TW550840B - Light emitting diode device - Google Patents

Abstract

A light emitting diode is made by a compound semiconductor in which light emitting from an active region with a multi-quantum well structure. The active region is sandwiched by InGaA1P-based lower and upper cladding layers. Emission efficiency of the active region is improved by adding light and electron reflectors in the light emitting diode. These InGaA1P-based layers are epitaxially grown by organometal1ic vapor-phase epitaxy (OMVPE) on a GaAs substrate with a thin thickness to improve the thermal gradient, reliability, brightness quality, and performance in light emitting.

Description

550840 V. Description of the invention (i) 5-1 Field of invention: The present invention relates to a semiconductor light emitting diode structure, and more particularly to a semiconductor light emitting diode element on a thin substrate. 5-2 Background of the Invention: Light emitting diodes (LEDs) are widely used in different fields, such as light sources to reduce power consumption, high efficiency and high reliability. More specifically, compound semiconductors such as GaP (green wavelength), GaAsP (yellow, orange, or red wavelength) and G a A 1 A s (red wavelength) are widely used as light emitting diodes in the visible light wavelength range. Body material. However, the luminous efficiency of each Ga P and Ga A s P is an indirect semiconductor material. Even if a transparent substrate is used as a material to eliminate the influence of light absorption, its luminous efficiency is less than about 0.5%. In other respects, influencing luminous efficiency is an indirect turning state in the short wavelength range. For example, when the visible light wavelength is 6 3 5 nm, its luminous efficiency is about 1%. In III-V (III-V) composite semiconductor mixed crystals do not contain nitrides, InGaAl P mixed crystals show the maximum energy band of the indirect transition type, and their light absorption capacity can be used as a light-emitting element. The wavelength of light emission is 0.5 to 0.6 microns (micr ο η). In particular, the light emitting diode contains

Page 5 550840 V. Description of the invention (2) G a A s substrate and I n G a A 1 P layer, the lattice coefficient of which is aligned with the G a A s substrate, through which the structure can be under high brightness Emit green to red wavelengths. However, in this type of light emitting diode, its light efficiency in the short wavelength range is still insufficient. Reference to the first figure is a schematic diagram showing a conventional light emitting diode structure 100. In this figure, the light emitting diode element structure 100 includes a double having a tetrahedral InQ.5 (G a! -XA 1 x) 〇, 5P alloy system and formed on a η — G a A s substrate 1 02 Dissimilar structure (DH; double hetero-structure), where the thickness of the n-GaAs substrate 102 is about 350 micrometers (um). In the conventional light emitting diode 102, the thickness of the substrate is an issue to be considered. Generally speaking, the GaAs substrate 102 is directly purchased from the manufacturer, and the G a A s substrate 102 is ground or the G is etched by a pre-process (pre-p cess). The thickness of a A s substrate 10 2 is ground to a thickness suitable for a light emitting diode substrate, such as 180 μm. However, whether it is a grinding or etching process, the consistency of Ga As substrate 102 and the reliability of the substrate material after the pre-processing process will affect the luminous efficiency of the entire light emitting diode after formation. In addition, the temperature of the GaAs substrate 102 is too high to maintain consistency due to the thickness of the substrate 102, which results in a temperature difference between the substrate 102 and the substrate 102 during the formation of the stupid substrate 102. The temperature of the obtained substrate 102 is relatively uncontrollable, so that the luminous efficiency of the light emitting diode structure 1000 is reduced. Next, referring also to the first figure, the light emitting diode 100 having a forward biased pn junction is formed by a p-type cladding layer (p-type 11 111 111 III I ill ill j _1 lilli 111 I lii iliiil iliiil! Page 6 550840 V. Description of the invention (3) The cladding layer 108 is injected into a hole, and the n-type (n-type: cladding layer 104) emits electrons into the active area. The active layer emits visible light due to the recombination of electrons and holes in the active area. The injected electrons and holes pass through the active area as a few carriers and the recombination of electrons and holes is achieved by Luminescent recombination or non-luminous recombination. The luminous wavelength of the light emitting diode structure 100, which is mainly composed of InGaAlP, can be adjusted by changing the composition of the In55 (Gai_xAlx) 〇5P alloy in the active layer, and InGaAlP-based light-emitting diodes 100 have appropriate energy bands to gather unique light-emitting wavelengths. For example, 'short wavelengths such as red light or yellow-green light, the concentration of aluminum components must be higher to generate light. In addition, Because of the low carrier density, the active layer 10 6 The degree will be reduced in the active area. The active area is used for carrier injection and carrier recombination to generate light, and the thickness of the active area is generally about 0.3 to 0.5 microns. In order to obtain higher luminous efficiency, it is located in the active area. The quality of the material required for the area is required. This requirement is that impurities in the active area will reduce the concentration of the non-luminescent recombination center. Generally, the Ino./GahAlU active layer 106 is an undoped layer, Φ and Its electrical property can be η or p-type, and its doping concentration is about 5 * 1 0 15 to 1 * 1 0 17 per square centimeter. In other aspects, the degree of doping in the active layer 106 is the same as that in the active layer. The increase in the content of the component in the region increases. This is due to the higher aluminum concentration in the active region to increase the composition of impurities. For short wavelengths, increasing the concentration of aluminum in the active region and the internal quantum effect of the emitted light Relevant. As mentioned above, higher concentrations of aluminum

