Extraction of admittance parameters of symmetrically doped AlGaN/GaN/AlGaN DH-HEMT for microwave frequency applications

An analytical model for determining intrinsic short-circuit admittance (Y) parameters of AlGaN/GaN/AlGaN Double Heterostructure (DH) High Electron Mobility Transistor (HEMT) is presented. These Y parameters obtained in terms of the various small signal equivalent circuit parameters are in turn used to evaluate the enhanced microwave performance of the DH-HEMT in terms of various parameters including Unilateral Power Gain and maximum oscillation frequency. The cut-off frequency has been evaluated from short circuit current gain. The cut-off frequency (fT) and maximum oscillation frequency (fmax) exhibited for DH-HEMT is 125 GHz and 215 GHz which is comparatively improved as obtained in Single Heterostructure (SH) HEMT (fT = 105 GHz and fmax = 165 GHz). The analytical results obtained for DH and SH-HEMT; have been compared and found to match well with the ATLAS 2D device simulation results thus proving the validity of the model.