RESEARCH ON THE THEORY AND DESIGN OF ACTIVE NETWORKS.
Annual summary rept. no. 4, 1 Jul 64-30 Jun 65,
FORSVARETS FORSKNINGSINSTITUTT KJELLER (NORWAY)
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The report is concerned with an experimental investigation of interactions between acoustic waves and conduction electrons in the piezoelectric semiconductor CdS. An acoustic amplifier has been built and tested. Net gain of 20 db at 60 MHz has been observed. Observations of gain, attenuation and phase velocity agree within a factor of two with the original theory of White. Saturation is observed when the rf charge density approaches the total charge density. The crystal becomes instable and current saturation occurs when the sound trip gain exceeds unity. The current saturation has been emploied to measure drift mobility in the temperature range from 184 to 438 degrees Kelvin. The temperature dependence can be explained by a combination of scattering from lattice vibration and trapping in two impurity levels. An advantage of the method is the fact that all experimental errors act in the same direction, and an absolute lower bound for the mobility is obtained. Double current saturation was observed in some samples. These are probably due to oscillations in two different acoustic modes, the principal mode of the cut and a mixed mode propagating obliquely to the end planes of the sample. Coherent current oscillations of 30 MHz were observed. They appear to be related to the double saturation, but their origin is not know. Author
- Electrical and Electronic Equipment
- Solid State Physics