For a simple model, we study the scattering of a polariton from a static point defect, in the presence of spatial dispersion. The polariton is scattered elastically by the defect, and in analogy with the theory of the reflection of light from the surface of a spatially dispersive medium, there are several final states possible. For example, when the medium is isotropic (the case considered here), an incident transverse polariton scatters into two transverse polariton final states, and into a longitudinal polariton final state upon striking the defect. The contributions to the cross section from these various scattering processes has been evaluated numerically, for a simple model and parameters appropriate to GaP in the infrared.
Submicrometer transistor gates have been fabricated in CMOS/SOS prototype VLSI circuits and GaAs digital integrated circuits. A hybrid lithography approach was used to take advantage of the rapid throughput of optical lithography and the high resolution capabilities of electron-beam lithography. The entire gate levels of these devices were defined with direct write electron-beam lithography. The six remaining lithographies in the CMOS/SOS device and the five remaining levels in the GaAs device were defined with various optical lithography systems. A unique electron-beam fiducial marker fabrication technique was required for each of the two devices. The goal of this approach was to substitute electron-beam lithography for optical lithography in the gate level only, leaving the remaining device process unaltered. Gate lengths as small as 0.6 μm were fabricated in the Si devices and 0.9 μm gates were achieved in GaAs. The CMOS/SOS gates were patterned in PMMA resist over MoSi2 and requires an Al liftoff and ion mill. The GaAs gates were patterned in AZ2400 resist which became an etch mask for underlying SiO2 and Si3N4 films. Circuits in both devices were sucessfully operated.
Impurity doped silicon detector arrays sensitive to long ir wavelengths, based on monolithic processing, were designed and developed. These arrays provide optimized performance utilizing ir transparent detector contacts and reflecting counterelectrodes while minimizing electrical and optical cross talk and providing precise optical definition for the detectors. The microelectronic batch processing procedures are discussed, and the array performance obtained using these procedures is presented. This includes spectral response, the dependence of detectivity on temperature and frequency, the electrical and optical cross talk, and the optical definition obtained. The development is expected to serve as a processing guide for future arrays which will include on-chip signal processing.
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