TW200300300A - Ultraviolet ray emitting element - Google Patents

Abstract

A laminate structure S including a GaN crystalline layer and a light emitting portion is formed directly or through a buffer layer on a crystalline substrate B. The light emitting portion is made in the form of a multiple layer quantum well structure wherein an InGaN capable of emitting ultraviolet ray is used for the well layers having 2 to 20 layers. A barrier layer having a thickness of from 7nm to 30nm is included on the light emitting portion. A high output of ultraviolet ray is obtained from a light emitting layer for which InGaN is used. In order to obtain a high quality GaN layer, an AlGaN primary layer is preferably disposed immediately above an AIN low- temperature grown buffer layer. The present invention recommends an embodiment avoiding the presence of an AlGaN layer in between the crystalline substrate and the well layer (in between the primary layer and the well layer in the case of having an AlGaN primary layer).

Description

200300300 V. Description of the invention (1) [Technical field to which the invention belongs] The present invention relates to a semiconductor light-emitting device, and particularly to a gallium nitride GaN-based material used as a light-emitting layer material using an InGaN-based material whose component emits ultraviolet nitride. UV light emitting element. [Prior art] It is generally known that even in GaN light-emitting elements such as GaN-based light emitting diodes (GaN light emitting diodes) or GaN-based semiconductor lasers (laser diodes), InGaN is still used as a light-emitting layer. The light-emitting elements (including blue and green light-emitting elements with a high light-emitting layer having an Indium In component) can obtain high-efficiency light emission. This is because the carrier component is localized due to fluctuations in the n component, so that the proportion of carriers injected into the light-emitting layer and landing in the non-light-emitting center is small, resulting in the result that high-efficiency light can be obtained. In G a N 糸 L E D and G a N-based L D, in order to emit ultraviolet light of less than 4 200 nm, InGaN (In component 0. 15 or less) is generally used as the light-emitting layer material. Generally speaking, the upper wavelength limit of ultraviolet light is shorter than the short wavelength end (380 nm to 400 nm) of visible light, while the lower limit is about 1 nm (0.2 nm to 2 nm). However, in this specification, The blue-violet light of 4200 nm or less emitted by InGaN containing 0.15 or less of the above-mentioned n component is also referred to as ultraviolet light. The wavelength of ultraviolet rays emitted by G a N households is 3 6 5 n m. Therefore, when I n G a N is a ternary compound that must contain an indium I η component and not an aluminum a 1 component, the lower limit of the emitted ultraviolet wavelength is a longer wavelength than the aforementioned 36.5 nm. Hereinafter, an ultraviolet light-emitting element using I n G a N as a light-emitting layer material is referred to as

200300300 V. Description of the invention (2) It is an I n G a N ultraviolet light emitting element. However, compared with the higher indium (I ndium) I η component of the light-emitting layer in the blue and green light-emitting elements, because the ultraviolet light of the I n G a N ultraviolet light-emitting element has a short wavelength, the I of the light-emitting layer must be reduced. η ingredients. Therefore, the localization effect caused by the fluctuation of the I η component described above will be reduced, and the proportion of falling non-luminous recombination centers will increase, leading to a result that hinders high output. On the other hand, the structure of the light-emitting part of the InGaN ultraviolet light-emitting device is made of a single quantum well (SQW, Single Quantum Well) structure or a multiple quantum well (MQW Multiple Quantum Well) structure (so-called • (double heterostructure, d 〇). ub 1 eheter 〇structure) structure is included in the SQW structure due to the extremely thin active layer), and the light emitting layer (well layer) is sandwiched by a cover layer formed of a material having a higher energy gap than the light emitting layer (in a quantum well The structure also includes the barrier layer). According to the literature (by Mizuhiro Hiroshi, published by Engineering Books Co., Ltd., "Optical Communication Component Engineering" on page 27), in general, it is required to set the band gap between the light emitting layer and the cover layer (Band Gap). Above "0 · 3e V". According to the above-mentioned prior art, when InGaN is used for a light emitting layer (well layer) to generate ultraviolet rays, in the cover layer and the barrier layer sandwiching the light emitting layer, AlGaN having a larger energy gap is used based on the consideration of load and confinement. Fig. 6 'is a diagram illustrating an example of a conventional ultraviolet LED device structure using I η 〇. G3G a 〇 97N (light emitting wavelength 380 nm) as a material of a light emitting layer. As shown in the figure, an η-type G a] \ 1 contact layer 1 0 1 is formed on a crystalline substrate B 1 0 via a buffer layer B 2 0, and a SQW structure is sequentially superimposed thereon to emit light by a crystal growth method. (N-type AluGauN cover layer 102, Inu3Ga (). 97N well layer (light-emitting layer) 103,?

