Monolithic III-V/SiN co-integration through a butt-coupling scheme towards O-band applications

Abstract

Over the last decade, silicon nitride (SiN) has been proven a promising CMOS-compatible material platform instead of the already established silicon-on-insulator (SOI) [1]. That arises mainly from its tuneable physical and optical properties [2], its wider transparency window (low absorption in visible and NIR) along with its mid-index identity (low propagation loss) [3], its low thermo-optic coefficient (WDM applications) [4] and its low two-photon absorption (TPA) (non-linear applications) [5]. Furthermore, the capability of a low-temperature 350 °C PECVD growth method [2] along with SiN’s amorphous identity, renders the back end of line (BEOL) integration with active devices achievable. At the same time, the exploitation of photonic integrated chips (PICs) based on silicon (Si) towards coherent communication applications, is restricted due to the absence of fully integrated optical sources on-chip [6]. Even though progress on the III-V/SiN heterogeneous/hybrid approaches has been reported [7], a large scale monolithic integration of lasers on-chip with compact passive devices, still remains a challenge [8] due to the thick III-V buffer and cladding layers [9].
In this paper, we demonstrate a monolithic III-V/SiN transition on a silicon substrate. The integration of our optically tunable silicon nitride platform [2] with high-gain GaAs-QD multi-layer stack hetero-epitaxially grown on silicon [10] is numerically investigated. In detail, a straight III-V waveguide (n=3.29-3.5) is connected to N-rich SiN waveguides (n=1.9) in a butt-coupling scheme. A Si-rich SiN layer of an intermediate refractive index (n=2.51) is placed at the active-passive interface, so as to alleviate the high-low refractive index difference, while it passivates the III-V waveguide. Using a protective tetraethylorthosilicate (TEOS) layer, a double layer anti-reflective coating (DLARC) is composed towards the minimization of the coupling loss (CL) and parasitic back-reflection (BR). Moreover, we report on a <−30 dB BR and <0.7 dB CL transition based on optical simulations (Lumerical). In addition, preliminary stand-alone characterization results of <2 dB/cm propagation loss and 0.1 dB/90° bending regarding a 1700 nm wide and 1600 nm thick N-rich SiN platform are demonstrated, setting the ground for a future realization of a single-mode Vernier-based laser.

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Identifiers

ORCID for Thalía Domínguez Bucio: orcid.org/0000-0002-3664-1403

ORCID for Yasir Noori: orcid.org/0000-0001-5285-8779

ORCID for Frederic Y. Gardes: orcid.org/0000-0003-1400-3272

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