Impact of a conducting interface layer on the characteristics of integrated InP photoreceivers

High-speed photoreceivers are important components for future high-bit rate communication systems. The use of a monolithical integration of waveguide, photodiode and amplifier avoids loss-making interconnections and enables high-speed performance, small size and cost-saving high-frequency packaging. Particularly with respect to a commercial use, the degree of reproducibility and reliability has to be very high. The elimination of process uncertainties is indispensable. Hence, in our photoreceiver development, e.g. the semi-insulating behavior of the substrate and the waveguide layer stack is verified as a matter of routine. By these measurements an occasionally occurring interface conduction was detected. This affects adversely the device insulation of the photoreceiver elements. On the performance side especially the high-frequency gain of the integrated amplifiers is reduced. To stabilize the fabrication process, a new treatment prior to epitaxial growth was developed to ensure a complete and reliable semi-insulating behaviour