JP2010135259A - Light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting element to emit light with superior light-emitting efficiency without unevenness. <P>SOLUTION: The light-emitting element includes: a substrate having a p-type semiconductor part and an n-type semiconductor part having pn junction at least on the upper face; a translucent insulator layer which is installed on the substrate and has a light-emitting body inside; a translucent electrode installed on the insulator layer; a first electrode installed on a surface of the p-type semiconductor part and on a part where the insulator layer is not installed above; and a second electrode installed on a surface of the n-type semiconductor part and on a part where the insulator layer is not installed above. The insulator layer and the translucent electrode are installed in this order on a part where the p-type semiconductor part and the n-type semiconductor part of the upper face of the substrate has the pn junction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light emitting element.

An inorganic electroluminescence (EL) element is expected to be used as a new display element that does not require a separate light source as a light source that emits light.
There are two types of conventional EL elements, “dispersion type” and “thin film type”, most of which emit light by alternating current drive.

As for the conventional dispersion type and thin film type EL elements, as described in Patent Document 1 and Non-Patent Document 1, inorganic EL elements are realized using inorganic compounds.
In a conventional dispersion-type EL element, an AC voltage is applied to an element having phosphor particles (for example, ZnS: Cu, Cl) whose current path is blocked between electrodes, whereby the phosphor particles emit electroluminescence. . The optimum particle diameter of the phosphor particles is considered to be about 10 μm, and it is known that the emission luminance is remarkably lowered when the particle diameter is smaller than 2 to 3 μm. This dispersion type EL element is considered to emit light by recombination between a donor and an acceptor.

  In addition, the conventional thin-film EL element has an alternating current with an element having a phosphor light-emitting layer (for example, ZnS: Mn doped with Mn as a light emission center in a base material ZnS) sandwiched between electrodes by an insulating layer. By applying voltage, the light emitting layer emits electroluminescence. This thin-film EL element is considered to emit light by collision excitation of the emission center by hot electrons running in the base material.

  On the other hand, development of a technique for producing an inorganic EL element on a silicon substrate has been actively performed. Since CMOS circuits, which are information processing devices and memory devices, are realized based on silicon, if an inorganic EL element can be manufactured on a silicon substrate, the information processing device, the memory device, and the light emitting element are placed on the same substrate. Can be produced. This is expected to enable inter-chip communication and optical computing technology using light, and lead to further development of digital electronic devices.

  For example, Patent Document 2 has a peak of about 650 nm by forming nanometer-order fine particles of silicon or germanium in a silicon nitride film (insulator) on a silicon substrate and applying a voltage to the silicon nitride film. It has been reported that electroluminescence has been confirmed.

Note that in a conventional light emitting element in which fine particles are formed in an insulator film, it is necessary to apply a voltage to the electrodes on both sides of the insulator film and to apply a strong electric field of about several MV / cm to the insulator film. . Thus, the electrons of the electrode are supplied to the conduction band of the insulator film by FN (Fowler-Nordheim) tunneling, and the electrons are accelerated by the electric field to obtain sufficient kinetic energy, and then collide with the fine particles. It is considered that the colliding electrons excite the energy level of the fine particles and emit light from the excited energy level.
JP 2007-265986 A Latest Inorganic EL Development Trends-Material Properties and Manufacturing Technology / Application Development-1st Edition, Information Organization, March 27, 2007 JP 11-310776 A

A conventional light-emitting element in which fine particles are formed in an insulator film needs to apply a strong electric field of about several MV / cm to the insulator film and has low luminous efficiency. In addition, there is a problem that when the electric field concentrates on one place of the insulator film and is destroyed, the entire device is destroyed. Further, the conventional light emitting device has a problem that unevenness in light emission occurs.
The present invention has been made in view of such circumstances, and provides a light-emitting element that emits light efficiently and uniformly.

Means for Solving the Problems and Effects of the Invention

  A light-emitting element of the present invention includes a substrate having at least an upper surface having a p-type semiconductor portion and an n-type semiconductor portion to be pn-junction, a light-transmitting insulator layer provided on the substrate and having a light emitter therein, A translucent electrode provided on the insulator layer, a first electrode provided on a portion of the surface of the p-type semiconductor portion on which the insulator layer is not provided, a second electrode provided on a surface of the n-type semiconductor portion and on which the insulator layer is not provided, and the p-type semiconductor portion and the n-type semiconductor portion on the upper surface of the substrate The insulator layer and the translucent electrode are provided in this order on the portion where the pn junction is formed.

