Heterogeneous GaSb/SOI mid-infrared photonic integrated circuits for spectroscopic applications

Abstract

Mid-infrared spectroscopy has gained significant importance in recent years as a detection technique for substances that absorb in this spectral region. Traditionally, a spectroscopic system consists of bulky equipment which is difficult to handle and incurs high cost. An integrated spectroscopic system would eliminate these disadvantages. GaSb-based active opto-electronic devices allow realizing mid-infrared light sources and detectors in the 2-3μm wavelength range for such integrated systems. Silicon photonics, based on Silicon-on-Insulator (SOI) waveguide circuits, on the other hand, is a well established technology based on high refractive index contrast waveguides, enabling ultra-compact passive integrated photonic circuits. Moreover, SOI waveguide circuit processing is compatible with CMOS processes. Hence, the integration of GaSb-based active devices onto SOI passive waveguide circuits potentially allows highly compact spectroscopic systems with a large degree of freedom in passive device design to improve the system performance. This approach has a high potential for several applications, e.g. an implantable glucose level monitor and gas sensing devices.In this paper, we report our work on the integration of GaSb-based epitaxy onto SOI waveguide circuits. The heterogeneous integration is based on an epitaxial layer transfer process using the polymer divinylsiloxanebenzocyclobutene (DVS-BCB) as a bonding agent. The process is performed by transferring the epitaxial layer to an SOI waveguide circuit wafer through a die-to-wafer bonding process. With this approach, a bonding layer of 150 nm thickness is easily achievable. We also report our results on the integration of waveguide-based GaSb p-i-n photodetectors coupled to SOI waveguide circuits using evanescent coupling, which show a responsivity higher than 0.4A/W. The design of active and passive structures and the overall fabrication process will also be discussed.

Mid-infrared laser diodes epitaxially grown on on-axis (001) silicon

“…The point that remains to be unlocked in order to achieve compact mid-IR sensors is the large-scale, cost-effective integration of III-V semiconductor lasers. Although most integration schemes until now have relied on heterogeneous bonding [10][11][12][13], there is increasing evidence that the direct epitaxial growth of the III-V semiconductor laser heterostructure on Si should outperform them, provided on-axis, CMOS-compatible (001)-oriented Si substrates can be used [14]. This last integration strategy, however, is challenged by the conjunction of large thermal, lattice, and polarity mismatches between the Si substrate and III-V materials [15].…”