Abstract
We report here the epitaxial growth of III-nitride material on freestanding HfO2 gratings by molecular beam epitaxy. Freestanding HfO2 gratings are fabricated by combining film evaporation, electron beam lithography, and fast atom beam etching of an HfO2 film by a front-side silicon process. The 60-μm long HfO2 grating beam can sustain the stress change during the epitaxial growth of a III-nitride material. Grating structures locally change the growth condition and vary indium composition in the InGaN/GaN quantum wells and thus, the photoluminescence spectra of epitaxial III-nitride grating are tuned. Guided mode resonances are experimentally demonstrated in fabricated III-nitride gratings, opening the possibility to achieve the interaction between the excited light and the grating structure through guided mode resonance.PACS: 78.55.Cr; 81.65.Cf; 81.15.Hi.
Highlights
Freestanding III-nitride structures can take advantage of the large refractive index contrast between III-nitride and air [1,2,3,4,5,6,7]
Since the original HfO2 grating beam has a trapezoidal profile, we use the designed air opening to describe the epitaxial III-nitride grating for simplicity
Since the epitaxial gratings are freely suspended with air as the low refractive index material on the top and bottom, the freestanding epitaxial gratings can serve as an optical cavity to support guided mode resonances, which are characterized in reflectance measurement with the tunable laser operating in the range of 1,460 nm to approximately 1,580 nm
Summary
Freestanding III-nitride structures can take advantage of the large refractive index contrast between III-nitride and air [1,2,3,4,5,6,7]. The as-grown III-nitride structures can provide a natural optical cavity to support guided mode resonances, opening the possibility to achieve the interaction between the excited light and the epitaxial structures. It is of great interest to implement the growth of III-nitride materials on freestanding HfO2 gratings.
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