InP-based membrane photodetectors on Si photonic circuitry

Abstract

The work presented in this thesis is about indium phosphide (InP) based photodetectors for use in optical interconnections on silicon (Si) integrated circuits (ICs). The motivation for this work comes from the bottleneck expected at the interconnect level for future generation electronic ICs: with the technology scaling down and the signal switching frequency increasing, three main issues are predicted for the complementary metal-oxide semiconductor (CMOS) ICs, namely signal propagation delay, power consumption and integration density. Electrical interconnects (EIs) strongly limit these characteristics and a promising solution is given by replacing EIs with optical interconnects (OIs). The implementation of intra-chip and chip-to-chip OIs requires the use of photonic integrated circuit (PIC) technology. The integration of optical sources, waveguides and detectors forming a photonic interconnect layer on top of the CMOS circuitry provides bandwidth increase, immunity to electromagnetic (EM) noise and reduction in power consumption. This solution was investigated within this work, which focuses on the detector part. InP-based membrane photodetectors were realized on InP dies bonded on Si and CMOS wafers, on top of which passive Si and Si3N4 photonic circuitry had been defined. This approach combines the advantages of high quality Si-based passive circuits with the excellent properties of InP-based components for light generation and detection. The technology used for the InP device fabrication is compatible with wafer scale processing steps, assuring compatibility towards future generation electronic ICs. The major results of this work are summarized as follows: InP membrane couplers and detectors were successfully fabricated on Si and Si3N4 photonic circuits. Experimental results show working active and passive devices, namely: passive Si photonic components (waveguides, MMIs, (de)-multiplexers), InP membrane couplers, InP-based detectors and heterogeneously integrated multiwavelength receivers. A working laser-to-detector integrated optical link on Si was successfully demonstrated. This work was carried out with the support of the European project IST-PICMOS and of the Dutch Ministry of Economic Affairs through the Smartmix Memphis project.