RF Linearity and Nonlinear Source Resistance in AlGaN/GaN HFET's

Nonlinear source resistance induced by the onset of space charge limited (SCL) transport at the gate-source access region has been previously reported as an important linearity limitation for AlGaN/GaN HFET devices. A physics based large signal model has been modified to investigate for the first time the AlGaN/GaN HFET's IMD behavior due to source resistance modulation as a function of device design parameters. The predictive capabilities of this model are demonstrated by comparing the results of measured and simulated RF performance. The variation of the IMD versus Lsg spacing and DC bias are investigated. Careful selection of Lsg spacing permits IMD improvement by reducing the nonlinear source resistance effect.