Luminous body

Abstract

The present invention provides a light-emitting device capable of emitting light in multiple colors depending on the energy of the incident electron beam. [Solution] The light-emitting body 1 converts an incident electron beam E into fluorescence. The light-emitting body 1 comprises a substrate 10 that is transparent to fluorescence, and a multiple quantum well structure 20 formed on the main surface 10a of the substrate 10 that emits fluorescence upon incidence of an electron beam E. The multiple quantum well structure 20 has a long-wavelength layer 20A that emits fluorescence SA of a first wavelength in response to the incidence of an electron beam E, and a short-wavelength layer 20B laminated on the long-wavelength layer 20A that emits fluorescence SB of a second wavelength in response to the incidence of an electron beam E.

Description

[Technical Field]

[0001] This disclosure relates to a light-emitting device. [Background technology]

[0002] Light-emitting materials that convert incident electron beams into fluorescence are known. As an example of this type of technology, Patent Document 1 describes a scintillator light-emitting part formed by creating a quantum well structure on a sapphire substrate. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 6666626 [Overview of the project] [Problems that the invention aims to solve]

[0004] In recent years, for example, in order to separate electron beams of different energies incident on a light-emitting material, there is a need for a light-emitting material that emits multiple colors corresponding to the energy of the incident electron beam. Therefore, the purpose of this disclosure is to provide a light-emitting material that can emit multiple colors corresponding to the energy of the incident electron beam. [Means for solving the problem]

[0005] The light-emitting material according to the present disclosure is [1] "a light-emitting material that converts an incident electron beam into fluorescence, comprising: a substrate transparent to fluorescence; and a quantum well structure formed on one surface of the substrate, which emits fluorescence upon incidence of the electron beam, wherein the multiple quantum well structure comprises: a first wavelength layer which emits fluorescence of a first wavelength in response to incidence of the electron beam; and a second wavelength layer laminated on the first wavelength layer which emits fluorescence of a second wavelength shorter than the first wavelength in response to incidence of the electron beam."

[0006] In this light-emitting material, when an electron beam is incident on it, fluorescence is emitted in the wavelength layer on the electron beam incident side of the first and second wavelength layers (hereinafter also referred to as the "incident wavelength layer"). At this time, for example, if the energy of the electron beam is low, the electron beam will not reach the wavelength layer on the opposite side of the electron beam incident side of the first and second wavelength layers (hereinafter also referred to as the "opposite wavelength layer"), and the opposite wavelength layer will not emit fluorescence. On the other hand, for example, if the energy of the electron beam is high, the electron beam is more likely to reach the opposite wavelength layer, and as a result, in addition to emitting fluorescence in the incident wavelength layer, fluorescence of a different wavelength from that fluorescence will be emitted in the opposite wavelength layer. In other words, the light-emitting material according to this disclosure makes it possible to emit light in multiple colors depending on the energy of the incident electron beam.

[0007] The light-emitting material according to this disclosure may also be [2] "the light-emitting material according to [1], wherein the quantum well structure is configured such that one of the first wavelength layer and the second wavelength layer, opposite to the electron beam incident surface of the quantum well structure, is sensitive to the electron beam having an energy of a predetermined value or higher." In this case, the light-emitting material can emit light in multiple colors depending on whether the energy of the incident electron beam is above a predetermined value or higher.

[0008] The light-emitting material according to this disclosure may also be the light-emitting material according to [2], wherein the quantum well structure is configured such that the thickness of the other of the first and second wavelength layers is set such that the side of the first and second wavelength layers opposite to the electron beam incident surface is sensitive to electron beams with energy equal to or greater than a predetermined value. In this case, the multi-color emission depending on whether the energy of the incident electron beam is equal to or greater than a predetermined value can be set by the thickness of the incident-side wavelength layer.