Page 7 550840 V. Description of the invention (4) As the deep plane is increased to cause non-luminescence to recombine in the light-emitting layer, the light-emitting efficiency is reduced. The n-type (104) or p-type has an energy level higher than that of the active coatings 104, 108, and needs to supply sufficient injection carriers. However, the backflow of the carriers in the InO5 (Ga and XA1 moving regions to an insufficient thickness will affect this. Most of the injected carriers are non-luminous, and in the traditional light-emitting diodes, the wavelength of the element follows the wavelength of the element. Shortened: 108) The cladding layer provides a source and area for injection carriers to limit injection carriers and luminescence. These packages have good conductivity and proper doping concentration to enter the active region to obtain a high luminous efficiency x) 0.5 P layer should have sufficient thickness to prevent the main cladding layer, but I η 0.5 (Ga 〖XA 1 x) Luminous efficiency of the entire light emitting diode 100 of the G.5P layer. Factors can overflow into the cladding layer and cause leakage currents due to these reorganizations. The polar body 100 includes a bi-different structure and the luminous efficiency is reduced. Φ After the P-type cladding layer 108, a current spreading layer 110 is formed to disperse the luminous efficiency. The current dispersing layer 110 needs to transmit the light emission wavelength from the active region to the semiconductor material. In addition, a window layer 112 needs to effectively disperse current into the active layer 106 and the cladding layer, and the window layer 1 2 needs a high doping concentration and a sufficient thickness. Then there is a metal contact (1116-731 (301 ^ & (: 1:) 114) above the window layer Π2, and there is also a metal contact below the substrate 10 2 1 1 6 〇

Page 8 550840 V. Description of the invention (5) According to the above, it can be known that the thickness of the GaAs substrate 102 in the traditional light emitting diode 100 is one of the main factors affecting the light emitting efficiency of the entire light emitting diode. First, it is difficult to obtain yellow light and green light with high luminous efficiency in the conventional light emitting diode 100 of the InGaA 1 P series. 5-3 Objects and Summary of the Invention: The main object of the present invention is to provide a G a A s substrate with a thin thickness and a chamfered angle orientation < 1 1 1 > Increase the immunity of light-emitting diodes. Yet another object of the present invention is to improve the reliability of the overall light-emitting diode device to increase the quality of the device and the light-emitting brightness. Another object of the present invention is to save the process of forming a light emitting diode element. Another object of the present invention is to improve the temperature gradient of the entire GaAs substrate to increase the heat dissipation efficiency of the light emitting diode. According to the above-mentioned object, the present invention provides a light-emitting diode structure having a thin-layer GaAs substrate. The structure contains a thin GaAs substrate and has a chamfered angle and tends to < 1 1 1 > A surface, a buffer layer (B u f f e r 1 a y e r) for improving the surface smoothness and consistency of the GaAs substrate is located

Page 9 550840 V. Description of the invention (6)

On the GaAs substrate, a distributed Bragg reflector (DBR; Distributed Bragg Reflector) is located above the buffer layer and is used to reflect the emitted light transmitted from the active region, and the lower cladding layer Located on the decentralized Bragg reflector, its role is to inject carriers into the active area and confine the carriers to the active area. Next, a multi-quantum well layer (MQW; multi-quantum we 1 1 s) is located above the lower cladding layer. This layer is used to replace the traditional active layer and increase the efficiency of the active layer in the short-wavelength light emission range. And reduce the content of Shao in multiple quantum wells. In addition, multiple quantum well layers can increase the luminous efficiency of light emitting diodes. An upper cladding layer is then located above the multiple quantum wells. This upper cladding layer is used to inject carriers into the active region and confine the carriers within the active region. The lower cladding layer and the upper cladding layer The cladding has the opposite conductivity. Next, a current blocking layer is located above the upper cladding layer. Its function is to form a low-resistance path on the vertical plane to inject carriers, and then above the current spreading layer. A window layer (window layer) is used in the light-emitting diode for current dispersion. Then there is a metal contact above the window layer and a metal contact below the GaAs substrate. In the light-emitting diode structure of the present invention, because the thickness of the GaAs substrate is 4 ′, the temperature difference during the growth of the worm crystal is small, and the opening temperature is easy to control> the formation temperature is consistent and reliable. It can also increase the luminous brightness of the light-emitting diodes. In addition, due to the thin thickness,

550840 V. Description of the invention (7) Therefore, the process of grinding the GaAs substrate to a thickness suitable for a light emitting diode structure by grinding or etching can be greatly simplified. 5-4 Detailed Description of the Invention: Some embodiments of the present invention will be described in detail as follows. However, in addition to the detailed description, the present invention can also be widely implemented in other embodiments, and the scope of the present invention is not limited, which is subject to the scope of subsequent patents. The light emitting color of the light emitting diode can be adjusted by the composition of the 0.5P alloy in the active layer, and I n G a A 1 P is: Change I nq 5 (G a and XA 1 and have appropriate The energy gap is focused on a special emission wavelength. I η 0.5 (Ga hA 1 x) 0.5P alloy in the active region tends to have an or der structure resulting in a width of the band gap. Decrease. Aluminum in the active region needs a higher content to achieve the same emitted light wavelength, but it will cause high impurity density and low radiation efficiency in the active region. The origin of the ordered structure is like in the semiconductor film, Changes in the order or composition of the atoms can be caused by the static displacement of the atoms, which results in local changes in the lattice tetrahedron deformation. In I n G. 5 (

