JP2009033076A - Diamond light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a light emitting element with ultraviolet luminescence using a diamond and a large output. <P>SOLUTION: By inserting a diamond layer mixed with impurity elements bonded at an interatomic distance longer than that of the diamond between a p-type diamond layer 2 and an n-type diamond layer 3, warps are generated in both of the interfaces of the p-type diamond layer 2, the n-type diamond layer 3, and the diamond layer 5 mixed with the impurity elements. On the side of the p-type diamond layer 2 and the n-type diamond layer 3 in the vicinity of both of the interfaces, optical transition is changed from an indirect transition type to a direct transition type, and holes and electrons are localized in the vicinity of both of the interfaces. Thereby, an ultraviolet light emitting element with high emission efficiency and a high output is achieved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor light-emitting device, and more particularly to a structure of a diamond light-emitting device that emits ultraviolet light and has a high output utilizing the characteristics of a wide band gap and high thermal conductivity of diamond.

Conventional light-emitting elements such as light-emitting diodes and semiconductor lasers have been developed on the basis of semiconductors with direct optical transition, such as gallium arsenide (GaAs). Since ternary and quaternary semiconductors such as aluminum gallium arsenide (AlGaAs) can adjust the composition ratio to make the lattice constant mismatch with GaAs relatively small by adjusting the composition ratio. It is possible to form a double heterostructure while maintaining the above, and a semiconductor laser was also developed in a relatively short period of time after the development of a light emitting diode.

  At the initial stage of development, the primary use of semiconductor lasers was as a light source for optical fiber communications, so there was a great demand for near-infrared semiconductor lasers with low optical attenuation due to absorption in optical fiber materials. The performance of semiconductor lasers has been improved. Furthermore, high-performance indium (In) -based ternary and quaternary compound semiconductors have been vigorously developed.

  On the other hand, as the demand for laser printers and optical disks increases, the light source is required to have a shorter wavelength.

  The photoconductor used in laser printers at that time was mainly selenium (Se), but Se is sensitive only to light having a wavelength of 500 nm or less. The adoption of semiconductor lasers is indispensable for making laser printers compact, and attempts have been made to reduce the wavelength of semiconductor lasers. However, it was technically very difficult to extend the GaAs system. Thus, a solution has been devised by devising materials and structures so as to improve the long wavelength sensitivity on the side of the photoreceptor, such as a SeTe / Se two-layer photoreceptor.

  On the other hand, in application to an optical disk, since the focused minimum spot diameter is determined by the wavelength of the semiconductor laser, it is indispensable to shorten the wavelength of the semiconductor laser for high-density recording. For this reason, research on shortening the wavelength of the semiconductor laser has been made in earnest, but there is a limit to the extension of the GaAs system. In recent years, with the advent of blue light emitting semiconductor lasers of the gallium nitride (GaN) system, a large density The next-generation high-density DVD is now in practical use.

  However, further densification is not always easy by extending the GaN system, and other materials have been searched for. As a candidate, diamond, which is a material having a wide band gap, was naturally considered, but since it is an indirect transition, efficient light emission cannot be expected from conventional common sense, and it has not been omitted much.

  However, recently, the evaluation of diamond has also been reviewed, and it has been reported that high-efficiency emission was observed using excitons (excitons), but the emission efficiency is significantly lower than conventional GaAs systems, etc. It is far from being practical.

Akio Sasaki, “Quantum Effect Semiconductor”, Corona Publishing Co., published March 10, 2000, p. 46-51

  As described above, it is unavoidable to realize efficient light emission with diamond having an indirect transition type optical transition. In order to realize a diamond light emitting device that can withstand practical use, a completely different approach to solving the fundamental problem is considered necessary.

    That is, the reason why the luminous efficiency is extremely low is because diamond is an indirect transition. Therefore, if diamond is changed to a direct transition type optical transition by some method, a practical light emitting device can be realized. There is enough sex.

  The present invention has been made in view of the various circumstances described above. That is, based on a completely different idea from the conventional one, the indirect transition diamond will be changed to a direct transition type optical transition by some method. In the present invention, a method of introducing strain due to stress in the crystal is adopted as means for changing diamond to direct transition.