  As a result of intensive research, the inventor applied a negative voltage to the first electrode connected to the p-type semiconductor portion and applied a positive voltage to the translucent electrode in the light emitting device of the present invention. By making the second electrode connected to the n-type semiconductor part a potential between the first electrode and the translucent electrode, for example, by grounding, light emission is performed at a voltage lower than that of a conventional light emitting element using FN tunneling. The present invention was completed upon obtaining the knowledge that the device can emit light efficiently. This will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a light emitting device according to an embodiment of the present invention. FIG. 2 is a band diagram of a semiconductor in the vicinity of the pn junction of the light emitting device according to the embodiment of the present invention. As shown in FIG. 1, when a negative voltage is applied to the first electrode 7 and the GND voltage is applied to the second electrode 8 of the light emitting element 9, a reverse bias occurs, and when the potential difference is low, the p-type semiconductor portion 2 and n No current flows between the type semiconductor parts 3. When a somewhat high negative voltage is applied to the first electrode 7, an energy band as shown in FIG. 2 is obtained, and the electric field applied to the junction is increased. Therefore, electrons in the valence band of the p-type semiconductor become the conduction band of the n-type semiconductor. A flowing tunnel current is generated. The electrons flowing from the valence band of the p-type semiconductor to the conduction band of the n-type semiconductor are translucent applied to the electric field between the first electrode 7 and the second electrode 8 or to the first electrode 7 and a positive voltage. It is accelerated by the electric field between the electrodes 6 and collides with lattice atoms to form a pair of hot electrons and hot holes. A part of the hot electrons is accelerated by the electric field between the first electrode 7 and the translucent electrode 6 or the second electrode 8 and the translucent electrode 6 and supplied to the insulator layer 4. It is considered that the hot electrons interact with the light emitter 5 inside the insulator layer 4 to excite the energy level of the light emitter 5 and cause the light emitter 5 to emit light.
Hereinafter, the description of the light emission principle will be made by taking the above hot electrons as an example. However, when the translucent electrode 6 is applied with a negative voltage, the hot holes interact with the light emitter 5 inside the insulator layer 4. In addition, since the energy level of the light emitter 5 is excited, it is considered that light emission similar to the above can be realized.

In order to cause the light emitting element 9 to emit light, an electric field capable of generating a tunnel current is applied between the first electrode 7 and the second electrode 8, and the generated hot electrons are supplied to the insulator layer 4. It is necessary to apply an electric field capable of generating a current between the first electrode 7 and the translucent electrode 6 or between the second electrode 8 and the translucent electrode 6. The electric field applied between the first electrode 7 and the translucent electrode 6 or between the second electrode 8 and the translucent electrode 6 is more than the electric field that can supply electrons to the conduction band of the insulator layer 4 by FN tunneling. It is a small electric field. Thus, in the light emitting element 9 of the present invention, the efficiency of electron injection into the insulator layer 4 is higher than that of FN tunneling. The ratio of the electron injection efficiency of the light emitting device 9 of the present invention and the electron injection efficiency of the conventional light emitting device using FN tunneling was calculated to be about 7: 1 from the experimental results. Therefore, the light-emitting element of the present invention can efficiently emit light at a lower voltage than a conventional light-emitting element using FN tunneling. Further, when the same voltage is applied to the light emitting element of the present invention and the conventional light emitting element, the luminance of the light emitting element of the present invention is higher. Further, in the light emitting device of the present invention, there is no problem that the electric field concentrates on one place of the insulator layer and the entire device is destroyed.
Furthermore, in the electron injection method using the FN tunneling found in the conventional example, since the hot electron generation site and the acceleration site are insulator layers, when the voltage necessary for light emission is applied, However, according to the electron injection method of the present invention, the location where hot electrons are generated is a pn junction, and the acceleration location is an insulator layer. There is an advantage that damage to the applied insulator layer is small.

In addition, in a conventional light emitting element using FN tunneling, strong light emission is generated at a portion where the electric field between the electrodes is the largest, and light emission is uneven at the portion where the electric field between the electrodes is small. Therefore, variations in the thickness of the insulator layer 4 directly affect the unevenness of light emission.
On the other hand, in the light emitting device 9 of the present invention, it is considered that hot electrons generated near the pn junction in the substrate 1 interact with the light emitter 5 to cause the light emitter 5 to emit light. The energy of hot electrons generated by this method is determined by the electric field applied between the first electrode 7 and the translucent electrode 6 or between the second electrode 8 and the translucent electrode 6, and the film thickness variation of the insulator layer 4. Regardless of, the energy gained by hot electrons is determined. Therefore, since the influence of the film thickness of the insulator layer 4 is small, it is possible to suppress the uneven light emission.
Further, by forming pn junctions on the upper surface of the substrate 1 in contact with the insulator layer 4 at regular intervals, or by forming the pn junctions uniformly, the light emitter 5 that emits light within the insulator layer 4 is set uniformly. Therefore, unevenness in light emission can be eliminated.
Further, the light emitter 5 can be fine particles containing GeO and GeO ₂ . Thus, the light emitting element can emit electroluminescence having an emission peak in a range of 340 to 440 nm. The light emission of a conventional light emitting device in which fine particles are formed in an insulator film such as Patent Document 2 is in the visible light region, most of which is light in a region with a relatively long wavelength such as red, and is applied to a display or the like. Therefore, a light emitting element that emits light in a shorter wavelength region is desired. Therefore, the light emitting device of the present invention can be expected to be applied to a display or the like.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configurations shown in the drawings and the following description are merely examples, and the scope of the present invention is not limited to those shown in the drawings and the following description.