Ga i-xA 1 x) 〇. In the 5P alloy system, indium (I n; i nd i um) has a larger tetrahedral covalent than gallium (Al; aluminum) atoms. radius. Therefore, the difference in the covalent radius of the tetrahedron will produce homogeneous aggregation. As a result, the local deformation and shrinkage of the crystal structure are relatively generated. Spin〇dal decomposition thermodynamics

Page 11 550840 V. Description of the invention (8) Thermodynamic) In the phase diagram, at a transition temperature, there is an order from order to di order). The difference between experiment and thermodynamic theory lies in the consideration of the formation of kinetic energy and surface structure order. It can be known from our experiments that the 1 n ◦ · 5 (G a ι-χΑ 1 x) Q # thin film follows the basic principle of thermodynamics of spinodal decomposition 'at the growth temperature of 770 ° C. (: There tends to be a certain degree of sequential structure between them. The temperature at which the light emitting diode grows is higher than about 700 ° C epitaxial growth temperature. On the other hand, <〇〇1> GaA s The re-growth of the side surface layer in the direction of "〖〖ο &gt;" has a region of variable compression and extension. Because indium has a larger tetrahedral covalent half-control than that of gallium or Shao, the Denaturation elongation and compressibility are suitable nucleation sites, which are inclined to individual indium, gallium or aluminum atoms, which are very suitable for their growth. This point implies that in addition to the above-mentioned orderly and non-ordered transition temperatures In addition, there is an ordered structure: The formation is related to the surface structure of the substrate. From our experiments, the degree of ordered · can be improved by using different substrates with different cut angles-ordered and unordered The turning temperature is reduced due to the increase of the cutting angle of the substrate GaAs. On the surface of the miscut GaAs substrate, the surface reconstruction area that is periodically extended and contracted can be improved by increasing the miscut angle of the substrate GaAs. From the above If know 'wrong GaAs substrate as the cut angle is increased, the degree of atomic order in the InGaA 1P rules will significantly reduced. In addition, the entire light-emitting Xin order to increase the rate of a polar body, except

Page 12 550840 V. Description of the invention (9) G a A s substrate grows beyond the surface of <110> A. Generally, the thickness of the GaA s substrate when obtained by the manufacturer is about 350 μm, and then By grinding or etching, the substrate is ground to a thickness suitable for use as a light emitting diode substrate, generally about 180 microns. However, etching from a thickness of 350 micrometers to 180 micrometers requires a larger process cost; therefore, in the preferred embodiment of the present invention, the thickness of the GaAs substrate used is 150 to 250. Micron, the optimal thickness is 210 micrometers. The advantage of forming a GaAs substrate in this thickness range is that the process cost required to form a thinner thickness is reduced, and a larger amount of GaAs substrate can be formed in the same process; in addition, When it is ground to 180 彳, the etching or grinding process used can also be greatly simplified, and the required substrate thickness can be quickly obtained. Furthermore, GaAs with this thickness can be formed by using stupid crystals. When the substrate is formed, its formation temperature can be well controlled, so that the temperature gradient between the top and bottom of the substrate does not change much, and a reliable substrate can be obtained. In addition, a substrate with a thinner thickness also has better heat dissipation, so that its luminous efficiency can be increased. In addition, the thin film formed on the GaAs substrate has a relatively uniform heat dissipation efficiency, so the heat dissipation effect of the light emitting diode can be improved and the light emitting efficiency of the entire light emitting diode can be increased. At a certain growth temperature, the regular structure in the I η 〇 5 (G a 1-χΑ 1 X) 〇 5P alloy system is considered as a factor that reduces the quantum efficiency. Therefore, it is necessary to increase the composition of aluminum in the active region of InQ.5 (Ga ^ Alx) G.5P to obtain a quantum well with a specific energy step width. 'So' can be achieved by In〇5 (Ga 卜 χΑ1χ). The crystals grow on a staggered substrate, which reduces the transition temperature to below 700 ° C. 550840

The efficiency of the ladder edge of the efficiency material is that the suction edge of the ladder seems to be sunk along the moving area and the light is reduced. The optimal rate is 0. In addition, aluminum-containing InG.5 (GaB XA1 x) Q 5P multiple quantum wells can be used Increasing the off-cut angle of the substrate improves it. On the second: the oblique cut is more toward the surface of &lt; 111> A, which will expose Yu Duo's cation terminated step ^, via-step traps g :) and: = The fusion impurities are related to the shape of the bond between the terminal steps. The positive edge has a single bond and provides a weaker adsorption site. Furthermore, the step trapping efficiency decreases with the increase of the chamfering angle of &lt; 1 1 1 &gt; ^ = The addition of impurities (such as silicon or oxygen) will increase with the miscut angle. These impurities can be used as the deep layer of the light emitting region and the center of the light emitting junction 'and affect the emission efficiency of the light emitting diode. The present invention ^ uses GaAs as the substrate and the angle of the chamfered angle &lt; 1 丄 丨 &gt; A is greater than 丨 0 degree angle, and the chamfered angle is 15 degree angle 'is regarded as the emitted light has a better effect In addition, the film smoothness and quality of light-emitting diodes based on I n G a A 1 P can be improved by forming a GaAs structure on a chamfered substrate. In the past, it has been used to improve the surface smoothness of semiconductors. Crystal technology such as liquid phase epitaxy (LPE) or gas phase epitaxy (chemical

Vapor Deposition (CVD) to improve the smoothness of the film. In the present invention, a light-emitting diode based on InGaA 1 P and an organic metal gas phase epitaxy method (Organometalic Vapor Phase Epitaxy, 0MVPE) is used.

