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Understanding and Control of Bipolar Doping in Copper Nitride



Angela N. Fioretti, Craig P. Schwartz, John Vinson, Dennis Nordlund, David Prendergast, Adele C. Tamboli, Filip Tuomisto, Stephan Lany, Eric S. Toberer, Andriy Zakutayev


Semiconductor materials that can be doped both n-type and p-type are desirable for diode-based applications and transistor technology. Copper nitride (Cu3N) is a metastable semiconductor with a solar-relevant bandgap that has been reported to exhibit bipolar doping behavior. However, deeper understanding and better control of the mechanism behind this behavior in Cu3N is currently lacking in the literature. In this work, we demonstrate both conduction types of phase-pure, sputter-deposited Cu3N thin films using a combinatorial growth temperature gradient. Room temperature Hall effect and Seebeck effect measurements show n-type Cu3N with 1017 e-/cm3 for low growth temperature (35C) and p-type with 1015-1016 h+/cm3 for elevated growth temperatures (60-120C). Mobility for both types of Cu3N was 0.1-1 cm2/Vs. Additionally, temperature-dependent Hall effect measurements indicate that ionized defects are an important scattering mechanism in p-type films. Using a combination of bulk and depth-dependent point defect formation enthalpies, in addition to near edge X-ray absorption spectroscopy, we determined that VCu defects form preferentially in p-type Cu3N while Cui defects form preferentially in n-type Cu3N. By comparing kinetic rate equations for the net arrival rate of the donor (Cui) and the acceptor (VCu) defect as a function of temperature, we were able to propose a mechanism for bipolar doping in Cu3N. This kinetics-driven doping mechanism explains the phenomenon as arising from a balance between surface and bulk kinetic processes. When surface diffusion is dominant and bulk diffusion is frozen (50-120C), p-type Cu3N is observed. When both surface and bulk diffusion is kinetically limited (no active heating), n-type Cu3N is observed. Overall, the results of this work highlight the importance of kinetic processes in the defect physics of metastable materials, and provide a framework that can be applied when considering the properties of such materials in general
Journal of Applied Physics


Fioretti, A. , Schwartz, C. , Vinson, J. , Nordlund, D. , Prendergast, D. , Tamboli, A. , Tuomisto, F. , Lany, S. , Toberer, E. and Zakutayev, A. (2016), Understanding and Control of Bipolar Doping in Copper Nitride, Journal of Applied Physics, [online],, (Accessed June 8, 2023)
Created May 4, 2016, Updated October 12, 2021