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Exploration of ZnGeN₂/GaN heterostructures for applications in light emitting diodes
Miller, Moira K.
Miller, Moira K.
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2024
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2025-10-09
Abstract
The family of III-V materials revolutionized the optoelectronics space, particularly in nitride-based light-emitting diodes (LEDs). LED efficiency has been limited, however, by the Green Gap, which is a drop in efficiency in the green and amber regions, arising from issues with the InGaN material used to reach those light colors. ZnGeN2 has recently been studied as a potential replacement for InGaN within GaN-based LEDs, due to its structural similarity to GaN (0.12% lattice mismatch), and theorized emission in the green wavelength region. ZnGeN2 is predicted to have different optical and structural properties when cation-ordered or cation-disordered. The ordered structure has a theory-predicted band gap of 3.4 eV and an orthorhombic crystal structure. As disorder is introduced to the cation sublattice, the band gap is expected to shrink, and the crystal structure becomes wurtzite. This thesis explores the growth of ZnGeN2 by molecular beam epitaxy (MBE) and then extends that growth to ZnGeN2/GaN superlattices. Next, the valence band offset of ZnGeN2, which lacks consensus in literature, is studied by XPS. Finally, the growth and characterization of ZnGeN2-based LEDs is explored, although the LEDs did not exhibit electroluminescence. ZnGeN2-based LEDs present an opportunity to reduce the Green Gap and assist with the adoption of solid-state lighting.
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