Page 14 550840 V. Description of the invention (11)) The angle of the bevel is greater than 10 degrees and is formed on the GaAs substrate to improve the smoothness of the film surface. It is known from our research that the smoothness of the light-emitting diode structure will increase with the increase of the substrate cut-off angle. This improvement in smoothness is for three-five mismatch dissimilar structures such as ga The epitaxial growth based on P, AlGaP and InGaAlP is particularly evident on GaAs substrates. The degree of lattice mismatch between these epitaxial layers such as 〇8 ?, 11033 and 11 ^ 3 八 11 alloy and the substrate is about 0-3.6%, and is related to the composition of the alloy. The initial growth of the thin film during the deposition on a non-matching substrate tends to

Crystals like small islands grow on the substrate. The size of these islands increases as the mismatch between the film and the substrate increases. This will result in a thread dislocation with a south divergence on the film, and increase the surface roughness of the film. These high-density crystal defects and rough seam film surfaces can be improved by increasing the number of crystalline points on the surface, reducing the area of nodule islands, and making a gradient change in the lattice constant of the unmatched heterostructure. Increasing the number of thin film nodules and reducing the island area are another focus of the claims in the present invention. GaAs substrate can be applied to cut an angle greater than 10 degrees, and an InGaAlP intermediate layer is inserted between the light emitting body In0.5 (Ga ^ AlJuP stupid crystal layer and the window layer as a ladder to achieve this effect. In the wrong Cut the substrate, the edges of the substrate step are combined

Inclination angle increases and increases. These step edges provide a ㈢ &amp; substrate placement to the nucleation site of the deposited film. Therefore, the density of the disease is lower than that of the low-density small island tuberculosis on the wrong cut substrate, which will result in a thin film of ^ plus the product of a small degree of slippage.

550840 V. Description of the invention (12) Output efficiency. In addition, the smoothness of the film surface can increase the range of device manufacturing processes, such as metal contact manufacturing and packaging of light-emitting diodes, the quality of thin films, the accuracy of light-emitting bodies, and the process window of device fabrication. By growing the In0.5 (Gah Α1 χ) ο # # base structure in the light-emitting diode on a GaAs substrate with a cut angle of 10 degrees or more.

Reference to the second figure is a schematic diagram showing the structure of a light emitting diode. According to the advantages described above, in the second figure, the structure of the light-emitting diode 10 includes at least a light reflecting layer and a tetrahedron alloy InG.5 ((GahAlJuP is n-type misoriented) GaAs substrate 12. The light emitting diode 10 is composed of an η-type GaAs buffer layer 14, and an 11-type one-eight-eight-eight-eight / eight-eight-three-one-one-one-one. 〇3 卜 41,) 0. 疋 -based distributed Bragg reflector (DBR; distributed Bragg reflector) 16, a first cladding layer over InG 5 (Gai_xAlx) Q 5p cladding layer ) 18. One strain (strain) is not doped with In / GahAlJuP / Ino. / Gabu xA1x). 0.5P multiple quantum well (MQW; multiple quantum well) 20. One is p-type In as the second cladding layer. 〇.5 (Ga, XA1 X) Q.5P upper cladding layer 22, a thin IruYGahAl X) Q.5P · Intermediate barrier layer 24, a p-type GaP or AlGaAs current meser layer (Current blocking layer) 26, a window layer 28, a top metal contact 30 as one of the first metal layers, and a bottom metal contact

16th page 550840

In the preferred embodiment of the present invention, multiple conventional active layers 106 are used (as shown in the first figure). Was replaced by Lizijing

AlAs / Ino ^ CGa ^ .AlJo,? ^ Tj A 1 1 The light reflection of the main dispersed Bragg reflective layer 16 is used to align the reflected light with GUI 5PU _. In addition, an In ΓΓ Λ1, The bottom layer of Μ polar body structure 10 (Ga "A 1 χ) 0.5P-based barrier layer cover layer 20 and window layer 28, and a gold system inserted into the substrate has been deposited in the ancient age of 8 MW 4 genus The contact 30 is located above the window layer 2 8 and the other metal contact 32 is located below the substrate ^. In the second figure, the light emitting diode structure 10 is grown with a sound as large as 0.4 micron silicon. Impregnated G aas buffer layer 1 4 长 在 # # Yue

