Rebecca Lentz

Student: Rebecca Lentz

Project: GaN/AlInO Waveguides for Visible Light Communications | View Poster (PDF)

Institution: Lehigh University

Major: Electrical and Computer Engineering

Advisor: Jonathan Wierer


Gallium Nitride (GaN) is most commonly and successfully used for light-emitters, high- speed transistors, and power devices. A more nascent application is III-nitride waveguides which have potential for various applications such as nonlinear optics, quantum photonics , and visible light communications (VLC). VLC can be accomplished using either light-emitting diodes (LEDs) or laser diodes (LDs), the latter offering faster modulation speeds due to stimulated emission. These speeds can be enhanced further, as shown in other material systems, by using waveguides and modulators to form photonic integrated circuits (PIC). PICs require routing of the photonic signals which is, for example, accomplished in Si-based PICs using a Silicon-on-insulator waveguiding structure. An analog semiconductor/buried oxide waveguide has yet to be demonstrated for III-nitrides.

Here a new oxidation process is used to transform AlInN to AlInO and form waveguides in III-nitride semiconductors. This process uses wet thermal oxidation (H2O/N2 at 800 - 900 °C) to form dense, insulating, and thick AlInO. This AlInO has a refractive index of n ~ 1.7 at λ=405 nm, making it ideal as a cladding layer for GaN, which has a refractive index of n ~ 2.4. To produce the waveguiding structure, a thick layer (> 200 nm) of AlxIn1-xN is grown lattice matched (x~0.82) on a GaN layer by metalorganic chemical vapor deposition (MOCVD). This is followed by a thin GaN core layer which is then post-growth patterned and etched to form waveguiding strips. The AlInN is then oxidized laterally, beginning on the exposed AlInN and proceeding underneath the GaN core to create the AlInO lower cladding. This air/GaN/AlInO waveguide is simulated using COMSOL multiphysics modeling software to determine mode characteristics and dimensional requirements. The structure is designed for single-mode propagation of blue laser light (λ=405 nm), but could potentially guide light in the infrared spectrum, if designed with the proper dimensions.

About Rebecca Lentz

Rebecca Lentz is a senior studying electrical engineering at Lehigh University with a focus in semiconductor materials. She began researching under the guidance of Professor Jonathan Wierer the summer after her sophomore year and plans to continue past receiving her bachelors by pursuing a PhD in the field. For this research she has received the Clare Boothe Luce Research Scholarship and Honorable Mention for her presentation at the David and Lorraine Freed Undergraduate Research Symposium in 2018. Additionally, she is a Rossin Junior Engineering Fellow, President of Eta Kappa Nu, Vice President of the IEEE student chapter and is a recipient of the Joseph C. Gabuzda Memorial Award for outstanding achievement in Electrical Engineering at Lehigh.


Lehigh Engineering Undergraduate Research Symposium

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