Theory of Li in ZnO: A limitation for Li-based<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi></mml:math>-type doping

Wardle, M. G.; Goss, JP; Briddon, P.R.

doi:10.1103/physrevb.71.155205

Cited by 338 publications

(223 citation statements)

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“…Formation energies (E form ) of interstitial and substitutional Li (Na) are intercepting around the middle of the band gap, resulting in a self-compensation and thus highly resistive, but still n-type, material. Wardle et al 18 also predicted that Na would be more stable on a zinc site as compared to Li, which has been experimentally confirmed. 22 Since E form (Na Zn ) + E form (Li i ) < E form (Na i ) + E form (Li Zn ), Na i causes Li Zn to change the configuration to Li i , which will diffuse and eventually get trapped in the sample bulk.…”

Section: A Na Configurations and Its Interplay With LI In Znomentioning

confidence: 71%

“…This can occur via, for instance, the reaction Na + i + Li − Zn → Na − Zn + Li + i in which the released Li i 's are highly mobile and subsequently would be trapped in the bulk through the reaction Li + i + V 2− Zn → Li − Zn (other reactions are also possible, including pair formation Li i − Li Zn ). 18 However, this can not explain why the Na concentration exceeds the HT-Li level in samples A 3 and B 2-B 4, so an additional process must take place. Under equilibrium conditions, V Zn is maintained and in n-type samples, the Na concentration is to a large extent anticipated to be controlled by the formation energy of Na Zn ; as discussed in Sec.…”

Section: Migration and Trapping Of Namentioning

confidence: 99%

“…Park et al 17 and Wardle et al 18 Li Zn , and Na i , Na Zn , respectively) as a function of E F . Their results show that the concentration of Li Zn (Na Zn ) prevails over the concentration of Li i (Na i )-meaning the defect has a lower formation energy-when E F is close to the conduction band edge, but Li i (Na i ) becomes favorable when E F moves toward the valence band edge.…”

Section: A Na Configurations and Its Interplay With LI In Znomentioning

confidence: 99%

“…In particular, atomic configurations of Li and Na in ZnO depend on the position of the Fermi level (E F ); for E F close to the conduction band edge, Li (Na) atoms on substitutional sites-Li Zn (Na Zn )-prevail, while Li (Na) atoms on interstitial sites-Li i (Na i )-are favoured when E F is close to the valence band edge. 17,18 Thus, in n-type hydrothermally grown (HT) ZnO, which contains 10 17 Li/cm 3 , the predominant configuration is Li Zn , often resulting in highly resistive material. 19,20 In this study, the interaction between Li and Na has been investigated by implanting Na into (i) HT samples with a Li content of ∼4 × 10 17 cm −3 and (ii) HT samples subjected to postgrowth anneals reducing the Li content to the 10 15 cm −3 range.…”

Section: Introductionmentioning

confidence: 99%

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Defect evolution and impurity migration in Na-implanted ZnO

et al. 2011

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Secondary ion mass spectrometry (SIMS) and positron annihilation spectroscopy (PAS) have been applied to study impurity migration and open volume defect evolution in Na + implanted hydrothermally grown ZnO samples. In contrast to most other elements, the presence of Na tends to decrease the concentration of open volume defects upon annealing and for temperatures above 600 • C, Na exhibits trap-limited diffusion correlating with the concentration of Li. A dominating trap for the migrating Na atoms is most likely Li residing on Zn site, but a systematic analysis of the data suggests that zinc vacancies also play an important role in the trapping process.

