(color online) (a) Optical image of a BP photodetector. Instead of a straight-edge metal electrode, the isotropic round photocurrent collector was employed to avoid the linear polarization that might arise from a straight metal edge (left). Corresponding photocurrent microscopy image of the device, with illumination at 1500 nm and polarization along the direction of the white arrow (x axis) (middle). Polarization dependence of photoresponsivity with illumination from 400 to 1700 nm, where the polarization angle of 0° corresponds to the x crystal axis and 90° corresponds to the y crystal axis (right).^[71] (b) Schematic of the waveguide integrated BP photodetector (left). The response of the BP photodetector is measured when BP is gated to low and high doping conditions (right). Receiver eye diagram at a data rate of 3 GHz (inset).^[73]