255-GHz InP HBT Power Amplifiers Using Custom-designed Two-finger Devices

Abstract

This paper investigates the possible advantages in using two-finger InP heterojunction bipolar transistors (HBT) for WR-3.4 (220 GHz – 320 GHz) power amplifiers (PA). The two-finger HBT is designed by combining two 6-mm emitter length single-finger HBTs provided by Teledyne. Expected performances of two versions of two-finger device are simulated. One is designed with two separate isolation layers and the other one with single joined isolation layer. Both two-finger devices have better power performance but shows poor f_max and MAG compared to a single-finger device. Two PA designs in common-base differential configuration utilizing two types of custom two-finger devices are fabricated. The joined-isolation-device PA shows better performance with the peak gain of 10.5 dB at 255 GHz and P_1dB and P_sat of -1.7 dBm and 5.2 dBm while the separated-isolation-device PA shows peak gain of 4.6 dB at 255 GHz and P_1dB and P_sat of -8.5 dBm and 4.4 dBm.