That's my question: how can I tell, from the molecular form of the compound, if a compound is an intrinsic semiconductor, an extrinsic type-N semiconductor, or an extrinsic type-P semiconductor? I can tell the pure intrinsic semiconductors: Si, Ge, C (diamond), etc. I know that if I add an element of the group III to a chain of one of these, I'll get an extrinsic type-N semiconductor, and that if I add an element of the group VI, I'll get an extrinsic type-P semiconductor. But what if I have no molecules of any element from the group IV? How about when I have InSb, or GaAs? And how about when I have more than two compounds, like GaAsSe? What's the parameter I have to look at to clasify these compounds?