Progress in Highly Linear and Efficient mm-Wave GaN HEMTs and MMICs

Realizing high-performance mm-wave 5G-and-beyond communication systems will require transistors with higher linearity and efficiency than current technology offers. While GaN HEMTs offer excellent power density, their limited linearity and efficiency compromise overall system performance; this requires substantial DC power consumption and power back-off to circumvent. Here, we will discuss the linearity and efficiency of graded-channel GaN HEMTs with the linearity figure-of-merit, OIP3/PDC, of 20dB at 30GHz, well beyond the 10dB rule of thumb. For power amplifier applications, a two-tone PAE of 62% was obtained experimentally at 30GHz, which is a state-of-the-art result. We find that ~3dB back-off from peak PAE is sufficient to achieve a carrier-to-third-order intermodulation (C/IM3) ratio of 30dBc. Recent Ka-band and W-band MMICs with graded-channel GaN technology illustrate their potential for future linear and efficient mm-wave applications.