Does the sentence "The bipolar junction transistor, the first type of transistor to be mass-produced, is a combination of two junction diodes, and is formed of either a thin layer of p-type semiconductor sandwiched between two n-type semiconductors (an npn transistor), or a thin layer of n-type semiconductor sandwiched between two p-type semiconductors (a pnp transistor)." answer the question "What is the name for a layer of n-type semiconductor set between two p-type semiconductors?"
yes