Browsing by Subject "III-V semiconductors"
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Item Low index channels embedded in III-V semiconductors(2018-08) Skipper, Alec Mason; Bank, Seth RobertLow index materials integrated with high-quality epitaxial semiconductors have wide ranging potential applications, including high-contrast photonics, gas sensing, and opto-fluidics. For example, encapsulated air gratings can be exploited to replace Bragg reflectors in VCSELs, create high-Q resonators, create lab-on-a-chip sensing systems, or utilize Fano resonance for all-optical switching. However, it is difficult to integrate these structures with standard III-V optoelectronic devices without compromising material quality as conventional III-V growth techniques offer limited lateral control and other techniques, such as wafer bonding of patterned structures, can introduce interfacial defects. Furthermore, previous attempts to create air gaps in zincblende III-V semiconductors have been limited in shape and size due to low III-adatom mobility. We have shown that tailored molecular beam epitaxy (MBE) can be used to encapsulate patterned silicon dioxide structures into a high-quality crystalline III-V matrix, yielding monolithically integrated high contrast photonic structures. Here, we increase the achievable refractive index contrast by post-growth selective etching of the silicon dioxide. Specifically, mesas were defined that extend through the silicon dioxide layers, followed by highly-selective lateral wet etching of the silicon dioxide with buffered oxide etch (BOE). This approach is capable of yielding interconnected air cavities of arbitrary shape and size, embedded in single-crystal III-V materials. We confirmed the successful fabrication of nanometer-scale air cavities in GaAs with scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Complete etching was confirmed by monitoring the silicon dioxide phonon resonance at 1063 cm-1. In addition, we confirm the high quality integration of a quantum emitter above the low index channels using photoluminescence spectroscopy. This work establishes a basis for improved high-contrast photonics and opens up new potential applications, including lab-on-a-chip sensing via seamless integration of microfluidics with III-V semiconductor devices.