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  • 1
    Electronic Resource
    Electronic Resource
    Thermal stability of W ohmic contacts to n-type GaN (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 278-281 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: W was found to produce low specific contact resistance (ρc∼8.0×10−5 Ω cm2) ohmic contacts to n+-GaN (n=1.5×1019 cm−3) with limited reaction between the metal and semiconductor up to 1000 °C. The formation of the β–W2N and W–N interfacial phases were deemed responsible for the electrical integrity observed at these annealing temperatures. No Ga out-diffusion was observed on the surface of thin (500 A(ring)) W contacts even after 1000 °C, 1 min anneals. Thus, W appears to be a stable contact to n+-GaN for high temperature applications. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362816
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  • 2
    Electronic Resource
    Electronic Resource
    Infrared absorption of Ge epitaxial films on a GaAs substrate (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7157-7160 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Germanium films were deposited on GaAs (100) substrates with or without an epiready surface oxide at temperatures between room temperature (RT) and 500 °C using an ultrahigh-vacuum e-beam deposition system. The film at 100 °C on a substrate with a surface oxide had a flat absorption curve over the wave-number range investigated, 500–4000 cm−1, with an absorption of less than 10/cm at 1000 cm−1 (10 μm wavelength). Films deposited at RT and 50 °C on substrates with a surface oxide had comparable low absorption, but they contained an absorption peak at 830 cm−1 associated with the Ge—O bonds. Although all three films were amorphous, the films deposited at the lower temperatures were more porous. This enabled oxygen to percolate in from the atmosphere to form the Ge—O bonds. The films deposited at 150 °C and above on substrates with a surface oxide and at 100 °C with the surface oxide removed thermally in situ prior to deposition the Ge films, and the single crystal films deposited at 400 and 500 °C on oxide-free substrates, had strong absorption in the vicinity of the Ge/GaAs interface with the characteristic of two-dimensional free-carrier absorption. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361486
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  • 3
    Electronic Resource
    Electronic Resource
    A surface modification study of InGaP etched with an electron cyclotron resonance source at variable microwave powers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3286-3289 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Etch-induced surface modifications, utilizing an electron cyclotron resonance source, have been studied as a function of controllable etch parameters. InGaP was etched with BCl3 at a constant substrate temperature (100 °C) and bias voltage (−145 V) using microwave powers varying between 250 and 1000 W. The surface morphology, residual etch damage, and surface stoichiometry were strongly influenced by changes in ion flux. The etch-induced lattice damage and surface smoothness increased as the ion energy was elevated. Low ion flux etching resulted in an In-enriched P-depleted surface suggesting nonuniform desorption of InClx which gave rise to the surface roughness observed at the low microwave powers. The smooth surfaces, achieved at the higher microwave power levels, were attributed to either efficient sputter-assisted desorption of the InClx etch products or to InClx desorption via plasma-induced surface heating. Results of this study demonstrate that etching at microwave powers between 500 and 750 W induce low residual damage and smooth surfaces while maintaining a reasonable etch rate for device processing. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361227
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  • 4
    Electronic Resource
    Electronic Resource
    Shallow ohmic contact to both n- and p-GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 754-756 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A shallow Pd/Ge/Ti/Pt/ohmic contact for both n- and p-GaAs has been investigated. The contacts were rapid thermally annealed in N2 for 15 s at temperatures from 350 to 550 °C. The lowest average specific contact resistances were 4.7×10−7 and 6.4×10−7 Ω cm2 for the n- and p-GaAs, respectively, when the n-GaAs was doped with Si to 2×1018 cm−3 and the p-GaAs was doped with carbon to 5×1019 cm−3. Electrical measurements and Auger depth profiles showed that the contacts were stable as they remained ohmic after an anneal at 300 °C for 20 h for both n- and p-GaAs. The p contact is more stable than the n contact at the higher temperatures where there is more As outdiffusion as determined by Auger depth profiles. Transmission electron microscopy showed that the interfaces between the p-GaAs and the contacts were smooth for both as-grown and annealed samples, and no oxides were detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355248
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  • 5
    Electronic Resource
    Electronic Resource
    A materials study of PtTiGePd ohmic contacts to p+-AlGaAs as a function of annealing temperature (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5225-5230 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Elemental diffusion, interfacial microstructure, and phase composition of Pt/Ti/Ge/Pd ohmic contacts to heavily C-doped Al0.26Ga0.74As were investigated at several annealing temperatures. Results of the material analyses were used to explain the previously determined specific contact resistances measured for each thermal treatment. Evidence of interdiffusion and compound formation between AlGaAs and Pd were visible in a Ga rich Pd-Ga-As reaction zone prior to heat treatment. This phase is critical for the formation of Ga vacancies, which upon heating are occupied by in-diffusing Ge. However, as the annealing temperatures are raised to 530 °C and above, As preferentially out diffuses. The As out diffusion, which is critical to the formation of good p-type ohmic contacts by creating vacancies that the amphoteric Ge can occupy, contributed to the creation and development of the two phase TiAs/Pd12Ga2Ge5 interfacial region overlying the AlGaAs substrate. In response to the enhanced As out diffusion at 600 °C, the interfacial region reached completion, that is, it became laterally continuous and compositionally uniform, and the specific contact resistance achieved its minimum value. At higher annealing temperatures ∼650 °C, the electrical measurements degraded in response to intensive chemical diffusion which resulted in the development of a broad, nonuniform multiphased interfacial region, and the Pt contacting layer ceased to be a homogeneous layer with a smooth surface. The As interfacial compounds form at higher temperatures in AlGaAs than in GaAs suggesting that As is more strongly bonded in the AlGaAs. This contributes to the greater temperature stability of the contacts to AlGaAs. