Bipolar field effect transistor (BiFET) structures and methods of forming the same are provided. In one embodiment, an apparatus includes a substrate and a plurality of epitaxial layers disposed over the substrate. The plurality of epitaxial layers includes a first epitaxial layer, a second epitaxial layer disposed over the first epitaxial layer, and a third epitaxial layer disposed over the second epitaxial layer. The first epitaxial layer includes at least a portion of a channel of a first field effect transistor (FET) and the third epitaxial layer includes at least a portion of a channel of a second FET.