First AlN/GaN HEMTs power measurement at 18 GHz on Silicon substrate

AlN/GaN heterostructure is an ideal candidate to push the limits of microwave GaN-based devices owing to the maximum theoretical spontaneous and piezoelectric difference between the epitaxial AlN barrier and the underlying GaN layer. If the tricky growth conditions of this binary can be controlled, AlN/GaN HEMTs promise breakthrough performances, superior to any other III-V nitride-based heterostructure [1]. In particular, this structure should allow the extension of the GaN-based frequency operation due to the possibility to significantly reduce the gate length while maintaining an appropriate gate-to-channel aspect ratio to mitigate short channel effects. However, gate leakage current remains a serious issue with such ultrathin barrier heterostructure and gate dielectrics that often leads to device instability are generally used to overcome this problem. Furthermore, there is an increasing interest in the growth of GaN-on-Si substrates because of its low cost, large size, good thermal conductivity and the potential for integration with Si-based devices. In this work, we developed a novel AlN/GaN HEMT technology on Si substrate. The highest GaN-on-Si drain current density as well as a record transconductance together with excellent RF performance have been achieved. Additionally, AlN/GaN HEMT power measurements at 18 GHz have been performed for the first time. These results show the outstanding potential of this structure to extend GaN-on-Si performances to millimeter wave applications.