The GaAs-level punching layer U is used to improve the smoothness and uniformity of the growth surface of the GaAs substrate 10. Growing the GaAs buffer layer 14 is necessary for the better quality of the light emitting diodes and hetero-interfaces thin films. After the GaAs buffer layer 14 is connected, a dispersed Bragg reflection layer 16 is positioned on the GaAs buffer layer 14 to provide light reflection. The material of this light reflecting layer 16 is made of a material selected from the prohibited band height of the energy level and the active region which are very similar. The choice of materials made in this layer 16 requires consideration of lattice matching, differences in energy bands and reflection coefficients, and doping limit of individual reflecting layers. Generally speaking, a periodic energy of ten to twenty Bragg reflectors

Page 17 550840 V. Description of the invention (14) Increase the external wave of the Bragg reflection layer 16 of the reflected wave number. The relationship between the reflected wave numbers is the reflection coefficient as follows. The incoming light energy gap to prevent any layer and layer anti-reflection layer 16 is better to perform 1.5 times than the ordinary quantum efficiency 1 i gh t that needs to enter the transmission layer. In a state where the light emitting diode is not used but the layer 16 is used. A 1 A s / A 1 XG a! _XA s The Bragg reflection wavelength λ is determined by the thickness of the individual reflection layer, and its function d / 4η, where η is the Lag reflection layer 16 of each layer of the Bragg reflection layer 16 The purpose is The energy gap used to reflect the line from the active area, A 1 XG a! _XA s must be greater than any light absorption in the active area. In addition, the difference of the respective reflection coefficients in the Bragg reflection layer 16 must be as large as possible to obtain the Bragg re-reflection efficiency. However, the Bragg reflector 16 also plays a high density 2 * 1 0 17 / cm2). The current injection energy of the conductive carriers is 0 due to the η-type impurity concentration in the Bragg reflector 16 of the A 1 A s-substrate. Intrinsic limitation. The Bragg reflective layer 16 is limited to achieve a low forward operating bias and at the same time to obtain an efficiency in the Bragg reflective layer 16 with a reflectance greater than or equal to 90-95%. In general, the period of the Bragg reflective layer 16 based on I n G a A 1 P-is about ten to twenty. Another candidate element for the Bragg reflective layer 16 is In0.5 (Ga i_xAl x) 0.5P-substrate alloy, which can achieve higher than the Bragg reflective layer 16 substrate of AlAs / AlGaAs-substrate Electrical conductivity, however, is offset by the lattice-matching controllability of growth on the GaAs substrate 12. In the second figure, the n-type lower cladding layer 18 is used to supply carrier injection.

a

Page 18 550840 V. Description of the invention (15) Active area and limit carriers to active area. The molecular composition of aluminum in the π-type lower cladding layer 18 is between approximately 0.7 to 1 and is related to the radiation wavelength of the active region. The thickness of the η-type lower cladding layer 18 must be thicker than the diffusion length of the carriers to prevent the carriers from diffusing from the active region to the η-type lower cladding layer 18 ° at InG.5 (Ga ^ Al X) G The doping concentration range of η-type or ρ-type in .5P results in the recombination of efficient electrons with hole luminescence in the active region is necessary. The overflow of any individual injected carriers will be caused by the non-rad i at i ve recombination center due to the deviation of the position of the ρ-η junction and the diffusion of the dopant molecules in the active area. Reduced efficiency of emitted light. Immediately after the n-type lower cladding layer 18, a strained Iny (Gai_x 八 10〇 丨-// 111 (), 5 (〇81_, 1: () (). 5? Multiple quantum wells 20 are inserted into type 11 (Lower layer) 18 and the P-type (upper layer) cladding layer 22 are used as active layers. The preferred embodiment in the present invention uses I n G a A 1 P as a superlattice (super 1 a 11 ice). Multiple quantum wells 20 are used to increase the efficiency of the active layer and reduce the aluminum content in the quantum wells. The structure of the quantum wells in the light emitting diode 10 can increase the efficiency of the emitted light. The quantum wells are formed by a narrow band gap. " The well is formed with a barrier with a higher band gap. As a result, the energy of electrons and holes is quantified (limited) and cannot move freely in the direction of current incidence. Freely move on the vertical plane and can be recombined. In multiple views; sub-well I ny (G a i_xA 1 x) 1-yP / I η 〇5 (G a ι-χΑ 1 x) 〇 5P 2 0 中 '

Page 19 550840 V. Description of the invention (16) In the conduction band, the energy level of the conductive band is urged upward, and the carriers confined to the valence band urge the energy level of the valence band downward. The multiple quantum well structure 20 shifts (sh i f t) the effective wavelength of the emitted light to a shorter wavelength. Therefore, the content of the inscription in the active region can be greatly reduced, so that for a specific radiation source wavelength, the multiple quantum structure of the light emitting diode 10 will increase the lifetime of non-radiative recombination and reduce the absorption of light radiation.

