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  • 1
    Electronic Resource
    Electronic Resource
    Growth and characterization of GaSe and GaAs/GaSe on As-passivated Si(111) substrates (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 7211-7222 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have grown and characterized epitaxial layered structure GaSe on As-passivated Si(111) and GaAs on GaSe on As-passivated Si(111) for the ultimate purpose of using the layered structure GaSe as a lattice mismatch/thermal expansion mismatch buffer layer in the GaAs on Si system. Films were grown on nominally (111) oriented Si substrates by molecular beam epitaxy and characterized by in situ reflection high energy electron diffraction, as well as by ex situ scanning electron microscopy and both plan-view and cross-sectional TEM (transmission electron microscopy). In this study, GaSe was grown epitaxially on As-passivated Si(111) substrates at 500 °C with Se/Ga BEP (beam equivalent pressure) ratios of ∼10 and ∼20. Small droplets were observed on the surface after GaSe growth. These are thought to be droplets of unreacted Ga. The density and size of the droplets decreases with the increasing Se/Ga BEP ratio. When the GaSe surface is exposed to As, the droplets become GaAs islands. Subsequent GaAs growth was carried out at 400 and 500 °C, giving the following results for 300-A(ring)-thick films: as grown GaAs films were highly twinned, and some polycrystalline GaAs was present in the film grown at 400 °C. In situ annealing at 650 °C for 10 min reduced the density of twins in both cases. In plan-view TEM, Moiré fringes from both GaAs and GaSe are observed and show conclusively that the GaAs grew epitaxially on the GaSe without contacting the Si substrate. Cross-sectional TEM shows the interface between the Si and GaSe is not smooth on the atomic scale. In spite of this, the GaSe becomes smooth with about 2 monolayers of growth and the GaAs/GaSe interface appears to be very smooth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355038
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  • 2
    Electronic Resource
    Electronic Resource
    In situ observation of the initial growth stages in GaAs/InAs by coaxial impact collision ion scattering spectroscopy: Transition from two-dimensional-like to three-dimensional island growth (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3802-3805 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The initial growth stages of the highly lattice-mismatched GaAs/InAs system was studied by coaxial impact collision ion scattering spectroscopy (CAICISS). The GaAs coverage on the InAs substrate during GaAs molecular beam epitaxial growth was monitored in situ by low incident angle CAICISS. The scattering intensity as a function of the deposited amount of GaAs can be divided into three characteristic regions. First, the scattering intensity from In decreases proportionally with the amount of deposited GaAs molecules. However, the intensity decrease stops abruptly before the surface is completely covered with a GaAs layer, and remains constant. Then, the intensity gradually decreases. This result shows that there exist three kinds of growth stages in the process of GaAs deposition on an InAs substrate. The mechanism of the growth mode transition, corresponding to the three kinds of growth stages is discussed from the viewpoint of a strain energy change on the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350893
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  • 3
    Electronic Resource
    Electronic Resource
    Dynamics of GaAs surfaces exposed to argon and hydrogen electron-cyclotron-resonance plasmas observed by real-time optical reflection spectroscopy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5987-5994 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamics of the interaction of electron-cyclotron-resonance (ECR) plasmas with the surface of GaAs substrates are studied by real-time optical reflection spectroscopy. Analysis with a three-phase ambient/overlayer/substrate model yields information on the time-dependent composition of the near-surface region, such as the thickness, degree of amorphization, and oxide and void fraction in the overlayer. Using this technique, it is observed that the thickness of the damaged layer formed by the impact of energetic ions increases linearly with the ion energy during argon ECR sputter etching. Furthermore, the dynamics of a cleaning process with a hydrogen ECR plasma have been studied. At temperatures between 300 and 500 °C this cleaning can be characterized by a two-step process. During the first few seconds of exposure, the oxide layer is removed; in the second step, the GaAs is etched gently, which leads to a surface region with little damage to the crystal. At lower temperatures, cleaning is not successful and a thick damaged overlayer is formed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359182
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  • 4
    Electronic Resource
    Electronic Resource
    In situ observations of As atoms at step sites of vicinal Si(100) surfaces by coaxial impact-collision ion scattering spectroscopy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1592-1597 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In situ observations of As atoms at step sites of vicinal Si (100) surfaces have been performed by coaxial impact-collision ion scattering spectroscopy. It is found that some As atoms remain at Si step sites even at a high substrate temperature of 780 °C under an As residual pressure, in spite of evaporation of As atoms from terrace sites. This result indicates that As atoms at step sites are energetically more stable than the As dimers on the terrace. Moreover, the angular profiles of the scattering intensity from As atoms at step sites suggest that there is atomic displacement of As atoms towards the Si substrate at the step sites. An atomic model of the As/Si system is proposed from the results of computer simulation for the scattering intensity profiles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357738
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  • 5
    Electronic Resource
    Electronic Resource
    Self-field ac losses in biaxially aligned Y–Ba–Cu–O tape conductors (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2695-2697 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Self-field ac losses were measured by the conventional ac four-probe method in biaxially aligned Y–Ba–Cu–O tapes using polycrystalline Hastelloy tapes with textured yttria-stabilized-zirconia buffer layers. The ac losses increased in proportion to the fourth power of transport current in the high Jc sample, and agreed well with Norris' equation for thin strip conductors. However, the low Jc sample had rather higher losses than Norris' prediction, suggesting excessive magnetic flux penetration caused by percolated current paths. The results confirmed Norris' prediction of the low ac losses for thin strip conductors, and indicated the importance of removing percolated structures of current paths to avoid higher ac losses than the theoretical predictions based on uniform conductors. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120180
