[en] Arsenic or phosphorus doped polycrystalline-Si (poly-Si) acts as a diffusion source when deposited on GaAs. Non-Fickian Si diffusion into GaAs has been observed following heat treatments above 700⁰C. In this paper, the diffusion of In and P from poly-Si at temperatures between 800 and 1020⁰C is presented. These impurities, introduced into the poly-Si by in-situ plasma deposition, implantation or vapor annealing, diffuse rapidly into the GaAs. Results from particle induced x-ray analysis, transmission electron microscopy, Rutherford backscattering and secondary ion mass spectroscopy indicate 80% substitutional In and P at interface concentrations of approximately 10 and 25 at %, respectively

[en] The dislocation densities, surface morphology, and strain of Ga/sub 1-//sub x/In/sub x/As/GaAs epitaxial interfaces as a function of indium composition and layer thickness have been investigated by transmission electron microscopy, medium energy ion blocking, and double-crystal x-ray diffractometry. The electron microscopy shows that in the thinnest dislocated films (90 and 160 nm, x = 0.07) 60⁰ α dislocations form first in one <110> direction at the interface. Surprisingly, however, an asymmetry in residual layer strain is not detected in these samples, suggesting that the dislocations have the same Burgers vector or are evenly distributed between two Burgers vectors. Orthogonal arrays of dislocations are observed in films thicker than 300 nm (60⁰ and edge-type, x = 0.07). In this case, dislocation densities in each <110> direction are equal to within experimental error while an asymmetry in in-plane strain is measured (18% and 30% for x = 0.07, 300, and 580 nm thick, respectively). An unequal distribution of Burgers vectors of 60⁰ or edge-type dislocations is considered responsible for the strain asymmetry in these thicker samples

[en] Heavily doped Si:Ga has been prepared by liquid phase epitaxy (LPE) and by ion-implantation with rapid thermal annealing (RTA) or laser annealing (LA). Peak substitutional Ga concentrations obtained by each technique were 1.5, 2.5 and 2.9 x 10²⁰ cm^-3, respectively. Substitutional fractions (> 90%) were similar in the three types of substitutional Ga atom in Si of +0.9 ± 0.1 x 10^-24 cm³/atom was measured by double crystal x-ray diffraction. The average nearest neighbor Si-Ga bond length measured with extended x-ray absorption fine structure (EXAFS) was 0.237 ± 0.004 nm, indistinguishable, to within experimental error, from the intrinsic Si-Si bond length, 0.235 nm, indistinguishable, to within experimental error, from the intrinsic Si-Si bond length, 0.235 nm. Combining these two results the lattice strain per hole in the Si valence band was calculated, +0.4 ± 0.8 x 10^-24 cm³. This result complements the lattice contraction per electron in the Si conduction band (-1.8 ± 0.4 x 10^-24 cm³) already reported for Si:As. 15 refs., 4 figs., 1 tab

[en] The historic abundance of salmonids returning to natal streams of the inland Pacific Northwest, USA, may have constituted a major nutrient influx into these commonly oligotrophic ecosystems. Inland ecosystems tend to be warmer and dryer and more nutrient limited than coastal ecosystems; therefore, understanding how these inland conditions influence the soil biogeochemical responses to salmon carcass deposition in riparian forests is a vital step in appropriately mitigating for the loss of this nutrient subsidy. Deposition of salmon carcasses in central Idaho riparian forests resulted in a 480-fold increase in soil nitrogen (N), a sevenfold increase in dissolved organic carbon (C), and a fourfold increase in soil respired CO₂, with significant biogeochemical responses persisting at one year after amendment. Despite these large increases in soil N and C, estimates of soil N and C loading only accounted for 31% and 16% of the fish carcass N and C, respectively. However, the magnitude and persistence of soil biogeochemical responses to the deposition of anadromous fish carcasses in central Idaho attests to the importance of this nutrient subsidy to inland riparian ecosystems of the Pacific Northwest. (author)

[en] Mismatched InGaAs-GaAs epitaxial layers were grown by molecular beam epitaxy (MBE) on substrates containing 9800 or <100 dislocations/cm/sup 2/. Cathodoluminescence (CL), transmission electron microscopy (TEM), Rutherford backscattering spectroscopy (RBS), and energy dispersive x-ray analysis (EDX) were used to analyze the effect of mismatch and substrate dislocation density on interface morphology. Surface ridges in scanning electron microscopy (SEM) images were found to correlate with areas of high recombination in CL. The spacing of dark recombination lines seen in CL was found to be an order of magnitude larger than the spacing of misfit dislocations seen in TEM. CL/TEM correlation reveals that some areas of the misfit array act more strongly as recombination centers than others. CL of step etched samples show that interface defects propagate into the GaAs buffer layer to depths of 4000 A below the interface. The substrate dislocation density does not have a major effect on the number or spacing of the dark recombination lines

