In this work, we present the first investigation into the impact mechanism of Fe doping tails on the radio frequency (RF) switching performance of AlGaN/gallium nitride (GaN) high electron mobility transistors (HEMTs). It is illustrated that a thicker unintentionally doped (UID) GaN layer combined with a thinner Fe-doped buffer layer significantly reduces Fe concentration in the near-channel region of the UID GaN layer. HEMTs with weaker Fe doping tails exhibit superior RF switching performance. This phenomenon occurs as the Fe tailing effect during high-power RF switch operation aggravates the dynamic resistance degradation of the series HEMT and modifies the channel potential distribution, which in turn induces a large vertical component capacitance in the shunt HEMT. Fabricated switch devices with 500 nm gate length on the optimized epitaxial structure demonstrated outstanding performance: Pmax = 32 dBm at 3.6 GHz under −10 V gate bias, and Pmax 38 dBm with OIP3 = 56 dBm at −20 V gate bias. These experimental results demonstrate that controlled Fe tail effect engineering enables HEMTs to achieve both high-power handling and high linearity simultaneously, demonstrating a viable approach for developing high-performance RF switches compatible with Fe-doped buffer power amplifiers.
Zou et al. (Mon,) studied this question.