  “Non-Patent Document 1” written by Akio Sasaki, “Quantum Effect Semiconductor”, Corona Publishing Co., Ltd., published March 10, 2000, p. As described in “46-51”, generally, when distortion occurs in the crystal, the band gap width changes. That is, when tensile strain occurs, the band gap narrows, and when compressive strain occurs, the band gap widens. Along with this, the position where the band gap is minimized in the momentum space can also change. When tensile strain is applied to diamond, the band gap at the Γ point decreases, so that the band gap between the bottom of the conduction band 31 and the top of the valence band 32 is minimized at the Γ point. It is possible to do.

  When a substitutional impurity element A bonded at a different interatomic distance from diamond is introduced so as to replace the position of carbon (C) in diamond, local distortion occurs in the diamond crystal. If the interatomic distance between the substitutional impurity element A and carbon (C) is smaller than the interatomic distance of diamond, tensile strain occurs in the surrounding diamond crystal, and the interatomic distance between the substitutional impurity element A and carbon (C) is diamond. If the interatomic distance is larger than that, compressive strain occurs. The strain increases substantially proportionally as the amount of the substitutional impurity element A increases.

  Here, an interface where the diamond layer and the substitutional impurity element-containing diamond layer 5 are joined is considered. Since the interatomic distance of diamond belongs to the smallest class of substances, the discussion proceeds here assuming that the interatomic distance between substitutional impurity A and carbon (C) is larger than the interatomic distance of diamond.

  Tensile strain is generated at the interface on the diamond side in contact with the substitutional impurity element-containing diamond layer 5 and the band gap is narrowed. On the other hand, compressive strain is applied to the interface on the side of the substitutional impurity element-containing diamond layer 5 in contact with the diamond. Occurs and the band gap widens. These strains are relaxed when they are separated from the interface, and band bending is reduced. Therefore, it is considered that light emission occurs in a very narrow region near the interface between the two layers.

  However, it is meaningless if the crystal structure collapses before direct transition. However, if it is a very thin diamond layer containing the substitutional impurity element A, a considerably large strain can be locally generated in the range of the critical film thickness before the crystallinity is impaired. Therefore, by adjusting the amount of the substitutional impurity element A, it is possible to optimize the amount of distortion of diamond and change it to direct transition.

  At each interface between an impurity element mixed diamond layer 5 in which an impurity element A bonded to diamond at a different interatomic distance from carbon (C) is mixed with a diamond layer of p-type, n-type, i-type, etc. It is possible to change the diamond layer to the direct transition type by optimizing the amount of distortion due to distortion caused by mismatch of constants. The p-type diamond layer 2 and the n-type diamond are formed on both sides of the impurity element-containing diamond layer 5 and, if necessary, an intrinsic diamond layer (i-type diamond layer 4) inserted between the impurity element-containing diamond layers 5. When the layer 3 is provided and current is injected in the forward direction, a very high concentration of free holes and free electrons are accumulated at the interface between the layers, and a light emitting device with higher luminous efficiency than a conventional direct transition type light emitting device is obtained. It is theoretically possible to achieve this.

  In this way, by using diamond with a large band gap and inserting a diamond layer mixed with a substitutional impurity element between the diamond layers, strain is generated in the vicinity of the interface between the above layers, and indirect transition This diamond can be converted into a direct transition to achieve practical high-efficiency ultraviolet light emission.

  Since the band gap of diamond is 5.47 eV, it is considered that ultraviolet light emission having energy close to the band gap can be realized. Furthermore, since diamond has the highest thermal conductivity among materials, it itself becomes a highly efficient heat sink and can be expected to have an extremely high output. Furthermore, if a resonator structure is introduced, an ultraviolet light emitting semiconductor laser can be realized. Ultraviolet light emitting diamond semiconductor lasers can be used not only for ultra-high density optical discs and ultra-high-speed writing, but also for various applications including ultra-high performance processing machines, and can be expected to have innovative industrial effects.