314182 · PK1 Page 10 200300300 V. Description of the invention (3) A1 uGauN cover layer 104), p-type GaN contact layer 105. In addition, an n-type electrode p 1 is formed on the partially-exposed n-type GaN contact layer 105. An element structure of a P-type electrode P20 is provided on the type GaN contact layer 105. The light-emitting part in the example shown in FIG. 6 has a SQW structure. When the light-emitting part is made into an MQW structure, the barrier layer between two well layers must be made to a thickness that can cause a tunneling effect. Generally speaking, it is 3 To a thickness of 6 nm.

However, even if various light-emitting portion structures are made as described above, the InFaN ultraviolet light-emitting element will not have sufficient output power because the In content of the light-emitting layer is too low. & f [Content of the invention] The subject of the present invention is to solve the above problems, even when using InGai ^ as the material of the light emitting layer, even in use! In the case of nGaN * materials, the structure of the element is also optimized to provide a variety of ultraviolet light-emitting devices that are capable of inserting more light into the glass. Line hair structure Round out Photon Crystallization This product is a semi-structure The inventors and others have discovered that gp made the light-emitting layer material to be an InGaN-based material with a light component, which was replaced by the West, T ^ r

^ ^ / Λ # ^ MQW power, and the completion of this item "Yu: 疋 is a specific value 'can enhance the part has the following characteristics: n ultraviolet light of the present invention (1) a kind of ultraviolet light emitting branch ^ on the substrate, forming The multilayer structure formed by Ga_ surname 1 through the buffer layer or directly in the layer structure contains a P-type anode layer / kg, and

The GaN of the light-emitting part composed of the layer of the conductor light-emitting element ’is formed by an InGaN-based material that can emit: the light-emitting part has multiple quantum wells that emit light outside the surface.

200300300 Fifth, the description of the invention (4) is completed, the number of well layers is 2 to 20, & it pill L and the thickness of the barrier layer is 7ηm to 30nm. (2) As described in item (1) above, the main layer structure of the inm is separated by A 1 _ Wen Cheng, Bu, and Quan Guangguang, where the above product

‘Buffer in the a1N low-temperature growth; == formed on the crystalline substrate, and $ 〇 bottom layer. Just above the sun, AlxGanIUtK X (3) is formed as described above. (2e hN (0 < g ^ bottom plate wells), external light emitting elements, of which AUGa f. "AlGaN does not exist between well layers" The formed (4) is the p-type plywood ultraviolet light-emitting element in the (1 ^ t) structure described above, in which the above-mentioned side and the P-type contact layer are formed by the positional relationship of "", and the P-type layer is disposed on the The above (5) is formed as in the above (1) nYGai-YN (〇 < Β υ). The multiple quantum well structure is an ultraviolet light emitting element which is invited, in which the thickness of the barrier layer connected above is thick; the p-type layer is connected The barrier layer and the P-type layer are between 10nm and 30nm. (6) As mentioned above (the ultraviolet light-emitting element of the above-mentioned item), among which, there are many, ^ ,,, and The f-series fines are composed of a well layer formed of undoped GaN-based crystals, and a barrier layer formed of ^ A a crystals. As described above, the ultraviolet light-emitting element of item (1), wherein the multi-substructure described above It is composed of: a well layer formed by InxGabu xN (〇 < g 〇) and a barrier layer formed by TaN. (8 紫 on it purple in item (7) Linear light-emitting element, in which the above-mentioned In component of the above-mentioned $ ^ xGabxN 〇 < 〇11. (9) The ultraviolet light-emitting element of the item (1) above, wherein the crystal substrate and the well layer are not There are layers formed by A IGaN.

