THE FIELDS OF MOVING CHARGES — Edward Purcell & David Morin
Physics — E&M · silicon-junction-diode
Problem
Silicon junction diode **
In a silicon junction diode the region of the planar junction between n-type and p-type semiconductors can be approximately represented as two adjoining slabs of uniform charge density, one negative and one positive. Away from the junction, outside these charge layers, the potential is constant, its value being ϕn in the n-type material and ϕp in the p-type material. Given that the difference between ϕp and ϕn is 0.3 volt, and that the thickness of each of the two slabs of charge is 10−4 m, find the charge density in each of the two slabs, and make a graph of the potential ϕ as a function of position x through the junction. What is the strength of the electric field at the midplane?