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  • 1
    Electronic Resource
    Electronic Resource
    Solution characterization of carboxybenzoquinone and the isolation of derived quinhydrones (1984)
    s.l. : American Chemical Society
    The @journal of organic chemistry 49 (1984), S. 4736-4738 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00198a035
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  • 2
    Electronic Resource
    Electronic Resource
    Detection wavelength of quantum-well infrared photodetectors (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5230-5236 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Long wavelength infrared detection using intersubband transitions has been progressing rapidly in recent years. One advantage of the quantum-well infrared photodetectors is the wavelength tunability as a function of their structural parameters. In this work, we have performed a systematic calculation on the detection wavelength, the absorption linewidth, and the oscillator strength of a typical GaAs/AlxGa1−xAs multiple-quantum-well photodetector, with aluminum molar ratio in the barriers ranging from 0.14 to 0.42 and the quantum-well width ranging from 20 to 70 A(ring). We found that within these material parameters, the detection wavelength can be varied from 5 to over 25 μm. In addition, we also discuss the photoconductive gain of the detectors with respect to the energies of the final state of the optical transition and the satellite valleys of the detector material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353751
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  • 3
    Electronic Resource
    Electronic Resource
    Optical properties of quantum wells grown upon gas source molecular-beam epitaxy low-temperature buffers (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7942-7944 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaAs/AlGaAs quantum wells are grown on gas source molecular-beam epitaxy (GSMBE) grown low-temperature buffers (LTB). Changes in LTB growth conditions produce noticeable changes in photoluminescence (PL) intensity and linewidths of the quantum wells. Layers grown at low temperatures (200–300 °C) incorporate excess arsenic which outdiffuses during subsequent quantum well growth. Reflection high energy electron diffraction and PL results are utilized to show strain and arsenic outdiffusion from the LTBs. Excess arsenic incorporation during the growth of GaAs at low temperatures is explained in 〈m1;&10q〉terms of the association reaction of As2 to form As4 at the surface. The optimum V/〈bx〉III〈ba〉 ratio for growth of LTB by GSMBE is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348908
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  • 4
    Electronic Resource
    Electronic Resource
    Spectroscopic studies of Sb3+ color centers in alkali halide single crystals (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 6420-6428 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The emission from KCl@B:Sb3+ and KI@B:Sb3+ excited in the A-absorption band was measured as a function of exciting photon energy and temperature. The A-band excitation produced two emission bands for KCl@B:Sb3+ and a single band for KI@B:Sb3+. The definitive assignment of these bands is presented in terms of the adiabatic potential energy surface (APES), in which the effect of the spin–orbit interaction (SO) on the Jahn–Teller (JT) interaction coupling to the Eg mode is taken into account. The polarization spectrum and the angular dependence of polarization ratio of the A-band emission were also studied to determine the symmetry axes of the Sb3+ –vacancies complex. The results indicate that the anisotropy is associated with the relaxed excited state (RES) of Sb3+. It is also found that the JT interaction coupling to the T2g mode and the vacancies, situated in the next-nearest-neighbor (nnn) and the nearest-neighbor (nn) positions to the Sb3+ ion, give rise to an additive perturbation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460271
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  • 5
    Electronic Resource
    Electronic Resource
    Study of photoluminescence in lead tungstates doped with Pr3+, Sm3+, and Er3+ ions (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2766-2768 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence (PL) in PbWO4 single crystals doped with Pr3+, Sm3+, and Er3+ ion, which were grown by the Czochralski method, was studied. By investigating the PL for incident radiation with wavelength of 325 nm (He–Cd Laser), the energy levels of the PL centers were found: The PL levels in the Pr doped single crystal are 3Po and 1D2, that in the Sm-doped one is 4G5/2, and those in the Er doped one are 2H11/2, 4S3/2, and 4F9/2. In conclusion, the characteristics of these single crystals are governed solely by those of the rare-earth dopants, not by the lead tungstate. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1436295
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  • 6
    Electronic Resource
    Electronic Resource
    Corrugated quantum well infrared photodetectors for material characterization (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 1612-1623 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, we discuss the utilities of corrugated quantum well infrared photodetectors (C-QWIPs) in detector material characterization. By measuring the detector responsivity as a function of corrugation period, several important detector parameters, such as the absorption coefficient α of parallel propagating light and the energy resolved photoconductive gain g, can be directly deduced. For the QWIP material presented, α at the peak was found to be 0.21 μm−1 under the usual operating condition. This value of α corresponds to an absorption length of 4.8 μm. Instead of being a constant, the value of g also varies significantly across the excitation spectrum, and the peak value is larger than the noise gain at large bias. Our results show that the present characterization technique is capable of providing accurate and detailed information on the intrinsic properties of QWIP materials under actual operating conditions. It is extremely useful in detector optimization. In addition, we also show the characteristics of C-QWIPs with an additional vertical trench at the center of each corrugation to gain more insights into the distribution of light intensity in a C-QWIP structure. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373862
