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.
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