DC performance of InP/InGaAs co-integrated metamorphic semiconductor devices grown on GaAs substrate by combining heterostructure bipolar and field-effect transistors (BiFETs) is first demonstrated. In the metamorphic co-integrated BiFETs, the field-effect transistor is stacked on the top of the metamorphic heterostructure bipolar transistor (HBT). For the HBT, the potential spike at base-emitter junction is effectively eliminated for reducing the collector-emitter offset voltage by lowering the energy band at emitter side. A maximum current gain of 255 and a low offset voltage of 105 mV are obtained. Furthermore, with respect to the field-effect transistor, the thin InGaAs channel between two undoped InP layers is heavily doped and two-dimensional electron gas is formed in the channel. An extrinsic transconductance of 265 mS/mm and a saturation current density of 281 mA/mm are achieved. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3610224] All rights reserved.