1. Structure of Light-Emitting Element A light-emitting element 9 according to this embodiment includes a substrate 1 having at least a p-type semiconductor portion 2 and an n-type semiconductor portion 3 that are pn-junction on the upper surface, and a light-emitting body 5 provided on the substrate 1. The translucent insulator layer 4 having, the translucent electrode 6 provided on the insulator layer 4, and the portion of the surface of the p-type semiconductor portion 2 where the insulator layer 4 is not provided A first electrode 7 provided on the substrate, and a second electrode 8 provided on a portion of the surface of the n-type semiconductor unit 3 on which the insulator layer 4 is not provided. The insulator layer 4 and the translucent electrode 6 are provided in this order on a portion where the p-type semiconductor portion 2 and the n-type semiconductor portion 3 on the upper surface of the pn junction are pn-junction.
Hereafter, each component of the light emitting element 9 of this embodiment is demonstrated.

1-1. Substrate The substrate 1 is not particularly limited as long as it has at least the p-type semiconductor portion 2 and the n-type semiconductor portion 3 that are pn-junction on the upper surface. For example, an n-type region may be formed on a p-type silicon substrate, or a p-type region may be formed on an n-type silicon substrate. It is also possible in which the formation of the p-type silicon and n-type silicon on top of SiO ₂ or the like substrate, an insulating layer such as SiO ₂ on a Si substrate, a p-type silicon and n-type silicon is formed thereon It may be formed. In that case, the element of the present invention may be formed on a crystalline silicon substrate on an SOI (Silicon On Insulator) substrate, or amorphous silicon is formed on an insulator layer such as SiO ₂ by using a CVD method or the like. The element of the present invention may be formed thereon.

  FIG. 3A is an example of a substrate of a light emitting device according to an embodiment of the present invention, in which n-type silicon is formed on a p-type silicon substrate in a comb shape, and the first electrode 7 is formed on the upper surface of the p-type silicon. 2 is a plan view of a substrate in which a second electrode 8 is formed on the upper surface of n-type silicon. Note that the insulator layer 4 and the translucent electrode 6 can be formed in a portion surrounded by a dotted line in FIG. FIG. 3B shows an example of the substrate of the light emitting device according to the embodiment of the present invention. In the p-type silicon substrate, n-type silicon is formed in a cross-beam shape on the upper surface, and the first electrode 7 is formed on the upper surface of the p-type silicon. 2 is a plan view of a substrate in which a second electrode 8 is formed on the upper surface of n-type silicon. Note that the insulator layer 4 and the translucent electrode 6 can be formed in a portion surrounded by a dotted line in FIG. FIG. 3C is a schematic cross-sectional view of the light emitting element taken along the dashed line XY in FIG. 3A or the dashed line ST in FIG. Specifically, the substrate 1 can be formed as shown in FIGS.

1-2. The p-type semiconductor part The p-type semiconductor part 2 is a part of the p-type semiconductor included in the substrate 1 and is not particularly limited as long as it is pn-junction with the n-type semiconductor part 3, but is, for example, p-type silicon, and the impurity concentration is, for example, 1 × 10 ¹⁹ to 1 × 10 ²⁰ / cm ³ (for example, a range between any two of 1 × 10 ¹⁶ , 1 × 10 ¹⁷ and 1 × 10 ¹⁸ ).

1-3. n-type semiconductor part The n-type semiconductor part 3 is a part of an n-type semiconductor included in the substrate 1 and is not particularly limited as long as it is pn-junction with the p-type semiconductor part 2, but is, for example, n-type silicon, and the impurity concentration is, for example, 1 × 10 ¹⁶ to 1 × 10 ¹⁸ / cm ³ .
The impurity concentration of the p-type semiconductor unit 2 and the n-type semiconductor unit 3 is such that a negative voltage is applied to the p-type semiconductor unit 2, a positive voltage is applied to the translucent electrode 6, and the GND voltage is applied to the n-type semiconductor unit 3. It is a standard when applying. As described above, the present invention is the same even when a GND voltage is applied to the p-type semiconductor portion 2, a negative voltage is applied to the translucent electrode 6, and a positive voltage is applied to the n-type semiconductor portion 3. In this case, the impurity concentrations of the p-type semiconductor portion 2 and the n-type semiconductor portion 3 may be replaced with the above-mentioned standard concentrations.