  On the diamond single crystal substrate 1, a p-type diamond layer 2, a substitutional impurity element-containing diamond layer 5 containing an element A bonded at an interatomic distance larger than diamond, and an n-type diamond layer 3 are sequentially formed. Of the interface of each layer, at least on the diamond layer side, it is converted into a direct transition by strain. Furthermore, when forward voltage is applied by band bending due to strain, high-concentration holes and electrons are confined in a very narrow region near each interface, so an ultraviolet light-emitting device with extremely high luminous efficiency can be realized. .

  An embodiment of the invention will be described based on examples and the like with reference to the drawings. Matters that are considered to be theoretically reliable without experimental verification will be explained with reference to books that are similar to existing textbooks.

FIG. 1 shows the structure of a diamond light emitting device according to the present invention.
First, a p-type diamond layer 2, a substitutional impurity element-containing diamond layer 5, and an n-type diamond layer 3 are sequentially formed on a high-pressure synthetic artificial diamond single crystal substrate 1. A metal electrode 8 is provided on the p-type diamond layer 2 and the n-type diamond layer 3 so that current can be injected from the outside.

First, a method for forming a diamond layer will be described.
A microwave plasma CVD (μ-wave p-CVD) apparatus shown in FIG. 2 was used for homoepitaxial growth of each diamond layer. First, a 5 mm square high-pressure synthetic artificial diamond single crystal substrate 1 is set on a substrate holder 11. Next, the inside of the chamber 15 is evacuated to a final vacuum of about 10 ⁻⁶ Torr by a rotary pump and an oil diffusion pump, and the gas in the chamber 15 is removed. At this time, the diamond single crystal substrate 1 is heated to 850 ° C. with a heater.

  Next, the evacuation system is switched between the rotary pump and the mechanical booster pump, the raw material gas is injected from the raw material gas introduction port 14, and the microwave 12 is introduced from the microwave waveguide 13 to generate the raw material gas plasma. In this way, a diamond layer containing carbon (C) or impurity element A in the source gas is sequentially formed on the diamond single crystal substrate 1.

What is important here is that the substrate pretreatment with only hydrogen plasma is performed prior to the formation of the diamond layer. That is, when 80 SCCM of only hydrogen (H ₂ ) gas is introduced into the chamber 15, the power of the microwave 12 of 600 W is applied, and the diamond single crystal substrate 1 is pretreated with only hydrogen plasma for 30 minutes. It has been confirmed by experiments that each layer does not contain graphite and a high-quality film with few defects can be formed with good reproducibility.

  After the pretreatment of the diamond single crystal substrate 1, each diamond layer constituting the diamond light emitting device of the present invention is sequentially formed.

First, for the formation of the p-type diamond layer 2, methane (CH ₄ ) gas and diborane (B ₂ H ₆ ) gas were used as source gases. 20 SCCM of diborane (B ₂ H ₆ ) gas diluted with hydrogen (H ₂ ) 0.01% concentration is added to 100% methane (CH ₄ ) gas with a flow rate of 0.4 SCCM, and further hydrogen for dilution (H ₂ ) A mixed gas in which 80 SCCM of gas was added was allowed to flow from the source gas inlet 14 at the top of the chamber 15 to reach the bottom of the chamber 15 through the vicinity of the diamond substrate. The gas pressure was maintained at 30 Torr, and a microwave 12 of 600 W was input from the microwave waveguide 13 to generate plasma in the vicinity of the diamond single crystal substrate 1. A p-type diamond layer 2 of about 1 μm could be formed by μ-wave p-CVD for 4 hours.

  On the p-type diamond layer 2, a substitutional impurity element-containing diamond layer 5 having three types of structures, which will be described in detail later, was formed. Here, with the platinum sheet having a 3 mm square opening closely attached to the p-type diamond layer 2, the substitutional impurity element-containing diamond layer 5 and the n-type diamond layer 3 are sequentially formed only on the opening. I went.

An n-type diamond layer 3 was formed on the substitutional impurity element-containing diamond layer 5 in the same manner as when the p-type diamond layer 2 was formed. The film formation conditions were as follows: methane (CH ₄ ) gas 0.4 SCCM as a source gas, hydrogen (H ₂ ) dilution 0.2% phosphine (PH ₃ ) gas 20 SCCM, hydrogen (H ₂ ) gas 80 SCCM Using the diluted mixed gas, the substrate temperature was set to 850 ° C., the gas pressure was set to 30 Torr, and the power of the microwave 12 was set to 600 W to form a film. An n-type diamond layer 3 having a thickness of about 1 μm could be formed by a 4 hour μ-wave p-CVD film formation.

