Understanding and control of bipolar self-doping in copper nitride

Fioretti, Angela N.; Schwartz, Craig P.; Vinson, John; Nordlund, Dennis; Tamboli, Adele C.; Caskey, Christopher M.; Tuomisto, Filip; Linez, Florence; Christensen, Steven T.; Toberer, Eric S.; Lany, Stephan; Zakutayev, Andriy

doi:10.1063/1.4948244

Cited by 33 publications

(26 citation statements)

References 36 publications

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“…4(b)]. These results are in good agreement with the calculations by Fioretti [19], reporting V Cu and Cu i as the dominant point defects. In the experimental section of this study [Sec.…”

Section: B Point Defect Formation Energies and Transition Levelssupporting

confidence: 90%

“…Due to its shallow defect transition level, it is the predominant acceptor defect in p-type films and its defect transition level is an excellent match for the acceptor ionization activation energy E A of 0.20 eV from temperature-dependent Hall effect data in [19]. This indicates that the Makov-Payne image charge correction employed in this study yields reasonable results, while the acceptor level E A of 0.12 eV calculated without any corrections for self-interacting errors in [19] underestimates the acceptor ionization energy. Cu i has a relatively deep (0/+) defect transition level of 0.64 eV above the VBM (0.31 eV below the CBM) and is the dominant donor-type defect given its significantly higher concentration compared to V N .…”

Section: B Point Defect Formation Energies and Transition Levelsmentioning

confidence: 82%

“…Experimentally, Cu 3 N has been synthesized by a variety of techniques, including radio frequency (RF) reactive magnetron sputtering [3,15,16] and molecular beam epitaxy [17,18]. Controlled bipolar doping of Cu 3 N has been demonstrated by varying the thin film deposition conditions [3,17,19]. Copper-poor growth conditions result in the formation of p-type films, while copper-rich growth conditions yield n-type films.…”

Section: Introductionmentioning

confidence: 99%

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Copper interstitial recombination centers in Cu3N

et al. 2018

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We present a comprehensive study of the earth-abundant semiconductor Cu 3 N as a potential solar energy conversion material, using density functional theory and experimental methods. Density functional theory indicates that among the dominant intrinsic point defects, copper vacancies V Cu have shallow defect levels while copper interstitials Cu i behave as deep potential wells in the conduction band which mediate Shockley-Read-Hall recombination. The existence of Cu i defects has been experimentally verified using photothermal deflection spectroscopy. A Cu 3 N/ZnS heterojunction diode with good current-voltage rectification behavior has been demonstrated experimentally, but no photocurrent is generated under illumination. The absence of photocurrent can be explained by a large concentration of Cu i recombination centers capturing electrons in p-type Cu 3 N. 1V) of 14. The large reverse-bias leakage current of 20 mA/cm 2 at-1 V is likely due to pinholes in the Cu 3 N absorber layer giving rise to a low shunt resistance. Under illumination, however, the Cu 3 N/ZnS p-n junction does not generate any photocurrent, suggesting either limitations in carrier transport in the Cu 3 N absorber layer due to defect states or energy barriers blocking carrier transport at the interfaces. From the inset of Fig. 9(a), linear current-voltage characteristics are observed for both Mo and In contacts on Cu 3 N with current levels commensurate with the film resistivity and thickness, confirming that Mo serves as a good ohmic contact for p-type Cu 3 N.

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“…4(b)]. These results are in good agreement with the calculations by Fioretti [19], reporting V Cu and Cu i as the dominant point defects. In the experimental section of this study [Sec.…”

Section: B Point Defect Formation Energies and Transition Levelssupporting

confidence: 90%

Section: B Point Defect Formation Energies and Transition Levelsmentioning

confidence: 82%

Section: Introductionmentioning

confidence: 99%

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Copper interstitial recombination centers in Cu3N

et al. 2018

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“…[10] and [12]). Temperature-dependent x-ray diffraction was performed at five temperatures between 100 and 280 K using a Supernova x-ray diffractometer (Rigaku Oxford Diffraction) with a monochromated molybdenum anode (λ Kα1 and λ Kα2 at 0.709 317 and 0.713 607Å) [33] and an Eos CCD detector, and separately at three temperatures between 4.2 and 100 K using the XMaS laboratory source (ESRF, Grenoble, France) with a monochromated copper anode (λ Kα1 and λ Kα2 at 1.540 593 and 1.544 427Å) [33] and a point detector (avalanche photodiode).…”