Therefore, the multiple quantum well structure 20 reduces the aluminum content, and the carrier lifetime of radiation recombination is also shortened. Therefore, the quantum efficiency of a light-emitting diode 10 with multiple quantum wells 20 active regions will increase significantly. The composition of the aluminum alloy in the multiple quantum well 20 is between 0 and 0.3, and the corresponding wavelength is between red and green-yellow light. It is adjusted according to the thickness of the quantum well and the number of quantum wells. In the multiple quantum well 20, a direct energy gap alloy Ino./GahAlJ^P is composed. The emission light wavelength of the multiple quantum well 20 has a great correlation with the thickness of the well. When the thickness of the multiple quantum well 20 is reduced, the quantized carriers of its conductive band push the effective sub-band up, and the quantized carriers of the covalent band push the effective sub-band down. The quantized band structure of the multiple quantum well 20 is quite sensitive at well thicknesses of about 1 to 10 microns. As a result, due to the quantization of the energy level structure, the wavelength becomes shorter when electrons and holes recombine. The general total thickness of the In0.5 (Ga ^ Alx) 0.5P alloy is between about 1 to 10 microns, and the optimal luminous efficiency period is 10 to 50. On the other hand, the internal quantum efficiency of luminescence is also related to the ratio of well-to-thickness (well / resistance) thickness. General efficient carrier recombination 550840 V. Description of the invention (17)-When the ratio of well to congestion is between about 0.75 and 25. Referring to the third figure, it shows the implementation of a 1 right night 3 1,.,, · "You Xi Zhong 3: the province of the sub-block (Mqb · multi-quantum barrier); ^ also a Λ iyD, which is the implementation of- In the example, two: f 5 ° junction f. In the present invention, the GaAs buffer layer 54 of the tilted GaAs substrate 52 is 54 °, == 50 °, and is formed by a dispersed Bragg reflective layer 56 located in the n • type: ：, The punching layer is above the n-type lower cladding layer 58 on the square of the scatter-type Bragg reflection 厣 t, and the Ku 辔 multiple quantum well 60 located above the n-type lower reed layer 5 to make the soil wide and a layer 5 8 Electron reflection layer located above the strained multiple quantum and Rnp ancient recognition + Nai Ai Zhili Kai 60

(electron reflector) 62. An upper cladding layer 64 located above the electron reflecting layer 62, a thin strained intermediate barrier layer I η 0.5 (G abu XA 1 x) located above the p-type upper cladding layer 64. 5P 6 6. The p-type GaP or p-type AlGaAs current blocking layer (current blocking 1 ay er) 6 located above the intermediate barrier layer β 6 6. The window layer 70 located above the current dispersing layer 6 8 The metal contact 72 above the light emitting monopole structure 50 and the lower metal contact 74 under the Ga As substrate 52 are formed. In the preferred embodiment of the present invention, a thin strained intermediate barrier layer 6 6 is inserted above the P-type upper cladding layer 64 to increase the barrier height of the p-type upper cladding layer 64 (barr i er he i ght). The electron reflecting layer 62 is also grown by an organic metal vapor phase stupid method 'and requires a very accurate interface ratio, accurate control of layer thickness and composition. In addition, the thin strained intermediate barrier layer 66 has an energy level that is equal to or greater than the energy level of the p-type upper cladding layer 64, and is located in an area close to the active layer 60 to prevent carriers from overflowing from the active area.

Page 21 550840 V. Description of the invention (18) The flow enters the p-type upper cladding layer 64 to improve the luminous efficiency of the light emitting diode 50. The p-type I η 0.5A 1 0.5P electron reflective layer 62 is strained, its position is close to the active region, and it has a considerable thickness and stress to prevent electron tunneling from the active region ( tunneling) effect. When the light emission efficiency of the active region of the periodic booster of the In〇.s (Ga ι-χΑ1 χ) 05P / Ino.5Alo.5P superlattice also increases, this is because of the reflectance of the electron reflection layer 62. Reason for increase.

However, this phenomenon is particularly noticeable when the thickness of the individual electron reflection layer 62 is in the range of 2 to 5 millimeters with a gradient or step thickness. The Ir ^ of the multilayer electron reflection layer 62 .XGahAl Jo ”P The thickness change indicates the reflected energy injected into the high-energy electrons from different active regions. Therefore, carriers are confined to gradient or step-like regions and obtain high electron incident energy. The electron reflection layer 6 The variety of 2 (variation in electron reflector) can be obtained by the gradient change of the thickness of the layer. In the preferred embodiment, the electron reflective layer 62 includes a strain barrier layer, followed by an Ino./GauAlU/InuAlo 5P supercrystalline structure layer close to the active layer 60 to reflect the overflow carriers from the active area. Next, above the multiple quantum well 60 and the electron reflection layer 62 is a p-type upper cladding layer 64. The p-type upper cladding layer 64 is used to inject carriers into the active region and confine the carriers to the active region. The thickness of the p-type upper cladding layer 64 must be greater than the diffusion length of the injected carriers to prevent carriers in the active region from entering the P-type upper cladding layer 64. In addition, the ρ-type upper cladding layer 6 4 must be 550840. 5. The description of the invention (19) must be thicker than the η-type lower cladding layer 58. The reason is that the P-type doping during the growth of the light-emitting diode 50 The diffusive 'relationship' of elements such as Zη atoms or Mg atoms. A typical P-type upper cladding layer 64 has a thickness of about 0.5 to 1.5 micrometers. Above the ρ-type upper cladding layer 6 4 is a thin I η 0.5 (Ga hXA 1 χ) 〇. 5P intermediate strain layer 6 6 which has a higher impurity density than the ρ-type upper cladding layer 64. The thin intermediate strain layer 66 is used to ensure that the injected carriers can pass through and disperse, and to ensure the high conductivity of the thin intermediate strain layer 66 to facilitate the effective spread of the current on a plane perpendicular to the injection direction, The composition of aluminum in the thin intermediate strain layer 6 6 (between 0.1 and 0.5) is smaller than that of the ρ-type upper cladding layer 彳 ® 6 4 and is coated with the ρ-type upper cladding layer. The lattices of layers 64 are matched. The intermediate current dispersion layer 68, which has a thickness of approximately 50 to 100 nm and a higher impurity density than the p-type conductivity layer, is a low-resistance channel designed to produce a vertical plane of injected current. In addition, the thin intermediate strain layer 66 has a larger energy gap than the active region to prevent: the light emitted from the active region from being absorbed. Since this thin intermediate strain layer 6 6 is very thin and has a doping concentration higher than that of the ρ-type upper cladding layer 64 but lower than the window layer 70, it can be used as a barrier layer in the direction of current growth and The low-impedance p-channel of current into the vertical plane of the growth direction. Therefore, according to the above, the light emission efficiency of the light emitting diode 50 is improved, and the current dispersion effect in the P-type upper cladding layer 64 and the active region will be blocked by In0.5 (Ga ^ Al x) G.5P The thickness, composition, and degree of doping of the layer depend.

