Hi Lumerical team,
I was experimenting with constant doping objects using the project downloaded from the
p-n Junction Diode example page on https://kb.lumerical.com/en/other_application_gs_pn_diode.html. I made some small changes to the project as follows:
- modified the x span to 220 nm for all the objects in the geometry group and the simulation region to avoid creating regions with undefined material parameters
- I also disabled the nepi doping object and created 2 further constant doping objects (p and n) without adding any heavily doped regions (Type A) - disabled the objects created in 3 below.
- I also added heavily doped regions (p++ and n++ of 2 microns), called this Type B.
When I simulated the two cases, I got completely different results for the I-V charactersitics, with the differences pronounced at low doping levels (and of course short Lp and Ln lengths). At Lp = Ln = 5 microns, there is almost a 5x difference between the two cases. This seems odd as the heavily doped regions are far away enough from the junction to influence it significantly. Is there something we are not doing right? Is this due to the absence of the background doping, which I disabled. The results do not seem to support the physics (the depletion region width is of the order of a micron in the doping range we are considering).
I have attached the simulation file and the two schematic for Type A and Type B, plus some representative results.
Thanks for your support.