Development of a high transconductance GaN MMIC technology for millimeter wave applications

In this paper we report on the development of high transconductance GaN-based high electron mobility transistors (HEMTs) to improve the performance at W-Band frequencies. At first, the influence of the barrier thickness on the maximum transconductance (gm,max) was investigated by using two different technologies: growth of thin barrier layers and deep gate recess. Second, the effect of a gate length reduction down to 100 nm on g_m,max was examined. The reduction of the barrier thickness results in a strong increase of the extrinsic transconductance up to 600 mS/mm. The technology was then used to fabricate HEMTs, with a cut-off frequency of 110 GHz, which are compatible to a MMIC technology.