The one‐flux analysis of double‐heterostructure bipolar transistors with composite collectors in the preceding article W. R. McKinnon, J. Appl. Phys. 79, 2762 (1996) is compared to drift‐diffusion calculations and to measurements on InP/InGaAs/InP/composite collectors‐double heterostructure bipolar transistors. For quantitative agreement we include the effects of ionized impurities in the space‐charge regions, and an approximate treatment of Fermi–Dirac statistics. ©1996 American Institute of Physics.