314182.ptd Page 12 200300300 V. Description of the invention (5) (1 0) The ultraviolet light emitting device according to the above item (1), wherein the surface of the crystal substrate is processed into a concave-convex shape, and the concave-convex is covered with a GaN-based crystal layer. The laminated structure is partially formed by a vapor phase growth method. [Embodiment] The G a N referred to in the present invention means: Indium gallium nitride I n XG a YA 1 ZN (0 S X-1, OS YS 1, OS 1, X + Υ + Zn = 1 Examples of the semiconductor compound include important compounds such as aluminum nitride A 1 N, gallium nitride G a N, aluminum gallium nitride AlGaN, indium gallium nitride InGaN, and aluminum gallium nitride InGaAIN. In addition, I n G a N means that the aforementioned I n XG a yA 1 ZN must contain an I η component and a Ga component. In addition to I n G a N, I n G a N may also Add Α1 ingredients. The ultraviolet light-emitting element of the present invention may be an ultraviolet LED, an ultraviolet LD, or the like, but the present invention will be described below using an ultraviolet LED as an example. In addition, in the element structure, any one of the P-type and n-type layers may be on the lower side (the crystal substrate side). For manufacturing reasons such as obtaining high-quality crystals of GaN-based semiconductors, the n-type layer is used. The lower side is ideal. In the following, the device structure is described with the n-type layer as the lower side, but the present invention is not limited to this. Fig. 1 is a diagram showing an example of the structure of an ultraviolet light emitting element (LCD element structure) of the present invention. As shown in the figure, on the crystalline substrate B, a layer 1 structure S composed of a GaN-based crystal layer is grown through a GaN-based low-temperature growth buffer layer B1. The layered structure S includes a p-type layer and The light-emitting portion composed of the n-type layer is provided with an electrode to form the ultraviolet light-emitting element of the present invention.

314182.ptd Page 13 200300300 V. Description of the invention (6) About Xu in the first figure ^ θ _ ^ Day 丨 丄 A example 'explains the structure of each layer in a more specific way. M 彳 r 厗 R 1 under ^ side In order: sapphire crystal substrate B, GaN low-temperature contact sound, Mnw, thermally doped GaN layer, and light-emitting portion [n-type GaN cover layer connection Q structure 3 (GaN barrier layer / InGaN well layer / GaN barrier layer well layer / GaN Barrier layer >, P-type AlGaN cladding layer 4], and? -Type contact layer 5. The n-type GaN contact layer system is partially exposed, n 'electrode P1 is formed in the exposed surface, and a p-type is formed on the p-type GaN contact layer. Electrode p2. An important feature in the MQW ^ 4 U-Nu structure is that the well layer material containing the 0W MQW structure in the light-emitting part is made of 30nm which can emit ultraviolet light, and the number of well layers is 2 to 20. The barrier layer The thickness is 7 至 to the material, ί =? The light part is limited to this structure, even if it is a 1 nGaN series material, and the UV light-emitting element using I nGaN as the light-emitting layer, it is also obtained by Ji Father 1. Higher output power. The light section is composed of a p-type cover layer and a ^ -type cover layer, and has a ^ T / i / QW structure. The n-type and p-type cover layers Can be used as the n-type and the 々 side plus the old wave guide layer and the gap layer, etc. Fee = 3, which shows the relationship between the number of well layers of MQw measured in the first embodiment below 2 to * output power It can be clearly seen from the figure that when the number of well layers must be out of this range between phases, the optical output power will be different from the previous value. In addition, the number of well layers is preferably between 8 and 15 At this time, the power of the light wheel of the Langya is being given out.

The material of s is InGaN series material, especially InxGa ^ NCiX

200300300 V. Description of the invention (7) 1. When Ga is required, it is 0 < x < 1). Ultraviolet light below 4 20 nm must be a light-emitting component. The more specific and ideal value of the indium I η component X of I n XG a is 0 < X S 0.1. The material of the well layer does not need to have all the same I η components, and can be appropriately selected according to the needs of tilting and the like. The thickness of the well layer may be the same as the generally known MQW structure, for example, a thickness of 2 nm to 10 nm may be sufficient. The barrier layer does not have to be limited to exist separately as the outermost layer adjacent to the two covering layers, and for example, it can also form the following ① to ③. ① Like (η-type cover layer / well layer / barrier layer / well layer / p-type cover layer), the cover layer also serves as the outermost barrier layer. ② As ((n-type cover layer / barrier layer / well layer / barrier layer / well layer / barrier layer / p-type cover layer)), the outermost barrier layer layer and the cover layer exist separately. ③ As ((n-type cover layer / well layer / barrier layer / well layer / barrier layer / ρ-type cover layer)), only the outermost layer of the barrier layer on one side exists independently. In the present invention, the thickness of all the barrier layers of the MQW structure is made from 7nm to 30nm. Figure 4 is a graph showing the relationship between the thickness of the barrier layer and the output power of the light-emitting element measured in the following examples. It can be clearly seen from the graph of the figure that when the thickness of the barrier layer is 7 nm to 30 nm, a UV light emitting element with higher light output power can be obtained. When the barrier layer is thinner than 7 nm or thicker than 30 nm , The optical output power will be reduced as in the past. In the range of the thickness of the above barrier layer, the most desirable is 8nm to 15nm, at which time the highest output power can be obtained