Here, the flow rate of pure phosphine (PH ₃ ) gas is significantly increased from the flow rate of pure diborane (B ₂ H ₆ ) in the case of the p-type diamond layer 2 because the donor level of the n-type diamond is deeper. This is to compensate for the low activation rate at room temperature. For n-type diamond, which has been a long-standing concern, a film-forming technology that can control valence electrons has been developed recently, but the donor level is still deeper than the acceptor level. Become.

Next, a method for forming the metal electrode 8 will be described.
When forming the substitutional impurity element-containing diamond layer 5 or the n-type diamond layer 3, the platinum sheet used as a mask is removed, and exposure, development, and the like are performed by a normal photolithography technique. A pattern is formed in which the resist is removed from the central 2.5 mm square region of the diamond layer 3 and the outer region 0.1 mm away from the substitutional impurity element-containing diamond layer 5 on the p-type diamond layer 2.

  Here, when applying the resist, the sidewalls of the substitutional impurity element-containing diamond layer 5 and the n-type diamond layer 3 are also surely covered with the resist.

  Next, a material for the metal electrode 8 is deposited on the entire surface of the diamond light-emitting element covered with the patterned resist by vacuum evaporation or sputtering to form a metal layer.

  Finally, all the resist is removed. At this time, the metal layer on the outer periphery of the n-type diamond layer 3 excluding the 2.5 mm square central resist opening, the metal layer on the side wall of the substitutional impurity element-containing diamond layer 5 and the n-type diamond layer 3, etc. are resists. During removal, it is removed by lift-off. Thus, a diamond light emitting device having the metal electrode 8 is completed.

  Here, three examples devised for the structure of the substitutional impurity element mixed diamond layer 5 which is the main part of the present invention will be described.

FIG. 3 shows a band diagram of the first embodiment.
A C _1-x A _x impurity element containing a substitutional impurity element A with respect to carbon (C) at a constant composition ratio x on the p-type diamond layer 2 without containing a valence electron controlling impurity for controlling the conductivity type. The mixed diamond layer 5 is formed. Next, the n-type diamond layer 3 is formed on the C _1-x A _x impurity element-containing diamond layer 5. Here, the thickness and the composition ratio x of the impurity element-containing diamond layer 5 are set in a range in which the crystallinity of diamond is maintained, and the composition ratio x is the p-type diamond layer 2 or the n-type diamond layer. 3 is set to a value larger than the value that can be changed from the indirect transition to the direct transition in the vicinity of the interface with the diamond layer 5 containing the C _1-x A _x impurity element.

Due to the above structure, distortion occurs due to mismatch of lattice constants at the interface between the p-type diamond layer 2 and the n-type diamond layer 3 and the impurity element-containing diamond layer 5 containing the substitutional impurity element A. Here, since the interatomic distance of diamond belongs to the smallest class among substances, the discussion proceeds on the assumption that the average interatomic distance of the diamond layer 5 mixed with C _1-x A _x impurity element is larger than the interatomic distance of diamond. . At this time, tensile strain occurs on the p-type diamond layer 2 and n-type diamond layer 3 sides of the both interfaces, and compressive strain occurs on both interfaces on the C _1-x A _x impurity element-containing diamond layer 5 side. Arise. When tensile strain occurs, the band gap narrows, and when compressive strain occurs, the band gap widens. The above phenomenon can be said to be a textbook in this field, “Non-Patent Document 1” written by Akio Sasaki, “Quantum Effect Semiconductor”, Corona Publishing Co., Ltd., published on March 10, 2000, p. 46-51 ".

