The breakdown behaviors of InP/InGaAs single heterojunction bipolar transistor (SHBT) and double heterojunction bipolar transistor (DHBT) are studied and demonstrated. By using a composite collector structure at the base-collector heterojunction, the undesired current-blocking effect, switching, hysteresis phenomenon usually found in an InP/InGaAs conventional DHBT are not observed in our DHBT device. Experimentally, as compared with the studied SHBT, the studied DHBT reveals the enhanced breakdown voltages, lower collector leakage current I-co, and smaller electron impact ionization alpha. Moreover, the temperature-dependent electron impact ionization characteristics and electrical reliability for both devices are also studied. Therefore, the studied DHBT device provides the promise for millimeter-wave and power circuit applications. (C) 2008 Elsevier Ltd. All rights reserved.