Yes, our GaN HEMT (under Discrete Transistors, GaN HEMTs) devices will usually have a Modelithics model available. The Modelithics weblink will be at the upper right of the product webpage. The model can be requested directly from Modelithics.
Our MMIC GaN (under Amplifiers, Power Amplifiers) do not have models. These PA’s are internally matched over the full band of operation.
S-parameters will be at the “Documents” tab on the product webpage. If not there, they can be requested by emailing appsupport@qorvo.com.