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359272
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of PdGeTiPt and NiGeAu ohmic contacts to n-GaAs and PdGeTiPt and TiPd contacts to p+-GaAs (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 1723-1729 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: NiGeAu and PdGeTiPt ohmic contacts to n-GaAs and TiPd and PdGeTiPt ohmic contacts to p+-GaAs are examined by comparing their contact resistances, chemical intermixing as determined by Auger electron microscopy, interface structure as determined by transmission electron microscopy, and surface roughness as determined by surface profiling all measured as a function of annealing time and temperature. The n-PdGeTiPt contact annealed for short times, ≤15 s, and at low temperatures, ≤395 °C, was superior to the NiGeAu contact because it had a comparable contact resistance, less interface mixing, better lateral homogeneity, and a smoother surface. However, its contact resistance increased substantially with the annealing time and temperature, whereas the NiGeAu contact was relatively unaffected. For all annealing times and temperatures except the one at 550 °C, the TiPd contact to p+ GaAs was superior as it had a lower contact resistance and a comparable amount of interface intermixing, lateral homogeneity, and surface roughness. However, it had a complete chemical breakdown at 550 °C, whereas the PdGeTiPt contact resistance remained relatively stable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365973
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of annealing conditions on heavily carbon-doped InGaAs (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2578-2580 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two heavily carbon doped InGaAs samples (2.20×1019 and 1.92×1019 cm−3) with low In mol fractions (1% and 8%) were annealed with or without silicon nitride caps in H2 containing 0.3% AsH3 over the temperature range 5000–800 °C. Hall effect, secondary ion mass spectroscopy, double crystal x-ray diffraction, and integrated photoluminescence measurements showed that H outdiffuses over the annealing temperature range when the films were capped with silicon nitride. However, there was almost no net H outdiffusion for uncapped samples annealed in the same ambient and temperature range. Recombination centers formed during high temperature anneals in samples with less In (1%), but did not appear to form as readily in the one with more In (8%).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109302
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  • 8
    Electronic Resource
    Electronic Resource
    Annealing effects on heavily carbon-doped GaAs (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 87-89 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The hole concentrations and lattice mismatch with the GaAs substrate of heavily carbon-doped epilayers (4.7×1019 and 9.8×1019 cm−3) were increased and the mobilities were decreased as compared with the as-grown samples by rapid thermal annealing silicon nitride capped samples at temperatures from 500 to 900 °C. However, for the more heavily doped sample, the hole concentration, mobility, and lattice mismatch decreased with increasing annealing temperature for annealing temperatures higher than 700 °C, but the hole concentration and lattice mismatch were still larger than those of the as-grown samples. Secondary ion mass spectroscopy results showed that annealing produced no change in the C concentration or distribution, but the hydrogen concentration decreased. Cross-sectional transmission electron microscopy indicated that no mismatch dislocations formed at the interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107622
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  • 9
    Electronic Resource
    Electronic Resource
    PdGeTiPt Ohmic contacts to p+-AlxGa1−xAs (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 273-275 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ohmic contacts to heavily C-doped AlGaAs were made using PdGeTiPt that had specific contact resistances Rc, as low as 1.7×10−6 Ω cm2 when annealed at 600 °C. The less heavily doped samples annealed at temperatures between 350 and 500 °C were non-Ohmic, and Rc decreased with increasing annealing temperature between 500 and 600 °C. For the more heavily doped samples, Rc decreased with increasing annealing temperature. Rc increased for all samples at annealing temperatures above 600 °C. Rc rose quickly by 102 when the samples were reannealed at 300 °C for 20 h, but remained unchanged with further reannealing for up to 100 h. This behavior is consistent with partial compensation generated by the rapid out-diffusion of Ga at low annealing temperatures and the subsequent in-diffusion of Ge into the Ga vacancies left behind. The lower Rc obtained with the 600 °C anneal can be explained by an increased As out-diffusion and the subsequent in-diffusion of Ge into the As vacancies at the higher annealing temperatures. Interfacial reactions and elemental diffusion of the contacts investigated via transmission electron microscopy and elemental depth profiles obtained by Auger electron spectroscopy are also consistent with this mode. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114780
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