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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of GaAs layers grown by low temperature molecular beam epitaxy using ion beam techniques (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2850-2856 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stoichiometry, crystallinity, defect concentration, and the excess As lattice location in GaAs layers grown by molecular beam epitaxy at low growth temperatures (≤300 °C) were studied using ion beam techniques. The excess As concentration in the layers was measured by particle induced x-ray emission and was found to increase as the growth temperature was lowered. Excess As concentrations up to 1.5 at. % were measured in layers grown at 190 °C. After annealing at temperatures higher than 400 °C under As overpressure, the excess As atoms coalesce to form As precipitates as revealed by transmission electron microscopy. Ion channeling on the unannealed layers grown at 200 °C revealed that they have good crystalline quality with a large fraction of the excess As atoms sitting at interstitial sites close to the normal As sites in the lattice. The rest of the excess As atoms are believed to be in an AsGa antisite position.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351538
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  • 2
    Electronic Resource
    Electronic Resource
    Lattice location of diffused Zn atoms in GaAs and InP single crystals (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2998-3006 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the saturation phenomenon of the free carrier concentration in p-type GaAs and InP single crystals doped by zinc diffusion. The free hole saturation occurs at 1020 cm−3 for GaAs, but the maximum concentration for InP appears at mid 1018 cm−3. The difference in the saturation hole concentrations for these materials is investigated by studying the incorporation and the lattice location of the impurity zinc, an acceptor when located on a group III atom site. Zinc is diffused into the III-V wafers in a sealed quartz ampoule. Particle-induced x-ray emission with ion-channeling techniques are employed to determine the exact lattice location of the zinc atoms. We have found that over 90% of all zinc atoms occupy Ga sites in the diffused GaAs samples, while for the InP case, the zinc substitutionality is dependent on the cooling rate of the sample after high-temperature diffusion. For the slowly cooled sample, a large fraction (∼90%) of the zinc atoms form random precipitates of Zn3P2 and elemental Zn. However, when rapidly cooled only 60% of the zinc forms such precipitates while the rest occupies specific sites in the InP. We analyze our results in terms of the amphoteric native defect model. We show that the difference in the electrical activity of the Zn atoms in GaAs and InP is a consequence of the different location of the Fermi level stabilization energy in these two materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348613
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of coimplantation on the electrical activity of implanted carbon in GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 7118-7123 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of radiation damage and stoichiometry on the electrical activity of carbon implanted in GaAs are studied. Damage due to implantation of an ion heavier than C increases the number of C atoms which substitute for As (CAs). Creation of an amorphous layer by implantation and the subsequent solid phase epitaxy during annealing further enhances the concentration of CAs. However, the free carrier concentration does not increase linearly with increasing concentration of CAs due to compensating defects. Activation of implanted C is maximized by maintaining the stoichiometry of the substrate which reduces the number of compensating defects in the crystal. Under optimum conditions for carbon implanted at a dose of 5×1014 cm−2, the carbon acceptor activity can be increased from 2% to 65% of the total implanted carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355027
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of rapid quenching on the impurity site location in Zn-diffused InP (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 86-90 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The lattice locations of Zn atoms in heavily Zn-doped InP single crystal have been investigated by ion channeling techniques. The InP samples were rapidly quenched in diffusion pump oil after high-temperature Zn diffusion. Ion channeling experiments performed along various major crystal axes suggest that a large fraction (20%–30%) of the Zn atoms are in the tetrahedral interstitial position in the InP lattice. It has been found that although the maximum hole concentration is not significantly affected by the cooling rate, there is a substantial increase in the incorporation of Zn on substitutional and tetrahedral interstitial lattice locations in the rapidly cooled samples as compared to the slowly cooled samples. The consequences of these results for understanding the mechanisms leading to the saturation of the free-hole concentration in compound semiconductors are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355202
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  • 5
    Electronic Resource
    Electronic Resource
    Amphoteric behavior and precipitation of Ge dopants in InP (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4907-4915 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have directly correlated the electrical behavior, the impurity lattice site location, ion damage, and the local bonding environments of Ge-dopant ions implanted into InP. We have found that after rapid thermal annealing the free electron concentration in the samples implanted at room temperature (RT) are always higher than those implanted at liquid nitrogen temperature (LNT). Although the macroscopic structure seems to be insensitive to the implantation temperature, significantly more local disorder is created in the LNT implanted amorphous layers. Moreover, the amphoteric bonding structure of the Ge atoms is found to be well established already in the as-implanted amorphous InP. After high temperature annealing ((approximately-greater-than)800 °C), the Ge atoms rearrange locally with more of the Ge substituting the In site than the P site resulting in n-type conductivity. The solid solubility of Ge in the InP is measured to be ∼1.4–1.6×1020/cm3 while the free electron concentration is estimated to saturate at ∼3.4×1019/cm3. The relatively low electron concentration can be explained by Ge precipitation and the compensation of GeIn donors by GeP acceptors in the RT implanted case. The further reduction in electron concentration in the LNT implanted samples is believed to be related to the high residual damage found in these samples. The high solubility of Ge in InP can be attributed to the availability of two possible sublattice sites for the dopant and the compensation of the local strains due to the amphoteric substitution of the Ge. The concentration ratio of the GeIn to GeP determined in the heavily implanted material has been used to estimate the difference in the formation energy of Ge substituting those two different sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363533
