Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 16: Functional Semiconductors for Renewable Energy Solutions I

HL 16.5: Talk

Tuesday, March 19, 2024, 10:45–11:00, ER 325

Oxygen incorporation as a route to non-degenerate zinc nitride — •Elise Sirotti, Bianca Scaparra, Stefan Böhm, Felix Rauh, and Ian D. Sharp — Walter Schottky Institute and TUM School of Natural Sciences, Technical University of Munich

Zinc nitride (Zn₃N₂) comprises earth-abundant elements, possesses a small direct bandgap, and is characterized by high electron mobilities. These characteristics make it, in principle, a promising compound semiconductor for photovoltaic and thin-film transistor applications. However, in practice, the unintentional degenerate n-type doping that is commonly reported and often assigned to oxygen impurity doping significantly impedes its development for technological applications. To systematically investigate this doping effect, epitaxial Zn₃N₂ were grown by plasma-assisted molecular beam epitaxy with controlled oxygen content up to 20 at.% on a-plane sapphire, resulting in single phase (222)-oriented Zn₃N₂ with variable oxygen content. A combination of structural, electrical, and optical measurements reveals how, contrary to expectations, oxygen incorporation can lift the degenerate conductivity and achieve films with charge carrier concentrations in the 10¹⁷ cm⁻³ range. Indeed, both electrical and optical measurements confirm that the material changes from a degenerate metallic to semiconductor behavior as the oxygen content increases, suggesting the formation of charge-compensating defect complexes. The understanding of the beneficial role of oxygen thus provides a route to bring Zn₃N₂ into reach for technological applications.

Keywords: Semiconductor; Nitride; Defects