[0009] The light-emitting material according to this disclosure may be [4] "the light-emitting material according to any one of [1] to [3], wherein the first wavelength layer and the second wavelength layer each include a plurality of light-emitting layers made of nitride semiconductors containing Ga and In, and the proportion of In in the composition of the plurality of light-emitting layers included in the first wavelength layer is greater than the proportion of In in the composition of the plurality of light-emitting layers included in the second wavelength layer." In this case, the first wavelength layer and the second wavelength layer can be specifically configured.

[0010] The light-emitting material according to this disclosure may be [5] "the light-emitting material according to any one of [1] to [4], wherein the first wavelength layer includes a plurality of barrier layers, and the plurality of barrier layers included in the first wavelength layer include a first barrier layer and a second barrier layer located on the electron beam incident surface side of the quantum well structure relative to the first barrier layer, and the first barrier layer is thicker than the second barrier layer." In this case, it is possible to improve the luminescence efficiency of the light-emitting material and increase the luminescence intensity.

[0011] The light-emitting material according to this disclosure may be [6] "the light-emitting material according to any one of [1] to [5] wherein the second wavelength layer includes a plurality of barrier layers, and the plurality of barrier layers included in the second wavelength layer have the same thickness as each other." In this case, it is possible to improve the luminescence efficiency of the light-emitting material and increase the luminescence intensity.

[0012] The light-emitting material according to this disclosure may be [7] "the light-emitting material according to any one of [1] to [6] wherein the first wavelength layer and the second wavelength layer each include a plurality of barrier layers, and the average thickness of the plurality of barrier layers included in the first wavelength layer is greater than the average thickness of the plurality of barrier layers included in the second wavelength layer." In this case, it is possible to improve the luminescence efficiency of the light-emitting material and increase the luminescence intensity.

[0013] The light-emitting material according to this disclosure may be [8] "the light-emitting material according to any one of [1] to [7] wherein the first wavelength layer is laminated on the electron beam incident surface side of the quantum well structure on the second wavelength layer." In this case, it is possible to suppress the excitation of the first wavelength layer by short-wavelength fluorescence emitted in the second wavelength layer. [Effects of the Invention]

[0014] According to one aspect of the present invention, it is possible to provide a phosphor that can emit multi-color light according to the energy of an incident electron beam.

Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of a phosphor according to an embodiment. [Figure 2] FIG. 2(a) is a cross-sectional view showing the configuration of the long wavelength layer of the phosphor in FIG. 1. FIG. 2(b) is a cross-sectional view showing the configuration of the short wavelength layer of the phosphor in FIG. 1. [Figure 3] FIG. 3 is a graph for explaining the fluorescence emitted from the multiple quantum well structure portion in FIG. 1. [Figure 4] FIG. 4 is a graph showing the relationship between the energy of the electron beam incident on the phosphor in FIG. 1 and the relative integrated intensity of each fluorescence. [[ID=​​​​​​​​​​​​​​​​​The substrate 10 is a plate-shaped member that is transparent (in other words, has light transmissivity) to the wavelength of the fluorescence emitted by the multiple quantum well structure portion 20. The constituent material of the substrate 10 is not particularly limited as long as it transmits the light emitted by the multiple quantum well structure portion 20 and enables epitaxial growth of the multiple quantum well structure portion 20. In one example, the substrate 10 is a sapphire substrate. Also, in one example, the substrate 10 transmits light with a wavelength of 170 nm or more. The substrate 10 has a main surface (one surface) 10a as the surface on the side of the conductive layer 30.

[0019] The multiple quantum well structure portion 20 is a portion that emits fluorescence upon incidence of the electron beam E and is formed on the main surface 10a of the substrate 10. Emitting fluorescence means outputting light with a certain or higher emission intensity, in other words, emitting light with a certain or higher emission intensity. The multiple quantum well structure portion 20 is a layer epitaxially grown on the main surface 10a of the substrate 10. The surface of the multiple quantum well structure portion 20 on the side of the conductive layer 30 constitutes the electron beam incident surface S of the multiple quantum well structure portion 20. The multiple quantum well structure portion 20 has a long wavelength layer (first wavelength layer) 20A and a short wavelength layer (second wavelength layer) 20B laminated on the substrate 10 side of the long wavelength layer 20A.

