I don't know any program of study that would get sufficiently deep enough to get to semi-conductor quantum tunneling (year 2/3 class) without having some foundational E&M to motivate the QM to begin with (pure math here being a more exceptional but rare case). I think the beauty of QM at that point is that it looks and feels a lot like differential field work of EM and Lagrangian mechanics but maps to quantized numerical spaces, where jumps and little shoots like that happen all the time (spontaneous crystal domain alignment in magnets for example). If you were able to get sufficiently skilled in intro QM, it would absolutely help study in E&M.

If you E&M questions are just node solving, linear algebra and difeq is all you need for E&M to solve "most" work. You do a lot of specialized versions of that in QM and as mentioned above the people doing the actual semiconductor design are so highly specialized that they are often not transferable to other problem domains and require fundamentally different approaches. Not sure any non-PHD study will really help one advance the field in a meaningful way. Study of QM i would say sufficiently enriches all physics verticals that if you are capable, it's worthy of individual pursuit, but also makes total sense to study as part of a curriculum taking place after intro E&M.

Quantum Tunneling in everyday life: https://www.discovermagazine.com/the-sciences/how-quantum-me...