Abstract
The oxidation of GaSb in aqueous environments has gained interest by the advent of plasmonic antimonide-based compound semiconductors for molecular sensing applications. This work focuses on quantifying the GaSb–water reaction kinetics by studying a model compound system consisting of a 50 nm thick GaSb layer on a 1000 nm thick highly Si-doped epitaxial grown InAsSb layer. Tracing of phonon modes by Raman spectroscopy over 14 h of reaction time shows that within 4 h, the 50 nm of GaSb, opaque for visible light, transforms to a transparent material. Energy-dispersive x-ray spectroscopy shows that the reaction leads to antimony depletion and oxygen incorporation. The final product is a gallium oxide. The good conductivity of the highly Si-doped InAsSb and the absence of conduction states through the oxide are demonstrated by tunneling atomic force microscopy. Measuring the reflectivity of the compound layer structure from 0.3 to 20 μm and fitting of the data by the transfer-matrix method allows us to determine a refractive index value of 1.6 ± 0.1 for the gallium oxide formed in water. The investigated model system demonstrates that corrosion, i.e. antimony depletion and oxygen incorporation, transforms the narrow band gap material GaSb into a gallium oxide transparent in the range from 0.3 to 20 μm.
Highlights
Antimonide-based compound semiconductors are promising narrow band gap materials for fast and low power consuming electronics [1], for mid-IR opto-electronic applications [2], for waveguide and optical parametric oscillator fabrication [3, 4], for photovoltaics [5,6,7] and for plasmonic applications [8, 9]
The slow, steady and selective oxidation of GaSb in water leads to an all-semiconductor midIR pedestal configuration consisting of highly doped InAsSb plasmonic resonators on top of GaSb pedestals embedded in an amorphous oxide layer [11]
The higher refractive index of anodically formed GaSb oxide is probably due to the presences of antimony oxides, which are depleted by a slow corrosion process when GaSb is immersed in water
Summary
Antimonide-based compound semiconductors are promising narrow band gap materials for fast and low power consuming electronics [1], for mid-IR opto-electronic applications [2], for waveguide and optical parametric oscillator fabrication [3, 4], for photovoltaics [5,6,7] and for plasmonic applications [8, 9]. The slow, steady and selective oxidation of GaSb in water leads to an all-semiconductor midIR pedestal configuration consisting of highly doped InAsSb plasmonic resonators on top of GaSb pedestals embedded in an amorphous oxide layer [11]. In the field of plasmonic applications, a recent work has demonstrated that the native oxide of GaSb can be exploited for stable surface functionalization based on phosphonic acid chemistry [27]. We study a model compound system consisting of a 50 nm thick GaSb layer epitaxially grown on a 1000 nm thick layer of highly Si-doped InAsSb. The reaction of the GaSb with water over a period of 14 h is investigated by Raman spectroscopy, energy-dispersive x-ray.
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