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  • 7
    Electronic Resource
    Electronic Resource
    Detection wavelength of InGaAs/AlGaAs quantum wells and superlattices (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 551-564 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InGaAs/AlGaAs quantum well structures have been shown to be versatile for infrared detection. By changing the material composition, one can tune the detection wavelength from 2 to 35 μm and beyond. However, there have been few systematic calculations on the absorption wavelength of these structures with respect to their structural parameters. In this work we have adopted the transfer-matrix method to calculate both their energy levels and the wave functions. From this calculation, the absorption and the responsivity spectra of the structures can be predicted. The theory agrees with the experimental result of the test structures. Supported by the experimental evidence, we applied the calculation to a general class of midwavelength detectors and thus established a useful guideline for the detector design in this wavelength range. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1421216
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of copper on the microstructure and electromigration lifetime of Ti–AlCu–Ti fine lines in the presence of tungsten diffusion barriers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4952-4959 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A systematic study was performed of the microstructural and electromigration characteristics of Ti–Al(Cu)–Ti laminate structures fabricated from two metal wiring levels 1 μm in width. The total Cu content in the Al(Cu) core layers was varied from 0.5 to 2.0 wt %. A high degree of 〈111〉 texture was found for all Cu concentrations except for the 0.5 wt % film. Grain size statistics were found to be independent of the Cu concentration. The Al grains were supersaturated with Cu which led to shifts in resistance during low temperature baking and electromigration testing. The electromigration lifetime of stripes connected to large reservoirs of Cu and Al was found to be linearly dependent on the total Cu content, whereas there was a "roll off'' in the lifetime of two-level W stud structures as the Cu content was increased. The activation energy for electromigration induced failure was found to be 0.78–0.93 eV. Resistance shifts during electromigration and temperature only stressing and the microstructural characteristics of failed structures were explained in terms of the distribution of Cu in the Al matrix and the geometry of the structures using a blocking boundary model. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363539
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  • 9
    Electronic Resource
    Electronic Resource
    Reduction of photoconductive gain in quantum well infrared photodetectors (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1257-1259 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work, we show that there is a reduction of photoconductive gain g in quantum well infrared photodetectors from its classical value. The reduction is caused by the quantum nature of electron transport in these structures. On the other hand, the generation-recombination noise is unaffected by the transport model, and remains to be the same as a classical photoconductor. The reduction of g leads to an apparent noise increase in these structures, i.e., the noise gain deduced from the noise measurement is larger than g deduced from the photoconductivity measurements. We compared the present theory with existing experimental data, and found reasonable agreement. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362868
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  • 10
    Electronic Resource
    Electronic Resource
    Long-wavelength λc=18 μm infrared hot-electron transistor (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4731-4736 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A long-wavelength λc=18 μm infrared hot-electron transistor (IHET) with low dark current is demonstrated. In order to achieve long-wavelength absorption, a low barrier height is required, which in turn results in a large dark current. Therefore, operation of a normal long-wavelength quantum-well infrared photodetector (QWIP) structure is limited to very low temperatures and biases due to the thermally activated dark current. In the IHET, a high-energy pass filter placed after 30 periods of GaAs/AlGaAs quantum wells blocks the temperature-activated dark current while allowing high-energy photoexcited electrons to pass and be collected as photocurrent. A comparison of the dark current to the 300 K background photocurrent shows that the QWIP structure without the high-energy pass filter demonstrates background-limited infrared photodetection (BLIP) only at T≤35 K. Furthermore, in order to avoid saturating a typical readout circuit, detector operation of the QWIP is restricted to biases less than 0.08 V at 35 K. In contrast, the filtered dark current in the IHET is reduced by two to four orders of magnitude such that BLIP performance can be achieved for temperatures up to T=55 K without saturating the readout circuit. Because of the preferential current filtering effect, the noise equivalent temperature difference of the IHET can be improved by a factor of 100 at T=55 K. The dark-current-limited detectivity was found to be D*=1×1010 cm Hz1/2/W at λp=15 μm, Ve=−0.2 V, and T=55 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355927
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