Low temperature direct bonding of InP and Si ₃N ₄-coated silicon wafers for photonic device integration

Low temperature (200°C) direct bonding of InP and Si ₃N ₄ coated silicon wafers using oxygen plasma surface treatment has been demonstrated, which transfers InP-based thin films onto Si substrates for heterogeneous photonic integration. Pulling test shows a high bonding energy comparable to the InP fracture energy. The high crystalline quality of the bonded thin film is preserved, as evident from photoluminescence and high resolution X-ray diffraction measurements. Cross-sectional transmission electron microscopy shows an intimately bonded interface with no observable defects generated near the bonded interface. A thin layer of amorphous oxide about 6 nm thick has been detected at the bonded interface. The hydrophilic interface obtained by oxygen plasma activation helps to achieve high quality bonding. Due to the high thermal conductivity of Si ₃N ₄, these high quality bonded structures of InPSi with Si ₃N ₄ sandwiched in-between have potential applications in enhancing performance of high power Si photonic integrated devices.