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Wet Chemical Etching of InP Waveguides

InP Waveguides

Wet chemical etching of InP based semiconductors is a viable alternative to dry etching techniques, as these materials display crystallographically defined anisotropic etching profiles under certain conditions [1]. As has been noted in other works, for epitaxial layers grown on the {001} surface, the etch profile is dependent on both the particular crystal axis along which a waveguide is oriented, as well as the composition of the etchant [1, 2]. Using a series of wet chemical etching solutions, the waveguides to the left were formed from InP-based InGaAsP/InGaAsP multiple quantum well wafer material. The waveguide etched along the [110] axis (a) presents nearly vertical sidewalls with effectively no undercut through the InP upper cladding. The waveguide etched along the [ī10] direction (b) shows a markedly different profile, with the InP layer forming a 41° angled plane with respect to the {001} surface.

[1]       S. Adachi and H. Kawaguchi, Chemical etching characteristics of (001) InP, Journal of The Electrochemical Society, 128 (1981) 1342.

[2]       K. Ikossi Anastasiou, et al., Wet Chemical Etching with Lactic Acid Solutions for InP based Semiconductor Devices, Journal of The Electrochemical Society, 142 (1995) 3558.