The quantitative effects of dislocations on the electrical and optical properties of long-wavelength infrared (LWIR) HgCdTe photovoltaic detectors was determined by deliberately introducing dislocations into localized regions of two high-performance arrays having cutoff wavelengths of 9.5 and 10.3 μm at T=78 K. Results show that dislocations can have a dramatic effect on detector R0A product, particularly at temperatures below 78 K. For large dislocation densities, R0A decreases as the square of the dislocation density; the onset of the square dependence occurs at progressively lower dislocation densities as the temperature decreases. A phenomenological model was developed which describes the dependence of the detector R0A product with dislocation density, based on the conductances of individual and interacting dislocations which shunt the p–n junction. Spectral response and quantum efficiency are only weakly affected, as is the diffusion component of the leakage current. The 1/f noise current was found to increase approximately linearly with dislocation density and also tracks with the magnitude of the leakage current similar to a data trendline established for undamaged HgCdTe detectors. These results can be used to understand the performance limitations of LWIR HgCdTe arrays fabricated on heteroepitaxial substrates.

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It is important to be able to nondestructively characterize (‘‘screen’’) the electrical properties of those areas of HgCdTe epitaxial material that will later be made into devices. This paper compares several noncontact techniques for measuring resistivity, carrier concentration, and mobility with the standard Hall-effect technique. The noncontact techniques examined are far-infrared reflection, Raman scattering, eddy–current absorption, and electroreflectance. Of these techniques, far-infrared reflection was found to be the best noncontact technique for measuring resistivity, carrier concentration, and mobility. Resistivity values were within a factor of 2 of Hall-effect values, while carrier concentration and mobility values that depend on an assumed effective mass were within a factor of 3. In Raman scattering, interference between the free-carrier plasmon–phonon mode and other modes makes it an inaccurate method for estimating carrier concentration. Eddy–current absorption is useful for quickly measuring epitaxial layer resistivities to within a factor of 3 of Hall-effect values, while electroreflectance gives a relative value for the surface doping density, which is useful in layer profiling.

<p>The weakness of the force of gravity compared to the electromagnetic force and the other fundamental forces has been referred to as the hierarchy problem. If gravity propagates in several additional spatial dimensions that are large compared to the Planck scale, the hypothesis is that gravity is stronger close-up, e.g., below a certain interaction distance the force of gravity is magnified. In the hard disk drive assembly, the magneto-resistor (MR) read sensor in the head assembly operates within 100nm of the spinning disk surface. Fourteen variable size nano-bumps and nano-pits were fabricated on a magnetic disk platen’s surface designed to be less than the Planck mass 21.77 μgrams. These nano-features were measured over the spinning disk with both piezoelectric and MR sensors. The data was validated using both atomic force microscope (AFM) and magnetic force microscope (MFM) measurements. Results are reviewed and theoretical implications are discussed. The results suggest that the force of gravity is magnified and there are two forms of gravitation. Implications to modified spacetime are discussed.</p>