Since the band gap of diamond belongs to a very large class of materials, the discussion proceeds on the assumption that the band gap of the C _{1 -x} A _x impurity element mixed diamond layer 5 is smaller than the band gap of diamond. At both interfaces of the p-type diamond layer 2 and the n-type diamond layer 3 and the C _1-x A _x impurity element mixed diamond layer 5, at the interface on the p-type diamond layer 2 and n-type diamond layer 3 side, Band bending occurs in the direction in which the band gap becomes larger at both interfaces on the C _1-x A _x impurity element mixed diamond layer 5 side in the direction in which the band gap becomes narrower, and the band as shown in FIG. Become a structure.

On the other hand, regarding the optical interband transition, in order to change from the indirect transition to the direct transition, a considerably large stress is generally required. However, when the C _1-x A _x impurity element-containing diamond layer 5 is very thin and can easily be applied to the stress just before the crystallinity breaks, the direct transition from the indirect transition is maintained while maintaining the crystallinity. It is fully possible to convert the optical transition type into

It is assumed that a forward current flows by applying a positive voltage to the p-type diamond layer 2 and a negative voltage to the n-type diamond layer 3 through the metal electrode 8 to the diamond light emitting device having the above structure. FIG. 3 (b) shows a case where _a forward voltage of Va of 3/8 of the band gap of diamond is applied. The thin C _1-x A _x impurity element-containing diamond layer 5 does not contain a valence control impurity that controls the conductivity type such as p-type or n-type, and therefore the bands of the conduction band 31 and the valence band 32 are steep. Tilt.

In the p-type diamond layer 2 and the n-type diamond layer 3, since free carriers (holes and electrons) have an energy distribution determined by the product of the Fermi distribution function and the state density distribution function, there are some barriers. Can get over to some extent. For this reason, a significant proportion of the holes injected from the p-type diamond layer 2 into the C _1-x A _x impurity element-containing diamond layer 5 by applying a positive voltage are the p-type diamond layer 2 and the C _{1- 1} The barrier of the interface of the _x A _x impurity element mixed diamond layer 5 cannot be overcome and is accumulated in the vicinity of the interface, or a part thereof is trapped at the interface level. The remaining holes pass through the interface, but most of the holes cannot overcome the barrier at the interface between the C1 _{- xAx} impurity element-containing diamond layer 5 and the n-type diamond layer 3, It accumulates in the vicinity of the interface, or a part is trapped in the interface state.

On the other hand, of the electrons injected from the n-type diamond layer 3 into the C _1-x A _x impurity element-containing diamond layer 5 by applying a negative voltage, a significant proportion of the electrons are in the n-type diamond layer 3 and C _{1 -x} A. _{The x-} impurity element mixed diamond layer 5 cannot overcome the barrier at the interface and is accumulated in the vicinity of the interface, or a part thereof is trapped at the interface state. The remaining electrons pass through the interface, but most of the electrons cannot overcome the barrier at the interface between the C1 _{- xAx} impurity element-containing diamond layer 5 and the p-type diamond layer 2, and the vicinity of the interface. Or a part is trapped in the interface state.

Here, if holes or electrons injected from the p-type diamond layer 2 or the n-type diamond layer 3 cannot get over the initial interface barrier and many accumulate at the interface, the band profile is affected. And the holes and electrons that come later tend to pass through the first barrier. In this way, the amount of holes and electrons accumulated in the interface barrier between the p-type diamond layer 2 and the n-type diamond layer 3 and the C _{1 -xA x} impurity element-contaminated diamond layer 5 is substantially equal. .

  In this way, a very large number of holes and electrons are localized at the two interfaces. In addition, at both the above interfaces, at least in the vicinity of the interface on the p-type diamond layer 2 and n-type diamond layer 3 side, it is changed to a direct transition by strain, so that very efficient light emission can be realized.

In addition, the impurity element composition ratio x of the impurity element-containing diamond layer 5 is determined at both interfaces of the C _1-x A _x impurity element-containing diamond layer 5, the p-type diamond layer 2, and the n-type diamond layer 3. Light emission with a short wavelength can be realized with a value that is larger than a value at which diamond changes from an indirect transition to a direct transition and is as small as possible.

As an example of the substitutional element A, silicon (Si) having the same diamond structure can be considered. In this case, a film is formed by adding a small amount of silane (SiH ₄ ) gas to methane (CH ₄ ) gas as long as the crystallinity is not impaired. In order to completely replace silicon (Si) with carbon (C), it is desirable to perform heat treatment.

