| AVS 64th International Symposium & Exhibition | |
| Electronic Materials and Photonics Division | Thursday Sessions |
| Session EM+MI+NS+SP+SS-ThM |
| Session: | Photonics, Optoelectronics, and Light Manipulation |
| Presenter: | Thomas Wong, Illinois Institute of Technology |
| Authors: | X. Fu, Illinois Institute of Technology and Argonne National Laboratory M. Haji-Sheikh, Northern Illinois University G. Westberg, Northern Illinois University S. Ross, Northern Illinois University E. Landahl, DePaul University K. Attenkofer, Brookhaven National Laboratory T. Wong, Illinois Institute of Technology |
| Correspondent: | Click to Email |
Integrating GaAs optoelectronic devices with Si- based platforms has attracted much attention and efforts in recent years, as a thin layer of GaAs can exhibitsuperior bulk quality. Wafer bonding, an emerging approach of monolithic integration of GaAs on Si-based substrate, overcomes the lattice mismatch in heterogeneous growth. Several techniques with a post-bonding annealing at temperature exceeding 800°C have been demonstrated to achieve high-energy covalent bonds between III-V compound semiconductors and Si/SiO2systems. However, the elevated temperature bonding process may create not only an inevitable thermal mismatch barrier but also damage the bonding materials. Thus, there is a need for improved technique to integrate GaAs with silicon based devices.
Low temperature grown (LTG) GaAs, which is typically obtained by molecular beam epitaxy (MBE) at temperatures as low as 200°C, offers very attractiveproperties such as ultra-short carrier lifetime, high electron mobility and high resistivity. It is verydesirable for applications such as ultrafast photoconductive switch, high efficiency solar cells and infrared LEDs. Pioneering work has demonstrated techniques to bond LTG-GaAs to Si/ SiO2 at temperature as low as room temperature by means of plasma activation and by wafer bonding under vacuum. However, very few techniques have been developed to bond LTG-GaAs layer to Si3N4 substrate, mainly because Si3N4 is naturally hydrophobic and bonding has been considered unachievable10. The existing Si3N4 bonding techniques employ high temperature fusion of Si3N4 layers or apply a layer of bonding agent such as SiO2.
In this paper, we report a room temperature approach to directly bond LTG-GaAs to Si3N4 by activating the surface of Si3N4 using weak HF acid solution. This method can be implemented on Si3N4 deposited over wide temperature range. Procedures to reduce the bonding voids and improve the bond strength are also described. In an application to utilize the developed method, we implemented this approach to fabricate a photoconductive switch on Si3N4 substrate bonded with LTG-GaAs and validated that the bonded LTG-GaAs retained the electro-optical properties. A THz opticalcross correlation test showed that the photoconductive switch responded swiftly to a femtosecond Ti-Sapphire laser pulse with a resolution of approximately 0.25ps. This wafer bonding method can be integrated with a wide range of microelectronic device fabrication thatrequires the bonding of LTG-GaAs layer with Si3N4.