Effect of Polarization Coulomb Field Scattering on Parasitic Source Access Resistance and Extrinsic Transconductance in AlGaN/GaN Heterostructure FETs

With the measured parasitic source access resistance under a different forward gate–source current for the AlGaN/GaN heterostructure FETs (HFETs) with different device sizes, the variation of the measured parasitic source access resistance with the polarization charge distribution at the AlGaN/GaN interface was compared and analyzed. It is found that the variation of the parasitic source access resistance originates from the polarization Coulomb field (PCF) scattering, and the effect of PCF scattering on the parasitic source access resistance is more significant for the device with a longer gate length or a shorter gate–source distance. The behaviors of the measured extrinsic transconductance for the fabricated AlGaN/GaN HFETs confirm the effect of PCF scattering. The possibility is demonstrated to take advantage of this effect to improve the performance of AlGaN/GaN HFETs.