An efficient waveguide photodetector fabricated in an InP-based amplifier layer stack

This article describes the fabrication and characterization of a waveguide pin-photodetector (WGPD) based on butt-joint integration of a passive waveguide and photodetector. The WGPD is fabricated in a layer stack that is designed to be used for an optical amplifier, which now acts as a detector by reversely biasing the pin-diode. The device is fabricated in active-passive material with a technology that uses two epitaxial regrowth steps. The static and high-frequency behavior of the photodetector are characterized and demonstrate a very low dark current of 20 nA at -4 V and an internal efficiency of more than 65% for a 60 µm long device at -5 V bias voltage around a wavelength of 1.5 µm. The output reflection coefficient shows more than 20 GHz bandwidth for a 70 µm long device.