1-4. pn junction The pn junction is an interface where the p-type semiconductor portion 2 and the n-type semiconductor portion 3 are in contact with each other. Further, the pn junction portions can be formed on the upper surface of the substrate 1 in contact with the insulator layer 4 at regular intervals. Further, the pn junction portion can be uniformly formed on the upper surface of the substrate 1 in contact with the insulator layer 4. Specifically, a pn junction can be formed as shown in FIG.
Accordingly, the insulator layer 4 can emit light evenly by applying a voltage to the light emitting element 9 of the present embodiment. This is because, in the light emitting element 9 of the present embodiment, electrons are supplied from the semiconductor in the vicinity of the pn junction to the insulator layer 4 to emit light. Therefore, light emission between the pn junction and the translucent electrode 6 is performed. This is because the body 5 emits light.

1-5. First electrode The first electrode 7 is an electrode that is provided on the surface of the p-type semiconductor portion 2 and on the portion on which the insulator layer 4 is not provided, and can make ohmic contact with the p-type semiconductor portion 2 If it is, it will not specifically limit. The first electrode 7 is, for example, Au, Pt, Ag, Co, Ni, Ti, Ta, W, or the like.

1-6. Second electrode The second electrode 8 is an electrode that is provided on the surface of the n-type semiconductor portion 3 and on the portion where the insulator layer 4 is not provided, and can make ohmic contact with the n-type semiconductor portion 3. If it is, it will not specifically limit. The second electrode 8 is, for example, Au, Pt, Ag, Co, Ni, Ti, Ta, W, or the like.

1-7. Translucent electrode The translucent electrode 6 is not particularly limited as long as the transmissivity of light having a wavelength of 300 nm to 500 nm is 60% to 99.99%. The translucent electrode 6 is, for example, a metal oxide thin film such as ITO, a metal thin film such as Al, Ti, or Ta, or a semiconductor thin film such as Si, SiC, or GaN.

1-8. Insulator layer The insulator layer 4 is not particularly limited as long as the insulator layer 4 is provided on the substrate 1 and has the light emitter 5 therein and is light-transmitting. For example, the insulator layer 4 is made of silicon oxide, silicon nitride, or silicon oxynitride. In this case, it is a silicon-based insulator, and silicon is more easily bonded to oxygen than germanium, so germanium atoms are not unnecessarily bonded to oxygen, and silicon oxide, silicon nitride, or silicon oxynitride relatively absorbs oxygen. Since it is difficult to permeate, germanium atoms are not oxidized by permeation of the outside air, so that light emission is stable and deterioration is small. Further, since silicon oxide, silicon nitride, or silicon oxynitride can be formed by a normal silicon semiconductor process, it is excellent in mass productivity and can be combined with other electronic circuits.
The thickness of the insulator layer 4 is, for example, 10 nm to 100 nm (for example, a range between any two of 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 nm).
In the present invention, translucency means that light emitted from the light emitting element 9 of the present invention can be transmitted. As for the light transmittance of the insulator layer 4, it is preferable that the transmittance | permeability of the light with a wavelength of 300-500 nm is 80% or more, for example. When the light emitter 5 is a fine particle containing GeO and GeO ₂ , the peak wavelength of the light emitted from the light emitter 5 is around 390 nm. Therefore, if the light transmittance at a wavelength of 300 to 500 nm is high, the light extraction efficiency is correspondingly increased. Because it becomes higher.

1-9. Light emitter The light emitter 5 is not particularly limited as long as it is formed on the insulator layer 4 and serves as a light source. A plurality of the light emitters 5 may be formed on the insulator layer 4.
The light emitter 5 is, for example, fine particles, metal atoms, or metal ions, and is, for example, fine particles of germanium, silicon, or tin. Further, the light emitter 5 can be a fine particle containing, for example, GeO and GeO ₂ . In this case, the light emitter 5 may contain germanium (metal). The number density of the light emitting body 5 is not particularly limited for example, 1 × 10 ¹⁶ atoms / cm ³ ~1 × 10 ²¹ atoms / cm ^3.

  When the light emitter 5 is a fine particle, the light emitter 5 preferably has a maximum particle diameter of 1 nm or more and 20 nm or less. This is because the luminous efficiency is particularly high in this case. In the present invention, the “maximum particle size” is a 100 nm square range of an arbitrary cross section of the insulator layer 4 (a cross section as shown in FIG. 1 or a cross section perpendicular to the paper surface). Means the particle diameter of the largest particle among the fine particles that can be observed by TEM observation. Further, in the present invention, the “particle diameter” means the length of the longest line segment that can be projected on the TEM photograph and included in the planar image of the fine particles when viewed in the cross-sectional TEM photograph. The maximum particle size of the fine particles that are the light emitter 5 is, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, or 20 nm. The maximum particle size of the fine particles that are the light emitters 5 may be within a range between any two numerical values exemplified here, or may be equal to or smaller than any one numerical value.

