Integrated Optics Utilizing GaN-Based Layers on Silicon Substrates
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1068-C05-05
Integrated Optics Utilizing GaN-Based Layers on Silicon Substrates Armand Rosenberg, Michael A. Mastro, Joshua D. Caldwell, Ronald T. Holm, Richard L. Henry, Charles R. Eddy, Konrad Bussmann, and Mijin Kim Naval Research Laboratory, Washington, DC, 20375 ABSTRACT It is now apparent that future generations of fast electronics and compact sensors may need to rely increasingly on integrated optical components. But integration of electronics and photonics in today’s IC’s is challenging. Silicon, the ubiquitous electronic material, is neither ideally suited for most photonic functions nor readily integrated with most of the common photonic materials, such as GaAs. The approach we describe here relies on GaN-based films, which can be grown directly on silicon substrates and hence can be potentially integrated with state-of-the-art Si-based electronics. We have demonstrated the fabrication of GaN structures on silicon wafers ranging in overall size from sub-micron to several millimeters, all containing highly accurate individual features on the nm scale. As proof of concept, we have fabricated GaN optical waveguides and photonic crystals containing optical cavities by patterning GaN membranes grown directly on Si wafers. Our optical cavities were designed to have resonant modes within the spectral region of the broad defect-induced luminescence of GaN. We have measured sharp resonant features associated with these cavities by optically pumping above the GaN band edge, and have compared the data to numerical simulations of the spectra. Our results to date demonstrate the feasibility of fabricating high-quality GaN photonic structures directly on Si wafers, thereby providing a possible path to achieving true integration of electronics and photonics in future generations of IC’s. INTRODUCTION Recent work has demonstrated the feasibility of fabricating photonic crystal structures in GaN-based films [1-3]. These optical structures contain typical feature sizes significantly smaller than the wavelength of light, and thus qualify as true “nanophotonic” devices when the submicron emission wavelength typical of GaN-based materials is taken into account. Potentially, based on such photonic crystal nanocavities, LED’s and lasers could be designed with enhanced light extraction efficiency and reduced lasing threshold, thus enabling optoelectronic integration on an unprecedented scale. However, although high-quality GaN layers can be grown directly on Si substrates [4], a significant roadblock to optoelectronic integration is the fact that fabrication of GaN photonic crystal membranes has only been demonstrated in GaN-based films grown on sapphire substrates [2], and hence the resulting GaN optical structures cannot be easily incorporated into Si-based devices. We have addressed this challenge, and our most recent results demonstrate that GaN-based suspended waveuides and photonic crystal membranes containing nanocavities can be successfully fabricated directly on Si surfaces [5], thus partially eliminating this remaining
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