Hi, though I'm strictly not electronics, but more electrical, my list is:
Charles Steinmetz - contributions in ac power theory
Nikola Tesla - ac power, 3-phase ac motors, transformers.
James Maxwell Michael Faraday - physicists in electromagnetic theory
AC transformer development - Károly Zipernowsky, Ottó Bláthy, Miksa Déri, Mikhail Dolivo-Dobrovolsky, William Stanley - there's probably more.
Transistor development - too many to list.