Reed

Appl. Phys. Lett. 66, 1343 (1995); http://dx.doi.org/10.1063/1.113195 (3 pages) | Cited 1 time

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Controlled registration of InAs clusters and selective‐area growth of InAs thin films on GaAs substrates is achieved via a combined high dose electron beam lithography/metalorganic chemical vapor deposition technique. Auger electron spectroscopy and secondary electron microscopy measurements show that growth inhibition is not a consequence of native oxide masking or processing related surface contamination, but instead is attributable to modification of the GaAs surface energy. This phenomenon is observed for a wide range of lithographic patterns and growth conditions on both (100) and (111)B oriented n‐type and semi‐insulating GaAs substrates. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.-c Methods of micro- and nanofabrication and processing
85.35.-p Nanoelectronic devices

Carrier recombination studies of ZnCdSe/ZnSe single quantum wells grown by molecular beam epitaxy

J. S. Massa, G. S. Buller, A. C. Walker, G. Horsburgh, J. T. Mullins, K. A. Prior, and B. C. Cavenett

Appl. Phys. Lett. 66, 1346 (1995); http://dx.doi.org/10.1063/1.113196 (3 pages) | Cited 15 times

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Temperature dependent time‐resolved photoluminescence has been used to study the excess carrier recombination in Zn0.75Cd0.25Se/ZnSe single quantum well structures grown by molecular beam epitaxy. For temperatures <100 K radiative excitonic recombination appears to dominate, and the photoluminescence (PL) decay time follows the linear dependence on temperature over the range 50–120 K. At higher temperatures the reduction in PL efficiency and decay time indicate that nonradiative processes associated with the ZnCdSe/ZnSe interfaces dominate the recombination. The results are consistent with theoretical predictions. © 1995 American Institute of Physics.
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78.55.Et II-VI semiconductors
78.47.-p Spectroscopy of solid state dynamics
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Alternating‐current excitation of InP based δ layers

J. J. Mareš, X. Feng, F. Koch, and J. Krištofik

Appl. Phys. Lett. 66, 1349 (1995); http://dx.doi.org/10.1063/1.113197 (3 pages)

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We have studied a nonlinear response of a field‐effect transistor multi δ‐layer structure to an external alternating‐current signal. A specific resonance behavior of the source‐drain resistance was observed in the MHz range depending on the orientation of the magnetic field. The results are discussed within the framework of a model of electron gas heating due to the parametric resonance between the ac electrical signal and the sound wave generated by an ac electrical signal by means of the piezoelectric effect. © 1995 American Institute of Physics.
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72.50.+b Acoustoelectric effects
72.20.Fr Low-field transport and mobility; piezoresistance
72.20.Ht High-field and nonlinear effects
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Studying the insulator–conductor interface with a scanning tunneling microscope

Michael I. Sumetskii and Harold U. Baranger

Appl. Phys. Lett. 66, 1352 (1995); http://dx.doi.org/10.1063/1.113198 (3 pages) | Cited 4 times

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We suggest that a scanning tunneling microscope (STM) may be used for investigating the insulator–conductor interface, in particular SiO2/Si, at nanometer scale. For an insulating film transparent to tunneling, we estimate, using a simple model, the roughness of the interface from the STM image. It is found that the interface roughness is less than the roughness of the image surface times the ratio of effective decay lengths in the film and in vacuum. For relatively wide films, of order 10 nm, STM measurement in the field emission regime can give the interface image with 1 nm precision. © 1995 American Institute of Physics.
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy
68.35.B- Structure of clean surfaces (and surface reconstruction)
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

Optical properties of ternary and quaternary IV–VI semiconductor layers on (100) BaF2 substrates

Patrick J. McCann, Lin Li, John E. Furneaux, and Robert Wright

Appl. Phys. Lett. 66, 1355 (1995); http://dx.doi.org/10.1063/1.113199 (3 pages) | Cited 12 times

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Fourier transform infrared (FTIR) absorption spectra and photoluminescence (PL) spectra for PbSe0.78Te0.22 and Pb0.95Sn0.05Se0.80Te0.20 layers grown by liquid phase epitaxy on (100) BaF2 substrates are reported. FTIR absorption edges varied from 213 to 275 meV (between 4 and 300 K) for the ternary alloy and from 118 to 200 meV (between 10 and 300 K) for the quaternary alloy. PL energies were 174 meV at 5 keV for the ternary alloy and 100 meV at 7.1 K for the quaternary alloy. The differences between the low temperature FTIR absorption edge energies and the PL energies are attributed to the Burstein–Moss effect. © 1995 American Institute of Physics.
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78.66.Li Other semiconductors
78.55.Hx Other solid inorganic materials
42.55.Px Semiconductor lasers; laser diodes

Piezoelectric effects in (001)‐oriented double barrier resonant tunneling structures

L. Cong, J. D. Albrecht, M. I. Nathan, P. P. Ruden, and D. L. Smith

Appl. Phys. Lett. 66, 1358 (1995); http://dx.doi.org/10.1063/1.113200 (3 pages) | Cited 9 times

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We show that piezoelectric effects can give rise to internal electric fields that modify the current–voltage characteristics of double barrier resonant tunneling devices, if suitable stresses are applied. Electric polarization fields in the direction perpendicular to the interfaces arise in heterostructures on (001)‐oriented substrates under uniaxial stress parallel to the (110) or (110) orientations. We measured current–voltage characteristics of (001)‐oriented AlAs/GaAs/AlAs double barrier structures as a function of uniaxial external stress applied parallel to the (110) and the (110) orientations. The substrate contact was grounded in all measurements. Under (110) stress, the resonance peaks shift to more positive voltages for both positive and negative bias. For (110) stress, the peaks shift toward more negative voltages. We also calculated the current–voltage characteristics of resonant tunneling structures under uniaxial stress, taking into account stress effects on the band alignment and piezoelectric effects. We obtain satisfactory agreement between our calculations which contain no adjusted parameters and the measured data. © 1995 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Gk Tunneling
77.65.-j Piezoelectricity and electromechanical effects

