Back-Side-on-BOX Heterogeneously Integrated III-V-on-Silicon O-Band Distributed Feedback Lasers

We introduce a new III-V-on-Silicon (Si) heterogeneous integration platform, where the III-V material is bonded to the back of a processed Si photonic wafer. This “Back-Side-on-Buried Oxide” (BSoBOX) process is fully compatible with active, multilayer Si photonics platforms. This article describes the process flow and reports on O-band hybrid distributed feedback (DFB) lasers of various grating periods fabricated on this platform. A comprehensive set of measurements show that the quarter-wave shifted DFB lasers have comparable performance to front-side platforms. Single-mode emission with a side mode suppression ratio around 50 dB was measured between 20  $^\circ$ C – 60  $^\circ$ C. The DFB lasers had threshold currents as low as 32 mA and produced output powers in the Si waveguide from a single-end of about 15 mW at 170 mA before the devices began to mode hop. Output powers of $\sim$ 20 mW were measured before the onset of thermal roll-off and operation up to 80  $^\circ$ C was achieved. The characteristic temperatures and thermal impedance of the lasers were evaluated and future improvements are discussed.