Next, another embodiment will be described with reference to a band diagram shown in FIG.
Here, a plurality of impurity element-containing diamond layers 5 are provided. Although FIG. 4A shows a case where two layers are provided, a larger number of layers may be used. That is, the first C _1-x A _x impurity element-containing diamond layer 5 a is formed on the p-type diamond layer 2. Next, an intrinsic diamond layer (i-type diamond layer 4) containing no impurity for valence electron control is provided on the first C _1-x A _x impurity element-containing diamond layer 5a, and a second diamond layer is further formed thereon. A C _1-x A _x impurity element mixed diamond layer 5b is provided. Finally, the n-type diamond layer 3 is formed.

In FIG. 4 (b), it shows a band diagram in the case of applying the forward voltage of 1/2 of V _b of the band gap of diamond. As can be seen from the band diagram of FIG. 4B, the interface between the p-type diamond layer 2 and the first C _1-x A _x impurity element-containing diamond layer 5a and the second C _{1- In} addition to the interface between the _x A _x impurity element-containing diamond layer 5 b and the n-type diamond layer 3, the interface between the first C _1-x A _x impurity element-containing diamond layer 5 a and the i-type diamond layer 4, and the i-type diamond layer 4 And at least each interface on the p-type diamond layer 2, n-type diamond layer 3 and i-type diamond layer 4 side of the interface between the diamond layer 5b and the second C _1-x A _x impurity element-contaminated diamond layer 5b. And light emission 34 due to recombination of electrons occurs. For this reason, further improvement in luminous efficiency can be expected.

It should be noted that the impurity elements of the first C _1-x A _x impurity element-containing diamond layer 5a and the second C _1-x A _x impurity element-containing diamond layer 5b are generated so that light having the same wavelength is generated at all the interfaces. The composition ratio x needs to be the same.

  Thus, if the number of layers of the light emitting layer 4 is further increased, further improvement in light emission efficiency can be expected.

In Example 1 and Example 2 above, in the vicinity of the interface between the p-type diamond layer 2, the n-type diamond layer 3, the i-type diamond layer 4, and the C _1-x A _x impurity element-contaminated diamond layer 5 or the like. In addition, at least at each interface on the p-type diamond layer 2, n-type diamond layer 3, and i-type diamond layer 4 side, it is changed to a direct transition, and holes and electrons are accumulated at a very high concentration. For this reason, laser oscillation may occur even in the above structure.

  However, in order to ensure coherency (coherence), in addition to the carrier confinement effect, an optical confinement effect is also required. For this purpose, it is certain to introduce an external resonator structure. For example, the above-described optical confinement effect can be expected to some extent even in the structure shown in FIG.

In Example 3, the composition ratio x of the impurity element A of the first C _1-x A _x impurity element-containing diamond layer 5a and the second C _1-x A _x impurity element-containing diamond layer 5b is set to at least a p-type diamond layer. 2 and n-type diamond layer 3 are larger than those in Example 2 in a range that can be changed to direct transition. Further, instead of i-type diamond, a C _1-x A _x low impurity element composition ratio diamond layer 6 is used, and the composition ratio x of the impurity element A is the first C _1-x A _x impurity element mixed diamond layer 5a, And the second C _1-x A _x impurity element-containing diamond layer 5b. By doing so, the band diagram as shown in FIG. 5A is obtained, and the holes and electrons entering the C _1-x A _x impurity element-containing diamond layer 5 from the p-type diamond layer 2 or the n-type diamond layer 3 are detected. The barrier is lowered, and the holes and electrons are likely to enter the C _1-x A _x impurity element-containing diamond layer 5.

The interface between the p-type diamond layer 2 and the first C _1-x A _x impurity element mixed diamond layer 5a, the interface between the second C _1-x A _x impurity element mixed diamond layer 5b and the n-type diamond layer 3, etc. It is smaller than the hole and electron recombination in the vicinity, adjacent to the first _{C 1-x a} x impurity element mixed diamond layer 5a, and a second _{C 1-x a} x impurity element mixed diamond layer 5b _{C 1 -XA x} Low impurity element composition ratio Light emission 34 due to recombination of holes and electrons by direct transition can occur at both interfaces on the diamond layer 6 side. Here, light emission occurring at both interfaces on the C _1-x A _x low impurity element composition ratio diamond layer 6 side has a shorter wavelength than light emission occurring at the other interface.

