摘要:

The diffusion of Sb in Si at concentrations around its solid solubility has been studied by isoconcentration experiments. The samples, grown by molecular-beam epitaxy, had constant Sb121background dopings and a Sb123spike embedded in this background. The diffusion was followed as a function of Sb background concentration at two different temperatures of 872 and 1019 °C by secondary ion mass spectrometry, differential Hall/resistivity measurements, and transmission electron microscopy. At concentrations exceeding the solid solubility Sb precipitates and interstitial-type dislocation loops were observed. At these concentrations the diffusivity decreased with increasing Sb background concentration. At concentrations below both the solid solubility and the intrinsic carrier concentration, for the highest diffusion temperature of 1019 °C, the diffusivity increases with increasing Sb background doping. This behavior is discussed considering mobile Sb2V complexes. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364286

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have shown that doping InGaAs/GaAs quantum well materials with 1019Si/cm3causes a time and temperature dependent diffusion process, which can be correlated with group III vacancy formation. This process can be modeled and shown to accurately fit other data in the literature. Samples with silicon doping concentrations below this value have no enhanced interdiffusion, in contradiction to the results of the Fermi level model. These results are shown to be comparable to data for AlGaAs/GaAs interdiffusion with doping concentrations between 5×1017cm−3and 1018cm−3. We have shown that the position of the Fermi level plays no role in III–V intermixing. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364270

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A series of InGaAs films, compressively or tensilely strained, were grown on (001)InP substrates at 490 °C by gas source molecular beam epitaxy. Compressively strained (−0.5&percent;) (and lattice matched) layers were morphologically stable, but layers grown under tension (+0.5 to +0.6&percent; strain) developed facets on (113)Aor (114)Aplanes. In the first stages of growth of films under tension, and throughout all stages of growth for the compressively strained films, a fine scale (10 nm wavelength) composition modulation was found in the [110] direction. In the later stages of growth of films under tension, the regions of composition segregation were confined to the peaks and valleys of the faceted surface. Regions of high and low stress concentration (the valleys and the peaks) exhibit In/Ga ratios higher or lower, respectively, than the flat faceted surfaces. The elastic strain energy built into the film, associated with the [110] composition modulation, depends on the ratio of the modulation wavelength to film thickness. In films grown under tension, facet coarsening provides a means for the system to reduce the strain energy associated with segregation. Faceting (and facet coarsening) leads to a reduction in the misfit strain energy stored in the film. However, an analysis of the first stages of faceting shows that faceting cannot be explained as a roughening transition. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364271

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have grown high-quality GaN films on sapphire using a new nitrogen precursor, hydrazoic acid (HN3). Films were grown at 600 °C on (0001) sapphire substrates in a low-pressure chemical-vapor-deposition system using triethylgallium and hydrazoic acid as precursors. Subsequently, we have conducted a complete study of the surface, structural, electrical, and optical properties of these GaN films, and our early results are very encouraging. All films were of wurtzite crystal structure, slightly polycrystalline, andntype at about 2×1017cm−3. We find the films to be efficient light emitters in the near-band edge region of the spectrum. Analysis of the emission energies and kinetics suggests that the midgap emission results from a superimposed deep-donor-to-shallow-acceptor emission and a deep-donor-to-valence-band emission, where the deep donor consists of a distribution of energy levels, thereby yielding a broad emission band. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364253

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The damage produced by implanting, at room temperature, 3-&mgr;m-thick relaxed Si1−xGexalloys of high crystalline quality with 2 MeV Si+ions has been studied as a function of Ge content (x=0.04, 0.13, 0.24, or 0.36) and Si dose in the dose range 1010–2×1015cm−2. The accumulation of damage with increasing dose has been investigated by Rutherford backscattering spectrometry, optical reflectivity depth profiling, and transmission electron microscopy. An enhanced level of damage, and a strong decrease in the critical dose for the formation of a buried amorphous layer in Si1−xGexis observed with increasingx. Electron paramagnetic resonance studies show that the dominant defects produced by the implantation are Si and Ge dangling bonds in amorphouslike zones of structure similar toa-Si1−xGexfilms of the samex, and that the effect of increasing the ion dose is primarily to increase the volume fraction of material present in this form until a continuous amorphous layer is formed. A comparative study of the optically determined damage in the alloys with the use of a damage model indicates a significant increase in the primary production of amorphous nuclei in the alloys of Ge contentx>0.04. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364288

