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  • 1995-1999  (6)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Correlation of substitutional hydrogen to refractive index profiles in annealed proton-exchanged Z- and X-cut LiNbO3 (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2697-2708 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Previous disagreements concerning a linear correlation between the hydrogen (H) concentration and the extraordinary refractive index ne in proton-exchanged lithium niobate (LiNbO3) have been resolved by partitioning the total H into optically active substitutional H and optically inactive interstitial H. The H and Li spatial variations in both Z- and X-cut crystals were determined by secondary-ion-mass spectrometry (SIMS) with a quantitative evaluation in atoms/cm3. These samples were proton exchanged in neat benzoic acid at 185 °C and then were annealed at 400 °C for times t from 6 to 240 min in wet flowing oxygen. For the Z-cut crystals, fit of the SIMS measured H profiles by expressions obtained from the diffusion equation for diffusion from a finite layer gave a substitutional H diffusivity of DZs=5.0±0.3×10−12 cm2/s and an interstitial H diffusivity of DZi=1.4±0.1×10−11 cm2/s. The wet flowing oxygen acts as a constant source of interstitial H at the surface with the diffusivity DZi and gives an integrated H concentration due to the flowing wet oxygen which increases as (square root of)t. The Li diffusivity was DLiZ=4.8±0.2×10−12 cm2/s which is nearly equal to DZs. For X-cut crystals, the substitutional H diffusivity was DXs=3.4±0.2×10−12 cm2/s and the interstitial diffusivity was DXi=1.3±0.2×10−11 cm2/s. The ne profiles were evaluated by means of optical prism-coupling measurements and numerical simulations. In both cases of crystal orientation, the effective index diffusivity is nearly equal to the diffusivity of substitutional H. Furthermore, there is an excellent linear relationship between the ne profile and the corresponding substitutional H distribution. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358738
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Optical transitions in Pr-implanted GaN (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 790-792 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence (PL) spectroscopy has been used to investigate praseodymium (Pr) related transitions in Pr-implanted GaN. Wurtzite GaN epilayers were grown by metalorganic chemical vapor deposition on sapphire substrates and subsequently ion implanted with Pr to a dose of 5.7×1013/cm2. The implanted samples were annealed in nitrogen to facilitate recovery from implantation related damage. Narrow PL emission bands related to 4f intrashell transitions of the trivalent Pr ion were observed near 650, 950, 1100, and 1300 nm. The dependence of PL emission on sample temperature, excitation intensity, oxygen incorporation, and annealing temperature was systematically studied. We find that the PL efficiency increases exponentially with annealing temperature up to the maximum temperature of 1050 °C applied in the current study. Furthermore, the PL emission shows no evidence of significant thermal quenching over the sample temperature range of 10–300 K. This thermal stability will have particular advantages for applications in high temperature optoelectronic devices. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124514
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal stability of implanted dopants in GaN (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2238-2240 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results are reported of measurements of depth profiles and stability against redistribution with annealing up to 800 or 900 °C, for implanted Be, C, Mg, Si, S, Zn, Ge, and Se as dopants in GaN. The results confirm the high-temperature stability of dopants in this material up to temperatures that vary from 600 to 900 °C. S redistributes for temperatures above 600 °C, and Zn and Se, for temperatures above 800 °C. All of the other elements are stable to 900 °C. These results indicate that direct implantation of dopants rather than masked diffusion will probably be necessary to define selective area doping of III–V nitride device structures based on these results for GaN. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113178
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  • 4
    Electronic Resource
    Electronic Resource
    Er doping of AlN during growth by metalorganic molecular beam epitaxy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2083-2085 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The doping of AlN during growth by metalorganic molecular beam epitaxy with an Er effusion source has resulted in AlN:Er films exhibiting strong room-temperature 1.54 μm photoluminescence (PL). The luminescence detected in the AlN:Er grown during this study was orders of magnitude greater in intensity than that from ion-implanted samples and represents the first demonstration of strong emission from rare-earth doped, epitaxial group III nitrides. Secondary ion mass spectroscopy was used to verify a dynamic range for this doping technique of 3×1017–2×1021 Er cm−3 with varying effusion cell temperature. The effects of growth temperature on Er incorporation and segregation behavior were also determined. PL studies, including room-temperature and thermal quenching experiments, were conducted. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116887
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  • 5
    Electronic Resource
    Electronic Resource
    Dominance of tunneling current and band filling in InGaN/AlGaN double heterostructure blue light-emitting diodes (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 2867-2869 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurement of the room temperature forward bias current-voltage behavior of InGaN/AlGaN double heterostructure blue light-emitting diodes demonstrates a significant departure from the usual Is exp(qV/ nkT) behavior where n is the ideality factor which varies between 1 and 2. The observed current-voltage behavior at room temperature may be represented as I=2.7×10−11 exp(5.7V) which suggests a tunneling mechanism. Measurement of the electroluminescence for currents from 0.5 to 100 mA demonstrates that the emission peak shifts to higher energy while increasing in intensity. The shifting peak spectra is due to band filling, a process which results from the injection of holes via tunneling into an empty acceptor impurity band and vacant valence band tails. At currents near 100 mA, a non-shifting band-to-band emission approaches the intensity of the shifting peak spectra. The active layer of these diodes is codoped with both the donor Si and the acceptor Zn. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116351
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal stability of hydrogen in LiAlO2 and LiGaO2 (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3848-3850 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogen as 2H has been incorporated into LiAlO2 and LiGaO2 by both ion implantation and by exposure to a plasma at 250 °C. In the implanted samples, approximately 50% of the hydrogen is lost from the surface during annealing at 500 °C for 20 min, and essentially all is gone by 700 °C. This hydrogen retention is considerably less than for other materials that are being used as substrates for III-nitride epilayer growth, such as SiC and sapphire. The indiffusion of 2H from a plasma is much faster for LiAlO2 with an apparent diffusivity at 250 °C of ∼10−13 cm−2 s−1, approximately two orders of magnitude larger than for LiGaO2. Hydrogen outdiffusion from LiAlO2 or LiGaO2 substrates during III-nitride epitaxy should not be a significant problem; the hydrogen should have left these materials at temperatures less than epitaxial layer growth temperatures. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117125
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