|
The dielectric constant ((Epsilon) ) and the dielectric loss factor (tan (delta) ) of vapor phase grown single crystals of (ZnTe)x(CdSe)1-x in the entire range of x have been measured in the frequency range 10 KHz - 1 MHz and in the temperature range 160 - 365 K using Ag contacts. Crystals of different compositions exhibited different frequency dependencies. In crystals with x equals 0.0 and 0.2, tan (delta) passes through a maximum. However, in crystals with x equals 0.4, 0.5 and 0.6, tan (delta) exhibits a minimum. In samples with x equals 0.8 and 1.0, tan (delta) decreases monotonically with frequency. This complex behavior of loss factor is explained by assuming an inclusion of two Schottky capacitors in series arising due to the metal (Ag) - semiconductor contacts and a frequency insensitive series resistor due to lead resistance and invoking a plasma effect due to free carrier dispersion. The inclusion of a double capacitor in the circuit was further confirmed by I - V studies on all the samples using Ag, Pb and In contacts. At 400 KHz (Epsilon) and tan (delta) increased monotonically with temperature. In samples with x equals 0.4, increased and tan (delta) decreased with temperature. For x equals 0.5, tan (delta) passed through a minimum around room temperature. For other compositions, no regular variation of (Epsilon) and tan (delta) is observed. This complex behavior could be due to the dielectric contribution arising due to the piezoelectric nature of the constituent compounds of the present system.
|
