We have simulated HEMT 15 nm length gate with ability in analysis DC, AC, Transit and high frequency characteristics. This work is the demonstration of motivation for HEMT with InAlN/GaN structure in different characteristics. The simulated HEMT devices with length gate 15 nm and materials InAlN show very good scalability. We have excellent exhibit gm=0.85 DSS=0.59A/956;m, VBR=120V. The LG = 15 nm devices also feature record highfrequency characteristics for HEMT design with fT = 875 GHz and fMax =1.1THz. More significantly, the periphery oxide of the Gate suppresses leakage current when compared with equivalent normal HEMTs.