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The purpose of this program was to study the clustering of defects in semiconductors. Silicon crystals were grown by the Czochralski and floating-zone techniques; GaAs was grown by the liquid-encapsulated Czochralski method. Characterization methods included Hall effect, infrared transmission, photoluminescence, neutron activation analysis, and charged particle activation analysis. Cal Tech studied the defect associated with the POR luminescence lines that they discovered in In-doped Si. Their experimental and theoretical program was aimed at first determining the chemical species that participate in the formation of the defect and then to study the formation and breakup of the defect under a number of experimentally varied conditions. The program to identify the defect consisted of selectively introducing various chemical species and studying the resulting increases or decreases in the concentration of the defect level,and then introducing isotopes of the chemical species to study the changes induced in the local phonon modes. Atom Sciences demonstrated the technique of Sputter Initiated Resonance Ionization Spectroscopy (SIRIS) for the detection of impurity atoms in silicon. Specifically, In, Al, and Ga were measured in samples of silicon. In addition, the concentrations of Al and V were determined in certified samples of stainless steel.

The harmonic content of solid state GaAs Gunn effect oscillators has been experimentally investigated using a lamellar grating far-infrared interferometer. The experiment has shown that power as low in frequency as 6 GHz can be modulated by the grating and that the instrument can be used in this frequency range with appropriate high-pass filters and above 60 GHz without filters. A number of the experimental difficulties encountered and instrumental modifications made to reduce the low frequency operating limit are discussed. A high dc bias mode of operation of a high-purity n-type epitaxial GaAs detector was discovered and its properties were investigated. This sensitive, broad-band detector, which had a response time of about 20 nsec, was used for the harmonic content measurements. In general, only a few harmonics of the X-band Gunn effect devices were observed and these died off rather rapidly. The experimental results were in fairly good agreement with theoretical predictions and indicate that the relative harmonic content increases with n/f. No definite correlation between harmonic content and bias voltage was found. The highest frequency at which power was observed was 82 GHz, a tenth harmonic. Thus the results do not contradict the predicted upper frequency limit of operation for these devices. (Author), See also Volume 1, AD-883 604L and Volume 3, AD-883 608L.

The report summarizes work done over a period of three years on a research program directed to the suppression of undesired emissions from active bulk-solid and epitaxial devices. Major emphasis was placed on the spurious emissions of Gunn devices. Both harmonic emission far from the fundamental and noise emission in the vicinity of the fundamental were studied. The technique of Fourier spectroscopy was newly applied to the study of harmonic emissions over the range 8 - 500 GHz. It was found that for Gunn devices operated in the hybrid and LSA modes harmonic power dropped rapidly with increasing frequency. The highest harmonic observed was the tenth (at 82 GHz) of a high-power pulsed LSA X-band device. (Author), See also Volume 2, AD-883 607L.