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4 Feb 1991

Volume 58, Issue 5, pp. 435-547

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Mobility‐lifetime products in hydrogenated amorphous silicon

Richard S. Crandall and I. Balberg

Appl. Phys. Lett. 58, 508 (1991); http://dx.doi.org/10.1063/1.104622 (3 pages) | Cited 13 times

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The most important parameters characterizing the photoelectronic quality of a semiconductor are its charge‐carrier mobility lifetime, μτ, products. The two common experimental methods used to determine these parameters in hydrogenated amorphous silicon, a‐Si:H, are the steady‐state photoconductivity measurement and the life‐of‐flight charge‐collection measurement. The two methods yield quite different results. We show that the difference can be resolved by an understanding of the physics involved in each of the measurements. We show that the steady‐state μτ is expected to be up to three orders of magnitude larger than the time‐of‐flight μτ in undoped a‐Si:H. This prediction is in excellent agreement with the corresponding experimental results.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.61.Ng Insulators

Characterization of dry etch‐induced damage in semiconductor materials using a noncontact photothermal radiometric probe

G. M. Crean, I. Little, and P. A. F. Herbert

Appl. Phys. Lett. 58, 511 (1991); http://dx.doi.org/10.1063/1.104623 (3 pages) | Cited 6 times

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Defects induced in n‐type silicon (Si) and gallium arsenide (GaAs) substrates by argon ion bombardment in reactive ion etch and reactive ion beam etch reactors, respectively, have been studied for the first time using photothermal radiometry (PTR). A significant shift in measured PTR signal amplitude has been observed as a function of isochronal bias voltage variation (0–600 V) etching studies. The experimental results have been interpreted using a model for the photothermal radiometric response from a layered semiconductor material. The detection of a threshold effect for dry etch induced process defects in GaAs has been correlated with Raman spectroscopy measurements. Both theory and experimental results indicate that PTR has the requisite surface sensitivity to variations in lattice quality to be a suitable technique for rapid and noncontact process control monitoring of dry‐etch‐induced damage.
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07.60.Dq Photometers, radiometers, and colorimeters
81.65.-b Surface treatments
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

ArF excimer laser induced photolytic growth of Si homoepitaxial films from Si2H6 at 330 °C

S. Lian, B. Fowler, D. Bullock, and S. Banerjee

Appl. Phys. Lett. 58, 514 (1991); http://dx.doi.org/10.1063/1.104599 (3 pages) | Cited 11 times

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This letter discusses low‐temperature Si homoepitaxy on Si(100) substrates by the photolytic decomposition of Si2H6 by the 193 nm emission of an ArF excimer laser. The chemical vapor deposition process at growth rates from 0.5–4 Å/min is performed in an ultrahigh vacuum chamber which, along with an ex situ HF dip and a novel in situ hydrogen clean using laser excitation, results in minimization of oxygen and carbon contamination which inhibits Si epitaxy. The growth involves photolytic decomposition of Si2H6 and the generation and adsorption of SiH2 precursors on the hydrogenated Si surface, which is the rate limiting step. Very low defect density films in terms of stacking faults and dislocation loops (less than 106 cm−2), and excellent crystallinity have been grown at 330 °C and 0.5 W laser power, as confirmed by Schimmel etching and Nomarski microscopy, transmission electron microscopy, electron diffraction and in situ reflection high‐energy electron diffraction.
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81.15.Kk Vapor phase epitaxy; growth from vapor phase
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

High carbon doping efficiency of bromomethanes in gas source molecular beam epitaxial growth of GaAs

T. J. de Lyon, N. I. Buchan, P. D. Kirchner, J. M. Woodall, G. J. Scilla, and F. Cardone

Appl. Phys. Lett. 58, 517 (1991); http://dx.doi.org/10.1063/1.104600 (3 pages) | Cited 30 times

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Carbon tetrabromide (CBr4) and bromoform (CHBr3) have been studied as carbon doping sources for GaAs grown by gas source molecular beam epitaxy (GSMBE) with elemental Ga and thermally cracked AsH3. Hole concentrations in excess of 1×1020 cm−3 have been measured by Hall effect in both CBr4‐ and CHBr3‐doped GaAs, which agrees closely with the atomic C concentration from secondary‐ion mass spectrometry, indicating complete electrical activity of the incorporated carbon. The GaAs growth rate is unaffected by the CBr4 and CHBr3 fluxes over the range of dopant flow investigated. The efficiencies of carbon incorporation from CBr4 and CHBr3 are, respectively, 750 and 25 times that of trimethylgallium (TMG), which is commonly employed as a carbon doping source in metalorganic MBE (MOMBE). The sensitivity of carbon incorporation to varying substrate temperature and V/III ratio has been observed to be significantly reduced with CBr4 and CHBr3 from that obtained under similar growth conditions with TMG in MOMBE.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.U- Doping and impurity implantation

Excitation transfer in donor‐acceptor pair luminescence

G.‐J. Yi, J. A. Tuchman, and G. F. Neumark

Appl. Phys. Lett. 58, 520 (1991); http://dx.doi.org/10.1063/1.104601 (3 pages) | Cited 4 times

