Is there a transverse component of the electric field in a reversely biased diode? I was recently simulating a diode at high reverse voltage and was faced with the fact that both software packages which I used (COMSOL and SILVACO), though correctly representing the longitudinal field in the p+nn+ diode base, compute the radial component of the electric field  to be approximately zero. It seemed a bit strange to me because the divergency of the electric field due to the Poisson's equation is proportional to the charge density in the depleted region. This divergency is readily seen on the longitudinal component of the electric field and in a diode with the n-base doping level of 10^14 cm^-3 it leads to the substantial slope of about 10^5 V/cm per 100 um base. The electric field therefore has a triangular profile shown in the picture which is totally fine. But in my opinion there also should be a transverse component of the divergency induced by the same charge in the depleted region by charged donors, which should lead to much higher radial electric fields than I observe in simulations. The size of the diode is 100 um in longitudinal direction and 1000 um diameter, so I first attributed the absence of the transverse field to the edge effects, but even reducing the diameter to 10 um did not change the situation. So I was wondering whether it is my simulations or my understanding of physics which is incorrect. Is there a transverse component of the electric field in a reversely biased diode base?

 A: "Is there a transverse component of the electric field in a reversely biased diode base?"
In the case of a conductor, the transverse component would essentially be zero because, if there were a transverse electric field, the charge carriers would rearrange themselves to cancel out the field. So, I guess the question could be rephrased as: "Are there enough charge carriers in a reverse-biased diode to cancel out any transverse component of the electric field?"
I don't know the answer for sure, but it wouldn't surprise me if the answer is "yes". If there were zero charge carriers, I'd expect the electric field to look something like that between the plates of a parallel plate capacitor. The transverse component of the field in a parallel plate capacitor is fairly small, so even a small density of charge carriers could well be enough to cancel it out.
You should be able to view the charge density in COMSOL (and presumably SILVACO, altho I haven't used it). How does the charge density vary in the transverse direction? If it's constant, I'd say that the simulation is taking some (possibly unrealistic) shortcut --- likely due to the boundary conditions. If the charge density is fairly flat towards the middle but changes towards the edges, I'd say that's evidence of charge carriers moving to cancel out the transverse field.
