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The broadening and the decrease of the superconducting transition temperature observed in high resistivity films of granular aluminum is analyzed in terms of a critical fluctuation model. Detailed grain size measurements indicate that the enhanced transition temperature observed in lower resistivity films is due to changes in the electron-phonon coupling rather than to an excitonic mechanism.

The secondary electron emission flux in a scanning electron microscope is a powerful tool for delineation of electrically active dopant concentration, built-in potentials, and surface electric fields in semiconductor junctions. In all the secondary electron images of p-n junctions, the p-doped regions appear brighter than n-doped regions. We present a theory for the doping contrast in p-n junctions that is based on the secondary electron emission yield and surface band bending extracted from Kelvin probe force microscopy measurements. We show that the contrast is governed by the secondary electron escape depth, and their escape probability which is related to the secondary electron energy distribution and the effective electron affinity. It is found that the escape depth is the main factor determining the dopant contrast, and the escape probability has a smaller effect. In addition, our theory explains the logarithmic dependence of the measured contrast on the acceptor concentration in silicon reported by many groups.

The effect of the dislocation line density produced by the relaxation of strain in GaAs/In x Ga 1Ϫx As multiquantum wells where xϭ0.155-0.23 has been studied. There is a strong correlation between the dark line density, observed by cathodoluminescence, before processing of the wafers into photodiode devices, and the subsequent low forward bias ͑Ͻ1.5 V͒ dark current densities of the devices. A comparison is made of the correlation between the reverse bias current density and dark line density and it is found that, in this range of strain, the forward bias current density varies more. Two growth methods, molecular beam epitaxy and metal organic vapor phase epitaxy, have been used to produce the wafers and no difference between the growth methods has been found in dark line or current density variations with strain.