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In the analysis of spectral and time dependencies of donor‐acceptor pair (DAP) spectra, it has usually been assumed that the primary factors are the distribution of pair separations together with the dependence of the decay and of the emitted energies on these separations. We have measured the time decay of the DAP luminescence in ZnSe as a function of excitation wavelength and show that, instead, excitation transfer via localized states cannot be neglected. We also point out that such transfer appears very reasonable, based on transfer versus luminescence decay rates.
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78.55.Et II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Fabrication of amorphous‐crystalline superlattices in GeSi‐Si and GaAs‐AlAs

D. J. Eaglesham, J. M. Poate, D. C. Jacobson, M. Cerullo, L. N. Pfeiffer, and K. West

Appl. Phys. Lett. 58, 523 (1991); http://dx.doi.org/10.1063/1.104602 (3 pages) | Cited 38 times

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A study is presented of MeV ion beam amorphization of epitaxial superlattices of GeSi‐Si and GaAs‐AlAs. In both superlattice systems, we observe preferential damage of one layer type (using transmission electron microscopy and Rutherford backscattering). Selective amorphization of the faster‐damaging layers is demonstrated at higher doses, allowing us to form amorphous‐crystalline (a‐c) superlattices of c‐Si/a‐GeSi and c‐AlAs/a‐GaAs. By studying the buildup of damage in the two systems, we deduce differences between the ion beam damage processes in group III‐V and IV semiconductors. The most marked distinction is that the AlAs layers inhibit amorphization of the GaAs contiguous with the interface, while Si layers do not appear to affect the amorphization of the adjacent GeSi. This leads us to the tentative conclusion that GaAs amorphization is strongly affected by the local concentration of point defects which may diffuse hundreds of angstroms at ≊80 K and recombine in the AlAs layer.
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61.80.Jh Ion radiation effects
61.72.U- Doping and impurity implantation
61.72.uf Ge and Si
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.

Growth of high optical and electrical quality GaN layers using low‐pressure metalorganic chemical vapor deposition

M. Asif Khan, J. N. Kuznia, J. M. Van Hove, D. T. Olson, S. Krishnankutty, and R. M. Kolbas

Appl. Phys. Lett. 58, 526 (1991); http://dx.doi.org/10.1063/1.104575 (2 pages) | Cited 103 times

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We report on the low‐pressure metalorganic chemical vapor deposition of high quality single‐crystal GaN layers over basal plane sapphire substrates. Optimization of growth conditions resulted in material with carrier densities of 1017 /cm3 at room temperature and corresponding mobilities around 350 cm2 /V s. The photoluminescence linewidths improved from 160 meV [full width at half maximum (FWHM)] to 25 meV (FWHM). With improved material quality we were able to observe the polar optical mode and the ionized impurity scattering regimes in the mobility versus temperature data. Good quality Schottky barriers were formed on the as‐grown material using a tungsten probe and an alloyed indium contact. Our observations indicate a direct correlation between electrical and optical characteristics of good material and strongly question nitrogen vacancies as the sole explanation for the high carrier densities observed in poor quality GaN growths.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Ey III-V semiconductors
78.55.Hx Other solid inorganic materials
78.66.-w Optical properties of specific thin films

Evidence for individual vortex pinning in ceramic YBa2Cu3O7−δ

Leandro R. Tessler, Jackie Provost, and Antoine Maignan

Appl. Phys. Lett. 58, 528 (1991); http://dx.doi.org/10.1063/1.104576 (3 pages) | Cited 5 times

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We measured the pinning force density Fp in high quality YBa2Cu3 O7−δ ceramics as a function of the temperature and magnetic field up to 5 T. The results indicate that near 60 K the magnetic vortices are pinned individually. This implies that at this temperature the main pinning mechanism involves localized pinning centers separated by short distances rather than twin boundaries.
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74.25.Uv Vortex phases (includes vortex lattices, vortex liquids, and vortex glasses)
74.70.-b Superconducting materials other than cuprates

Biaxially aligned high Tc superconductors

F. Chen, B. Zhang, R. S. Markiewicz, and B. C. Giessen

Appl. Phys. Lett. 58, 531 (1991); http://dx.doi.org/10.1063/1.104577 (3 pages) | Cited 6 times

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A new technique is described for preparing polycrystalline samples of high Tc superconductors, which should have superior properties for many applications, including potentially much higher critical currents.
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74.70.-b Superconducting materials other than cuprates
74.25.Sv Critical currents
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Continuous fabrication of high‐temperature superconductor coated metal fiber and multifilamentary wire

L. D. Woolf, W. A. Raggio, F. E. Elsner, M. V. Fisher, R. B. Stephens, T. L. Figueroa, C. H. Shearer, J. D. Rose, K. M. Schaubel, R. A. Olstad, T. Ohkawa, D. M. Duggan, M. DiMartino, and R. L. Fagaly