314182.ptd Page 15 200300300 V. Description of the invention (8) Light-emitting element with high efficiency. Relative to the thickness of the barrier layer in the conventional MQW structure is 3 nm to 6 nm, the thickness of the barrier layer in the present invention is set to 7 nm to 30 nm. By thickening the barrier layer to the above value without the overlap of wave functions, the resulting state is not so much an MQW structure as a multi-layered SQW structure, but it can achieve the purpose of increasing output power. When the thickness of the barrier layer exceeds 30 nm, the hole injected by the p-layer will fall into the non-luminous center defect in the non-luminous center of the G a N barrier layer before reaching the well layer, resulting in a decrease in luminous efficiency. , So it is not ideal. ® The ideal form of the MQW structure of the present invention is the form in which the outermost barrier layer must exist on the p-type cover layer side (that is, the above-mentioned ② or ③.), The outermost barrier on the P-type side The thickness can be set to 10 to 30 nm. As a result, the well layer will not be susceptible to damage caused by heat or gas generated during the growth of the layer after the P-type cladding layer, so the damage can be reduced, and the doped material of the P-type layer (Mg, etc.) The probability of diffusion to the well layer. In addition, the degree of inclination generated in the well layer will be reduced accordingly, so not only the output power can be increased, but the effect of prolonging the service life of the component can be obtained. The material of the barrier layer may be any GaN-based semiconductor material that can form a barrier layer of the I n G a N well layer, but in the present invention, GaN is the best. material. In the conventional MQW structure, a barrier layer having a larger energy gap than the well layer is used based on the consideration of confining carriers in the well layer. Especially in the case of an ultraviolet light emitting element, compared with a blue light emitting element, the well layer itself has a larger energy gap, and a material with a larger energy gap must be used as the barrier layer. example

314182.ptd Page 16 200300300 V. Description of the invention (9) For example, when the well layer is InGaN (In composition 0.03), AlGaN is used on the barrier layer or cover layer. On the other hand, the present invention aims at: by combining the InGaN well layer and the A 1 GaN barrier layer, the optimum value of the crystal growth temperature will be greatly different, and this point is the subject of the present invention. . In other words, A1N based on AlGaN has a higher melting point than GaN, and I nN based on InGaN has a lower melting point than GaN. Specific crystal growth optimal temperature is: GaN is 100 (TC, InGaN is 100 ° C or less (preferably 600 to 800 ° C)), and the optimal temperature ratio of A 1 G a N GaN is high. Therefore, after the combination of the InGaN well layer and the A 1 G a N barrier layer, when the well layer and the barrier layer are grown, if the growth temperature cannot be converted to the optimal value as much as possible, the maximum Layers with good crystal quality. However, changing the growth temperature in each well layer / barrier layer will cause the growth to be interrupted, while the thickness of the 3nm thin film well layer will change due to etching during the growth interruption, or the surface will have crystal defects. Because of the relationship between the two, it is difficult to obtain high-quality products through the combination of AlGaN barrier layers and InGaN well layers. In addition, if A 1 GaN is used as a barrier layer, it will cause deformation of the well layer. Instead, it increases the output power. Therefore, in the present invention, GaN is used as the material of the barrier layer to reduce the above-mentioned problems that are difficult to take into account. This can reduce the energy gap between the barrier layer and the well layer, and the two layers Crystal The improved results, the overall output power will be improved. Further 'in I n G a N Ito materials' also mixed with the use of InGaN

314182.ptd Page 17 200300300 V. Description of the invention (ίο) A1's A1 InGaN is used as a well layer, which can obtain the same effect and effect as InGaN. -In addition, according to the present invention, in order to solve the above problems by combining the InGaN well layer and the AlGaN barrier layer, it is recommended to adopt the positive between the crystalline substrate and the well layer (the A 1 N low temperature growth buffer layer described later). In the aspect of forming the bottom layer of A 1 GaN above, it refers to the state where the A 1 G a N layer is not provided between the bottom layer of A 1 G a N and the well layer). This can alleviate the above-mentioned problems caused by the difference in crystal growth temperature. For a specific example of not having an AlGaN layer, there is a case where a GaN layer is used instead of the A 1 G a N layer. In the example in Fig. 1, a non-doped non-doped G a N crystal layer (thickness: 0 · 1 # m to 2 · 〇 // m) was grown on the G a N low temperature buffer layer, and then An n-type GaN crystal layer (contact layer and cover layer) is grown over the undoped .GaN crystal layer. In addition, an undoped GaN crystal layer may be omitted. In addition, the n-type GaN crystal layer can be provided separately from the n-type GaN contact layer and the n-type GaN cover layer by changing the carrier concentration. Other ideal aspects of the MQW structure are those in which there is no impurity in the well layer and Si in the barrier layer. Figure 5 is a graph showing the relationship between the carrier concentration and the optical output-output power after doping Si in the barrier layer. The sample used in the measurement, although the number of well layers II is set to 6 and the thickness of the barrier layer is set to 10 nm, it is also applicable to other ¥ shapes. According to the graph in the figure, it is known that the light output power of "When S i is switched into S i" is small, and even if the amount of S i added is higher than 5x 1 0 18 ciir3, the light output power will be reduced. The reason why Si is added to the barrier layer is to increase the luminous intensity, but when the amount is too much, the luminous intensity is reduced due to the decrease in crystallinity. The ideal S i doping amount is 5x 10 16cnr3 to 5x 1 0 18cm-3.

