III–V gain region/Si waveguide hybrid lasers by chip-on-wafer hydrophilic bonding process using UV-ozone treatment

Abstract

The direct bonding process of InP chips on a silicon-on-insulator (SOI) wafer is investigated using surface hydrophilization by ultra-violet (UV)-ozone treatment. The influence of the treatment on surface roughness is observed by atomic force microscopy, and found to be negligibly small. A high-quality III-V/Si bonding interface without crystal defects is verified in a scanning transmission electron microscope observation. The III-V layers remaining on the SOI wafer after the removal process of the InP substrate show uniform photoluminescence intensity over the whole region of the chip, indicating a bonding interface without the influence of lateral etching and peeling-off. From this bonding process, Fabry-Perot lasers with III-V gain and Si waveguide regions are fabricated, and continuous-wave operation is successfully achieved at a stage temperature from 20 to 85oC. Stable operation is also confirmed from the changes of threshold current in the aging test (200 mA at 85oC) after 2,000 hours.