A composite multi-spectrum light emitting diode structure and preparation method thereof

Abstract

The present invention relates to the technical field of LED manufacturing, and specifically relates to a composite multi-spectral light-emitting diode structure and a preparation method thereof. The composite multi-spectral light-emitting diode structure includes a substrate material layer, a buffer layer, a first conductive layer, a quantum well structure layer, a second conductive layer, and a transparent contact layer arranged in sequence. The quantum well structure layer includes quantum well units, and each quantum well unit includes a first multi-quantum well layer, a second multi-quantum well layer, a third multi-quantum well layer, and a fourth multi-quantum well layer arranged in sequence, with band gaps of Eg1, Eg2, Eg3, and Eg4 respectively, and Eg2 < Eg1 < Eg3 < Eg4. Through a unique quantum well design, a composite multi-wavelength light emission composed of controllable electroluminescence and photoluminescence spectra is realized, and the spectral continuity is good, solving the problem that the industry's LED chips can only emit a single wavelength.

Description

Technical Field

[0001] The invention relates to the technical field of LED manufacturing, and in particular to a composite multi-spectrum light emitting diode structure and a preparation method thereof. Background Art

[0002] The chip size of the LED industry has evolved from a single lighting requirement to a quality requirement for comfortable light. As an important preparation material for LEDs, gallium nitride has long been able to emit only a single peak wavelength. However, the single peak wave not only has high energy, but also has poor comfort.

[0003] At present, the commonly used method in the industry to solve this type of comfortable spectrum is to use multiple chips with different wavelengths for combination and matching. However, the present invention does not require the combination of multiple chips and can emit different spectra through one chip, which can effectively solve technical problems in related fields such as lighting and display, and can reduce costs at the same time.

[0004] In summary, there is an urgent need for a light emitting diode structure with a simplified structure and improved light quality and a manufacturing method thereof to solve the problems existing in the prior art. Summary of the invention

[0005] The purpose of the present invention is to provide a light-emitting diode structure with a simplified structure and improved light quality and a preparation method thereof. The light-emitting diode structure adopts a composite light-emitting structure design, which can not only emit the corresponding peak wave as required, but also solve the comfort problem, improve the light quality, and meet the requirements of mass industrialization. The technical solution is as follows:

[0006] A composite multi-spectrum light-emitting diode structure comprises a substrate material layer; a buffer layer is arranged on the substrate material layer; a first conductive layer is arranged on the buffer layer; a quantum well structure layer is arranged on the first conductive layer; a second conductive layer is arranged on the quantum well structure layer; a transparent contact layer is arranged on the second conductive layer; along the direction from the substrate material layer to the transparent contact layer, the quantum well structure layer comprises a quantum well unit, the quantum well unit comprises a first multi-quantum well layer, a second multi-quantum well layer, a third multi-quantum well layer and a fourth multi-quantum well layer arranged in sequence, the first multi-quantum well layer has a bandgap width of Eg1, the second multi-quantum well layer has a bandgap width of Eg2, the third multi-quantum well layer has a bandgap width of Eg3, the fourth multi-quantum well layer has a bandgap width of Eg4, and Eg2< Eg1< Eg3< Eg4. Eg1 itself can realize electroluminescence under the action of current, and Eg3 and / or Eg4 can realize photoluminescence of Eg2.

[0007] Preferably, the emission wavelength of the emission light of Eg2 is greater than or equal to 400nm. Further preferably, the emission light corresponding to Eg2 is green light of 500-550nm or blue light of 470-500nm.

[0008] Preferably, the emission wavelength of the emission light of Eg1 is 440-470 nm.

[0009] Preferably, the emission wavelength of the emission light of Eg3 is 255-440 nm, the emission wavelength of the emission light of Eg4 is 250-435 nm, and the wavelength difference between Eg4 and Eg3 is between 5-30 nm.

[0010] Preferably, the quantum well structure layer includes 2-20 overlapping quantum well units.

[0011] Preferably, the materials of the first multi-quantum well layer, the second multi-quantum well layer, the third multi-quantum well layer and the fourth multi-quantum well layer are all AlGaN and / or InGaN.

