EFFECT OF SURFACE CONDUCTIVITY ON ACOUSTIC AND GALVANOMAGNETIC PROPERTIES OF HIGH-RESISTIVITY N-TYPE INSB AT LOW-TEMPERATURES

Inversion and accumulation layers at the surface of high-resistivity n -type InSb single crystals doped with chromium and manganese have been studied. The experiments were carried out in magnetic fields up to 30 kOe at low temperatures (1.5-20 K), at which the surface conductivity is predominant. The carrier densities in the n- and p-type surface la yers were determined. A negative magnetoresistance is observed in thes e layers. Its magnitude depends on the orientation of the magnetic fie ld with respect to the surface of the sample. It also depends on IR il lumination. While the n-type surface conductivity does not influence t he propagation of sound waves in the interior of the crystal, it degra des the generation of ultrasonic waves because the resistance of the s urface layer depends strongly on the magnetic field. A method is propo sed for coupling ultrasonic waves into a sample in this case.