Improved N-Polar GaN mm-Wave Linearity, Efficiency, and Noise
N-polar GaN deep recess MISHEMTs devices have shown record mm-wave power density and efficiency under CW conditions, and high linearity receive performance. Digital communication systems require high linearity from both transmitters and receivers, and low noise figure and high transmit efficiency. This manuscript shows several advances to enable this, including a very high 20 dB OIP3/PDC with 1.9 dB NF at 30 GHz, which uses a peaked OIP3 at a gm3 zero-crossing. Two approaches for reducing bias sensitivity of distortion are shown. A transmit device is shown at a higher current density with a high power 30 GHz OIP3 to PDC of 6.7 dB, with low bias sensitivity of linearity, and associated high power and PAE. Initial results of an approach to broaden OIP3 peaks versus gate bias is shown with a multi-threshold device structure. To reduce power consumption, a fabrication process for deeper gate length scaling was used to obtain a 94 GHz CW efficiency of 34% at 6.25 W/mm power density, a 5% increase, with the shorter gate length increasing linear gain to above 8 dB.