[0020] The long wavelength layer 20A is a wavelength layer that emits fluorescence SA (see FIG. 3) with a first wavelength in response to the electron beam E. The long wavelength layer 20A is laminated on the electron beam incident surface S side on the short wavelength layer 20B. The short wavelength layer 20B is a wavelength layer that emits fluorescence SB (see FIG. 3) with a second wavelength shorter than the first wavelength in response to the electron beam E. The short wavelength layer 20B is laminated on the substrate 10 side (that is, the side opposite to the electron beam incident surface S side) of the long wavelength layer 20A.

[0021] FIG. 2(a) is a cross-sectional view showing the configuration of the long wavelength layer 20A of the light emitter 1 in FIG. 1. As shown in FIG. 2(a), the long wavelength layer 20A includes a plurality of light emitting layers 21A and a plurality of barrier layers 22A. The light emitting layer 21A is a layer configured to include a material that emits fluorescence upon receiving the electron beam E. The light emitting layer 21A is made of, for example, a nitride semiconductor containing Ga and In. Specifically, In x Ga 1-xIt is composed of a nitride semiconductor mainly containing crystals of N(0 < x < 1). In one example, the light-emitting layer 21A is In doped with Si x Ga 1-x composed of crystals of N. The compositions of the plurality of light-emitting layers 21A constituting the long-wavelength layer 20A are identical to each other. The thicknesses of the plurality of light-emitting layers 21A constituting the long-wavelength layer 20A are equal to each other.

[0022] The barrier layer 22A has a bandgap energy larger than that of the light-emitting layer 21A. By sandwiching the light-emitting layer 21A between the barrier layers 22A, electrons can be collected in the light-emitting layer 21A and efficiently converted into fluorescence. The barrier layer 22A is a nitride semiconductor layer mainly containing GaN crystals. In one example, the barrier layer 22A is composed of crystals of GaN doped with Si. Note that the barrier layer 22A may further contain group III atoms other than Ga (for example, In). The compositions of the plurality of barrier layers 22A constituting the long-wavelength layer 20A may be equal to each other. The long-wavelength layer 20A is configured such that the thicknesses of the plurality of barrier layers 22A become thinner as they approach the electron beam incident surface S. In other words, in the long-wavelength layer 20A, the plurality of barrier layers 22A have an inclined structure.

[0023] FIG. 2(b) is a cross-sectional view showing the structure of the short-wavelength layer 20B of the light emitter 1 in FIG. 1. As shown in FIG. 2(b), the short-wavelength layer 20B includes a plurality of light-emitting layers 21B and a plurality of barrier layers 22B. The light-emitting layer 21B is a layer configured to include a material that emits light upon receiving the electron beam E. The light-emitting layer 21B is composed of, for example, a nitride semiconductor containing Ga and In. Specifically, In y Ga 1-y It is composed of a nitride semiconductor mainly containing crystals of N(0 < y < 1). In one example, the light-emitting layer 21B is In doped with Si y Ga 1-y composed of crystals of N. The compositions of the plurality of light-emitting layers 21B constituting the short-wavelength layer 20B are identical to each other. The thicknesses of the plurality of light-emitting layers 21B constituting the short-wavelength layer 20B are equal to each other.

