We investigate the performance of an 18 nm gate length AlInN/GaN heterostructure underlap double gate MOSFET,using 2D Sentaurus TCAD simulation.The device uses lattice-matched wideband Al_(0.83)In_(0.17)N and narrowband GaN layers,along with high-k Al_2O_3 as the gate dielectric.The device has an ultrathin body and is designed according to the ITRS specifications.The simulation is done using the hydrodynamic model and interface traps are also considered.Due to the large two-dimensional electron gas(2DEG) density and high velocity,the maximal drain current density achieved is very high.Extensive device simulation of the major device performance metrics such as drain induced barrier lowering(DIBL),subthreshold slope(SS),delay,threshold voltage(V_1), I_(on)/I_(off) ratio and energy delay product have been done for a wide range of gate and underlap lengths.Encouraging results for delay,I_(on),DIBL and energy delay product are obtained.The results indicate that there is a need to optimize the I_(off) and SS values for specific logic design.The proposed AllnN/GaN heterostructure underlap DG MOSFET shows excellent promise as one of the candidates to substitute currently used MOSFETs for future high speed applications. We investigate the performance of an 18 nm gate length AlInN / GaN heterostructure underlap double gate MOSFET using 2D Sentaurus TCAD simulation. The device uses lattice-matched wideband Al_ (0.83) In_ (0.17) N and narrowband GaN layers along along with high- k Al 2 O 3 as the gate dielectric. The device has an ultrathin body and is designed according to the ITRS specifications. The simulation is done using the hydrodynamic model and interface traps are also considered. Due to the large two-dimensional electron gas (2DEG) density and high velocity, the maximal drain current density achieved is very high. Extensive device simulation of the major device performance metrics such as drain induced barrier lowering (DIBL), subthreshold slope (SS), delay, threshold voltage (V_1), I_ (on ) / I_ (off) ratio and energy delay product have been done for a wide range of gate and underlap lengths.Encouraging results for delay, I_ (on), DIBL and energy delay product are obtained. The results indicate that there is a need to optimize t The I_ (off) and SS values ​​for specific logic design. The proposed All All / GaN heterostructure underlap DG MOSFET shows excellent promise as one of the candidates to substitute currently used MOSFETs for future high speed applications.