[en] This relates to compound type semiconductor materials that exhibit self-compensated n-type conductivity. The process described imparts p-type conductivity to a body of normally n-conductivity self-compensated compound semiconductor material by bombarding it with charged particles, either electrons, protons or ions. Other possible steps include introducing an acceptor impurity and applying a coating onto the crystal body. This technique will allow new semiconductor structures to be made. For example, there are some compound semiconductor materials that exhibit n-conductivity only that have energy gap widths that would permit electrical to light conversion at frequency and colours not readily achieved in semiconductor devices. (U.K.)

No abstract available

[en] A model is presented which relates the observed effects of substrate temperature and growth flux magnitudes upon layer quality to the presence of volatile oxides and the thermodynamics of the formation of nonvolatile oxides on the growth surface. A means for reducing oxide contamination is presented and the consequent benefits explored

[en] We present the first direct measurement of proton energy-loss straggling in Ga/sub 1-x/Al/sub x/As/GaAs, enabling us to take maximum advantage of the ²⁷Al (p, γ) ²⁸Si nuclear reactions as a powerful nondestructive technique for measuring Al profiles in these structures. Results were obtained using samples produced by molecular beam epitaxy and fabricated to have step-function Al concentration distributions to prescribed depths. The exact straggling width was obtained by a least-square comparison of the experimental spectra with curves calculated using a parameterized straggling distribution. With these results, profiling measurements can now be made giving the Al concentration fall-off at the GaAl/GaAs interface with a spatial depth resolution of about 4% and epilayer thickness determinations to about 2%. We have also observed in one sample a nonabrupt transition at the GaAlAs/GaAs interface, due to differences in substrate surface preparation procedures prior to growth of the GaAlAs layer

[en] A conformal antireflective coating of WO₃ on a textured tungsten surface is found to significantly increase the optical absorptance of the surface over a broad selected band of wavelengths. The coating enhances the selectivity of solar absorbing surfaces on dendritic tungsten and increases the solar absorptance of such surfaces. The average solar absorptance measured at air mass 2 was increased from 0.95 to 0.985 for large dendrite surfaces and from 0.76 to 0.90 for small dendrite surfaces. Emittance values for the anodized surfaces at 300 ⁰C range from 0.18 for the small dendrites to 0.5 for the larger dendrites. The WO₃ conformal coating, produced by anodization of the tungsten, forms an antireflective coating with a minimum at a wavelength between 0.43 and 0.8 μ for anodization voltages between 20 and 40 V, respectively. Total reflectances as low as 0.00025 have been measured

[en] We report on the fabrication and characterization of planar superconductor-normal-superconductor (SNS) weak links in which the normal region is deposited n-InAs. The InAs is part of a heterostructure consisting of 100 nm of n-InAs grown on an undoped GaAs buffer layer on a semi-insulating GaAs substrate. The superconductor is Nb, patterned by electron beam lithography with interelectrode spacings as small as 260 nm. Device behavior is well explained by SNS weak link theory, with coherence lengths calculated from measured material parameters. These heterostructure weak links can be the basis for superconducting field-effect devices. They have the significant advantage of allowing simple device isolation compared with bulk InAs, which has been used in previous attempts to make such devices

[en] The defect structure of lattice-mismatched 1-μm In/sub x/Ga/sub 1-//sub x/As (x≅0.12, misfit Δa/a≅8.5 x 10^-3) epilayers on GaAs was studied with scanning cathodoluminescence (CL), transmission electron microscopy (TEM), high-voltage electron microscopy, and scanning electron microscopy. CL shows that nonradiative recombination lines exist in the GaAs buffer layer as far as 4000 A from the interface. The density of these defects is independent of substrate dislocation density. Plan-view TEM analysis indicates that the majority of these dislocations in the buffer layer are sessile edge half-loops. Cross-sectional TEM shows that loops also extend into the InGaAs epilayer, but the majority of the loops are located on the buffer layer (substrate) side of the interface. A model is proposed to explain sessile edge dislocation formation in the buffer layer. A comparison of CL and high-voltage electron microscopy images from the same interface area reveals that the dark nonradiative recombination lines seen in scanning luminescence images in this high misfit system do not correspond to the normal, isolated misfit dislocation. The nonradiative recombination line spacing is 3 μm, whereas the interface dislocation spacing is 400--1000 A. It is shown that the nonradiative recombination lines observed in CL of the interface correspond to specific groups of dislocations with different TEM contrast behavior. The dark nonradiative recombination lines also correlate with asymmetric surface ridges, suggesting that they introduce preferred nucleation sites, and that these effects are different for the two <110> directions

[en] For thin (Ga_1-xIn_x)As films on GaAs (100) substrates the authors have measured the phonon frequencies (Raman technique) and the strains (x-ray rocking curve technique). The films range from perfect epitaxial (the thinner films) to those that have relaxed by different amounts (thicker films). Using the measured strains and the phonon deformation constants, the strain-induced frequency shift was calculated for each sample. From the measurements and calculation, they find that the frequency shifts due to strain give equivalent bulk phonon frequencies that are in good agreement with each other. This indicates that the Raman technique can be used for in-situ monitoring of the growth process

[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 have eliminated interface defects from the mismatched In/sub 0.05/Ga/sub 0.95/As/ (001)GaAs interface by controlling the size of the growth area. 2-μm-high pillars with different lateral shapes and dimensions were defined within the GaAs substrate before the molecular beam epitaxial growth of 3500 A of In/sub 0.05/Ga/sub 0.95/As, greater than four times the critical thickness. On the pillars, the linear density of misfit dislocations was reduced from >5000 dislocations/cm for large (several hundred μm lateral dimensions) growth areas to nearly zero for 25 μm lateral dimensions. The dislocation density remains less than 800 dislocations/cm for lateral dimensions up to 100 μm. We find that there is also a decrease in dislocation density in narrow channels between the pillars; therefore, the pillars also block the glide of misfit dislocations