Publication Date:
2016-05-06
Description:
Semiconductor materials that can be doped both n-type and p-type are desirable for diode-based applications and transistor technology. Copper nitride (Cu 3 N) 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 Cu 3 N 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 Cu 3 N thin films. Room temperature Hall effect and Seebeck effect measurements show n-type Cu 3 N with 10 17 electrons/cm 3 for low growth temperature (≈35 °C) and p-type with 10 15 holes/cm 3 –10 16 holes/cm 3 for elevated growth temperatures (50 °C–120 °C). Mobility for both types of Cu 3 N was ≈0.1 cm 2 /Vs–1 cm 2 /Vs. 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 V Cu defects form preferentially in p-type Cu 3 N, while Cu i defects form preferentially in n-type Cu 3 N, suggesting that Cu 3 N 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 Cu 3 N 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.
Print ISSN:
0021-8979
Electronic ISSN:
1089-7550
Topics:
Physics
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