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1

Digitale Medien

Ohmic, superconducting, shallow AuGe/Nb contacts to GaAs (1986)

Gurvitch, M. ; Kastalsky, A. ; Schwarz, S. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 60 (1986), S. 3204-3210

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: An emerging new class of superconductor-semiconductor devices requires Ohmic superconducting contacts which do not diffuse deeply into a semiconductor. We developed a contact to GaAs based on ∼150 A(ring) of AuGe covered with ∼2000 A(ring) of Nb annealed in reducing atmosphere at 390–420 °C for 1–5 s. The resulting contact has linear I-V characteristics at all temperatures down to 4.2 K, resistivity of ∼2×10−6 Ω cm2 (∼0.1 Ω mm), and superconducting transition temperature Tc (approximately-greater-than)8 K. Secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM) studies revealed very shallow penetration of the active dopant Ge into GaAs; the upper limit for the thickness of the doped layer with Ge concentration over 1017 cm−3 is estimated as 200–300 A(ring). Gold, a nonactive dopant (deep level) drops to below 1018 cm−3 within the same distance, with the possible tail extending further. Morphology and uniformity of a contact, as revealed in TEM and optical microscopy, is good, owing to the Nb overlayer which prevents AuGe from "balling up'' upon melting. These contacts can be used in low-temperature devices and conventional devices based on GaAs.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.337738

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2

Digitale Medien

Mutual phase locking in series arrays of Josephson tunnel junctions at millimeter-wave frequencies (1986)

Lee, G. S. ; Schwarz, S. E.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 60 (1986), S. 465-468

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Mutual phase locking has been demonstrated in series arrays of two and four Josephson junctions at millimeter-wave frequencies. Experimental observations are in good agreement with theory reported earlier. This technique increases the output power available from a Josephson junction source. Available output power is expected to be proportional to the square of the number of junctions until the array impedance approaches the load impedance. The output frequency is voltage tunable over as much as an octave. Theory indicates that the technique can be extended to even larger arrays.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.337625

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3

Digitale Medien

Study of interdiffusion in a Te-doped AlAs-GaAs superlattice (1989)

Mei, P. ; Schwarz, S. A. ; Venkatesan, T. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 65 (1989), S. 2165-2167

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The enhanced layer interdiffusion in Te-doped AlAs/GaAs superlattices has been studied by secondary ion mass spectrometry. The superlattice sample was grown by organometallic chemical vapor deposition with Te doping at concentrations of 2×1017–3×1018 cm−3 during the growth process. In the temperature range from 800 to 1000 °C, the Al diffusion coefficient has an activation energy of 3.0 eV and is approximately proportional to the Te concentration. These results contrast sharply with Si-induced mixing which, in an analogous experiment, yielded an activation energy of 4.1 eV for the Al diffusion coefficient with a high power law dependence on the Si concentration.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.342848

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4

Digitale Medien

Substrate effects on the properties of Y-Ba-Cu-O superconducting films prepared by laser deposition (1988)

Venkatesan, T. ; Chang, C. C. ; Dijkkamp, D. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 63 (1988), S. 4591-4598

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Superconducting thin films of Y1Ba2Cu3Ox with superconducting transition temperature (Tc) near 90 K have been prepared by a laser deposition technique. We show that films prepared on sapphire, lithium niobate, and strontium titanate under identical processing conditions exhibit different electrical characteristics. The film surfaces, interfaces, and crystallinity have been studied by a number of analytical techniques. We conclude that the substrate influences the film properties primarily in three ways: the thermal expansion mismatch introduces cracks in the film, the interface reaction changes the film composition, and the substrate lattice influences the crystallographic orientation of the film.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.340136

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5

Digitale Medien

Annealing behavior of ion-implanted Fe in InP (1985)

Schwarz, S. A. ; Schwartz, B. ; Sheng, T. T. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 58 (1985), S. 1698-1700

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The annealing behavior of implanted Fe+ in InP is studied using secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM). Dual implants (275 keV, 1.25×1014 cm−2 and 400 keV, 1.25×1014 cm2) were performed at room temperature (RT) and at 200 °C and then annealed at 725 °C for one hour. TEM reveals a 3100-A(ring) amorphous region in the unannealed RT implant. Significant defect production is observed in this sample at the amorphous-crystalline interface following the anneal. SIMS reveals an Fe pileup at this interface. No such pileup is observed in the samples implanted at 200 °C. The data also suggest an Fe diffusion constant which is lower than typically reported in the literature. The results are contrasted with the SIMS study by M. Gauneau, H. L'Haridon, A. Rupert, and M. Salvi [J. Appl. Phys. 53, 6823 (1982)].