Appl. Phys. Lett. 58, 534 (1991); http://dx.doi.org/10.1063/1.104578 (3 pages) | Cited 19 times

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Long superconductor fibers have been continuously produced by electrophoretically depositing REBa2Cu3O7−x (where RE=Y or a selected rare‐earth element) powder onto a metal substrate fiber and sintering, then electrophoretically depositing silver and sintering. After collecting the coated fiber on a take‐up spool, the entire spool is batch‐oxygenated to form the 90 K superconducting phase. Multiple fibers are then continuously unspooled and soldered into a copper channel to form the final multifilamentary high‐temperature superconductor wire. Superconducting fibers over 1000 m long and multifilamentary wire 70 m long have been produced.
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84.71.Ba Superconducting magnets; magnetic levitation devices
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy

Performance of a narrow band microwave filter implemented in thin‐film YBa2Cu3O7−δ with ohmic contacts

D. Kalokitis, A. Fathy, V. Pendrick, E. Belohoubek, A. Findikoglu, A. Inam, X. X. Xi, T. Venkatesan, and J. B. Barner

Appl. Phys. Lett. 58, 537 (1991); http://dx.doi.org/10.1063/1.104579 (3 pages) | Cited 14 times

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Using in situ deposited thin‐film Y1Ba2Cu3O7−δ on LaAlO3 substrates, we have developed a pseudo‐interdigital three‐pole stripline filter with a minimum passband loss under 3.5 dB at 9.5 GHz and 77 K. The passband is very narrow, having a bandwidth of only 50 MHz (0.5%). The filter occupies a volume of less than 0.1 cm3. An equivalent copper filter produced a loss of 18.5 and 28 dB at 77 and 300 K, respectively. The input and output coupling is achieved by ex situ sputtered Au thin‐film contacts defined on the Y1Ba2Cu3O7−δ by a lift‐off technology and ultrasonically bonded to hermetic K connectors. Some of the major concerns in the realization of narrow band filters such as air gaps between high dielectric constant substrates and uniformity of the substrate’s dielectric constant are addressed.
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85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
84.40.Ba Antennas: theory, components and accessories

Texturing of epitaxial in situ Y‐Ba‐Cu‐O thin films on crystalline substrates

J. P. Zheng, S. Y. Dong, and H. S. Kwok

Appl. Phys. Lett. 58, 540 (1991); http://dx.doi.org/10.1063/1.104580 (3 pages) | Cited 25 times

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The degree of texturing of the grains in epitaxial in situ Y‐Ba‐Cu‐O films was studied by x‐ray pole‐figure measurements. These high Tc and Jc laser deposited films were all aligned with the c axis perpendicular to the substrate surface. It was found that films on SrTiO3(001) and LaAlO3(001) were totally aligned with the YBCO a axis parallel to the 〈100〉 direction on the substrate. For MgO(001), 4% of the grains are aligned in the 〈110〉 direction. For yttria stabilized zirconia (001), the a axes of the YBCO grains were distributed between the 〈100〉 and 〈110〉 directions on the substrate. These observations are consistent with the degree of lattice mismatch in the various crystal orientations.
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68.35.Fx Diffusion; interface formation
68.35.B- Structure of clean surfaces (and surface reconstruction)
74.78.-w Superconducting films and low-dimensional structures
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Substrate step‐edge YBa2Cu3O7 rf SQUIDs

K. P. Daly, W. D. Dozier, J. F. Burch, S. B. Coons, R. Hu, C. E. Platt, and R. W. Simon

Appl. Phys. Lett. 58, 543 (1991); http://dx.doi.org/10.1063/1.104581 (3 pages) | Cited 67 times

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We have developed a technique which permits high‐yield fabrication of microbridges and low noise YBa2Cu3O7 superconducting quantum interference devices (SQUIDs) in epitaxial thin films. These SQUIDs operate over a wide temperature range extending from 4 K to close to the superconducting transition temperature. Measurements of an rf SQUID operating at 77 K give a peak‐to‐peak flux sensitivity of 36 μV/Φ0 and a flux noise at 10 Hz of 1.5× 10−4 Φ0/√Hz. Device yields over 80% have been obtained.
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74.50.+r Tunneling phenomena; Josephson effects
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
85.25.Dq Superconducting quantum interference devices (SQUIDs)

Detection of ferromagnetic resonance in metallic glass by fiber interferometric strain measurement

D. M. Dagenais, F. Bucholtz, K. P. Koo, S. Vohra, and J. M. Pond

Appl. Phys. Lett. 58, 546 (1991); http://dx.doi.org/10.1063/1.104582 (2 pages)

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We report the first detection of ferromagnetic resonance in a magnetostrictive amorphous alloy using a fiber interferometer. By measuring the strain at the difference frequency resulting from the application of two rf magnetic fields, we observe a natural (zero field) ferromagnetic resonance near 400 MHz. We discuss novel features of this technique and outline modifications to the existing theory of dynamic magnetostriction suggested by the results.
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76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.80.+q Magnetomechanical effects, magnetostriction
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