High-frequency small-signal capacitances of semiconductor junction vs temperature, from the initial conditions of filled and emptied traps in the junction depletion region, are used to determine the trap concentration and the thermal activation energies of trapped electrons and holes. Illustrations are given for silicon N + P diodes doped with gold impurity or irradiated with 1-MeV electrons, showing the room-temperature annealing for the latter.
The liquid-crystal-adaptive lens (LCAL) is an electro-optical device that utilizes a graded index of refraction to bring light to focus. A set of electrodes controls the index variation in a liquid-crystal thin film. One can vary the focal length of the LCAL by changing the voltages applied to the device. The discrete nature of the electrodes causes phase aberrations. We introduce a novel electrode architecture, called conductive ladder meshing (CLM), that we developed to greatly reduce the static phase aberration (caused by the electrode structure). To reduce the dynamic phase aberration (associated with inaccurate voltages), we used a simulated-annealing voltage-dithering technique. The coherent transfer function of the LCAL was derived so that the performance of the CLM LCAL could be predicted theoretically. Theoretical analysis indicates that the CLM LCAL scatters less than 30% of incident light compared with scattering of 65% in the previous version. The focal-spot performance of the spherical LCAL was measured under coherent illumination for plane-wave illumination. Because of the improved quality of the spherical LCAL, true imaging experiments are demonstrated for a single incoming polarization under white-light illumination. Images formed by the spherical LCAL are comparable with those formed by a fixed lens in terms of resolution, although the contrast is worse.
A linear 500×1 charge-coupled device (CCD) surface channel imager is thinned to less than 30 μm, with the thinned back surface accumulated to reduce the surface recombination velocity. Photoresponsivity is measured to be 90 mA/W of incident wide-band power from a 2854-K blackbody light source. This sensitivity is a factor of 3 higher than previously reported values. Spectral responsivity reaches a peak of 90% quantum efficiency at 7000-Å wavelength, and over 50% quantum efficiency for the spectral range from 5000 to 9000 Å. A 32% square wave amplitude response at the Nyquist limit is obtained at a location 150 resolution elements from the output diode. Optical imager resolution obtained by using the backside-illuminated device is illustrated.
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