(Invited) Fabrication of Ge Waveguides by Epitaxial Lateral Overgrowth toward Monolithic Integration of Light Sources

Ge waveguides (WGs) were fabricated on an SiO2 layer by combining epitaxial lateral overgrowth, chemical mechanical polishing (CMP), and reactive ion etching (RIE) of a Ge layer selectively grown on SiO2 patterns using low pressure chemical vapor deposition. Selectivity was promoted by increasing growth temperature; length of the epitaxial lateral overgrown Ge layer reached 5 μm on the SiO2 layer under conditions of optimal selective growth at a temperature of 750°C. The Ge layers were planarized by using CMP down to a thickness of 1 μm, and then Ge WGs as active regions for light emitting devices were formed by using RIE on the planarized Ge layers. After defective regions around the Ge/Si interface were removed, four-times-higher photoluminescence was obtained from the Ge WGs compared with one that contained the Ge/Si interface. These results indicate that this combined technique efficiently improved the performance of Ge light-emitting devices.