I. Introduction
The 5G new radio (NR) band allocation is primarily divided into two frequency ranges: FR1, which operates below 6 GHz (sub 6 GHz), and FR2, which includes bands above 24 GHz extending into the frequency range above 50 GHz. There is an increasing interest in making wide use of the mm-wave frequency spectrum, specifically the U-band (40–60 GHz) and the V-band (50–75 GHz) for high-data-rate wireless communication, including point-to-point and wireless back-haul radio link applications [1]–[3]. Existing silicon device technologies face inherent limitations in terms of low breakdown voltages, power density, and relatively lower [4]–[7]. On the contrary, within III–V technologies, gallium nitride (GaN) offers promising power density but is often limited in terms of gain above 40 GHz [8]. In contrast to CMOS, SiGe, and GaN, the indium phosphide (InP) heterojunction bipolar transistor (HBT) technology offers promising performance advantage in terms of output power, efficiencies, and gain above 40 GHz due to better Johnson figure of merit (FOM), high RF output power density, large intrinsic transconductance, excellent threshold control and high levels of integration [9].