Page 23 550840 V. Description of the invention (20) Next, it is one of the important features of the present invention. One will make I η 0.5 (G a hA 1 χ) 0.5 P light-emitting body 5 and produce the maximum function. The way to play is to add a window layer 70 on the p-type I η 〇5 (Ga 丨 -χΑ 1 X) 0 5ρ layer. Using GaP,

AlGaP or AlGaAs is used as the window layer 70. Since GaP or GaAsP has a relatively light-transmittable energy gap for light emitted from the active area of the light emitting diode 50. In the present invention, an organic metal vapor phase epitaxy method is used to grow a light emitting diode structure 50 on a Ga As substrate 5 2 at an angle <1 1 1> in a beveled direction including p

Type GaP, AlGaP or AlGaAs window layer 70. Epitaxial deposition AlGaAs, GaP or other group semiconductor surfaces are epitaxially grown by liquid-phase vapor phase or chemical vapor deposition to improve the smoothness of the deposited film. In the present invention, Group III-V compounds such as GaP and AlxGahP, in which X is less than 0 · AlyGai_y As 'where y is less than 1 and greater than 0.5' GaP and A 1 xGa hxp are both at the light emitting diode emission wavelength at In the range of 6 5 0 to 5 6 5 nm, it is used as the window layer 7 to disperse the injected current, because GaP and AlxGai_xP are transparent to the emission wavelength “ο to 5 6 5 nm. In addition, the luminous efficiency is also the same as that of the window layer 7 The thickness of 0 is related. When the thickness of the window layer increases, the wider the current spreading area and the light emitted from the side of the light emitting diode will increase, the output of the light emitting diode will also increase. Therefore, 'we can get' the use of The thinner thickness and the inclination angle towards the &lt; 111 &gt; A surface and the GaAs substrate whose stagger angle is greater than 10 degrees as the substrate of the light emitting diode can save process costs; in addition, when the substrate is formed,

Page 24, 550840 5. The minimum temperature gradient (therma 1 grad i ent) of the invention description (21) can easily control the temperature during epitaxial growth; moreover, its luminous efficiency and heat dissipation are also more traditional than G a A s substrate comes well. The above are merely preferred embodiments of the present invention, and are not intended to limit the scope of patent application for the present invention; all other equivalent changes or modifications made without departing from the spirit disclosed by the present invention shall be included in the following Within the scope of patent application.

550840 on page 25 illustrates the schematic diagram of the first structure of the light-emitting diode according to the conventionally disclosed technology, and the second diagram is the cross-sectional view of the structure of the light-emitting diode according to the technology disclosed in the present invention; and the third FIG. Is a schematic diagram of a light emitting diode structure wearing surface according to the technology disclosed in the present invention. Representative symbols of main parts: 10 Light-emitting diode structure 12 G a A s substrate 14 Buffer layer 16 Dispersive Bragg reflector 1 8 η-type lower cladding layer 20 Multi-layer quantum well 2 2 ρ-type upper cladding layer 24 Middle Barrier layer 2 6 Current blocking layer 28 Window layer 3 0 Metal contact 3 2 Metal contact 50 Light emitting diode structure 5 2 G a A s substrate

P.26 550840 Brief description of the drawing 5 4 Buffer layer 5 6 Dispersive Bragg reflection layer 5 8 η-type lower cladding layer 60 Strain multiple quantum wells 62 Electron reflection layer 6 4 ρ-type upper cladding layer 66 Intermediate strain barrier layer 68 current blocking layer 70 window layer 7 2 metal contact 7 4 metal contact 1 0 0 light emitting diode structure 1 0 2 G a A s substrate 1 0 4 η-type lower cladding layer 1 0 6 active layer 1 0 8 ρ Type upper cladding layer 1 1 0 current dispersion layer 112 window layer 1 1 4 metal contact 1 1 6 metal contact

Page 27

Claims (1)