[0012] The application of the technical solution of the present invention has the following beneficial effects:

[0013] The composite multi - spectral light - emitting diode structure of the present invention includes a substrate material layer, a buffer layer, a first conductive layer, a quantum well structure layer, a second conductive layer, and a transparent contact layer arranged in sequence. Along the direction from the substrate material layer to the transparent contact layer, the quantum well structure layer includes quantum well units, and each quantum well unit includes a first multi - quantum well layer, a second multi - quantum well layer, a third multi - quantum well layer, and a fourth multi - quantum well layer arranged in sequence. The band - gap widths of the first multi - quantum well layer, the second multi - quantum well layer, the third multi - quantum well layer, and the fourth multi - quantum well layer are Eg1, Eg2, Eg3, and Eg4, respectively, and Eg2 < Eg1 < Eg3 < Eg4. Through the unique design of the quantum well, a composite multi - wavelength light output composed of controllable electroluminescence and photoluminescence spectra can be realized, and the spectral continuity is good, solving the problem that the industry's LED chips can only emit a single wavelength. The detailed mechanism is as follows: (1) The core of the design of the present invention is that Eg1, Eg2, Eg3, and Eg4 can independently achieve electroluminescence, and at the same time, through photoluminescence (that is, Eg3 and / or Eg4 can achieve photoluminescence of Eg2, with electroluminescence being the main one); (2) The growth of the multi - quantum well layers of the present invention is continuous, and the rule must be Eg2 < Eg1 < Eg3 < Eg4. The main connotation of its design is to change the distribution of electrons and holes in different quantum wells, thereby realizing different emission wavelengths at different band - gap widths; (3) Different from other photoluminescence in the prior art: the present invention does not use the wavelength of one LED chip to excite another layer of material to emit light (i.e., the quantum wells are not continuous) or to excite another LED chip to emit light. Instead, after the continuous growth of the quantum wells is completed, the internal band - gap width of the quantum wells is used to achieve the excitation of the low - energy band by the high - energy band inside the quantum wells, which is an interaction inside the quantum wells. In this process, electroluminescence plays a major role. In addition, there is no other epitaxial structure layer (such as a p - type doped GaN layer, etc.) between the quantum wells of the present invention. Combining with the band - gap widths of the multi - quantum well layers satisfying Eg2 < Eg1 < Eg3 < Eg4, each band - gap width can independently achieve electroluminescence.

[0014] The present invention also discloses a preparation method of the composite multi - spectral light - emitting diode structure as described above, including the following steps:

[0015] Step 1: Grow a buffer layer and a first conductive layer on the substrate material layer in sequence;

[0016] Step 2: Grow a quantum well structure layer on the first conductive layer, specifically including:

[0017] First, grow a first multi - quantum well layer on the first conductive layer. The corresponding emission wavelength of the band - gap width Eg1 of the first multi - quantum well layer is 440 - 470 nm;

[0018] A second multi-quantum well layer is grown on the first multi-quantum well layer, wherein the emission wavelength corresponding to the bandgap width Eg2 of the second multi-quantum well layer is 500-550 nm or 470-500 nm;

[0019] A third multi-quantum well layer is grown on the second multi-quantum well layer, and the emission wavelength corresponding to the bandgap width Eg3 of the third multi-quantum well layer is 255-440nm;

[0020] A fourth multi-quantum well layer is grown on the third multi-quantum well layer, and the bandgap width Eg4 of the fourth multi-quantum well layer corresponds to an emission wavelength of 250-435 nm;

[0021] Step 3: growing a second conductive layer on the fourth multi-quantum well layer;

[0022] Step 4: growing a transparent contact layer on the second conductive layer.

[0023] Preferably, the method further includes preparing the P electrode, the N electrode and the transparent insulating layer through a chip process.