[0024] The barrier layer 22B has a bandgap energy larger than that of the light-emitting layer 21B. By sandwiching the light-emitting layer 21B between the barrier layers 22B, electrons can be collected in the light-emitting layer 21B and efficiently converted into fluorescence. The barrier layer 22B is a nitride semiconductor layer mainly containing GaN crystals. In one example, the barrier layer 22B is composed of Si-doped GaN crystals. Note that the barrier layer 22B may further contain group III atoms other than Ga (e.g., In). The compositions of the plurality of barrier layers 22B constituting the short-wavelength layer 20B may be equal to each other. The plurality of barrier layers 22B are configured such that the thicknesses of the plurality of barrier layers 22B are the same as each other. In other words, in the short-wavelength layer 20B, the plurality of barrier layers 22B have a constant-thickness layer structure. In this embodiment, when the thickness of one layer is equal to that of another layer, it means that the difference between the thickness of one layer and the thickness of the other layer is ±10% or less of the thickness of one layer.

[0025] In the example of this embodiment, the long-wavelength layer 20A includes six light-emitting layers 21A and six barrier layers 22A. The thicknesses of the plurality of light-emitting layers 21A are the same, 1.5 nm. The thicknesses of the plurality of barrier layers 22A are 10 nm, 20 nm, 15 nm, 200 nm, 240 nm, and 260 nm in order from the electron beam incident surface S. The short-wavelength layer 20B includes ten light-emitting layers 21B and eleven barrier layers 22B. The thicknesses of the plurality of light-emitting layers 21B are the same, 1.5 nm. The thicknesses of the plurality of barrier layers 22A are the same, 100 nm.

[0026] The ratio of In in the composition of the plurality of light-emitting layers 21A included in the long-wavelength layer 20A is larger than the ratio of In in the composition of the plurality of light-emitting layers 21B included in the short-wavelength layer 20B. In the above-described composition formulas of the light-emitting layer 21A and the light-emitting layer 21B, y < x < 1 and 0 < y < x < 1. In the light-emitting layer 21A and the light-emitting layer 21B, the wavelength of the emitted fluorescence becomes longer as the composition of In increases (shorter as the composition of In decreases). The average thickness of the plurality of barrier layers 22A included in the long-wavelength layer 20A is thicker than the average thickness of the plurality of barrier layers 22B included in the short-wavelength layer 20B. In other words, the average thickness of the plurality of barrier layers 22B is less than or equal to the average thickness of the plurality of barrier layers 22A.

[0027] Figure 3 is a graph illustrating the fluorescence SA and SB emitted from the multiple quantum well structure 20. In Figure 3, the horizontal axis represents wavelength, and the vertical axis represents relative emission intensity. As shown in Figure 3, for example, the first wavelength fluorescence SA emitted from the long-wavelength layer 20A has a peak wavelength of 440 nm. For example, the second wavelength fluorescence SB emitted from the short-wavelength layer 20B has a peak wavelength of 390 nm. The first wavelength of fluorescence SA and the second wavelength of fluorescence SB correspond to their respective peak wavelengths. The difference ΔP between the first and second wavelengths is, for example, 50 nm. Note that the first wavelength of fluorescence SA and the second wavelength of fluorescence SB are not limited to peak wavelengths, but may be, for example, the average value of the emission peak wavelength range.

[0028] Figure 4 is a graph showing the relationship between the energy of the electron beam E incident on the light emitter 1 and the relative integrated intensity of each fluorescence SA and SB. In Figure 4, the horizontal axis represents the acceleration voltage of the electron beam E, which corresponds to the energy of the electron beam E incident on the light emitter 1. The vertical axis represents the relative integrated intensity, which is, for example, the relative value of the intensity at the peak wavelength. As shown in Figure 4, when the energy of the electron beam E incident on the light emitter 1 is above the lower threshold α and below a predetermined value β, fluorescence SA is emitted in the long-wavelength layer 20A, but fluorescence SB is not emitted in the short-wavelength layer 20B.

