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

Abstract

Abstract The direct bonding process of InP chips on a silicon-on-insulator (SOI) wafer is investigated using surface hydrophilization by 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 cw operation is successfully achieved at a stage temperature from 20 °C to 85 °C. Stable operation is also confirmed from the changes of threshold current in the aging test (200 mA at 85 °C) after 2000 h.