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.336040

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6

Digitale Medien

Integrated external cavity GaAs/AlGaAs lasers using selective quantum well disordering (1989)

Werner, J. ; Kapon, E. ; Stoffel, N. G. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 55 (1989), S. 540-542

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Integrated external cavity GaAs/AlGaAs single quantum well lasers were fabricated by selective quantum well disordering. Lasers with 2.07-mm-long passive sections and 0.48-mm-long active sections had threshold currents of 33 mA, compared to 9.8 mA for lasers without passive sections. Lasing data indicate a residual modal loss of 11 cm−1 in the passive sections, consistent with direct waveguide loss measurements. Control composite structures with a nondisordered quantum well in the passive sections showed significantly higher threshold currents and a large red shift of as much as 11.4 nm in the lasing wavelength compared to lasers without a passive cavity. This red shift is the main reason for the reduced resonant losses in integrated external cavity lasers with a nondisordered quantum well in the passive section.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.101848

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7

Digitale Medien

Comparative studies of ion-induced mixing of GaAs-AlAs superlattices (1988)

Mei, P. ; Venkatesan, T. ; Schwarz, S. A. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 52 (1988), S. 1487-1489

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The species dependence of ion-induced superlattice mixing has been examined in AlAs-GaAs superlattice samples grown by molecular beam epitaxy. The interdiffusion of the superlattices induced by ion implantation with comparable ranges, doses, and subsequent thermal anneals were measured with secondary ion mass spectrometry. The effects of elements of comparable mass (Ga, As, and Ge) and comparable valence (Si and Ge) were studied. The experimental results show that Ga and As implantation cause primarily collision-induced mixing, while Ge implantation results in collision-induced mixing with additional impurity-induced mixing beyond the implant range. In comparison with Ge, Si-induced mixing is similar in nature though there is significant difference in the depth and extent of the mixing. The extent of mixing is found to depend on the local Ge or Si concentration.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.99107

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8

Digitale Medien

Conversion of InP/In0.53Ga0.47As superlattices to Zn3P2/In1−xGaxAs and Zn3P2/Zn3As2 superlattices by Zn diffusion (1989)

Hwang, D. M. ; Schwarz, S. A. ; Mei, P. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 54 (1989), S. 1160-1162

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: A standard 600 °C closed-tube Zn diffusion into an unstrained InP/In0.53Ga0.47As superlattice was found to produce new superlattices containing Zn3P2 layers, and in some cases Zn3As2 layers. Crystalline properties and diffusion profiles were examined by transmission electron microscopy and secondary-ion mass spectrometry. Initial doping of Zn enhances the diffusion of In and Ga and results in a superlattice of uniform In and Ga distribution. Upon further infusion of Zn, Zn3P2 forms selectively in the phosphorus layers and propagates from the surface while maintaining an atomically abrupt Zn3P2/In1−xGaxP interface. Zn3As2 conversion is also observed to occur under sufficiently stringent conditions. Diffusion of P and As was not observed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.101480

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9

Digitale Medien

Reduced optical waveguide losses of a partially disordered GaAs/AlGaAs single quantum well laser structure for photonic integrated circuits (1988)

Werner, J. ; Kapon, E. ; Von Lehmen, A. C. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 53 (1988), S. 1693-1695

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: We present TE and TM waveguide loss measurements of partially disordered GaAs/AlGaAs quantum well separate confinement laser structures. Disordering is accomplished by silicon ion implanation and subsequent annealing. Propagation losses as low as 9 cm−1 are observed at the lasing wavelength of the corresponding untreated laser wafer. The waveguides are shown to be compatible with fabrication and dimensional requirements of high quality semiconductor lasers; ridge waveguide lasers fabricated in unimplanted portions of the same wafer exhibit threshold currents of only 8 mA. The results show that impurity-induced quantum well disordering is suitable for monolithic integration of low-threshold quantum well lasers and transparent optical waveguides.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.99799

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10

Digitale Medien

Mixing inhibition and crystalline defects in heavily Si-doped AlAs/GaAs superlattices (1988)

Mei, P. ; Schwarz, S. A. ; Venkatesan, T. ; [weitere]

Woodbury, NY : American Institute of Physics (AIP)

Applied Physics Letters 53 (1988), S. 2650-2652

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ISSN: 1077-3118

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Superlattice mixing in heavily silicon-doped AlAs/GaAs superlattices has been examined by secondary-ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). Samples were grown by molecular beam epitaxy with Si concentrations of 1018 to 1020 cm−3 introduced during the growth process. Interdiffusion of Al was inhibited at a Si concentration of 1020 cm−3. Defect clusters and prismatic dislocation loops were found to be associated with Si concentrations of 1020 and 1019 cm−3, respectively. Si was observed by SIMS to segregate preferentially into the GaAs layers and TEM observation revealed defect formation in these same layers during the diffusion process, suggesting a strong correlation between Si segregation and defect formation. In the range of Si concentrations employed, the Al diffusion coefficient is found to vary as the third power of the estimated electron concentration, consistent with our previous results at lower concentrations. These results suggest that the diffusion inhibition at high Si concentrations may arise from the trapping of mobile Si species by defects with a consequent reduction of the carrier concentration.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.100183

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