[0029] On the other hand, if the energy of the electron beam E incident on the light emitter 1 is greater than or equal to a predetermined value β, in addition to the emission of fluorescence SA in the long-wavelength layer 20A, fluorescence SA is also emitted in the long-wavelength layer 20A. In other words, the multiple quantum well structure 20 is configured such that the short-wavelength layer 20B is sensitive to electron beam E incident on the light emitter 1 when the energy of the electron beam E is greater than or equal to a predetermined value. The predetermined value is not specifically defined, but for example, it is 15kV.

[0030] Specifically, in the multiple quantum well structure 20, the thickness of the long-wavelength layer 20A is set such that the short-wavelength layer 20B is sensitive to electron beams E whose energy is greater than or equal to a predetermined value β when incident on the light-emitting body 1. More specifically, it is set as follows: That is, for example, if the long-wavelength layer 20A is thicker, the energy required to pass through the long-wavelength layer 20A increases accordingly. For example, if an electron beam E with high energy is incident on the electron beam incident surface S, the electron beam E will reach the short-wavelength layer 20B on the substrate 10 side, but if an electron beam with low energy is incident on the electron beam incident surface S, the electron beam E will not reach the short-wavelength layer 20B. In other words, if an electron beam E with high energy is incident on the electron beam incident surface S, the short-wavelength layer 20B will emit fluorescence SB, but if an electron beam E with low energy is incident on the electron beam incident surface S, the short-wavelength layer 20B will not emit fluorescence SB.

[0031] On the other hand, if the long-wavelength layer 20A is thin, the energy required for the electron beam E to pass through the long-wavelength layer 20A is reduced accordingly. Therefore, even if an electron beam E with low energy is incident on the electron beam incident surface S, the electron beam E will reach the short-wavelength layer 20B. In other words, even if an electron beam E with low energy is incident on the electron beam incident surface S, the short-wavelength layer 20B will emit fluorescence SB. Based on this understanding, in the multiple quantum well structure 20, the thickness of the long-wavelength layer 20A is set such that when an electron beam E with an energy of a predetermined value β or more is incident on the long-wavelength layer 20A from the electron beam incident surface S, it will pass through the long-wavelength layer 20A while emitting fluorescence SA, reach the short-wavelength layer 20B, and emit fluorescence SB there.

[0032] The conductive layer 30 is used as one of the electrodes that guides electrons to the light emitter 1. The conductive layer 30 mainly contains, for example, a metal, and in one embodiment, mainly contains aluminum (Al). The thickness of the conductive layer 30 is, for example, 10 nm or more and 1000 nm or less, and in one embodiment, it is about 300 nm. When the conductive layer 30 mainly contains a metal, the conductive layer 30 also functions as a light reflection film. That is, a part of the fluorescence generated in the multiple quantum well structure portion 20 reaches the substrate 10 directly from the multiple quantum well structure portion 20, passes through the substrate 10, and is emitted to the outside of the light emitter 1. However, the remaining part of the fluorescence generated in the multiple quantum well structure portion 20 reaches the conductive layer 30 from the multiple quantum well structure portion 20, is reflected by the conductive layer 30, and then passes through the substrate 10 and is emitted to the outside of the light emitter 1.

[0033] An example regarding the manufacturing method of the light emitter 1 will be described. First, the substrate 10 is introduced into the growth chamber of a metal-organic vapor phase epitaxy (MOVPE) apparatus, and heat treatment is performed at 1100 °C for 10 minutes in a hydrogen atmosphere to clean the main surface 12a. Then, the temperature of the substrate 10 is lowered to 500 °C to 800 °C, and In x Ga 1-x A multiple quantum well structure portion 20 of N / GaN is formed. Then, the substrate 10 is transferred into a vapor deposition apparatus, and the conductive layer 30 is formed on the multiple quantum well structure portion 20, thereby completing the manufacturing of the light emitter 1.