Ratio of GeO to the entire germanium oxide (GeO ₂ + GeO), in spectrum around 3d peak of Ge XPS spectra, determined as the peak area S _GeO2 due to GeO _2, an area S _GeO the peak due to GeO, It can be obtained by calculating S _GeO / (S _{GeO 2} + S _GeO ). As an X-ray source for XPS measurement, for example, monochromatic Al and Kα rays (1486.6 eV) can be used. The peaks caused by GeO ₂ and the peaks caused by GeO have overlapping bases. However, as shown in FIG. 4, the Gaussian fitting is performed to separate the areas of the peaks caused by GeO ₂ and the peaks caused by GeO by waveform separation. S _GeO2 and S _GeO can be determined. The peak energies of GeO ₂ and GeO are about 33.5 and 32 eV, respectively.

When the light emitter 5 is a fine particle containing GeO and GeO ₂ , GeO can be contained at 10% or more when the total of GeO and GeO ₂ contained in the light emitter 5 is 100%. If the proportion of GeO is too small, there is a possibility that no light is emitted or the light emission intensity is too small. Specifically, the proportion of GeO is, for example, 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, 99, 100%. The ratio of GeO may be within a range between any two of the numerical values exemplified here.

Incidentally, in the spectrum around 2p peak of Ge XPS spectra, determined the area S _Ge of peaks due to germanium (Ge), the area S _Ge oxide of peak caused by germanium oxide _{(GeO + GeO 2), S} GeO / ( The oxidation rate of Ge can be obtained by calculating (S _Ge + S oxide _Ge ). Although the average value of this oxidation rate is not specifically limited, For example, 1, 5, 10, 15, 20, 25, 30, 34.9, 35, 40, 45, 50, 55, 60, 60.1, 65 , 70, 70.1, 75, 80, 85, 90, 95, 99, 100%. The average value of the oxidation rate may be within a range between any two of the numerical values exemplified here.

1-10. Light emitting wavelength In the light emitting device 9 of the present embodiment, the peak of the electroluminescence (EL) wavelength when the above voltage is applied is 340 to 440 nm (more strictly speaking, 350 to 430 nm, 360 to 420 nm, 370 to 410 nm, 380-400 nm or 385-395 nm). Or the peak of the wavelength of cathode luminescence (CL) when irradiating the insulator layer 4 with an electron beam at 5 keV is 340 to 440 nm (more strictly, 350 to 430 nm, 360 to 420 nm, 370 to 410 nm, 380). ˜400 nm or 385 to 395 nm). The EL wavelength may be slightly different from the CL wavelength, but is approximately the same as the CL wavelength.

1-11. Usage Method of Light-Emitting Element The light-emitting element 9 of the present embodiment applies a negative voltage to the first electrode 7, applies a positive voltage to the translucent electrode 6, and transmits the second electrode 8 to the first electrode 7. Light can be emitted by setting the potential between the photoelectrodes 6, for example, by grounding.
The magnitude of the applied voltage can apply an electric field that allows a tunnel current to flow between the first electrode 7 and the second electrode 8, and supply hot electrons generated by the tunnel current to the insulator layer 4. There is no particular limitation as long as an electric field that can be applied can be applied. For example, light can be emitted by applying a voltage of −10 V to the first electrode 7, applying a voltage of +25 V to the translucent electrode 6, and grounding the second electrode.
In addition, in the light emitting element 9 of this embodiment, in addition to light emission by hot electrons, light emission by FN tunneling may be accompanied.

2. 2. Manufacturing method of light emitting element 2-1. Formation of Substrate A substrate 1 having a p-type semiconductor portion 2 and an n-type semiconductor portion 3 to be pn-joined at least on the upper surface is formed. The formation method is not particularly limited. For example, a mask is formed in a desired shape on a p-type silicon substrate, phosphorus, which is an n-type impurity, is ion-implanted, and then the mask is removed. A substrate on which type silicon is formed can be formed.

2-2. Formation of Insulator Layer A translucent insulator layer 4 is formed on the substrate 1. For example, silicon oxide or silicon nitride can be deposited and formed by CVD or sputtering.

