Photonic crystals in deeply etched InP-based materials

A double layer mask strategy involving ebeam lithography, pattern transfer to a SixNy-mask layer with reactive ion etching and deep inductively coupled plasma InP-etching, has been applied to fabricate 2D photonic crystals in InP-substrates. The feasibility of using a 30 kV e-beam tool for photonic crystal fabrication has been demonstrated. Key issue for the RIE-process is the RIE-lag. The first InP-etching tests produced conical shaped holes with a depth around 0.8 µm and a diameter around 250 nm. Significant difference between n-type and semi-insulating InP after ICP etching, in terms of floor roughness, sidewall roughness and sidewall angle of the holes, has been observed.