[0024] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 It is a structural schematic diagram of the composite multi-spectrum light emitting diode structure in the preferred embodiment 1 of the present invention;

[0027] FIG. 2 is a light spectrum diagram of the LED composite light emitting diode in the preferred embodiment 1 of the present invention, wherein: FIG. 2 (a) shows the test result at 60 mA, and FIG. 2 (b) shows the test result at 150 mA;

[0028] FIG3 is a light spectrum diagram of the LED composite light emitting diode in the preferred embodiment 2 of the present invention, wherein: FIG3 (a) represents the test result at 10 mA, FIG3 (b) represents the test result at 40 mA; FIG3 (c) represents the test result at 60 mA, and FIG3 (d) represents the test result at 150 mA;

[0029] FIG4 is a light emission spectrum diagram of the LED composite light emitting diode in comparative example 1, wherein: FIG4 (a) represents the test result at 60 mA, and FIG4 (b) represents the test result at 150 mA;

[0030] FIG5 is a graph showing the luminous spectrum of the LED composite light-emitting diode in Comparative Example 2, wherein: FIG5(a) shows the test result at 10 mA, FIG5(b) shows the test result at 40 mA; FIG5(c) shows the test result at 60 mA, and FIG5(d) shows the test result at 150 mA;

[0031] Among them, 1. substrate material layer, 2. buffer layer, 3. first conductive layer, 4. quantum well structure layer, 4.1. first multi-quantum well layer, 4.2. second multi-quantum well layer, 4.3. third multi-quantum well layer, 4.4. fourth multi-quantum well layer, 5. second conductive layer, 6. transparent contact layer. DETAILED DESCRIPTION

[0032] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims. Embodiment 1:

[0033] See also Figure 1 , a composite multi-spectrum light emitting diode structure, comprising a substrate material layer 1;

[0034] A buffer layer 2 is provided on the substrate material layer 1; the substrate material is a sapphire substrate, a silicon substrate, a silicon carbide substrate, or other substrate material that can be used to grow a gallium nitride buffer layer material. In this embodiment, a sapphire substrate is preferred.

[0035] A first conductive layer 3 is provided on the buffer layer 2;

[0036] A quantum well structure layer 4 is provided on the first conductive layer 3;

[0037] A second conductive layer 5 is provided on the quantum well structure layer 4;

[0038] A transparent contact layer 6 is provided on the second conductive layer 5;

[0039] Along the direction from the substrate material layer 1 to the transparent contact layer 6, the quantum well structure layer 4 includes quantum well units ( Figure 1 A quantum well unit is schematically shown in the figure), the quantum well unit includes a first multi-quantum well layer 4.1, a second multi-quantum well layer 4.2, a third multi-quantum well layer 4.3 and a fourth multi-quantum well layer 4.4 arranged in sequence, the band gap width of the first multi-quantum well layer 4.1 is Eg1, the band gap width of the second multi-quantum well layer 4.2 is Eg2, the band gap width of the third multi-quantum well layer 4.3 is Eg3, the band gap width of the fourth multi-quantum well layer 4.4 is Eg4, and Eg2<Eg1<Eg3<Eg4, Eg1 itself can realize electroluminescence under the action of electric current, and Eg3 and / or Eg4 can realize photoluminescence of Eg2.

[0040] In this embodiment, the emission wavelength of the emission light of Eg2 is greater than or equal to 400 nm. In this embodiment, the wavelength corresponding to the second multi-quantum well layer is preferably 465 nm, and the material used is InGaN.

[0041] In this embodiment, the emission wavelength of the emission light of Eg1 is preferably 440-470 nm. In this embodiment, the emission wavelength corresponding to the bandgap width Eg1 is preferably 452.5 nm, and the material used is InGaN.

[0042] In this embodiment, the wavelength of the emitted light of Eg3 and Eg4 is 250-440nm, and the wavelength difference between Eg4 and Eg3 is between 5-30nm. In this embodiment, the wavelength corresponding to the third multi-quantum well layer is 440nm, and the material used is InGaN; the wavelength corresponding to the fourth multi-quantum well layer is 435nm, and the material used is InGaN.

[0043] In this embodiment, wavelength=1240 / bandgap width value.

[0044] In addition, the quantum well structure layer 4 may also include 2-20 overlapping quantum well units.

