I have seen a number of questions on PN-Junctions, Avalanche Breakdown, Biasing and MOS...etc, that have gone largely untouched; which is understandable, do these types of questions belong here or should they be relegated to Electrical Engineering SE?
There’s absolutely a place for semiconductor physics questions here. I’m pretty sure I’ve asked some.
Some questions on the topics you list are actually questions about electromagnetism and the movements of charges in materials, about the energies associated with those moving charges, and how those charges and fields are influenced by the various types of perfect and nearly-perfect crystals which make up semiconductors. Those questions are more likely to get satisfactory answers from our audience of physicists.
Other questions about semiconductor topics are about typical voltage-current response curves, about power requirements and thermal stability, or about a device’s response time. Those types of questions are more likely to get a good answer over at Electrical Engineering.
A rule of thumb that I use is if I think the answer to my electronics question will involve remembering some numbers from the periodic table, then I’ll ask a physicist; if I think it will involve remembering some numbers from a parts catalogue, I’ll ask an engineer.
If you ask a question in the wrong place, once in a blue moon, it’s not a big deal to migrate questions from one site to the other. And if you think that there are existing semiconductor questions that have been neglected here, you’re encouraged to highlight them for a few days by offering a bounty.