A low-distortion and high-efficiency E-mode GaAs power FET based on a new method to improve device linearity focused on g/sub m/ value

In this paper we propose a new method to improve linearity of GaAs power FETs. Based on a Volterra series analysis, the 3rd order intermodulation distortion (IM3) ratio was found to be proportional to g/sub m//sup -2/ when output power P/sub out/ is fixed. Increasing g/sub m/ is hence a very effective method to improve IM3. To enlarge g/sub m/ while keeping the breakdown voltage high, two possible ways are considered for our GaAs power FET. One way is to thin the AlGaAs barrier layer. The other is to increase donor density in the n-GaAs channel layer and to thin the channel layer simultaneously. Since either way gives rise to an increase in the threshold voltage, one of the embodiments of the new method is an E-mode FET. An E-mode GaAs power FET based on the new method exhibited an IM3 ratio of -36 dBc and a power added efficiency (PAE) of 35% at an average P/sub out/ of 47 dBm and a frequency of 2.2 GHz. The IM3 ratio and the PAE achieved are 8 dB better and 10% higher than those of the prior work.