MISHEMT vs GITs

What is the difference between HEMTs, MISHEMTs, GITs and HFETs?
I have seen several of these words being used in relation to GaN transistor but cannot find what is the difference between them?

Hello,
EPC is a leader in GaN HEMTs power devices and ICs. You can find more details on the basic device technology here: What is Gallium Nitride (GaN)? GaN Semiconductors Explained | EPC (epc-co.com)