In this paper, we introduce an analytical surface potential based model for sheet carrier density and current in N-polar GaN/AlN/AlGaN metal insulator semiconductor high electron mobility transistors (MIS-HEMTs). The proposed sheet carrier density model is derived in terms of Fermi-level (E-{f}), gate potential (V-{g}) and channel potential (V-{c}). The surface potential current model using charge control equations and high field saturation Canali mobility model are in close agreement with simulation and experimental data over a wide range of applied gate biases. © 2018 IEEE.