Ultra-low-temperature a-Si:H sputtering for high-quality photonic integration.

We demonstrate the fabrication of high-quality hydrogenated amorphous silicon (a-Si:H) photonics using the low-temperature high-power impulse magnetron sputtering (HiPIMS) process. The deposited a-Si:H films exhibit a high refractive index (n ≈ 3.52) and a wide optical bandgap (≈ 1.96 eV), enabling low-loss photonic devices suitable for integrated silicon photonics. By employing an ultra-low-temperature deposition process of 70 °C, a-Si waveguide resonators are investigated, exhibiting quality (Q) factors on the order of 105 and high extinction ratios around 20 dB. These results highlight the potential of HiPIMS-deposited a-Si:H film in realizing compact, low-loss photonic devices, while also enabling low-thermal-budget hybrid integration that facilitates heterogeneous photonic integration and serves as a key step toward future co-packaged optics (CPO) implementations.