314182.ptd Page 18 200300300 V. Description of the invention (11) Used for growing crystalline substrates, any substrate that can grow GaN-based crystals can be used. The ideal crystal substrates are, for example: sapphire (crystal plane C, crystal plane A, crystal plane R), siC (6H, 4H, 3C), GaN, AIN, Si, spinel, ZnO, GaAs, NG0 Wait. It is also possible to use a substrate having these crystals as a surface layer. In addition, the direction of the crystal plane of the substrate is not particularly limited, and may be a substrate with a crystal plane just or a substrate with an inclined crystal plane. Between the crystal substrate and the GaN-based crystal layer, a buffer layer may be interposed therebetween if necessary. However, when a substrate made of GaN or A 1N crystal is used as the crystalline substrate, a buffer layer is not required. In order to obtain a high-quality G a N film with less difference in displacement, an A1 GaN film (A IGaN bottom layer) having a different crystal constant from the G a N film can be configured as a bottom layer for growing a GaN film. When GaN is grown on an A1 GaN film, compressive stress is generated on the GaN. When growing in this state, the differential row will bend at the A1GaI ^ / GaN film interface (correctly, the first stage of GaN growth on the AlGa thief) to be perpendicular to the growth direction and cannot move in the growth direction. That is to say, a high-quality GaN film can be obtained. When this A1Ga layer is grown, it is preferable to use a buffer layer in the bottom layer. An ideal buffer layer is a GaN-based low-temperature growth buffer layer. The material, formation method, and formation conditions of the buffer layer can refer to commonly known technologies. The materials of the GaN-based low-temperature growth buffer layer are exemplified.

GaN, AIN, InN, etc., and the growth temperature can be between 300 ° C and 600 ° C. Slowly, the thickness of the layer is 1011111 to 50nm, but 20111] to 4nm is most preferable. A preferred form is an A 1 N buffer layer. Figure 2 shows an example of the device structure in this state. As shown in the figure, the base layer structure S formed of the GaN-based crystal layer is grown on the crystalline substrate b via A 丨 N low-temperature growth buffer layer 丨 0.

314182.ptd Page 19 200300300 V. Description of the invention (12) An AlxGai_xN (0 < X S 1) bottom layer 1 1 is formed directly above the A1N low temperature growth buffer layer 10. A 1 xGa〗 _χΝ The optimal thickness of the bottom layer varies according to the a 1 component (the value of X). For example, when the A 1 component is 30% (χ = 0.3), the thickness is preferably 10 nm to 5 // m, and most preferably 50 nm to 1 // m. When it is thinner than 10 [1] [11, it is not ideal because it loses the above effect. When the thickness exceeds 5 // m, the crystallinity of the GaN layer is reduced, which is not ideal. In addition, the a 1 component (value of X) of the bottom layer of A 1 xGa i_xN may be tilted ^ toward the growth direction. In addition, the A 1 component can be changed continuously or stepwise into multiple steps. In addition, when the thickness of the AlGaN bottom layer is relatively thick (for example, when the A1 content is 30% • hours) is about 500 nm to 5000 nm, a light emitting portion can be directly formed thereon. According to the present invention, one of the ideal aspects is to form a p-type contact with InGaN. In other words, the "known GaN-based light-emitting element using a p-type GaN contact layer" has a P-type contact resistance of up to 1 × 1 0-Ώ cm 2, preferably The person also meals at lx 1 0 -Ώ cm. In contrast, the use of nGaN as the material of the p-type contact layer has the advantage that the acceptor level (A ccept 〇 r Le eve 1) becomes shallower, the hole concentration increases, and the contact resistance is reduced to lx i 〇_ 6q cm lack of degree and other advantages. The P-type contact layer used to form the P-type electrode is preferably doped with N ((K-1). N2 + nh is used as the gas environment for the growth of the InGaN layer, thereby reducing Mg after growth. The so-called p-type treatment conditions for activation even omit this treatment. This is because when there is less production in the gaseous environment during growth, the inertization of Mg into the film can be suppressed. In addition, since __

