Simulation of GaN MOS-HEMT using Synopsys Sentaurus (Lombardi Mobility Model)

Hi,

I am currently conducting simulation of AlGaN/GaN MOS-HEMTs using Sentaurus TCAD. I need a vertical electric field mobility model for the simulation and tried to use Lombardi model available in the TCAD. However, the Lombardi coefficients available is still in Silicon, are there any way I can get  Lombardi GaN coefficients?

Thank you