[0034] In the example described above, trimethylgallium (Ga(CH3)3:TMGa) can be used as the Ga source, trimethylindium (In(CH3)3:TMIn) as the In source, ammonia (NH3) as the N source, hydrogen gas (H2) or nitrogen gas (N2) as the carrier gas, and monosilane (SiH4) as the Si source. Alternatively, other organometallic raw materials (e.g., triethylgallium (Ga(C2H5)3:TEGa), triethylindium (In(C2H5)3:TEIn), etc.) and other hydrides (e.g., disilane (Si2H4), etc.) may be used. Furthermore, although a MOVPE apparatus is used in the example described above, a hydride vapor phase epitaxy (HVPE) apparatus or a molecular beam epitaxy (MBE) apparatus may also be used. The growth temperatures are not limited to those described above.

[0035] In the light-emitting device 1 configured as described above, when an electron beam E is incident on it, fluorescence SA is emitted in the long-wavelength layer 20A. At this time, if the energy of the electron beam E is low, the electron beam E does not reach the short-wavelength layer 20B, and the short-wavelength layer 20B does not emit fluorescence SB. On the other hand, if the energy of the electron beam E is high, the electron beam E is more likely to reach the short-wavelength layer 20B, and as a result, in addition to emitting fluorescence SA in the long-wavelength layer 20A, fluorescence SB is also emitted in the short-wavelength layer 20B. In other words, with the light-emitting device 1, it is possible to emit light in multiple colors depending on the energy of the incident electron beam E. For example, with the light-emitting device 1, it is possible to separate multiple electron beams E with different energies that are incident simultaneously.

[0036] In the light-emitting body 1, the multiple quantum well structure 20 is configured such that the short-wavelength layer 20B is sensitive to electron beams E with an energy of a predetermined value β or higher. In this case, the light-emitting body 1 can emit light in multiple colors depending on whether the energy of the incident electron beam E is above the predetermined value β or higher.

[0037] In the light-emitting body 1, the thickness of the long-wavelength layer 20A of the multiple quantum well structure 20 is set such that the short-wavelength layer 20B is sensitive to electron beams E with an energy of β or higher than a predetermined value. In this case, the thickness of the long-wavelength layer 20A can be set to emit light in multiple colors depending on whether the energy of the incident electron beam E is above a predetermined value or not.

[0038] In the light-emitting body 1, the long-wavelength layer 20A and the short-wavelength layer 20B each contain multiple light-emitting layers 21A and 21B, respectively, composed of nitride semiconductors containing Ga and In. The proportion of In in the composition of the multiple light-emitting layers 21A contained in the long-wavelength layer 20A is greater than the proportion of In in the composition of the multiple light-emitting layers 21B contained in the short-wavelength layer 20B. In this case, the long-wavelength layer 20A and the short-wavelength layer 20B can be specifically constructed.

[0039] In the light emitter 1, the multiple barrier layers 22A contained in the long-wavelength layer 20A are configured such that their thickness decreases as they approach the electron beam incident surface S. That is, the multiple barrier layers 22A have a first barrier layer and a second barrier layer located on the electron beam incident surface S side relative to the first barrier layer, with the first barrier layer being thicker than the second barrier layer. In this case, it is possible to improve the luminescence efficiency of the light emitter 1 and increase the luminescence intensity.

[0040] In the light emitter 1, the multiple barrier layers 22B contained in the short-wavelength layer 20B are all the same thickness. In this case, it is possible to improve the luminescence efficiency of the light emitter 1 and increase the luminescence intensity.

[0041] In the light emitter 1, the average thickness of the multiple barrier layers 22A contained in the long-wavelength layer 20A is greater than the average thickness of the multiple barrier layers 22B contained in the short-wavelength layer 20B. In this case, it is possible to improve the luminescence efficiency of the light emitter 1 and increase the luminescence intensity.