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  • 6
    Electronic Resource
    Electronic Resource
    Electrical activation and local structure of Se atoms in ion-implanted indium phosphide (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8445-8450 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The solid phase regrowth, dopant activation, and local environments of Se-implanted InP are investigated with ion-beam techniques and extended x-ray-absorption fine structure spectroscopy. We find that the local Se–In structure is already established in the as-implanted amorphous InP although the Se atoms have a lower average coordination number (∼3.5) and no long-range order. After high-temperature rapid thermal annealing (950 °C, 5 s), the amorphous InP regrows, becoming a single crystal with the Se atoms bonded to four In neighbors; however, only ∼50% of the Se becomes electrically active. Part of the Se precipitates in the form of an In–Se phase, another part is compensated by defects which are not totally removed by annealing. The Se—In bond distance for a Se on a P site is 4.5% longer than the matrix In—P bond length, introducing large strains in the crystal. The solid solubility of Se in InP is estimated from our results to be ≈8.7×1019/cm3 while the electron concentration saturates at 5.4×1019/cm3. Se atoms in InP regrown at lower temperatures in a furnace are only ∼7% electrically active and are found to have different local environments (higher coordination number and shorter bond distance) than those in the InP perfectly regrown at higher temperature. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362519
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  • 7
    Electronic Resource
    Electronic Resource
    High dose Cl implantation in ZnSe: Impurity incorporation and radiation damage (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1378-1383 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural characteristics of ZnSe thin films grown by organometallic vapor phase epitaxy and implanted heavily with Cl ions (5×1015 and 1×1016/cm2) were investigated using ion beam techniques, x-ray diffraction, and Raman spectroscopy. We have found that although the as-implanted ZnSe layers were severely damaged, no amorphous layer was formed with an implant dose as high as 1×1016 Cl ions/cm2. Crystalline damage in the ZnSe layers was not fully removed even after annealing at 700 °C for 10 s. Ion channeling reveals that after annealing over 50% of the Cl atoms sit substitutionally in the lattice and they are preferentially located in the Se site. However, a significant fraction of the substitutional Cl are found to be slightly displaced from the normal Se sites. The projected displacement was found to be ≈0.2 A(ring). Electrical measurements and Raman spectroscopy results suggest that a large concentration of Zn vacancies (VZn) are present in the annealed samples. We believe that the Cl displacement and the low conductivity in these samples are due to the formation of (ClSe−VZn) complexes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356417
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  • 8
    Electronic Resource
    Electronic Resource
    The effects of x-ray induced structural changes on the microstructure of a-Si after thermal crystallization (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2032-2034 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the effects of intense x-ray irradiation on the local relaxation in amorphous silicon films doped with Ge(a-Si:Ge) and subsequently the crystallization behavior of these films. The Ge–Si bond distance in the as-grown a-Si:Ge is slightly longer (∼0.004 Å) than for the crystalline case (2.378 Å). When the a-Si:Ge film was exposed to synchrotron x rays, the Ge–Si bond distance increased to a value closer to the sum of the covalent radii of Si and Ge (2.39 Å). This x-ray-induced bond length dilation is found to be x-ray dose dependent and is strongest in the sample irradiated with x rays for 20 h (corresponding to a dose of ∼1 photon/Si atom). The x-ray-induced bond dilation in the a-Si:Ge directly affects the crystallization of the films after irradiation. We found that the final grain size of the annealed Si crystal depends on the initial Ge–Si bond length in the amorphous film. The larger the RGe–Si (due to x-ray irradiation) the larger is the Si grain size after thermal annealing. The mechanism leading to the lattice relaxation in the amorphous phase and subsequently the crystal grain size after annealing due to x-ray irradiation will be discussed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124906
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  • 9
    Electronic Resource
    Electronic Resource
    Zinc and phosphorus co-implantation in indium phosphide (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 52-54 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electrical activation and dopant diffusion in Zn-implanted InP after rapid thermal annealing have been investigated. For an as-implanted Zn concentration of ∼4×1019 cm−3, only ∼7% of the implanted Zn atoms formed electrically active shallow acceptors following a 950 °C/5 s annealing cycle. The low activation was the result of rapid Zn out-diffusion—only ∼14% of the implanted dopant was retained after annealing. A significant enhancement in electrical activation and a reduction in Zn loss were achieved in Zn+P co-implanted samples which yielded a net hole concentration of ≤6×1018 cm−3 and 〉50% Zn retention. The saturation of the free hole concentration in Zn+P co-implanted samples was attributed to the formation of Zn interstitial donors and Group-V-related donor-type native defects. For comparison, Zn+Al and Zn+Al+P co-implanted samples were also examined to distinguish the relative influences of implantation-induced disorder and nonstoichiometry on electrical activation and dopant diffusion. For the given implant conditions, we found that nonstoichiometry was the dominant influence. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121720
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  • 10
    Electronic Resource
    Electronic Resource
    Ion channeling investigation of the lattice location of Sn atoms in GaAs thin films grown by molecular beam epitaxy (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1784-1786 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the lattice location of Sn atoms in Sn-doped GaAs thin films grown by molecular beam epitaxy using ion channeling techniques. Accumulation of ≈2×1014 atoms/cm2 of Sn on the GaAs surface was detected. These surface Sn atoms were determined to be randomly distributed within ≈20 A(ring) of the surface of the GaAs. Angular scans of the Ga Kα, As Kβ, and Sn L x rays across the 〈100〉, 〈110〉, and 〈111〉 axial channels indicated that the Sn atoms in the GaAs layer are mostly substitutional. No displacement of the Sn atoms larger than 0.14 A(ring) from the substitutional sites was detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103099
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