2-3. Formation of Light Emitter A light emitter 5 is formed inside the insulator layer 4. A method of forming a light emitter 5 in the insulating layer 4 is not particularly limited, when the light-emitting element 5 of microparticles comprising GeO and GeO _2, germanium ion implanted into the insulating layer 4, then, A method of performing heat treatment is conceivable. Ions are aggregated by heat treatment after the ion implantation to form a large number of fine particles in the insulator layer 4 and Ge is oxidized to form GeO and GeO ₂ . The ion implantation of germanium can be performed, for example, under conditions of an implantation energy of 5 to 100 keV and an implantation amount of 1 × 10 ¹⁴ to 1 × 10 ¹⁷ ions / cm ² .

Ratio of GeO and GeO _2, the injection amount of the germanium, heat treatment time, the heat treatment temperature can be appropriately adjusted by changing the heat treatment atmosphere and the like. Specifically, the GeO ratio can be increased by adjusting the partial pressure and flow rate of oxygen in the heat treatment atmosphere. For example, when the atomic concentration of germanium in silicon oxide having a film thickness of 100 nm is 10% or less, in the heat treatment at 800 ° C. for 1 hour, an inert gas is supplied while evacuating (400 liters per minute) (50 minutes per minute). In the case of milliliter), germanium partially binds to oxygen, but oxygen is insufficient, so that it is not completely oxidized and GeO can be generated. In an atmosphere of 1 atm in which oxygen of 20% volume is mixed with an inert gas, a large amount of GeO ₂ is formed due to excessive supply of oxygen, and GeO decreases. The atmosphere suitable for increasing the proportion of GeO depends on other parameters such as germanium implantation conditions, heat treatment time, and temperature, but in one example, the atomic concentration of germanium is relatively high and oxygen is added to the inert gas. The ratio of GeO can be increased by supplying the mixed gas while evacuating.

  Further, germanium is preferably ion-implanted so that the germanium concentration in the insulator layer 4 is 0.1 to 10.0 atomic%. This is because when the inert gas is supplied (50 milliliters per minute) while evacuating (400 liters per minute) in a heat treatment at 600 ° C. for 1 hour, the luminous efficiency is relatively high in this range. Specifically, the germanium concentration is, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2 0.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0 atomic%. This concentration may be within a range between any two of the numerical values exemplified herein. The germanium concentration can be measured, for example, by a high resolution RBS (Rutherford backscattering) method. In addition, it can be measured by various analysis methods such as SIMS (secondary ion mass spectrometry). The germanium concentration is measured in a range where the germanium concentration is 1/100 or more of the peak value. 400-900 degreeC is preferable and the temperature of heat processing has more preferable 500-800 degreeC. This is because the luminous efficiency is relatively high in this range.

2-4. Formation of Translucent Electrode A translucent electrode 6 is formed on the insulator layer 7 on which the light emitter 5 is formed. For example, an ITO electrode can be formed by a coating method, sputtering, or the like.

2-5. Formation of the first electrode and the second electrode The first electrode 7 is formed on the surface of the p-type semiconductor portion 2 and on the portion on which the insulator layer 4 is not provided. The second electrode is formed on the surface of the n-type semiconductor portion and on the portion where the insulator layer 4 is not provided. Although the formation method is not particularly limited, for example, it can be formed by a coating method, sputtering, or the like.

3-1. EL experiment An EL experiment was conducted as a reference experiment for confirming the emission wavelength characteristics and the cause of emission of the present invention by the following method.
First, a silicon thermal oxide film was formed on the surface by thermally oxidizing the silicon substrate in an oxygen atmosphere at 1050 ° C. for 100 minutes.
Next, Ge ions in the silicon thermal oxide film are 1.4 × 10 ¹⁶ ions / cm ² at 50 keV, 3.2 × 10 ¹⁵ ions / cm ² at 20 keV, and 2.2 × 10 ¹⁵ ions / cm ^{2 at} 10 keV. In this order, multiple injections were made in this order.

Next, nitrogen was introduced while pulling with a rotary pump, and heat treatment was performed at 800 ° C. for 1 hour. Ge is oxidized by aggregation and oxidation of Ge implanted during the heat treatment, and at least a part thereof is oxidized to GeO and GeO ₂ .
Next, an ITO electrode was formed on the silicon thermal oxide film, an aluminum electrode was formed on the silicon substrate side, and a light emitting element used for EL experiments was obtained.
When a voltage of about 30 V was applied between the ITO electrode and the aluminum electrode of the light emitting element, blue light emission was confirmed.
Further, the emission spectrum of this blue light emission is shown in FIG. Referring to FIG. 5, it was found that the confirmed blue emission was light having a wavelength of 340 nm to 550 nm, and electroluminescence emission having a peak between 340 nm and 440 nm.

3-2. By the method shown in the following relation between the emission and GeO and GeO _2, GeO, and GeO ₂ it was confirmed to be involved in light emission of the light emitting element of the present invention.

