Single crystal of highly purified hexagonal boron nitride capable of far ultraviolet high-luminance light emission, process for producing the same, far ultraviolet high-luminance light emitting device including the single crystal, and utilizing the device, solid laser and solid light emitting unit

Abstract

A highly pure hexagonal boron nitride single crystal not influenced by impurities and capable of high-luminance short wave ultraviolet light emission reflecting inherent characteristics is provided; a high-luminance ultraviolet light emitting element is provided by using the above single crystal; and utilizing the above element, a simple compact low-cost long-lived far ultraviolet solid-state laser and far ultraviolet solid-state light emitting apparatus are provided. A highly pure hexagonal boron nitride single crystal having a single light emission peak in the far ultraviolet region of up to a wavelength of 235 nm is produced by melting said boron nitride crystal as raw material in the presence of a highly pure solvent under high-temperature and high-pressure, followed by crystallization. A light emitting element or a light emitting layer comprised of the obtained crystal is excited with electron beams, and the thus generated far ultraviolet light resonated or without resonation is taken out.

Description

FIELD OF THE INVENTION [0001] The present invention relates to (i) a highly pure hexagonal boron nitride single crystal capable of emitting high-luminance far ultraviolet light with a single emission peak at a wavelength of 235 nm or shorter, particularly at 210 nm to 220 nm and remarkably at 215 nm, a producing method thereof, and a far ultraviolet light emitting element consisting of said single crystal. The present invention also relates to (ii) a solid-state laser using a solid-state light emitting element consisting of said highly pure hexagonal boron nitride single crystal. Further, the present invention relates to (iii) a solid-state far ultraviolet light emitting apparatus which includes said highly pure hexagonal boron nitride crystal as the light emitting layer with an exciting means incorporated thereinto. More particularly, the present invention relates to a solid-state far ultraviolet light emitting apparatus, wherein said exciting means of the light emitting layer is a...

AI Technical Summary

Benefits of technology

[0035] In the present invention, the first group inventions make it possible to create hexagonal boron nitride single crystals having specific light emission characteristics showing a strong and high-luminance light emission at a wavelength of 235 nm or shorter, particularly at 210 nm to 220 nm, remarkably at 215 nm in wavelength, not obtained by the prior art. Hereby, designing of solid-state high-luminance ultraviolet light emitting elements have become possible and various requirements for such as developments of more and more highly densified recording mediums and stronger sterilization by higher power output are able to be satisfied.

[0036] Also, in the present invention, the second group inventions make it possible to provide a compact solid-state light emitting element and a small solid-state laser having an oscillation wavelength of around 200 nm which has been difficult to be provided hitherto, by using a simple means to excite the element consisting of a highly pure hexagonal boron nitride single crystal with an electron beam.

[0037] Moreover, in the present invention, the third group inventions make it possible to provide a solid-state high-luminance light emitting apparatus compact, low cost, highly efficient, long lived, and having a single peak at the wavelength of 210 nm to 220 nm, especially at 215 nm at room temperature, by using a highly pure boron nitride crystal as the emitting layer and by incorporating integrally this emitting layer and an exciting means, especially an electron beam exciting means utilizing a substrate having an electron beam emitting part consisting of a diamond, into a vacuum chamber.

[0038] As described above, the present invention has succeeded in providing the compact solid-state light emitting element and the compact solid-state light emitting apparatus having the oscillation wavelength of 210 to 220 nm, especially at 215 nm, which has been difficult hitherto to be realized, and is expected to contribute largely to the development of various industrial fields. The compact, high power output, low cost and long lived solid-state far ultraviolet light emitting element and the solid-state laser, or the solid-state light emitting apparatus are desired in many fields, and the range of their utilization has broad divergence such as the field of semiconductors (for making the photolithography highly minute), the field of the information (next generation high capacity optical discs), the field of the medical care and living body (ophthalmological treatment, DNA cleavage and the like), and environmental field (sterilization and the like), and the benefit obtained therefrom may be immeasurable.

Problems solved by technology

However, hBN obtained by the above described gas phase reaction has contained impurities to make it difficult to obtain hBN having the far ultraviolet light emission characteristics corresponding to its specific band gap.

As for the synthesizing method, hBN has been known to be synthesized by the thermal decomposition reaction or by the gas phase reaction between boron compounds such as boron oxide and ammonia, but it has been difficult to obtain highly pure single crystals by these reactions.

Especially, they have never been considered established as the manufacturing methods of single crystal materials to use for semiconductors or the like.

However, every cBN single crystal hitherto reported is colored in amber, orange or the like, and the light emitting behavior corresponding to cBN specific band gap has not yet been able to be observed in this situation.

However, from the crystal-growth solvent used in the synthesis experiment in this report, only colored cBN crystals were obtained, and about the hBN crystal that was formed concurrently as a by-product, there was no description on the light emission behavior thereof at all or no suggestion on short wavelength light emission thereof.

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