Section: Methodsmentioning

confidence: 98%

“…Lately, Cu 3 N has attracted interest as a candidate nontoxic, earth-abundant absorber for thin-film photovoltaics [10]. Favorable characteristics for photovoltaics include a beneficial band structure for AM1.5 solar illumination; strong above-onset absorption; material that is dopable both p and n type [11,12]: suggesting the potential realization of pn homojunctions; defect tolerance, and a surface which may be passivated by a native oxide; as well as good material stability and established polycrystalline growth routes [10,13]. Cu 3 N crystallizes in a rather open, cubic anti-ReO 3 structure (space group Pm3m, number 221, first determined by Juza and Hahn [14]), comprising a cubic network of vertex-connected NCu 6 octahedra.…”

Section: Introductionmentioning

confidence: 99%

Atypically small temperature-dependence of the direct band gap in the metastable semiconductor copper nitrideCu3N

et al. 2017

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The temperature-dependence of the direct band gap and thermal expansion in the metastable anti-ReO 3 semiconductor Cu 3 N are investigated between 4.2 and 300 K by Fourier-transform infrared spectroscopy and x-ray diffraction. Complementary refractive index spectra are determined by spectroscopic ellipsometry at 300 K. A direct gap of 1.68 eV is associated with the absorption onset at 300 K, which strengthens continuously and reaches a magnitude of 3.5×10 5 cm −1 at 2.7 eV, suggesting potential for photovoltaic applications. Notably, the direct gap redshifts by just 24 meV between 4.2 and 300 K, giving an atypically small band-gap temperature coefficient dE g /dT of −0.082 meV/K. Additionally, the band structure, dielectric function, phonon dispersion, linear expansion, and heat capacity are calculated using density functional theory; remarkable similarities between the experimental and calculated refractive index spectra support the accuracy of these calculations, which indicate beneficially low hole effective masses and potential negative thermal expansion below 50 K. To assess the lattice expansion contribution to the band-gap temperature-dependence, a quasiharmonic model fit to the observed lattice contraction finds a monotonically decreasing linear expansion (descending past 10 −6 K −1 below 80 K), while estimating the Debye temperature, lattice heat capacity, and Grüneisen parameter. Accounting for lattice and electron-phonon contributions to the observed band-gap evolution suggests average phonon energies that are qualitatively consistent with predicted maxima in the phonon density of states. As band-edge temperature-dependence has significant consequences for device performance, copper nitride should be well suited for applications that require a largely temperature-invariant band gap.

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High‐Mobility p‐Type and n‐Type Copper Nitride Semiconductors by Direct Nitriding Synthesis and In Silico Doping Design

et al. 2018

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Thin-film photovoltaics (PV) have emerged as a technology that can meet the growing demands for efficient and low-cost large-scale cells. However, the photoabsorbers currently in use contain expensive or toxic elements, and the difficulty in bipolar doping, particularly in a device structure, requires elaborate optimization of the heterostructures for improving the efficiency. This study shows that bipolar doping with high hole and electron mobilities in copper nitride (Cu N), composed solely of earth-abundant and environmentally benign elements, is readily available through a novel gaseous direct nitriding reaction applicable to uniform and large-area deposition. A high-quality undoped Cu N film is essentially an n-type semiconductor, while p-type conductivity is realized by interstitial fluorine doping, as predicted using density functional theory calculations and directly proven by atomically resolved imaging. The synthetic methodology for high-quality p-type and n-type films paves the way for the application of Cu N as an alternative absorber in thin-film PV.

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Understanding and control of bipolar self-doping in copper nitride

Cited by 33 publications

References 36 publications

Copper interstitial recombination centers in Cu3N

Copper interstitial recombination centers in Cu3N

Atypically small temperature-dependence of the direct band gap in the metastable semiconductor copper nitrideCu3N

High‐Mobility p‐Type and n‐Type Copper Nitride Semiconductors by Direct Nitriding Synthesis and In Silico Doping Design

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