Monolithic displacement encoder sensor integrating GaN LED and Si photodiodes

A GaN blue light emitting diode (LED) and Si photodiodes (PDs) are integrated monolithically on Si substrate for a micro optical displacement encoder sensor. A GaN-LED crystal layer was grown epitaxially on a Si substrate. Si pn-junction was formed subsequently on the Si substrate by P ion implantation. Therefore, all components necessary for the encoder sensor are integrated on a Si chip after patterning encoder gratings. The blue light is useful for improving diffraction effect and suitable for Si photodetector.