A physics-based simple and accurate compact model of drain current for GaN-based high electron mobility transistors (HEMTs) is presented. The model is developed using analytical relations for charges in the 2-D electron gas and barrier layer. For the first time, a simple charge linearization approach has been used for GaN-based HEMTs. The access regions are accurately modeled using transistors. The model is rigorously validated over a wide range of geometries and parameters for AlGaN/GaN and AlInN/GaN HEMTs. The model also passes the DC Gummel symmetry test. © 1963-2012 IEEE.