Recent improvements in the understanding and fabrication of GaN have led to its application in high frequency communication and high voltage switching systems. Requirement for operation at even higher frequency and voltages is driving the research currently on design of GaN based devices. In this paper, we present the result of our study of two-dimensional (2-D) High Electron Mobility Transistors (HEMTs) based on GaN/AlGaN/GaN heterostructure using Sentaurus TCAD tools. Exhaustive RF simulations were performed to study the effect of various device parameters such as Gate length, Gate-to-Source spacing, Gate-to-Drain spacing, etc. as well as the effect of various Gate shapes such as T-Gate, Y-Gate, etc., on the high frequency performance of the Transistor. Simulation result shows very promising result with fT and fMAX value of 1691.43 GHz and 2650.84 GHz respectively. © 2018 IEEE.