PHYSICAL RESEARCH ON FUNDAMENTAL PROPERTIES OF II-VI COMPOUND SEMICONDUCTORS.
BROWN UNIV PROVIDENCE R I METALS RESEARCH LAB
Pagination or Media Count:
It is well known that cadmium sulfide can act as a very nonlinear acoustic conductor under the appropriate conditions of acoustic frequency, specimen conductivity and applied dc electric field. Direct distortion of the acoustic waveform was observed, at 20 Mcsec, as a function of conductivity and applied electric field. The maximum distortion appears to occur at the value of electric field where the acoustic velocity shear waves were used equals the charge carrier drift velocity. Ultrasonic attenuation measurements have been made at 12, 30 and 46 Mcsec and from room temperature to 1.8K on a cadmium sulfide specimen. The specimen had a dark room temperature conductivity of about 10 to the minus 2nd powerohm-cm. A very large attenuation peak was observed in the neighborhood of 15 - 20K. Conductivity measurements, made concurrently with the attenuation measurements, showed that the peak was almost surely caused by the relaxation associated with space charge bunching. The attenuation data did not seem to show the proper frequency dependence above the peak temperature, but this issue is clouded because there was considerable uncertainty in the non-electronic background damping to be subtracted from the observed attenuation. Thin film, vacuum evaporated, acoustic transducers of cadmium sulfide and zinc sulfide were prepared and used on a variety of substrate materials.
- Solid State Physics