Waveguide-integration of 2D Heterostructures for High-speed Photodetection

Abstract

Intensive efforts are being devoted to develop innovative solutions to keep up with the growing demands of information and communication technology (ICT) applications. Among the candidates for novel energy efficient and high-performance devices are structures based on two-dimensional (2D) materials. The members of this emerging class of layered crystals exhibit a strong light-matter interaction and allow the fabrication of so-called van der Waals heterostructures with tailer-made properties. These features render them an ideal complement to silicon photonics, adding the functionalities that are necessary to satisfy the requirements of ICT devices. In this thesis we develop and study waveguide-integrated 2D material based photodetectors, operating at telecommunication wavelengths. We investigate lateral and vertical device configurations assembled from flakes of graphene, MoTe2 and hexagonal boron nitride. By engineering the device design we minimize the carrier transit path length and thus achieve control over the charge carrier transport and extraction process. This lets us overcome the intrinsic material constraints and enables record-high directly measured bandwidths of up to 50 GHz. Our studies also shed light on performance trade-offs and present design guidelines for fast and efficient 2D devices. The combination of van der Waals heterostructures and integrated guided-wave nano photonics defines an attractive platform to realize a multitude of novel high-performance optoelectronic devices.