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Repeated temperature modulation epitaxy for p-type doping and light-emitting diode based on ZnO

Abstract

Since the successful demonstration of a blue light-emitting diode (LED)1, potential materials for making short-wavelength LEDs and diode lasers have been attracting increasing interest as the demands for display, illumination and information storage grow2,3,4. Zinc oxide has substantial advantages including large exciton binding energy, as demonstrated by efficient excitonic lasing on optical excitation5,6. Several groups have postulated the use of p-type ZnO doped with nitrogen, arsenic or phosphorus7,8,9,10, and even p–n junctions11,12,13. However, the choice of dopant and growth technique remains controversial and the reliability of p-type ZnO is still under debate14. If ZnO is ever to produce long-lasting and robust devices, the quality of epitaxial layers has to be improved as has been the protocol in other compound semiconductors15. Here we report high-quality undoped films with electron mobility exceeding that in the bulk. We have used a new technique to fabricate p-type ZnO reproducibly. Violet electroluminescence from homostructural p–i–n junctions is demonstrated at room-temperature.

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Figure 1: Thin films of ZnO grown in persisting layer-by-layer mode show high-quality optical and electronic properties.
Figure 2: Atomically smooth ZnO films doped with nitrogen can be grown by a repeated temperature modulation technique.
Figure 3: Temperature dependence of hole concentration (p) in a p-type ZnO doped with nitrogen.
Figure 4: Zinc oxide homostructural p–i–n junction shows rectifying current–voltage characteristics and electroluminescence (EL) in forward bias at room-temperature.

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Acknowledgements

We thank T. Ohnishi and M. Lippmaa for measurement of coaxial impact-collision ion scattering spectroscopy. This work was supported by MEXT Grant of Creative Scientific Research 14GS0204, MEXT Grant-in-Aid for Young Scientists 15685011, the Asahi Glass Foundation, and the inter-university cooperative program of the IMR. A.T. is supported by a JSPS fellowship and S.F.C. is supported by the MEXT-COE21 program.

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Correspondence to Masashi Kawasaki.

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Tsukazaki, A., Ohtomo, A., Onuma, T. et al. Repeated temperature modulation epitaxy for p-type doping and light-emitting diode based on ZnO. Nature Mater 4, 42–46 (2005). https://doi.org/10.1038/nmat1284

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