摘要:

Low‐temperature anneals (500–650 °C) of 2, 4, and 8×1015cm−2As+implanted in ⟨100⟩ silicon at 50 keV were studied by x‐ray double crystal diffraction. The rocking curves were analyzed by a kinematical model. Two regions of strain were found in the solid‐phase epitaxially regrown layer. One layer was uniform and positively strained. The other was nonuniform and negatively strained. By comparing rocking curves of repeatedly etched layers it was found that the surface layer is negatively strained, corresponding largely to the substitutional As in the regrown layer. The positively strained region lies at the interface between the implanted layer and the undamaged silicon substrate.

ISSN:0021-8979    

DOI:10.1063/1.335638

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The columnar morphologies commonly found in all vapor‐deposited thin films prepared under low mobility conditions have been classified by several variations of what have been termed structure zone models. Such morphological structures are found to have a strong similarity in shape and form over six orders of magnitude in film thickness and three orders of magnitude in magnification for films of a given thickness. Thick (45‐mm) pyrolytic graphite films are shown to be a good demonstration of the continuous growth evolution of conical‐shaped units. Due to competition for growth each cone eventually goes through a death stage. A model based upon these general structural observations is presented and is shown to be a geometric construction similar to a Sierpinski gasket. The origin of this morphology seems to be the natural clustering which occurs due to the random process of ballistic aggregation.

ISSN:0021-8979    

DOI:10.1063/1.335639

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The growth kinetics and surface morphology of erbium silicide formation from Er layers on Si(100) substrates are examined using both faste‐beam annealing and furnace annealing. Very smooth erbium silicide layers have been grown using a line‐sourceebeam to heat and react the Er overlayers with the substrate. This contrasts to the severe pitting observed when Er layers are reacted with Si in conventional furnace annealing. The pitting phenomenon can be explained by a thin contaminant layer at the interface between Er and Si. Our results suggest the contamination barrier is not due to oxygen, as usually assumed, but may be related to the presence of carbon. Rapide‐beam heating to reaction temperatures of ∼1200 K permits dispersion of the barrier layer before substantial silicide growth can occur, allowing smooth silicide growth. Heating to shorter times to just disperse the interface barrier allows uniform layer growth by subsequent furnace annealing and has permitted measurement of the kinetics of erbium silicide formation on crystalline Si. The reaction obeys (time)1/2kinetics but is shown to be not totally diffusion limited by the ability to sustain multiple interface growth from a single Si source. The growth rates are nearly an order of magnitude slower for the Er/Si(100) interface than for the Er/amorphous‐Si, but with a similar activation energy near 1.75 eV in both cases.

ISSN:0021-8979    

DOI:10.1063/1.335640

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Evolution of Au‐GaAs (001) interface structures with increasing Au exposure was studied. This study utilized photoelectron spectroscopy, electron diffraction, and He‐ion Rutherford backscattering spectrometry. This was accomplished with the aid of molecular‐beam epitaxy for surface preparation. The thermal stability of Au‐GaAs (001) interfaces are presented in the following paper [N. Watanabe, K. L. I. Kobayashi, T. Narusawa, and H. Nakashima, J. Appl. Phys.58, 3766 (1985)]. New phenomena were observed on overlayer growth, electronic structure change, and Schottky barrier formation. The present results apparently differ from previous Au‐GaAs (110) system results; however, they support the surface defect model for Schottky barrier formation by W. E. Spicer, I. Lindau, P. Skeath, C. Y. Su, and P. Chye [Phys. Rev. Lett.44, 420 (1980)].

ISSN:0021-8979    

DOI:10.1063/1.336290

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Au/GaAs (001) interface reactions due to annealing have been studied using the XPS, RHEED, SEM, RBS, EPMA, and AES methods. The samples were prepared by Au deposition on MBE‐grown GaAs (001)‐c(4×4) surfaces at room temperature. The Au films were epitaxially grown twin crystals, about 50 A˚ thick. Two phenomena were observed: Au shrinkage and erosion of GaAs by Au. The Au shrinkage occurs in the early stage of annealing. Rectangular or connected rectangular GaAs surfaces are exposed due to Au shrinkage. The sides of these rectangular surfaces are parallel to the GaAs ⟨110⟩ and ⟨1¯10⟩ directions. The higher the annealing temperatures, the greater the Au shrinkage and erosion of GaAs by Au. For the sample annealed at 450 °C for 3 h, Au‐Ga alloy agglomerates formed on the GaAs (001) and GaAs (111) B surface. The one‐dimensional disordered structure was observed by RHEED for the sample annealed at 305 °C for 14 h. The Au crystal quality is improved by annealing at temperatures above 100 °C.

