Recent GaN related research efforts on both GaN based transistors and passive devices like self-biased circulators will be discussed. Commercial mmW Applications are demanding for GaN technology with more aggressive device scaling, starting from the gate length of 150 nm, towards 90 nm and below. New epitaxy design is required to further reduce parasitic resistances below that can be achieved from traditional AlGaN/GaN structures. We have developed 90 nm GaN (GaN09) HEMT technology based on an AlN/GaN based digital barrier. This new structure, combined with our T-Gate process, has enabled great efficiency improvement in both devices and circuits. The GaN transistors have shown a peak PAE of 51% with the output power density of 2.25 W/mm at 35 GHz. In future phased array mmW applications where full-duplex communication is desirable, conventional circulator technology can not be used due to the bulky device sizes. Our new Ka-band self-biased circulator technology integrated on GaN/SiC provides superior SWaP performance by showing an insertion loss of <0.5 dB and isolation >25 dB within an active device junction area of 1.5 mm in diameter. This technology will pave the path for 5G duplex communication systems using phased array antennas.