Linearity Limitations of AlGaN/GaN HFET´s

Due to high mobility (1000-1500 cm/V²), high sheet charge density (~10¹³ cm^-2), and high electron saturation velocity (~2.0times10⁵ cm/s), AlGaN/GaN HFET´s were shown to have great potential for linear operation in high dynamic range module. However, significant linearity degradation was found in practical devices compared to that predicted from theoretic derivation. In this work it is demonstrated that nonlinear source resistance that varies in magnitude with the channel conduction current limits these device´s RF performance by suppressing the channel I_MAX value and introducing nonlinearity under large signal operation. The nonlinear source resistance can be affected by changing the length of the gate-source access region. RF performance is improved by minimizing the nonlinearity in the source resistance.