ISSN:0021-8979    

DOI:10.1063/1.335641

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Three types of oxygen precipitate morphologies at 1050 °C have been identified to be plate‐type, pyramidal, and polyhedral. This study was carried out using a set of slices with the same initial oxygen concentration but varying carbon concentrations. The morphology is shown to depend on carbon concentration and heat treatment. It is demonstrated that increasing carbon concentration tends to change the morphology from the plate to polyhedra and enhance the nucleation rate at low temperatures.

ISSN:0021-8979    

DOI:10.1063/1.335590

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Neutron activation measurements of arsenic concentration have been made on a set of samples cut from melt‐grown crystals of Si:As in the concentration range from 7.8×1018cm−3to 1.1×1019cm−3. Measurements of electrical resistivity at room temperature on the same samples provide information for a calibration curve of resistivity &rgr; versus the donor concentrationnD. The data are combined with earlier measurements of &rgr; andnDmade by Backenstoss using radioactive tracer techniques at lower As concentration to yield a calibration curve covering the donor concentration range from 1.0×1018cm−3to 1.1×1019cm−3. A fourth‐order polynomial expression for the function &rgr; vsnDis compared with data derived from Hall constant determinations of donor concentration. Using the expression relating the Hall constant to the electron density,RH=A(nD)/ne, we are able to obtain values of the functionA(nD) for arsenic concentrations in the range 3.0×1018cm−3to 8.6×1018cm−3. These values for Si:As are compared to theA(nD) values for Si:P.

ISSN:0021-8979    

DOI:10.1063/1.335591

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The vacuum metalorganic‐chemical‐vapor‐deposition (Vacuum MOCVD) process was combined with two source purifications to growp‐GaAs epitaxial films of high quality. Theoretical modeling of quantum yield spectra measured on a specially configuredn+‐psample determined the minority‐carrier electron diffusion length to be 10 &mgr;m to within a factor of 2 in theplayer. Thepdoping was reduced to the 5×1017cm−3level to avoid suppression of the diffusion length by Auger recombination. Multiple vacuum sublimations of dicyclopentadienyl magnesium (CP2Mg), the source of Mg forpdoping, reduced the contamination by air and by cyclopentadiene (CP) by an order of magnitude. A dry ice/acetone cold trap was operated at slightly below 180‐Torr pressure to reduce the water vapor content of arsine, used as the As source, from the hundreds of ppm down level down to the 2 ppm range. The vacuum growth process reduced residual gas contamination. These techniques were combined to grow aponnGaAs solar cell with an efficiency of 24% at air mass 1.5 (AM1.5).

ISSN:0021-8979    

DOI:10.1063/1.335592

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Perturbation expansions of the effective electrical conductivity &sgr;eof any two‐phase isotropic composite medium of arbitrary dimensionalityd(whered=2,3) are derived. It is shown that certain Pade´ approximants of a particular series representation of &sgr;eyield known rigorous bounds on the conductivity of the composite. The relationships between the conductivities of certain models that are exactly realized by some of these bounds and the perturbation expansions are discussed. A new expression for the conductivity of a broad class of three‐dimensional dispersions of inclusions is derived. The formula for &sgr;e, which depends upon, among other quantities, a certain three‐point probability function of the composite medium, is shown to accurately predict &sgr;eof both periodic and random arrays of impenetrable spheres, for a wide range of phase conductivities and inclusion volume fractions.

ISSN:0021-8979    

DOI:10.1063/1.335593

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Surface photovoltage (SPV) in hydrogenated amorphous silicon (a‐Si:H) has been measured as a function of temperature and wavelength, intensity and chopping frequency of light. Effects of surface treatments on SPV, including etching and exposure to moisture, are also studied. It is concluded that SPV cannot be directly related to the band bending at the surface ofa‐Si:H. By solving Poisson’s equation in dark and light, it is shown that in a material such asa‐Si:H, the observation of a finite SPV necessarily implies a transfer of charge between the surface states and the space‐charge region. This explains our experimental observations since it means that SPV measurement may not be relied upon to give the surface potential ofa‐Si:H. Notwithstanding this handicap, it is shown that by measuring SPV and conductance on ana‐Si:H sample subjected to cycles of moisture and light soaking, we can conclude that light soaking affects the surface as well as the bulk ofa‐Si:H.

ISSN:0021-8979    

DOI:10.1063/1.335594

出版商:AIP    

年代:1985

数据来源: AIP