In this paper GaN based HEMT structures characterized by a 6.3 nm InAlN barrier layer and a different gate contact (Mo/Au and Ni/Pt/Au) are described. The effects of a different gate contact structure on DC and pulsed main characteristics are discussed. Despite no meaningful variation is noticed during DC analysis, pulsed evaluation demonstrates that the use of a Mo/Au gate contact leads to an improvement of trapping characteristics. Reliability performances of the devices are finally investigated by means of a OFF state three terminals step stress, proving that the use of a Mo/Au stack does not affect significantly the device stability during the stress.