Material-based comparison for power heterojunction bipolar transistors

Various materials are studied to determine their potential in power heterojunction bipolar transistors (HBTs). The authors first start by generating an HBT figure of merit (FOM) which is defined as the product of operating frequency and output power of the HBT with 3-dB power gain. By using the FOM and available material parameters, a material-based comparison of HBT performance is done. The general tendency is for use of narrow-bandgap materials, such as Ge or InGaAs, as the base and wide-bandgap materials, such as AlGaAs, InP, SiC, or GaN, as the collector, technology permitting