The temperature-dependent dc characteristics of InGaP/GaAs heterojunction bipolar transistors with and without full sulfur passivation are systematically studied and demonstrated. The studied device with full sulfur passivation shows lower specific contact resistance rho(C), lower sheet resistance R-sh, lower collector-emitter offset voltage Delta V-CE, and higher dc gain beta(F) than devices without sulfur passivation. The device with full sulfur passivation also exhibits better rf performance. In addition, the studied device with full sulfur treatment shows lower temperature variation coefficients of rho(C), R-sh, Delta V-CE, and beta(F). Thus, the device with sulfur treatment presents relatively temperature-independent characteristics that can extend the transistor action to higher temperature regimes. (c) 2006 American Vacuum Society.