Embodiments of the present invention include a method for forming a tunable semiconductor device. In one embodiment, the method comprises: forming a semiconductor substrate; patterning a first mask over the semiconductor substrate; doping regions of the semiconductor substrate not protected by the first mask to form a first discontinuous subcollector; removing the first mask; patterning a second mask over the semiconductor substrate; doping regions of the semiconductor substrate not protected by the second mask and on top of the first discontinuous subcollector to form a second discontinuous subcollector; removing the second mask; and forming a single continuous collector above the second discontinuous subcollector.