Multicomponent Oxynitride Thin Films: Precise Growth Control and Excited State Dynamics

摘要

Multicomponent oxynitrides significantly broaden the library of material design and promise wide applications for optoelectronics and solar energy conversion. Controlled growth of multicomponent oxynitrides with defined stoichiometry, uniformity, morphology, and scalability has been challenging. In this work, we demonstrate wafer-scale growth of uniform, crystalline GaN:ZnO thin films with tunable stoichiometry, digitally controlled film thickness, and an atomically smooth surface at a process temperature as low as room temperature. In comparison to the particle form that is commonly encountered, the GaN:ZnO thin films studied here bypass the limitations imposed by surface or size implications and reveal the intrinsic nature of optical absorption in this system. The GaN:ZnO thin films demonstrate strong visible light absorption at the composition of (GaN)(0.67)(ZnO)(0.33) and enable the first quantitative determination of bulk absorption coefficients in this system. On the basis of transient absorption spectroscopy measurements, photocarriers of GaN:ZnO thin films, excited by an ultraviolet or visible pump, present nearly identical relaxation dynamics, indicating a direct gap origin of the visible light absorption. This is consistent with complimentary steady-state optical absorption measurements and first-principle calculations. The ability to precisely control the growth of functional oxynitrides across the multicomponent scale is critical to advance material modeling and design for various applications.