[castle-bravo]

Well, he did ask about band gaps. Is there a way to understand band gaps without quantum mechanics? I think you only need a little Fourier analysis to get the basics of band gaps.

Anyway, that text and along with Kittel's are the references for an undergraduate solid state course that I'm taking. No prior exposure to solid state physics for me and only introductory quantum mechanics (first half of Griffiths' QM); I find the text totally approachable.

[silman]

Semiconductor Device Fundamentals by Robert F. Pierret was my go-to for undergraduate text. The diagrams speak a thousand words and Pierret is a funny dude. Builds everything up from basic quantum.

Don't mistake it with his graduate text, Advanced Semiconductor Fundamentals, though. That's also a great text, but very short and focuses almost exclusively on the quantum aspect without getting too much into the higher level meat of putting it together to form devices.

For a comprehensive guide, though, Physics of Semiconductor Devices by Simon M. Sze was my reference bible. It's big and bulky, very heavy on the first principles math and physics, and has everything from quantum to devices and variants on devices.