First, two hypotheses were considered for the light emission mechanism. The first hypothesis is that the Ge nanoparticles emit light due to the quantum size effect. This light emission mechanism is the same as the light emission mechanism of normal nanoparticles, and the emission wavelength depends on the particle size. The second hypothesis is that GeO and GeO ₂ are involved in light emission. Since the energy level difference between the excited state and the ground state of GeO is 2.9 to 3.2 eV (387 to 427 nm) (L. Skuja, J. Non-Cryst. Solids, 239 (1998) 16-48. According to the second hypothesis, the emission wavelength is about 387 to 427 nm, and this wavelength is considered to be independent of the particle size.

  In order to verify which of these hypotheses is correct, a light emitting device was manufactured under various temperature conditions and injection conditions different from each other, and the EL wavelength when a voltage was applied to the device by the above method was measured. For the measurement of the EL wavelength, “Spectrofluorophotometer RF-5300PC manufactured by Shimadzu Corporation” was used. The method for manufacturing the light-emitting element is as described in “3-1. EL experiment” except that the heat treatment temperature and the Ge implantation amount are appropriately changed.

  The obtained results are shown in FIGS. The temperature in FIG. 6 shows the heat treatment temperature (time is 1 hour). “Atom%” in FIG. 7 indicates the Ge concentration in the silicon oxide film after Ge implantation. The Ge concentration in FIG. 6 is 5.0 atomic%, and the heat treatment temperature in FIG. 7 is 700 ° C. (time is 1 hour).

  6 and 7, it can be seen that the peak wavelength of EL is constant at about 390 nm even when the heat treatment temperature and the Ge concentration are changed. When the heat treatment temperature or Ge concentration changes, the size of the formed nanoparticles also changes, so that the EL peak wavelength should be shifted if the light emission mechanism follows the first hypothesis. Therefore, the EL wavelength confirmed in FIGS. 6 and 7 cannot be explained by the first hypothesis. On the other hand, the wavelength of 390 nm is within the range of the emission wavelength (387 to 427 nm) predicted by the second hypothesis.

From the above, it can be seen that the EL wavelength from the light-emitting element of the present invention cannot be explained by the first hypothesis but can be explained by the second hypothesis. Therefore, it was confirmed that GeO and GeO ₂ were involved in light emission of the light emitting device of the present invention.

  By the way, referring to FIG. 6, it is understood that the heat treatment temperature is preferably 600 to 700 ° C. Further, referring to FIG. 7, it can be seen that the Ge concentration is preferably 3.0 atomic% or more, and more preferably 3.0 to 5.0 atomic%.

3-3. Ge, GeO, to produce a light-emitting device according to the method described in the depth direction distribution of the ratio of GeO ₂ "3-1.EL experiment", Ge in the silicon oxide film, GeO, the depth direction of the ratio of GeO ₂ The distribution was examined. The light-emitting element manufactured here has a Ge concentration of 5.0 atomic% and a heat treatment temperature of 800 ° C. (time is 1 hour).
Since XPS can usually analyze the depth of several nm from the sample surface, by alternately performing etching with an argon ion beam and XPS measurement, the depth of Ge, GeO, GeO ₂ in the region up to a depth of 50 nm can be obtained. The change in the direction was examined. The argon ion beam energy was 4 kV, the beam current was 15 mA, and irradiation was performed for 300 seconds per time. FIG. 8A shows the XPS measurement results at that time in which the graphs are translated and arranged in the vertical direction for easy understanding. Also shows the state of the Ge atoms contained in each depth, the Ge (metal Ge), GeO, a graph showing a ratio of GeO ₂ FIG 8 (b).

According to this, in the region of a depth of 10 to 50 nm where the Ge implantation concentration is relatively high by the implantation method described in “3-1. EL experiment”, the proportion of unoxidized Ge is 30 to 70%. GeO ₂ is between 0-20% and approximately 10%. GeO in which Ge is not completely oxidized but partially oxidized is between 10% and 50%.

Ge at each depth, GeO, ratio of GeO _2, in XPS spectrum around 3d peak of Ge spectra, the area S _Ge of peaks due to Ge, the area S _GeO the peak due to GeO, GeO It obtains the peak area S _GeO2 caused by _2, was determined by calculating at each depth _{(S G, S GeO, S} GeO2) / (S G + S GeO + S GeO2). Further, the ratio of GeO and GeO _{2 to} the whole germanium oxide (GeO ₂ + GeO) at each depth is shown in the graph of FIG.