Since diamond has the highest refractive index among substances, in most cases, when an impurity element is mixed, the refractive index of the impurity element mixed diamond layer is smaller than the refractive index of diamond, The larger the composition ratio x, the smaller the refractive index. Therefore, the light into a small composition ratio of the impurity element C _1-x A _x low impurity elemental ratios diamond layer 6 confinement also allows the possibility of laser oscillation are considered to be adequate.

However, the interface between the p-type diamond layer 2 and the first C _1-x A _x impurity element-containing diamond layer 5a, and the interface between the second C _1-x A _x impurity element-containing diamond layer 5b and the n-type diamond layer 3 It is necessary to separate the long wavelength light generated by the recombination of holes and electrons in the laser beam from the laser light generated in the diamond layer 6 with a low C1 _{- xAx} low impurity element composition ratio. However, it is considered that there is a sufficient possibility that an ultraviolet-emitting semiconductor laser will be realized.

  Since the band gap of diamond is 5.47 eV, ultraviolet light emission having energy close to the band gap can be expected. Furthermore, if a resonator structure is introduced, an ultraviolet light emitting semiconductor laser can be realized. The ultraviolet light emitting semiconductor laser is considered to have many uses such as ultra-high density optical discs, and the demand from the industry is very strong.

  Furthermore, since diamond has the highest thermal conductivity among materials, it itself becomes a highly efficient heat sink and can be expected to have an extremely high output. This is not only for ultra-high-speed writing of optical discs but also for various applications including ultra-high-performance processing machines, and a revolutionary industrial effect can be expected.

1 is a diagram schematically showing the structure of a diamond light emitting device according to the present invention. It is the schematic of the manufacturing apparatus of the diamond light emitting element concerning this invention. It is a band figure of the 1st Example of the diamond light emitting element concerning this invention. (A) No voltage applied (b) During forward voltage application It is a band figure of the 2nd Example of the diamond light emitting element concerning this invention. (A) No voltage applied (b) During forward voltage application It is a band figure of the 3rd Example of the diamond light emitting element concerning this invention. (A) No voltage applied (b) During forward voltage application

Explanation of symbols

1 diamond single crystal substrate 2 p-type diamond layer 3 n-type diamond layer 4 i-type diamond layer 5 C _1-x A _x impurity element mixed diamond layer 5a first C _1-x A _x impurity element mixed diamond layer 5b second C _1-x A _x impurity element mixed diamond layer 6 C _1-x A _x low impurity element composition ratio diamond layer 7 power supply 8 metal electrode 11 substrate holder 12 microwave 13 microwave waveguide 14 source gas inlet 15 chamber 16 substrate holder Support rod 17 Quartz tube 18 Cooling water 19 Water cooling jacket 20 Plunger 21 Viewport 31 Conduction band 32 Valence band 33 Fermi level 34 Light emission

Claims (2)

In a light emitting device in which a plurality of diamond-based layers are formed by epitaxial growth on a diamond single crystal substrate, an element A bonded between the p-type diamond layer and the n-type diamond layer at an interatomic distance different from that of diamond. A diamond light-emitting element, wherein one or more impurity element-contained diamond layers are formed. In the above-mentioned “claim 1”, a p-type diamond layer, an n-type diamond layer, and an i-type diamond layer that are in contact with a C _1-x A _x impurity element-containing diamond layer composed of carbon (C) and an impurity element A are included. In the case where an i-type diamond layer and a C _1-x A _x low impurity element composition ratio diamond layer are included, a crystal in the vicinity of the interface of each side of the C _1-x A _x low impurity element composition ratio diamond layer A diamond light emitting device characterized in that an optical transition type is changed from an indirect transition to a direct transition by strain while retaining the property, and an impurity element having a composition ratio x is mixed so that light emission occurs in the vicinity of each interface. .

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