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We studied two-step tungsten-silicidation processes, which consist of low-energy W implantation followed by high-energy Xe irradiation. The formation of silicides was studied by Rutherford backscattering spectroscopy, x-ray diffraction and transmission electron microscopy. The formed silicide layer is richer in Si than that formed by thermal annealing. The transformation from the hexagonal to tetragonal (usually formed by thermal annealing above 600 °C)WSi2phase occurred and a tetragonalWSi2layer was successfully formed by 1-MeVXe+and 5-MeVXe++ion irradiation at under irradiation temperatures of 410 and 450 °C. The transformation did not occur by 0.5-MeVXe+ions at the same substrate temperature. The tetragonal phase was also observed after irradiation by 1-MeVXe+at 250 °C. The phase transformation rate normalized to the nuclear energy deposition densityEnincreases with the electronic energy deposition densityEe.This fact indicates that the phase transformation is enhanced by the inelastic electronic scattering of high-energy ion irradiation. The irradiation temperature dependence of the phase transformation was also studied. The mechanism of the silicidation by elastic nuclear scattering and that of the phase transformation by inelastic electronic scattering of high-energy heavy-ion-beam irradiation are qualitatively discussed. ©1997 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.364272

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

W1−xSix/Simultilayers (MLs) (x⩽0.66) were deposited onto oxidized Si substrates, heat treated by rapid thermal (RTA) and standard furnace annealing up to 1000 °C for 30 s and 25 min, respectively, and analyzed by various x-ray techniques and Rutherford backscattering spectrometry.W1−xSix/SiMLs are more stable the higher the value ofxbecause the driving force for interdiffusion is suppressed by the doping; the temperature for complete interdiffusion increases from 500 to 850 °C asxincreases from 0 to 0.66. The as-deposited MLs were amorphous. Their thermal stability increases with increasingx. The interface roughness is independent ofxbut increases with increasing RTA temperature. The reflectivity ofW1−xSix/SiMLs is lower than that of W/Si because of lower optical contrast. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364273

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The dependence of the exciton linewidth broadening due to scattering by free carriers on carrier concentration, temperature, and well width, in semiconducting quantum well structures is theoretically studied using a finite confining potential model. The contribution to the linewidth due to ionization scattering of the exciton to the continuum electron-hole states, is included in the present calculations, which is shown to further enhance the importance of free carrier scattering in the broadening of the exciton linewidth. Quasi 3 dimensional features in the very narrow wells due to the finite confinement are also presented and discussed. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364274

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The interplay between single electron tunneling effects and the discrete molecular levels ofC60molecules is studied using scanning tunneling microscopy. IsolatedC60molecules were deposited onto a gold substrate, covered by a thin insulating layer. The tunneling current–voltage characteristics of isolated molecules, both at room temperature and at 4.2 K, exhibit rich structures, resulting from the interplay between charging effects and the electronic spectrum. In particular, we observe degeneracy lifting within theC60molecular orbitals, probably due to the Jahn–Teller effect and local electric fields. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364275

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The intrinsic carrier concentrations, Fermi energies, and the electron effective masses are calculated for Hg1−xZnxTe with 0<x⩽0.4 and 50 K⩽T⩽400 K. The numerical calculations are based on the Kanek⋅pmodel and no further analytical simplification or approximation is made for the energy band structure beyond those inherent in the Kane model. The results are compared to the previous calculations. ©1997 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.364289

出版商:AIP    

年代:1997

数据来源: AIP