According to this, the proportion of germanium oxide that is completely oxidized to GeO ₂ is approximately the same except for the vicinity of the surface where germanium is easily oxidized due to the low concentration of germanium and the strong influence of the atmosphere. Between 20 and 60%, Ge is not completely oxidized but partially oxidized GeO is between approximately 40 and 80%. In the region of a depth of 10 to 40 nm where the Ge implantation concentration is relatively high by the implantation method described in “3-1. EL experiment”, the proportion of germanium oxide that is completely oxidized to GeO ₂ is approximately 50% or less and approximately 20 to 30%. GeO that is partially oxidized but not completely oxidized is approximately 50% or more and 70 to 80%. GeO at each depth, the ratio of GeO _2, in XPS spectrum around 3d peak of Ge spectra, determined the area S _GeO the peak due to GeO, and a peak area S _GeO2 due to GeO _2, (S _GeO, S _GeO2) was determined by calculating in / (S _GeO + S _GeO2) each depth. The XPS spectrum was measured using monochromatic Al and Kα rays (1486.6 eV) as an X-ray source.

It is a schematic sectional drawing of the light emitting element of one Embodiment of this invention. It is a semiconductor band diagram of the vicinity of the pn junction of the light emitting element of one Embodiment of this invention. (A) And (b) is an example of the board | substrate of the light emitting element of one Embodiment of this invention, (a) is a top view of the board | substrate in which the comb-type n-type semiconductor part was formed, (b) is a cross-beam type | mold. It is a top view of the board | substrate in which the n-type semiconductor part was formed. (C) is a schematic sectional drawing of the light emitting element in the dashed-dotted line XY of FIG. 3 (a), or the dashed-dotted line ST of FIG.3 (b). It is the graph which showed an example which carried out Gaussian fitting decomposition | disassembly of the XPS spectrum in order to calculate the ratio of GeO. It is the graph which showed the emission spectrum of the light emitting element produced for EL measurement experiment. It is the graph which showed the EL wavelength measurement result about the light emitting element produced by heat-processing at various temperature. It is the graph which showed the EL wavelength measurement result about the light emitting element of various Ge density | concentrations. (A) shows XPS spectra measured at various depths. (B) is a graph showing the ratio of Ge, GeO, GeO ₂ at various depths. It is a graph showing GeO, the ratio of GeO ₂ to the total germanium oxide (GeO ₂ + GeO) at various depths.

Explanation of symbols

  1: Substrate 2: p-type semiconductor part 3: n-type semiconductor part 4: insulator layer 5: light emitter 6: translucent electrode 7: first electrode 8: second electrode 9: light-emitting element

Claims (12)

a substrate having a p-type semiconductor portion and an n-type semiconductor portion to be pn-junction at least on the upper surface;
A translucent insulator layer provided on the substrate and having a light emitter therein;
A translucent electrode provided on the insulator layer;
A first electrode provided on a surface of the p-type semiconductor portion and on a portion on which the insulator layer is not provided;
A second electrode provided on the surface of the n-type semiconductor portion and on the portion on which the insulator layer is not provided,
The light emitting element, wherein the insulator layer and the translucent electrode are provided in this order on a portion of the upper surface of the substrate where the p-type semiconductor portion and the n-type semiconductor portion are pn-junctioned. The device according to claim 1, wherein the light emitter is a fine particle containing GeO and GeO ₂ .   3. The element according to claim 1, wherein portions where the p-type semiconductor portion and the n-type semiconductor portion are pn-junction are formed at regular intervals on the upper surface of the substrate in contact with the insulator layer.   The element according to any one of claims 1 to 3, wherein a portion where the p-type semiconductor portion and the n-type semiconductor portion are pn-junction is uniformly formed on an upper surface of the substrate in contact with the insulator layer. 5. The device according to claim 1, wherein at least one of the p-type semiconductor portion and the n-type semiconductor portion has an impurity concentration of 5 × 10 ¹⁸ cm ⁻³ or more.   The element according to claim 1, wherein the p-type semiconductor part and the n-type semiconductor part are mainly composed of silicon.   The element according to any one of claims 1 to 6, wherein the translucent electrode has a light transmittance of 60% to 99.99% in a wavelength range of 300 nm to 500 nm.   The element according to claim 1, wherein the translucent electrode is made of a metal oxide thin film, a metal thin film, or a semiconductor thin film.   The device according to claim 1, wherein the light emitter is a fine particle having a maximum particle diameter of 1 nm to 20 nm.   The light emission is performed by applying a negative voltage to the first electrode, applying a positive voltage to the first electrode to the second electrode, and applying a positive or negative voltage to the translucent electrode. The device according to any one of the above.   The light emitter is within a range of 340 to 440 nm when a negative voltage is applied to the first electrode, a positive voltage is applied to the second electrode, and a positive or negative voltage is applied to the translucent electrode. The device according to claim 1, which exhibits electroluminescence having a peak of an emission wavelength. The light emitter is a fine particle containing GeO and GeO _2, and contains 10% or more of GeO when the total of GeO and GeO ₂ contained in the light emitter is 100%. The described element.

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