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of hydrogenated amorphous silicon by capacitance-voltage and surface photovoltage measurements using liquid Schottky barriers (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 1916-1927 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental studies have been made on the electrical properties of hydrogenated amorphous silicon (a-Si:H) using liquid Schottky barriers. We have found that the quasi-static capacitance-voltage (C-V) method can be applied to the a-Si:H/quinone-hydroquinone (Q-HQ) liquid Schottky junction. This method enables us to determine the net density of positive space charge due to ionized traps and impurities in a-Si:H (Ne), the built-in potential (Vb), and the width of the surface space-charge layer (W), of this liquid junction. The barrier height of an undoped a-Si:H/Q-HQ junction has been estimated to be more than 1 eV from the value of Vb thus obtained. By C-V and surface photovoltage (SPV) measurements on the same samples, we have studied the changes in the properties of a-Si:H with doping and with prolonged illumination. It has been found that phosphorous (P) doping drastically decreases the hole diffusion length measured by the SPV method and increases the value of Ne. Slight boron (B) doping increases the ambipolar diffusion length L1 and the field assisted carrier collection length L2, both of which have been determined by SPV. These results explain the observed enhancement of the photovoltaic properties of a-Si:H p-i-n solar cells with the slight B doping to the i layers. The values of L1 and L2 have a distinct correlation with the photo-voltaic properties in the slightly B-doped samples, which has confirmed the effectiveness of the SPV method in characterizing a-Si:H as a photovoltaic material. We have found that the increase in Ne and the decrease in L1 occur simultaneously in undoped a-Si:H with prolonged illumination. On the other hand, the increase in Ne does not always accompany the decrease in L1 in the photoinduced changes in P-doped or slightly B-doped a-Si:H, which suggests the difference in the mechanism of the changes between undoped and doped samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338038
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  • 7
    Electronic Resource
    Electronic Resource
    Temperature-dependent dry cleaning characteristics of GaAs (111)B surfaces with a hydrogen electron cyclotron resonance plasma (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2870-2872 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The cleaning of the GaAs (111)B surface with a hydrogen electron cyclotron resonance discharge plasma is investigated at temperatures between 200 and 500 °C and compared with the GaAs (100) surface. It is found that during the exposure the GaAs (111)B is etched in a non-Arrhenius way with a higher etch rate at low temperatures. For temperatures 300–500 °C, the surface is severely roughened after exposure, while the (100) surface remains smooth in all cases. The near-surface crystalline quality of GaAs (111)B remains higher than that of (100).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113457
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  • 8
    Electronic Resource
    Electronic Resource
    In situ monitoring of electron cyclotron resonance plasma processing of GaAs surfaces by optical reflection spectroscopy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2661-2663 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In situ reflection spectroscopy is demonstrated to be a useful technique for monitoring the damage to the surface of GaAs substrates induced by ions from an electron cyclotron plasma. Distinct differences in the reflectance spectra of GaAs substrates are observed between etching by argon ions and chemical cleaning by hydrogen ions. For argon it is found that the damage layer thickness increases linearly with the argon ion energy. Hydrogen ions induce a damage layer of 3.1 nm and arsenic atoms are preferentially removed from the surface as the ion energy increased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111484
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  • 9
    Electronic Resource
    Electronic Resource
    Real-time investigations of GaAs surface cleaning with a hydrogen electron cyclotron resonance plasma by optical reflection spectroscopy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 3117-3119 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The composition changes during GaAs oxide removal and the subsequent cleaning with a hydrogen electron cyclotron resonance plasma have been investigated with real-time optical reflection spectroscopy. It is found that the oxide is not completely removed at low temperatures, resulting in a thick damaged surface region. At moderate temperatures (300–500 °C) the plasma exposure is characterized by a two-step process: a removal of the native oxide in a few seconds followed by a gentle etch of the GaAs. In the latter step the plasma exposure leads to a surface region with little damage to the crystal. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112454
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  • 10
    Electronic Resource
    Electronic Resource
    Stability of CdSe and ZnSe dots self-organized on semiconductor surfaces (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 3886-3888 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Several monolayers (ML) of CdSe were deposited on (001) GaAs surfaces to study the stability of the CdSe films. The CdSe film with the 2 ML thickness showed atomically flat surfaces just after the growth. However, in three days after the growth, self-organization into dots at room temperature was clearly observed. This unexpected self-organization of dots observed at room temperature from the once coherently-grown CdSe film will be closely correlated to the enhancement of the heterointerface diffusion observed in this combination of CdSe and GaAs. This correlation between the stability of the dots and the heterointerface diffusion was examined in the common cation case of ZnSe/ZnS, which is known to show low interface diffusion. Self-organization of ZnSe dots was observed with an atomic force microscope on (001) ZnS surfaces. The ZnSe dots were stable as expected and did not show instability such as observed for the CdSe dots on GaAs or on ZnSe. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120534
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