Experimental Investigations of Single Injection in Compensated Silicon at Low Temperatures

Experimental investigations of the phenomenon of single carrier, space-charge limited injection in silicon at liquid-helium temperatures have been performed in an attempt to validate the model for space-charge limited currents (SCLC) in an insulator with traps. Comparisons between predicted and experimental characteristics were performed on p₊pp₊ devices fabricated by diffusion techniques. Pulse and dc measurements were made to obtain steady-state current-voltage characteristics for the above devices. Modifications were observed in the SCLC characteristics due to field-dependent carrier mobilities, the exact nature of which could be determined from the experimental steady-state characteristics. The density of deep trapping centers in the above material at liquid-helium temperature, corresponding to the compensation, was obtained by measurements of the traps-filled voltage. An independent value for the compensation in the same material was obtained by Hall measurements in the temperature range 20^∘K<T<77^∘K. Transient measurements of the single-carrier current were performed, from which values for the capture probability and capture cross section for the deep trapping center could be obtained. A comparison was made between the capture cross section obtained in this manner and the theoretical prediction of the "giant trap" model.