II i Ί'ρί

SIB i

Ml if lifci 314182.ptd Page 20 200300300 V. Description of the invention (13) The energy level of the acceptor formed when Mg is doped in I nGaN becomes shallower, so that the hole carrier concentration at room temperature increases, so that the same The P-type processing conditions can be relaxed or the processing can be omitted. By applying a p-type I n G a N contact layer to an ultraviolet light emitting device, the light output power can be increased. This is based on the above reasons, which can relax the conditions of P-type treatment (especially thermal annealing) or omit the treatment itself, which helps to suppress the diffusion of doped impurities into the well layer. In particular, when the MQW structure is composed of a well layer formed of a non-doped GaN-based crystal and a barrier layer formed of a Si-doped GaN-based crystal, a steep impurity distribution can be obtained because heat treatment can be omitted. . As a result, the output power of light can be further improved. In order to reduce the differential density of the GaN-based crystal layer grown on the crystal substrate, a structure capable of reducing the differential density can be appropriately introduced. With the introduction of a structure for reducing the differential density, a part formed of a Si 0 heterogeneous material may be included in a multilayer structure formed by a GaN-based crystal layer. Examples of the structure for reducing the difference in row density include the following. (Ii) A masking layer such as a stripe pattern is formed on the crystalline substrate (using Si 0 2 etc.) so that a conventional selective growth method (EL0 epitaxial lateral overgrowth method, Epitaxial Lateral Over growth) can be implemented. (B) A structure in which spot-shaped and strip-shaped unevenness processing is performed on a crystalline substrate so that GaN-based crystals can be grown in a lateral (1 at era 1) or facet (facet) growth. It is only necessary to appropriately combine the above structure and the buffer layer. In the structure for reducing the density of the differential discharge, the (B) structure described above does not use

314182.ptd Page 21 200300300 V. Description of the invention (14) Ideal structure using mask layer. This structure is described below. As for the concave-convex processing method, for example, a general light lithography technique can be used to pattern the concave-convex shape according to the desired concave-convex morphology, and the RIE (Reactive Ion Carved Reactive I ο η E ΐ ching) technology can be used to perform the worm. Engraving method to obtain desired unevenness, etc. Concave and convex arrangement patterns include the following items: · Arranged with dot-like concave portions (or convex portions), and arranged at regular or non-fixed intervals into linear or curved grooves (or ridges), respectively Or concentric patterns. The pattern of convex ridges crossing in a grid can be regarded as a pattern of dots (square holes) and the arrangement of recesses. In addition, the cross-sectional shape of the unevenness includes square (including trapezoidal) wave shape, triangular wave shape, sine wave shape, and the like. Among the various concave-convex forms described above, strip-shaped concave-convex patterns (rectangular wave-shaped cross-sections) arranged in straight grooves (or ridges) at regular intervals are not only simplifying the production steps, but also make the pattern easier. More desirable. When the concave-convex pattern is formed into a stripe shape, the longitudinal direction of the strip is not limited in any way, but for a GaN-based crystal grown by covering the pattern, the &lt; 1 1-2 0 &gt; direction is taken as the length In the side direction, because the horizontal growth is suppressed, it is easier to form small bevels such as U-1 0 1 丨 plane. As a result, the difference in which the substrate moves from the substrate side to the C-axis direction is arranged on the facet to bend laterally, and it is not easy to move upward, so that a low-diffusion-row density region can be formed. When the long side of the strip is used as the <1-1 0 0> direction of the growing Ga N-based crystal, the GaN-based crystal that starts to grow from above the convex portion will rapidly grow in the lateral direction, while maintaining the cavity in the concave portion. Forms GaN-based crystals

314182.ptd Page 22 200300300 V. Description of Invention (15) layer. However, even if the long-side direction of the strip is set to the <bu 1 〇 &gt; direction, the same effect as the &lt; 11-2 0 &gt; direction can be obtained by selecting a growth condition in which facets are easily formed. The optimum size when the cross section of the unevenness is formed into a square wave is as follows. The width of the grooves is from 0.1 // m to 20 // m, particularly preferably from 0.5 // m to 10 // m. The width of the protrusions is 0 · 1 // m to 20 μm, but 0.5 // m to 10 μm is best. The amplitude of the concavities and convexities (the depth of the grooves) is preferably to a depth of more than 20% of the wide portion of the concave portion and the inside of the portion. The same applies to the above-mentioned dimensions and the pitches calculated from the dimensions.

