Abstract
Monolithic integration of silicon and germanium devices is essential in state-of-the-art electronic and optoelectronic applications; for example, high speed photodetectors, high speed heterojunction bipolar transistors and so on, have been reported with superior performances. However, direct epitaxial growth of Ge on Si is critical due to the 4% lattice mismatch between Ge and Si. Moreover, to reduce the threading dislocation defects at the growth interface, high-temperature annealing or processing is required, challenging the integratibility with electronic devices. Furthermore, for some applications, the Ge structure should be integrated with Si devices on the same plane, which cause the process even critical. In this thesis, we develop a novel process using self-aligned microbonding technique in combination with rapid melt growth method, successfully demonstrating a Ge metal-semiconductor-metal photodetector butt-coupled to a Si waveguide. Compared with evanescently coupled Ge photodetectors, butt-coupling devices have been presented with large photo-responsivity and operation bandwidth. However, they are very difficult to be implemented by the conventional epitaxy process. Here, we design and fabricate this device by using our approach in a much simple way. The measured dark current is small about 0.29μA at 1310nm at -1V bias. The absorption efficiency is very high and the operation speed can be up to 25 GHz, if a contact barrier modulation technique is applied. This device potentially can be integrated with electronic devices and other photonic components, for an application of high-speed optical interconnects.