A Measurement method of the injection dependence of the conductivity mobility in silicon

A new electrical method to measure the conductivity mobility as a function of the injection level is proposed in this paper. The measurement principle is based on the detection of the voltage drop appearing across a n/sup +/-n-n/sup +/ (p/sup +/-p-p/sup +/) structure when a current step is forced into it at a given injection level in the intermediate region. This is obtained by using a three-terminal test pattern consisting of p/sup +/, n/sup +/ layers realized on top of a n-n/sup +/ (p-p/sup +/) epitaxial wafer, where the p/sup +/-n-n/sup +/ (n/sup +/-p-p/sup +/) surface diode is forward biased to monitor the conductivity of the epilayer. The use of separate terminals for injection control and mobility measurement allows this technique to overcome some limitations presented by other electrical methods available in literature, Mobility values measured up to 2/spl middot/10/sup 17/ cm/sup -3/ are in good agreement with those predicted by the Dorkel and Leturcq's model (1981).