determine the impurity doping concentration

run_margaret

I have a question on semiconductor device,,

A drift current density of Jdrf=150 A/cm2 is required in a semiconductor device using n-type silicon with an applied electric field of E=25V/cm. Determine the imjpurit doping concentration that will achieve this specification.

i don't really understand this topic, can someone help me plz..

the answer is, If Nd = 3.13 * 10power 16 per cmcube,, then impurity doping concentration will be 1200..

i don't know how can i find Nd..