1. The problem statement, all variables and given/known data 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 charge, one negative and one positive. Away from the junction, outside these charge layers, the potential is constant, with a value of Vn in the n-type material and Vp in the p-type material. Given that the difference between Vp and Vn is 0.3 V, 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 V as a function of position through the junction. What is the strength of the electric field at the midplane? 2. Relevant equations I using the relationship that the second derivative of the potential is equal to σ/ε. I have certain conditions. Putting the middle of the bar at x=0, the potential must be continuous through the middle and I have conditions set at the endpoints phi_1(-10^-4)=0 phi_2(10^-4)=.3 phi_1(0)=phi_2(0) σ1+σ2 = 0 3. The attempt at a solution I get two expressions phi_1(x)= σ1/(2ε)x^2+Ax + B phi_2(x) = σ2/(2ε)x^2+Cx+D I found that A=C and B=D using the conditions, but now I have too many unknowns and not enough equations.