Study of the Effect of an Electric Field on Trap Filling in CdS Single Crystals by the Use of Thermally Stimulated Currents

Abstract

Thermally stimulated currents (T.S.C.) in CdS are measured for electric fields of 10 to 104 V/cm and are found, in general, to change linearly. When trap filling is accomplished not by illumination, but with electrons injected from the cathode, the T. S. C.‐maximum depends on the voltage, according to the law Imax ∼ Un, where n varies from 3 to 6 for the various crystals. It is concluded that the fields at which measurements are made have no significant effect on trap emptying. T.S.C. are also measured at various voltages after the initial application of a higher voltage, and these measurements show a strong increase in the dark current and a negative resistance. It is, therefore, concluded that the steep rise of the dark current is not due to trap emptying or to the complete filling of traps. The most probable cause for it is the injection of holes from the anode.

Thermally Stimulated Currents without Optical Excitation. Application to Copper Phtalocyanine

“…i Retaining only the first term of the asymptotical expansion of the integral in ( 5 ) we finally have Ja1 = Q p " 8 o e x P (-;)[I -,-GexP(-;)], a q p v kT2 (7) which is maximum a t a temperature T* given by (1 + T)] w log Hence, T * is independent of go.…”

“…The first-order approximation used here is the reverse of that used to obtain equation (5), that is we assume 8, = E0 and replace (3) by a more exact expression for n,, which takes into account the exact situation. 8, is the applied field which means that we neglect the space-charge field.…”