[0042] In the light emitter 1, the long-wavelength layer 20A is stacked on the short-wavelength layer 20B on the electron beam incident surface S side. In this case, the excitation of the long-wavelength layer 20A by the short-wavelength fluorescence SB emitted in the short-wavelength layer 20B can be suppressed. In other words, by passing the fluorescence SB through the long-wavelength layer 20A as it approaches the substrate 10, the emission of fluorescence SA in the long-wavelength layer 20A due to the incidence of fluorescence SB rather than the incidence of the electron beam E can be suppressed. Furthermore, since the absorption of the short-wavelength fluorescence SB emitted in the short-wavelength layer 20B by the long-wavelength layer 20A can be suppressed, the emission efficiency of fluorescence SB in the light emitter 1 can be increased.

[0043] Furthermore, the multiple quantum well structure 20 may have one or more intermediate layers (buffer layers) that are light-transmitting to the wavelength of fluorescence emitted by the multiple quantum well structure 20, between the substrate 10 and the short-wavelength layer 20B, and between the long-wavelength layer 20A and the short-wavelength layer 20B. In the above, nitride semiconductor refers to a compound that contains at least one of Ga, In, and Al as a group III element and N as the main group V element. Light transmittance means, for example, the property of transmitting 50% or more of the target light.

[0044] Figure 5 is a table showing the results of evaluating the brightness of the fluorescent SA in the long-wavelength layer 20A and the fluorescent SB in the short-wavelength layer 20B for each example in which the configuration of the multiple quantum well structure 20 was changed. The presence or absence of an intermediate layer in the figure indicates the presence or absence of the aforementioned intermediate layer between the long-wavelength layer 20A and the short-wavelength layer 20B. The total thickness of the long-wavelength layer 20A represents the total thickness of the long-wavelength layer 20A, and the total thickness of the short-wavelength layer 20B represents the total thickness of the short-wavelength layer 20B. For the fluorescent SA and SB of the long-wavelength layer 20A and the short-wavelength layer 20B, "△", "〇", and "◎" indicate that the brightness is highest in that order.

[0045] In the evaluation results illustrated in Figure 5, the highest fluorescence SA and SB were obtained when the configuration of the multiple quantum well structure 20 was that of the fifth example. In other words, as shown in the fifth example, it was confirmed that the multiple quantum well structure 20 having at least one of the following configurations contributes to the increased fluorescence SA and SB. (a) The barrier layer 22A of the long-wavelength layer 20A has a gradient structure, (b) The barrier layer 22B of the short-wavelength layer 20B has a constant-thickness layer structure, (c) The average thickness of the barrier layer 22A of the long-wavelength layer 20A > the average thickness of the barrier layer 22B of the short-wavelength layer 20B, (d) The number of light-emitting layers 21A of the long-wavelength layer 20A < the number of light-emitting layers 21B of the short-wavelength layer 20B, (e) The total thickness of the long-wavelength layer 20A < the total thickness of the short-wavelength layer 20B, (f) There is no intermediate layer.

[0046] One aspect of the present invention is not limited to the above embodiment, and various other modifications are possible.

[0047] In the above embodiment, the long-wavelength layer 20A is stacked on the electron beam incident surface S side on the short-wavelength layer 20B, but the stacking order may be reversed (i.e., the short-wavelength layer 20B is stacked on the long-wavelength layer 20A). In the above embodiment, the multiple quantum well structure 20 may further have a third-wavelength layer stacked on the long-wavelength layer 20A and the short-wavelength layer 20B, which emits fluorescence at a third wavelength different from the first and second wavelengths in response to the incidence of the electron beam E.

[0048] In the above embodiment, the composition of the light-emitting layers 21A, 21B and barrier layers 22A, 22B constituting the multiple quantum well structure 20 is not limited to the example described above. In the above embodiment, an example was shown in which the light-emitting layers 21A, 21B and barrier layers 22A, 22B of the multiple quantum well structure 20 are doped with Si, but the embodiment is not limited to this, and other impurities may be doped. Alternatively, the light-emitting layers 21A, 21B and barrier layers 22A, 22B may be composed of semiconductors other than nitride semiconductors.

