The Power MOSFET Tool through Synopsys® Saber® can estimate static and dynamic behaviors of devices given measured static and dynamic characteristic curves. Model parameters are made accessible for behavior simulation and design optimization even if a datasheet is unavailable or more advanced device properties are in developmental stages. This functionality makes the tool ideal for predicting the behavior of a new GaN semiconductor in a circuit. Therefore, this paper first demonstrates a SiC model with accurate static and dynamic waveforms confirming the efficacy of the tool beyond Si. Second, this paper presents a model of a vertical GaN transistor using the Power MOSFET Tool which is compared against experimental static and dynamic measurements. The vertical GaN subcircuit model matches the experimental static results within 8.42% error. The model predicts the 8.48 ns turn-on and 30.2 turn-off time within a couple nanoseconds. With optimization of the parasitic elements in the circuit, the model matches the rise and fall rates as well as the frequency and magnitude of the ringing. Therefore, the model would simulate reliable switching times and losses critical for predicting devices' behavior in prospective applications.