Use of double-channel heterostructures to improve the access resistance and linearity in GaN-based HEMTs

Double-channel structures have been used in AlGaN/GaN high electron mobility transistors to reduce the access resistance. Carrier densities as high as 2.9/spl times/10/sup 13/ cm/sup -2/ and mobilities in the 1300 cm/sup 2//V/spl middot/s range have been obtained in the access region. Also, the correct design of the potential barrier between the different channels allowed tailoring the differential access resistance to enhance the linearity of the transistors. This increase in linearity has been measured as a flatter profile of the transconductance and cutoff frequency versus current and as an improvement of more than 2 dB in large-signal two-tone linearity measurements.