Methods for GaN-based crystal layers include hydride vapor phase epitaxy growth method HVPE, Hydrolyte Vaper Phase Epitaxial, HVPE method, organic metal vapor phase growth method, MOVPE, Metal Organic Vapor Phase Epi taxial, MOVPE method, molecular beam epitaxy Growth method, MBE, Moleculaar Beam Epitaxial, MBE method, etc. The HVPE method is preferred when making thick films, and the MOVPE or MBE method is preferred when forming thin films. "簋" should be shame 1— In this embodiment, the UV leds shown in Figure 1 are made to form a sample with a thickness of 10 nm and a barrier layer thickness of 10 to 25 to form a total of 25 samples. To measure its output power separately. The device formation steps are as follows: Regardless of the sample, the crystal plane C sapphire substrate is first mounted on a MOVPE device 'and heated to 1 10 in a hydrogen atmosphere to perform thermal contact engraving. Then reduce the temperature to 500 ° C, and pour into the trimethylgallium (hereinafter referred to as TMG, Trimethylgallium), a raw material of Group I, I, and the ammonia of the N raw material to make the thickness

314182.ptd page 23 200300300 V. Description of the invention (16) The G a N low temperature buffer layer with a length of 30 n m grows. Next, the temperature is heated to 100 (TC), and then the raw material is added to grow the non-doped G a N crystal layer 1 by 2 // m, and then the s gas-type GaN crystal layer (contact layer and cover layer) is poured. ) Grows 3 // m. Γ of the known Si [quantum well structure] The temperature is adjusted to 80 0. (: After that, a GaN barrier layer (thickness 10 nm) of 17 cmt Si in pairs in each sample, And InGaN well layer (^ H0nm, In composition (0.03, thickness 3nm)) to change it to ^ to ^ of the ancient times; in addition, in each sample, the final GaN barrier is connected to the? Layer (Heart has 5x 1 〇] 7cm- si, thickness is 20nm. After heating the growth temperature to 1000 ° C, each sample is formed in order of thickness _ A1GaN cover layer 4, thickness 50nm The p-type GaN contact layer is further formed into an ultraviolet LED wafer with a light wavelength of 38 Onm, and then the electrode is formed and the components are separated to form an ultraviolet LED wafer. In the above-mentioned samples of the ultraviolet LED wafers with different numbers of well layers, respectively In order to connect θ Η and Θ, measure the output of a wavelength of 3 8 0 nm with a current of 20 mA: 'The number of well layers and output can be obtained as shown in Figure 3. The relationship of power &quot; ° As mentioned above, the number of well layers must be 2 to obtain the output power at 2mWa. Especially when the number of well layers is 6 to 15 layers, since 5mW or more can be obtained = optical output power , So it is the ideal number of wells.

寒 "~ 实 j ^ In this embodiment, the ultraviolet LED shown in Fig. 1 is made by the same steps as in the first embodiment described above, and the number of well layers is fixed to 6, and the degree of the barrier layer # is changed from 3nm to 40nm sample, and measure the output work of each sample η 182 314182.ptd page 24 200300300 V. Description of the invention (17). In the case where the UV LED wafer samples with different barrier layer thicknesses obtained in this embodiment are bare wafers, the output power at a wavelength of 380 nm is measured at a current of 20 mA, and the thickness of the barrier layer shown in FIG. 4 can be obtained. Relationship with output power. As described above, the thickness of the barrier layer must be 7 nm to 30 nm to obtain an output power of 2 mW or more, and especially when the thickness is 8 nm to 15 nm, the light barrier power of 5 mW or more can be obtained, which is the ideal thickness of the barrier layer. In the above-mentioned first embodiment, the thickness of the barrier layer is fixed to one kind, and in the above-mentioned second embodiment, the number of well layers is fixed to one kind, but as in the above-mentioned element formation step, it is manufactured in 7 to 30 Samples that change the thickness of the barrier layer in the range of nm, and in each thickness, form a sample of elements that change the number of well layers in the range of 2 to 20. In this way, regardless of the thickness of the barrier layer, the change in the number of well layers A curve similar to that in FIG. 3 can be obtained. In addition, regardless of the number of wells, the thickness change of the barrier layer can obtain a curve with the same inclination as that in FIG. 4. Third Example In this example, all the samples produced in the first and second examples described above use a GaN low-temperature buffer layer as the A 1 N low-temperature buffer layer and an undoped G a N crystal layer as the A 1 G a N bottom layer, a p-type G a N contact layer as a p-type I nGaN contact layer was used to make a UV LED sample, and the respective output power was measured. The component formation steps are as follows: Regardless of the above-mentioned samples, first, the C-plane sapphire substrate is mounted on a MOVPE device, and heated to 1100 ° C in a hydrogen environment for thermal

