A physical based equivalent circuit modeling approach for ballasted InP DHBT multi-finger devices at millimeter-wave frequencies

Abstract

Multifinger InP DHBTs can be designed with a ballasting resistor to improve power capability. However accurate modeling is needed to predict high frequency behavior of the device. This paper presents two distinct modeling approaches: one based on EM simulations and one based on a physical equivalent circuit description. In the first approach, the EM simulations of contact pads and ballasting network are combined with the small-signal model of the intrinsic device. In the second approach, the ballasting network is modeled with lumped components derived from physical analysis of the layout and then combined with EM simulated contact pads and with the device model. The models are validated against S-parameters measurements of real devices up to 65 GHz showing good agreement in terms of maximum available gain. In addition, a MAG of 2-4 dB at 170 GHz shows that ballasted devices can be employed for power amplifiers in D band.