title: Understanding and Control of Bipolar Self-Doping in Copper Nitride.
abstract: 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 use combinatorial growth with a temperature gradient to demonstrate both conduction types of phase-pure, sputter-deposited Cu3N thin films. Room temperature Hall effect and Seebeck effect measurements show n-type Cu3N with an electron density of 1017cm-3for low growth temperature (≈ 35 °C) and p-type with a hole density between 1015cm-3and 1016cm-3for elevated growth temperatures (50 °C to 120 °C). Mobility for both types of Cu3N was ≈ 0.1 cm2/Vs to 1 cm2/V. Additionally, temperature-dependent Hall effect measurements indicate that ionized defects are an important scattering mechanism in p-type films. By combining X-ray absorption spectroscopy and first-principles defect theory, we determined that VCudefects form preferentially in p-type Cu3N while Cuidefects form preferentially in n-type Cu3N; suggesting that Cu3N is a compensated semiconductor with conductivity type resulting from a balance between donor and acceptor defects. Based on these theoretical and experimental results, we propose a kinetic defect formation mechanism for bipolar doping in Cu3N, that is also supported by positron annihilation experiments. 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.
authors.affiliation: National Renewable Energy Laboratory, Golden, Colorado 80401 USA; Colorado School of Mines, Golden, Colorado 80401 USA.
authors.forename: Angela N
authors.initials: AN
authors.lastname: Fioretti
authors.affiliation: Stanford Synchrotron Radiation Laboratory, SLAC National Accelerator Lab, Menlo Park, California 94720 USA.
authors.forename: Craig P
authors.initials: CP
authors.lastname: Schwartz
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899 USA.
authors.forename: John
authors.initials: J
authors.lastname: Vinson
authors.affiliation: Stanford Synchrotron Radiation Laboratory, SLAC National Accelerator Lab, Menlo Park, California 94720 USA.
authors.forename: Dennis
authors.initials: D
authors.lastname: Nordlund
authors.affiliation: Lawrence Berkeley National Laboratory, Berkeley, California 94720 USA.
authors.forename: David
authors.initials: D
authors.lastname: Prendergast
authors.affiliation: National Renewable Energy Laboratory, Golden, Colorado 80401 USA; Colorado School of Mines, Golden, Colorado 80401 USA.
authors.forename: Adele C
authors.initials: AC
authors.lastname: Tamboli
authors.affiliation: National Renewable Energy Laboratory, Golden, Colorado 80401 USA; Colorado School of Mines, Golden, Colorado 80401 USA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Caskey
authors.affiliation: Aalto University School of Science, Espoo, Finland.
authors.forename: Filip
authors.initials: F
authors.lastname: Tuomisto
authors.affiliation: Aalto University School of Science, Espoo, Finland.
authors.forename: Florence
authors.initials: F
authors.lastname: Linez
authors.affiliation: National Renewable Energy Laboratory, Golden, Colorado 80401 USA.
authors.forename: Steven T
authors.initials: ST
authors.lastname: Christensen
authors.affiliation: National Renewable Energy Laboratory, Golden, Colorado 80401 USA; Colorado School of Mines, Golden, Colorado 80401 USA.
authors.forename: Eric S
authors.initials: ES
authors.lastname: Toberer
authors.affiliation: National Renewable Energy Laboratory, Golden, Colorado 80401 USA.
authors.forename: Stephan
authors.initials: S
authors.lastname: Lany
authors.affiliation: National Renewable Energy Laboratory, Golden, Colorado 80401 USA.
authors.forename: Andriy
authors.initials: A
authors.lastname: Zakutayev