Femtosecond hole thermalization in bulk GaAs

R. Tommasi, P. Langot, and F. Vallée

Appl. Phys. Lett. 66, 1361 (1995); http://dx.doi.org/10.1063/1.113201 (3 pages) | Cited 28 times

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Ultrafast hole relaxation dynamics is selectively investigated in intrinsic bulk GaAs using a high sensitivity two‐wavelength pump‐probe technique. Nonequilibrium carriers are photoexcited close to the bottom of their respective bands and hole heating is followed by monitoring the transient bleaching of optical transitions involving higher momentum states. Hole heating is found to be dominated by hole‐phonon interactions with a thermalization time of the order of 150 fs for carriers densities in the 1017 cm−3 range. © 1995 American Institute of Physics.
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78.47.-p Spectroscopy of solid state dynamics
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.80.Ey III-V and II-VI semiconductors

Semi‐insulating 6H–SiC grown by physical vapor transport

H. McD. Hobgood, R. C. Glass, G. Augustine, R. H. Hopkins, J. Jenny, M. Skowronski, W. C. Mitchel, and M. Roth

Appl. Phys. Lett. 66, 1364 (1995); http://dx.doi.org/10.1063/1.113202 (3 pages) | Cited 64 times

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Semi‐insulating 6H–SiC crystals have been achieved by using controlled doping with deep‐level vanadium impurities. High resistivity undoped and semi‐insulating vanadium‐doped single‐crystals with diameters up to 50 mm were grown by physical vapor transport using an induction‐heated, cold‐wall system in which high purity graphite materials constituted the hot zone of the furnace. Undoped crystals were p‐type due to the presence of residual acceptor impurities, mainly boron, and exhibited resistivities ranging up to 3000 Ω cm. The semi‐insulating behavior of the vanadium‐doped crystals is attributed to compensation of residual acceptors by the deep‐level vanadium V4+(3d1) donor located near the middle of the band gap. © 1995 American Institute of Physics.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
61.72.up Other materials
71.55.Ht Other nonmetals
73.61.Le Other inorganic semiconductors

Reverse biased photoconductive detectors and switches with separate absorption and detection area

P. Riel, E. Greger, K. Reingruber, M. Ennes, P. Kiesel, M. Kneissl, G. H. Döhler, G. Tränkle, and G. Weimann

Appl. Phys. Lett. 66, 1367 (1995); http://dx.doi.org/10.1063/1.113203 (3 pages) | Cited 9 times

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We report on reverse biased photoconductive detectors with novel design and improved high‐frequency performance. Taking advantage of the ‘‘giant ambipolar diffusion constant’’ which has been observed previously in n‐i‐p‐i doping superlattices very fast carrier transfer from the inner absorption area to the outer detection area is achieved. The combination of narrow contact spacings and small RC and diffusion time constants results in very high gain‐bandwidth products (≳20 GHz) with adjustable 3 dB frequencies. © 1995 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
42.79.Pw Imaging detectors and sensors
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Carbon incorporation in silicon for suppressing interstitial‐enhanced boron diffusion

P. A. Stolk, D. J. Eaglesham, H.‐J. Gossmann, and J. M. Poate

Appl. Phys. Lett. 66, 1370 (1995); http://dx.doi.org/10.1063/1.113204 (3 pages) | Cited 108 times

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The effect of substitutional C on interstitial‐enhanced B diffusion in Si has been investigated. Substitutional C was incorporated into B doped Si superlattices using molecular‐beam‐epitaxial growth under a background of acetylene gas. Excess Si self‐interstitials were generated by near‐surface 5×1013/cm2, 40 keV Si implants and diffused at 790 °C. The interstitial‐enhanced diffusion of the B marker layers is fully suppressed for C concentrations of 2×1019/cm3, thus demonstrating that substitutional C acts as a trap for interstitials in crystalline Si. Uniform C incorporation of 5×1018/cm2 significantly reduces the transient enhanced diffusion of a typical B junction implant without perturbing its electrical activity. © 1995 American Institute of Physics.
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66.30.J- Diffusion of impurities
61.72.J- Point defects and defect clusters
61.72.uf Ge and Si

High quality 4H‐SiC epitaxial layers grown by chemical vapor deposition

O. Kordina, A. Henry, J. P. Bergman, N. T. Son, W. M. Chen, C. Hallin, and E. Janzén

Appl. Phys. Lett. 66, 1373 (1995); http://dx.doi.org/10.1063/1.113205 (3 pages) | Cited 28 times

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High quality, homoepitaxial layers of 4H‐SiC have been grown by chemical vapor deposition in a hot‐wall reactor. The residual doping concentration obtained by capacitance versus voltage measurements was as low as 2×1014 cm−3. The high quality is confirmed by photoluminescence measurements performed at low temperatures (1.8–4.2 K) showing strong free exciton related luminescence and by the fact that optically detected cyclotron resonance signals could be observed (at 6 K), as a result of the highest mobility reported in SiC. © 1995 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Hx Other solid inorganic materials
72.20.Fr Low-field transport and mobility; piezoresistance
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