550840 VI. Scope of patent application 1. A light emitting diode structure, the light emitting diode structure includes: a bottom metal contact; a G A A s substrate having a first conductivity is located above the bottom metal contact, wherein The G a A s substrate has an inclination angle greater than 10 degrees and is chamfered toward the &lt; 1 1 1 &gt; A surface; a light reflective layer having the first conductivity is located above the GaAs substrate and f has the first A conductive first coating layer is located on the photoreflection layer and an active layer is located above the first coating layer; a second conductive layer having a second conductivity is located on the active layer, wherein the first Two conductivity is opposite to the first conductivity; a current blocking layer is located above the second cladding layer; a window layer is located above the current blocking layer; and a top metal contact is located above the window layer. 2. For the light-emitting diode structure of the first patent application, wherein the optimal tilt angle of the GaAs substrate is 15 degrees. 3. For example, the light-emitting diode structure of the first patent application, wherein the thickness of the GaAs substrate is about 150 to 250 microns. 4. For the light-emitting diode structure of the first patent application, the optimal thickness of the GaAs substrate is about 210 microns. 550840 VI. Application for patent scope 5. If the light emitting diode structure of the first patent application scope, further includes a buffer layer having a first conductivity between the GaAs substrate and the light reflective layer 6. Such as patent application The light-emitting diode structure of the first item, wherein the light reflective layer includes a distributed Bragg reflector (DBR). 7. The light-emitting diode structure according to item 6 of the patent application, wherein the Bragg reflective layer includes an A1 As / AlxGa and xAs-structure having the first conductivity. 8. The light emitting diode structure according to item 6 of the patent application scope, wherein the Bragg reflecting layer includes a structure having a second conductivity, mainly InG.5 (Ga ^ Alx) 0.5P. 9. For example, the light-emitting diode structure of the scope of the patent application, wherein the active layer includes a strained and undoped in / GanAl x) i-yP / Ino.ZGabu XA1 x) 0.5P structure · 1 0 . For example, the light-emitting diode structure of the first patent application scope further includes an intermediate barrier layer between the second cladding layer and the window layer. Page 29 550840 6. Scope of patent application Ί 1. The light-emitting diode structure according to item 1 of the scope of patent application, wherein the above intermediate barrier layer includes a structure mainly composed of I n G a A 1 P. 1 2. The light-emitting diode structure according to item 1 of the scope of the patent application, wherein the current blocking layer includes a Gai x Al X) P layer having the second conductivity. 1 3. The light-emitting diode structure according to item 1 of the scope of patent application, wherein the window layer is used to disperse the current in the light-emitting diode. 1 4. A light emitting diode structure 'The light emitting diode structure includes: a bottom metal contact; a GaAs substrate having a first conductivity and a thickness ranging from about 150 to 250 microns is located on the bottom metal Contacting above, wherein the GaAs substrate has an inclination angle greater than 10 degrees and is chamfered toward the &lt; 1 1 1 &gt; plane A; a light reflective layer having the first conductivity is located above the GaAs substrate and has the first conductivity A first cladding layer is located above the light reflective layer; an active layer is located above the first cladding layer; an electron reflective layer is located above the active layer; a second cladding layer having a second conductivity is located Above the electron reflection layer, wherein the thickness of the second cladding layer is thicker than the first cladding layer and the second conductivity is opposite to the first conductivity; a current blocking layer is located above the second cladding layer ; Page 30 550840 6. Scope of patent application A window layer is located above the current blocking layer, wherein the window layer is used to disperse the current located in the light emitting diode structure; and a top metal contact is located above the window layer. 15. The light-emitting diode structure according to item 14 of the scope of patent application, wherein the optimal angle of the aforementioned G a A s substrate tilt is about 15 degrees. 16. The light-emitting diode structure according to item 14 of the scope of patent application, wherein the optimal thickness of the G a A s substrate is 210 micrometers. 17. The light-emitting diode structure according to item 14 of the scope of patent application, further comprising a buffer layer having the first conductivity between the GaAs substrate and the light reflective layer. 18. The light-emitting diode structure according to item 14 of the scope of patent application, wherein the light-reflective layer includes a distributed Bragg reflector (DBR). 19. The light-emitting diode structure according to item 18 of the scope of patent application, wherein the above-mentioned dispersed Bragg reflective layer includes an A1 As / Al xGahAs-structure having the first conductivity. 2 0. The light-emitting diode structure according to item 18 of the scope of patent application, wherein the above-mentioned dispersed Bragg reflective layer includes a second conductive material (Ino. ^ GahAl X) Page 31 550840 VI. The structure of patent application is mainly 0.5p. 2 1. The light emitting diode structure according to item 14 of the scope of patent application 5 wherein the active layer includes a strained and undoped I ny (Ga i_xA 1 x) yP / I η 0.5 (Ga ^ AlJ ^ P multiple quantum well. 2 2. The light-emitting diode structure according to item 14 of the patent application scope, wherein the above-mentioned electron reflection layer includes an Iny (Gai-xAlx) i-yP / In〇5 (Gai-xAlx) Q5P superlattice structure. 2 3. For example, the light emitting diode structure of item 14 of the scope of patent application, further includes an intermediate barrier layer between the second cladding layer and the current blocking layer. 2 4 The light-emitting diode structure of the scope of patent application No. 14 in which the above intermediate barrier layer includes a structure mainly composed of I n G a A 1 P. 2 5. The light-emitting diode of the scope of patent application No. 14 Structure, wherein the current blocking layer includes an Ino. ^ GanAl X) P layer having the second conductivity. Page 32