Influence of Gate Head Dimensions on the Device performance of 0.12um PHEMT

In this paper, the fabrication technology of SiN- assisted 0.12 um double deck T-gate AlGaAs/InGaAs p-HEMT and 60 GHz-band MMICs for high rate personal area network (WPAN) systems is described. The effect of the gate head dimension, such as the 1^st-deck and the 2^nd-deck gate head size, on the DC and RF characteristics of the p-HEMT device and the device performance at the optimum gate head size are also presented. At the optimum gate head size, the p-HEMT device with two finger gates of 0.12 um length and 50 um width showed an extrinsic transconductance of 511 mS/mm and a drain current of 20.6 mA at 1.5 V of drain voltage. The cut-off frequency and the maximum frequency of oscillation were 96.8 GHz and 192.6 GHz, respectively. Gate head dimensions of the p-HEMT device are correlated to parasitic capacitances, including C_gs, which effect the RF performance including a cut-off frequency (f_T) and a maximum frequency of oscillation (f_max).