Heterogeneously Integrated Membrane III-V Compound Semiconductor Devices With Silicon Photonics Platform

Abstract

Silicon photonics is a key technology for constructing large-scale photonic integrated circuits (PICs) because it enables large-scale wafer processes with high uniformity and quality. To further improve device characteristics, heterogeneous integration of III-V compound semiconductors that provide optical gain, a high modulation efficiency, and optical non-linearity is desired. This paper describes the heterogeneous integration of membrane III-V compound semiconductor photonic devices that have a similar structure including thickness and refractive index. These devices provide efficient optical coupling with a Si waveguide using a simple taper waveguide structure. If the total thickness of the film structure is designed to be less than the critical thickness (calculated to be 430 nm for fabrication conditions such as bonding and growth temperatures), high-quality epitaxial layers can be grown on a thin InP layer directly bonded to the Si substrate. Therefore, regrowth techniques are employed on bonded InP layer on SiO2/Si substrate. We fabricate two kinds of laser-integrated Mach-Zehnder modulators using epitaxial regrowth on Si substrates. One uses Si phase modulators, and the other uses InP-based modulators. A micro-transfer-printing technology is also important when the number of III-V devices is relatively small. Furthermore, the micro-transfer-printing technology enables devices to be selected that meet the required characteristics before integration. For this purpose, we try to integrate a membrane laser on a Si substrate, in which the membrane laser is fabricated on InP substrate. The device shows a threshold current of 0.8 mA when the active region length is 140 μm. Finally, we briefly describe a transmission module, in which directly modulated membrane lasers and electronic drivers are integrated by flip-chip bonding through Au bumps. To reduce power consumption, it is important to design driver circuits that incorporate semiconductor lasers as electronic components. We demonstrate a 2-channel 53-Gbit/s 4-level pulse amplitude modulation (PAM4) transmitter front-end consisting of a 2-channel PAM4 shunt laser driver and 2-channel O-band directly modulated membrane lasers. The total power consumption is only 60.7 mW, resulting in 0.57 mW/Gbit/s.