HEMT suffers from parasitic resistance (R
) and capacitance(C
) effects with the shrinking of channel length, leading to degraded performance in logic and RF applications. A new while simple method to extract parasitic RC has been proposed to construct accurate transport parameters in HEMTs. In comparison to the constant-R
method, this new voltage dependent method provides more convincing results, especially for very short channel devices. On the other hand, an accurate C
correction method has also been incorporated to adequately represent the mobility. Finally, a guideline to design high performance HEMTs has been proposed.