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314182.ptd Page 27 200300300 Brief description of drawings [Simplified description of drawings] Fig. 1 is a schematic view showing a structural example of the ultraviolet light emitting element of the present invention. The symbols in the figure are marked with the following symbols, respectively. B: crystalline substrate, S: laminated structure formed by GaN-based crystalline layer, 2: η-type cladding layer structure, 3: MQW structure, 4: ρ-type cladding layer sample, P 1: η-type electrode, P 2: p-type electrode. Fig. 2 is a schematic diagram showing another configuration example of the ultraviolet light emitting element of the present invention. Fig. 3 is a graph showing the relationship between the well layer ϋ and the optical output power of the MQW measured in the first embodiment of the present invention. Fig. 4 is a graph showing the relationship between the thickness of the MQW barrier layer and the optical output power measured in the second embodiment of the present invention. Fig. 5 is a graph showing the relationship between the carrier concentration of the barrier layer (unit cnn3) formed by adding silicon Si to the barrier layer and the light output power in the ultraviolet device of the present invention. FIG. 6 is a diagram illustrating an example of a conventional ultraviolet LED element structure using In0.03Ga0.97N as a material of a light emitting layer. Non-doped GaN layer η-type GaN crystal layer (contact layer and cover layer MQW structure (multiple quantum well structure) ρ-type cover layer crystalline substrate η-type electrode P1 5 η-type G a Ν contact layer B1 G a N low-temperature growth buffer layer PI ρ-type electrode

II ill _ _

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Claims (1)

200300300 VI. Scope of patent application 1 · An ultraviolet light emitting element is formed by a GaN-based crystal layer through a buffer layer or directly on a crystalline substrate, and the multilayer structure includes a P-type layer and η The GaN-based semiconductor light-emitting element of a light-emitting portion composed of a type layer is characterized in that: the light-emitting portion has a multiple quantum well structure; and the well layer is formed of an InGaN-based material that can emit ultraviolet light. The number of well layers is 2 To 20, and the thickness of the barrier layer is 7 nm to 30 nm. 2 _ The ultraviolet light emitting element according to item 1 of the scope of patent application, wherein the laminated structure is formed on a crystalline substrate via an A 1 N low temperature growth buffer layer, and directly above the A 1 N low temperature growth buffer layer. A1 xGahNCiK xS 1) bottom layer is formed. 3. The ultraviolet light-emitting element according to item 2 of the patent application scope, wherein there is no layer formed by A! GaN households between the bottom layer of A 1 xGa hN (0 &lt; 1) and the well layer. 4 5 The ultraviolet light-emitting element according to item 1 of the scope of the patent application, wherein the positional relationship between the p-type layer and the _ layer in the above-mentioned laminated structure is that the p-type layer is provided on the upper side, and the p-type contact layer is formed by n YGa ι γΝ (〇 &lt; 丨). For example, the ultraviolet light emitting element of the first patent application range, wherein the above multiple 2: sub-well structure is provided with a barrier layer connected to the p-type layer, and the thickness of the barrier layer connected to the p-type layer is 10 to Between 30. For example, the ultraviolet light-emitting element of the first patent scope, wherein the above-mentioned multi-cavity well structure is a well layer formed by the GaN crystal of Yisong, ..., and the GaN crystal crystal pressed into Si. r ^ ^ ^ m formed by the barrier layer. For example, the purple ice 3 I external light-emitting element of claim 1 of the patent scope, wherein the above 314182.ptd Number 3〇 Page 200300300 6. Scope of patent application Multiple quantum well structure system: a well layer formed by InxGai_xN (0 &lt; 1) and a barrier layer formed by GaN. 8. For example, the ultraviolet light-emitting element of the scope of patent application item 7, wherein the X of the above I n XG a and XN I η component is 0 &lt; 0 · 1 1 〇9. For the ultraviolet light-emitting device of scope item 1 of the patent application Among them, there is no layer formed of AlGaN between the crystalline substrate and the well layer. 10. The ultraviolet light emitting device according to item 1 of the scope of patent application, wherein the surface of the crystalline substrate is processed into a concavo-convex shape, and the concave-convex portions are covered with a GaN-based crystal layer for vapor-phase growth to form a laminated structure. 314182.ptd Page 31