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Section: A Na Configurations and Its Interplay With LI In Znomentioning

confidence: 71%

Section: Migration and Trapping Of Namentioning

confidence: 99%

Section: A Na Configurations and Its Interplay With LI In Znomentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Defect evolution and impurity migration in Na-implanted ZnO

et al. 2011

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“…This LVM frequency is in good agreement with theoretical predictions for the sodium-hydrogen complex, with hydrogen in an antibonding configuration (AB^, 3389 cm À1 ). 20 In deuterated samples (cermet-D), we found a peak at 2466 cm À1 , with a sideband at 2461 cm À1 (Fig. 2).…”

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confidence: 94%

Vibrational Spectroscopy of Na–H Complexes in ZnO

Parmar

McCluskey

Lynn

2013

Journal of Elec Materi

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Sodium acceptors were diffused into ZnO bulk single crystals to a depth of $1 lm, with a near-surface concentration of $10 18 cm À3 . An O-H local vibrational mode (LVM) was observed at 3304 cm À1 , at a temperature of 9 K, in hydrogenated samples. The LVM is attributed to an O-H bond-stretching mode adjacent to a Na acceptor. When deuterium substitutes for hydrogen, a peak is observed at 2466 cm À1 . The isotopic frequency ratio is similar to values found in other hydrogen complexes. In the deuterated sample, a sideband at 2461 cm À1 is attributed to a Fermi resonance.Key words: ZnO, infrared, acceptor, SIMS Demand for white light-emitting diodes (LEDs), 1 high-power solid-state emitters, and lasers for use in displays, illumination, and optical storage has fueled research on wide-bandgap semiconductors. GaN, with a 3.42 eV bandgap at room temperature, 2 is a preferred material for optoelectronic applications. Wurtzite zinc oxide (ZnO), a wide-bandgap semiconductor with a 3.37 eV direct gap at room temperature, 3 has emerged as a possible competitor. ZnO has several potential advantages over GaN. With a 60 meV exciton binding energy, 4 ZnO is a more efficient emitter than GaN (25 meV exciton binding energy) at room temperature. Large ZnO wafers can be purchased for epitaxial growth, and wet chemical processing is straightforward. A problem with ZnO is that, while it can easily be made n-type, it is difficult to dope p-type in a reliable and controlled way. There are several reports on p-type doping with group IA and group V elements. 5-7 However, reproducibility and reliability of p-type doping remain controversial. 8,9 Recent theoretical 10,11 and experimental 12 studies showed that nitrogen is a deep acceptor, with a level $1.3 eV to 1.7 eV above the top of the valence band, and is therefore unsuitable for p-type doping. Sodium is a potential acceptor dopant in ZnO. In addition to behaving as deep acceptors, Meyer et al. 13 reported that Li and Na, incorporated either by diffusion or during thin-film growth, can also result in relatively shallow acceptors. Several other groups have reported first-principles calculations for column IA impurities (Li, Na, and K) in ZnO. 14,15 Park et al. 16 performed calculations for substitutional Li, Na, and K in ZnO, reporting ionization energies of 0.09 eV, 0.17 eV, and 0.32 eV, respectively. Du and Zhang, 17 using hybrid densityfunctional calculations, found acceptor levels near 0.3 eV for Li and Na.In the present study, sodium acceptors and sodium-hydrogen complexes were investigated experimentally. Melt-grown cermet ZnO single crystals 18 were used in this work. Alkali-metal dispensers from SAES Advanced Technology were used as the alkali-metal source. The alkali-metal-generating material is a mixture of an alkali-metal chromate with a reducing agent. The chromates used were anhydrous alkali-metal salts of chromic acid with general formula Me 2 CrO 4 , where Me denotes an alkali metal (Li, Na, K, Rb or Cs). Sodium dispensers of 50 mm slit length with 6 mg cm À1 yield wer...

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Native Point Defects and Doping in ZnO

Janotti

Walle

2011

Zinc Oxide Materials for Electronic and Optoelectronic Device Applications

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Theory of Li in ZnO: A limitation for Li-basedp-type doping

Cited by 338 publications

References 35 publications

Defect evolution and impurity migration in Na-implanted ZnO

Defect evolution and impurity migration in Na-implanted ZnO

Vibrational Spectroscopy of Na–H Complexes in ZnO

Native Point Defects and Doping in ZnO

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