Two frequently observed problems with Schottky diodes are soft current–voltage characteristics and low avalanche breakdown voltages. These problems are sometimes found immediately upon fabrication, or they may develop during use. It is proposed that these phenomena can be explained by the existence of a thin layer (25–250 Å thick) between the metal and semiconductor which (i) has a high charge density, (ii) has a high trap density, and (iii) is conducting. Observed barrier height changes are explained by the trapping of charge carriers flowing through the layer and the lowered avalanche breakdown voltage by heating of carriers in the high field in the intervening layer. These explanations have been confirmed by measurements on GaP and GaAs diodes having a deliberately grown thin interfacial oxide ∠100 Å thick. Such an interfacial layer can be detected using a pulsed current–voltage technique described in the paper.

The etch rate of silicon in solutions of various compositions selected from the system HF , HNO3 , H2O , and HC2H3O2 has been investigated over the temperature range 0° to 50 °C. The activation energy of the etching process has been found to be different in the different composition regions. In the high HNO3 region values of about 4 kcal/mole have been observed and interpreted as characteristic of a diffusion governed reaction. In compositions containing H2O or HC2H3O2 diluents the activation energy increases, and two values are found. In the high HF region two values are also observed, one in the range of 10–14 kcal/mole, and the other in the range of about 20 kcal/mole. The significance of the various values of the activation energy is discussed.

High-resolution spectrometry of charged particles from inertial-confinement-fusion ͑ICF͒ experiments has become an important method of studying plasma conditions in laser-compressed capsules. In experiments at the 60-beam OMEGA laser facility ͓T. R. Boehly et al., Opt. Commun. 133, 495 ͑1997͔͒, utilizing capsules with D 2 , D 3 He, DT, or DTH fuel in a shell of plastic, glass, or D 2 ice, we now routinely make spectral measurements of primary fusion products ͑p, D, T, 3 He, ␣͒, secondary fusion products ͑p͒, ''knock-on'' particles ͑p, D, T͒ elastically scattered by primary neutrons, and ions from the shell. Use is made of several types of spectrometers that rely on detection and identification of particles with CR-39 nuclear track detectors in conjunction with magnets and/or special ranging filters. CR-39 is especially useful because of its insensitivity to electromagnetic noise and its ability to distinguish the types and energies of individual particles, as illustrated here by detailed calibrations of its response to 0.1-13.8 MeV protons from a Van de Graaff accelerator and to p, D, T, and ␣ from ICF experiments at OMEGA. A description of the spectrometers is accompanied by illustrations of their operating principles using data from OMEGA. Sample results and discussions illustrate the relationship of secondary-proton and knock-on spectra to capsule fuel and shell areal densities and radial compression ratios; the relationship of different primary fusion products to each other and to ion temperatures; the relationship of deviations from spherical symmetry in particle yields and energies to capsule structure; the acceleration of fusion products and the spectra of ions from the shell due to external fields; and other important physical characteristics of the laser-compressed capsules.