This work describes a procedure to implement a two-dimensional hydrodynamic simulation of InP/GaAs0.51Sb0.49/InP double heterojunction bipolar transistor (DHBT). It concerns the DC characteristics and allows to fit some very sensitive but still unknown or uncertain parameters of GaAs0.51Sb0.49 material, such as the band gap energy and the minority carrier lifetime. In particular, the influence of the band gap narrowing on the DHBT DC operation is analyzed. Thereafter, the mechanisms of electron-hole recombination into GaAs0.51Sb0.49 are discussed and a typical value of the electron lifetime is calculated. Finally, the drop of DHBT performances at high collector current densities is highlighted. (c) 2005 Elsevier Ltd. All rights reserved.