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

Abstract

In this paper, the fabrication technology of SiNassisted 0.12um double deck T-gate AlGaAs/InGaAs p-HEMT and 60GHz-band MMICs for high rate personal area network (WPAN) systems is described. The effect of the gate head dimension, such as the 1st-deck and the 2nd-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 0.12um length and 50um width showed an extrinsic transconductance of 511mS/mm and a drain current of 20.6mA at 1.5V of drain voltage. The cut-off frequency and the maximum frequency of oscillation were 96.8GHz and 192.6GHz, respectively. Gate head dimensions of the p-HEMT device are correlated to parasitic capacitances, including Cgs, which effect the RF performance including a cut-off frequency (fT) and a maximum frequency of oscillation (fmax). I. INTRODUCTIONRecently, millimeter wave applications such as high speed wireless communications, collision avoidance car radar systems and millimeter wave video transmission systems have been developed. Especially, unlicensed 60GHz-bands are of growing interest for high rate personal area networks (WPAN) (IEEE 802. 15. 3) and high rate wireless local area networks (WLAN) [1]. Millimeter wave MMICs of such applications have been fabricated through a III-V compound based technology related to active devices such as GaAs-based HEMT, InP-based HEMT and InP-based HBT [2]. p-HEMT devices are especially widely utilized as active devices of millimeter wave MMICs due to their excellent and stable RF performace [3]. The gate shape of the p-HEMT device has a major effect on parasitic capacitances, including the gate-to-