The microwave and power performance of fabricated InP-based single and double heterojunction bipolar transistors (HBT's) is presented. The single heterojunction bipolar transistors (SHBT's), which had a 5000-Angstrom InGaAs collector, had BVCE0 of 7.2 V and J(Cmax) of 2 x 10(5) A/cm(2). The resulting HBT's with 2 x 10 mu m(2) emitters produced up to 1.1 mW/mu m(2) at 8 GHz with efficiencies over 30%, Double heterojunction bipolar transistors (DHBT's) with a 3000-Angstrom InP collector had a BVCE0 of 9 V and J(Cmax) of 1.1 x 10(5) A/cm(2), resulting in power densities up to 1.9 mW/mu m(2) at 8 GHz and a peak efficiency of 46%. Similar DHBT's with a 6000-Angstrom InP collector had a higher BVCE0 of 18 V, but the J(Cmax) decreased to 0.4 x 10(5) A/cm(2) due to current blocking at the base-collector junction. Although: the 6000-Angstrom InP collector provided higher f(max) and gain than the 3000-Angstrom collector, the lower J(Cmax) reduced its maximum power density below that of the SHBT wafer. The impact on power performance of various device characteristics, such as knee voltage, breakdown voltage, and maximum current density, are analyzed and discussed.