[en] We investigated strain relaxation in (001) InGaAs/GaAs structures using both double and triple axis high resolution x-ray diffraction techniques. We determined that broadening which is observed in double axis scans stems primarily from mosaic spread and not from lattice constant variations in the layer, demonstrating that relaxation is uniform along the growth direction. These observations held for layers with both low and high medium content and extents of relaxation. Triple axis measurements showed that the peak broadening was due exclusively to mosaic spread for the low medium content samples and also confirmed earlier double axis measurements that a crystallographic tilt of the epitaxial layer was attributed to substrate miscut. The ability to distinguish the source of peak broadening and crystallographic tilts makes triple axis diffraction a powerful characterization technique for the study of mismatched epitaxial layers. 18 refs., 3 figs., 1 tab

[en] We have grown modulation-doped In_0.53Ga_0.47As/In_0.52Al_0.48As heterostructures on GaAs substrates using compositionally step-graded In_xGa_1-xAs buffers. Triple-axis x-ray diffraction measurements indicate nearly complete and isotropic strain relaxation in the buffer, lattice matching of the active layers with the top of the buffer, and no significant epilayer tilt. The temperature dependence and the photoresponse of the electron mobility suggest that transport in the heterostructures is limited principally by remote ionized-impurity scattering, with mobility values comparable to those of heterostructures grown lattice-matched to InP. copyright 1996 American Vacuum Society

[en] NiFe/Cu multilayers were grown sequentially by pulsed electrodeposition on copper (Cu) substrates. The layers were prepared in galvanostatic mode using a dual bath technique. The morphology, thickness, roughness and composition of the layers were studied using scanning electron microscopy, scanning transmission electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction and atomic force microscopy. Analysis showed that the resulting multilayers were continuous layers with a root mean square roughness of 30 nm and a grain size of 20-60 nm. The Cu substrate and the electrodeposited Cu layer were preferentially (200) oriented while the NiFe layers were polycrystalline but with a preferred (200) texture. The thinnest multilayers produced were 20/40, NiFe/Cu, respectively. - Research Highlights: → Thin MLs of Cu and Py can be ED utilizing a pulsed-galvanostatic, DBT. → The resulting multilayers were continuous layers with an rms of 30 nm. → The smallest average thickness achieved by DBT was 40 nm/20 nm for Cu/NiFe.

[en] The effect of dilute N alloying and Bi surfactant growth on strain relaxation in highly strained InGaAs single quantum well (QWs) was investigated by using high resolution X-ray diffraction and transmission electron microscopy. Dilute nitride In_xGa_1-xAs_0.99N_0.01 QWs of varying thickness, constant lattice mismatch 1.7%, were grown by molecular beam epitaxy on oriented GaAs (001) substrates. Some samples were exposed to a flux of Bi surfactant during the growth procedure, which acts to enhance the N incorporation, increase the optical emission, and create smoother interfaces. The QWs were observed to relax through the formation of pure edge-type, misfit dislocations aligned with in-plane left angle 100 right angle directions. These were found to be directly associated with degradation in the optical emission, however, 1% N addition, with or without Bi surfactant, did not have a detectable effect on the critical thickness nor the rate of this relaxation mechanism. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] The structural and magnetic properties of NiMnSb films, 5-120 nm thick, grown on InGaAs/InP(001) substrates by molecular-beam epitaxy, were studied by x-ray diffraction, transmission electron microscopy (TEM), and ferromagnetic resonance (FMR) techniques. X-ray diffraction and TEM studies show that the NiMnSb films had the expected half-Heusler structure, and films up to 120 nm were pseudomorphically strained at the interface, greater than the critical thickness for this system, about 70 nm (0.6% mismatch to InP). No interfacial misfit dislocations were detected up to 85 nm, however, relaxation in the surface regions of films thicker than 40 nm was evident in x-ray reciprocal space maps. TEM investigations show that bulk, planar defects are present beginning in the thinnest film (10 nm). Their density remains constant but they gradually increase in size with increasing film thickness. By 40 nm these defects have overlapped to form a quasicontinuous network aligned closely with <100> in-plane directions. The associated strain fields and or compositional ordering from these defects introduced a reduction in crystal symmetry that influenced the magnetic properties. The in-plane and perpendicular FMR anisotropies are not well described by bulk and interface contributions. In thick films, the in-plane uniaxial and fourfold anisotropies increased with increasing film thickness. The lattice defects resulted in a large extrinsic magnetic damping caused by two-magnon scattering, an increase in the coersive field with increasing film thickness, and a lower magnetic moment (3.6 Bohr magnetons) compared to the expected value for the bulk crystals (4 Bohr magnetons)