Linearity Improvement of GaN HEMT for RF Power Amplifiers

The linearity has become more important to expand GaN HEMTs into microwave amplifier markets. This paper describes the outline of the large signal model of our 0.4μm AlGaN/GaN HEMT, considering the pulse biased 24 V operation. The analysis which utilizes the constructed Angelov model proved that the intermodulation distortion (IMD) of more than 10 dB backed off region is determined by the sub-threshold gm profile, namely steep rising gm profile degrades IMD. Thus, we proposed a thin n-GaN layer inserted buffer structure (ini-buffer), which realizes the significant IMD improvement of 8 dB, in the backed-off region.