[0049] In the above embodiments, the number of light-emitting layers 21A, 21B and barrier layers 22A, 22B is not particularly limited, and the number of light-emitting layers 21A, 21B and barrier layers 22A, 22B can be any number of two or more. In the above embodiments, the barrier layer 22A of the long-wavelength layer 20A has a gradient structure, but it may also have a constant-thickness layer structure. In the above embodiments, the barrier layer 22B of the short-wavelength layer 20B has a constant-thickness layer structure, but it may also have a gradient structure. In the above embodiments, some of the multiple barrier layers 22A included in the long-wavelength layer 20A may have a gradient structure, while the other parts may have a constant-thickness layer structure.

[0050] The configurations in the above embodiments and modifications are not limited to the materials and shapes described above, and various materials and shapes can be applied. The configurations in the above embodiments and modifications can be arbitrarily applied to the configurations in other embodiments or modifications. The numerical values ​​above may include errors in measurement, manufacturing, and design. The terms "equal" and "same" above include not only cases where they are exactly equal and exactly the same, but also cases where they are approximately equal and approximately the same. [Explanation of Symbols]

[0051] 1...Emitting element, 10...Substrate, 10a...Main surface (one side), 20...Multiple quantum well structure (quantum well structure), 20A...Long-wavelength layer (first wavelength layer), 20B...Short-wavelength layer (second wavelength layer), 21A,21B...Emitting layer, 22A,22B...Barrier layer, E...Electron beam, S...Electron beam incident surface, SA,SB...Fluorescence.

Claims

1. A light-emitting device that converts an incident electron beam into fluorescence, A substrate that is transparent to the aforementioned fluorescence, The substrate comprises a quantum well structure formed on one surface of the substrate, which emits fluorescence upon incidence of the electron beam, The aforementioned quantum well structure is A first wavelength layer that emits fluorescence of a first wavelength in response to the incidence of the electron beam, The first wavelength layer is laminated with a second wavelength layer which emits fluorescence at a second wavelength shorter than the first wavelength in response to the incidence of the electron beam, The first wavelength layer is laminated on the electron beam incident surface side of the quantum well structure on the second wavelength layer, and is a light-emitting body.

2. The light-emitting body according to claim 1, wherein the quantum well structure is configured such that one of the first wavelength layer and the second wavelength layer, on the side opposite to the electron beam incident surface of the quantum well structure, is sensitive to the electron beam having an energy of a predetermined value or higher.

3. The light-emitting body according to claim 2, wherein the quantum well structure is configured such that the thickness of the other of the first and second wavelength layers is set such that the side of the first and second wavelength layers opposite to the electron beam incident surface is sensitive to the electron beam having an energy of or greater than a predetermined value.

4. The first wavelength layer and the second wavelength layer each include a plurality of light-emitting layers made of nitride semiconductors containing Ga and In, The light-emitting body according to claim 1 or 2, wherein the proportion of In in the composition of the plurality of light-emitting layers included in the first wavelength layer is greater than the proportion of In in the composition of the plurality of light-emitting layers included in the second wavelength layer.

5. The first wavelength layer includes a plurality of barrier layers, The plurality of barrier layers included in the first wavelength layer comprises a first barrier layer and a second barrier layer located on the electron beam incident surface side of the quantum well structure relative to the first barrier layer, The light-emitting body according to claim 1 or 2, wherein the first barrier layer is thicker than the second barrier layer.

6. The aforementioned two-wavelength layer includes a plurality of barrier layers, The light-emitting body according to claim 1 or 2, wherein the plurality of barrier layers included in the second wavelength layer have the same thickness as one another.

7. The first wavelength layer and the second wavelength layer each include a plurality of barrier layers, The light-emitting body according to claim 1 or 2, wherein the average thickness of the plurality of barrier layers included in the first wavelength layer is greater than the average thickness of the plurality of barrier layers included in the second wavelength layer.

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