[0045] In this embodiment, the materials of the first multi-quantum well layer 4.1, the second multi-quantum well layer 4.2, the third multi-quantum well layer 4.3 and the fourth multi-quantum well layer 4.4 are all AlGaN and / or InGaN, but are not limited to AlGaN, InGaN and other materials that can be used for quantum well production.

[0046] The method for preparing the composite multi-spectrum light emitting diode structure in this embodiment comprises the following steps:

[0047] Step 1: sequentially growing a buffer layer 2 and a first conductive layer 3 on the substrate material layer 1;

[0048] Step 2: growing a quantum well structure layer 4 on the first conductive layer 3, specifically comprising:

[0049] First, a first multi-quantum well layer 4.1 is grown on the first conductive layer 3;

[0050] Growing a second multi-quantum well layer 4.2 on the first multi-quantum well layer 4.1;

[0051] Growing a third multi-quantum well layer 4.3 on the second multi-quantum well layer 4.2;

[0052] Growing a fourth multi-quantum well layer 4.4 on the third multi-quantum well layer 4.3;

[0053] Step 3: growing a second conductive layer 5 on the fourth multi-quantum well layer 4.4;

[0054] Step 4: growing a transparent contact layer 6 on the second conductive layer 5;

[0055] Step 5: Complete the preparation of the P electrode, N electrode and transparent insulating layer through chip processing.

[0056] After the finished LED chip is prepared, the final preparation of the chip is completed through processes such as grinding, cutting, testing, and sorting to form an independent LED composite light-emitting diode.

[0057] In this embodiment, the spectrum is a spectrum jointly determined by photoluminescence and electroluminescence. It can be a single-peak spectrum, a double-peak spectrum, or a multi-peak spectrum. The emitted light can be one or more spectra of ultraviolet light, purple light, blue light, green light, etc. The spectrum can change with the change of current. The color of the spectrum changes with the change of current, and the spectrum can change without changing the color.

[0058] The luminescence spectrum after the test is shown in Figure 2 (the spectral morphology is not limited to the test results; Figure 2 (a) shows the test results at 60mA, and Figure 2 (b) shows the test results at 150mA). Under different currents, the spectrum can change with the input of current. This change is due to the difference caused by the change in the ratio of electroluminescence to photoluminescence.

[0059] Compared with the existing LED manufacturing technology, the present invention has the following advantages:

[0060] (1) It is possible to convert different colors of light on a single LED chip, or to controllably adjust the spectrum of the same color of light.

[0061] (2) The present invention can achieve multi-peak or multi-color light output, solving the long-standing problem that gallium nitride LEDs can only emit single-peak wavelength or single-color light. It also solves the problem that single-peak waves have high energy but poor comfort.

[0062] (3) The present invention can control electroluminescence and photoluminescence by current, thereby achieving stable light emission of the spectrum and controllable spectral wavelength.

[0063] (4) The present invention provides a structural design that can be mass-produced. The structure achieves product spectrum stability through composite luminescence through the design of composite quantum wells, and can be mass-produced. The product is easy to mass-produce and has stable product performance. Embodiment 2:

[0064] A method for preparing a composite multi-spectrum light emitting diode structure comprises the following steps:

[0065] Step 1: growing a buffer layer and a first conductive layer in sequence on a substrate material, wherein the substrate material is a sapphire substrate.

[0066] Step 2: growing a first multi-quantum well layer on the first conductive layer, wherein the emission wavelength corresponding to the bandgap width Eg1 of the first multi-quantum well layer is 460 nm, and the material used is InGaN;

[0067] Step 3: grow a second multi-quantum well layer on the first multi-quantum well layer. The quantum well has a bandgap width of Eg2. The wavelength corresponding to the second multi-quantum well layer is 535 nm, and the material used is InGaN.

[0068] Step 4: growing a third multi-quantum well layer on the second multi-quantum well layer. The bandgap width of the third multi-quantum well layer is Eg3, the wavelength corresponding to the third multi-quantum well layer is 440 nm, and the material used is InGaN.

[0069] Step 5: grow a fourth multi-quantum well layer on the third multi-quantum well layer. The bandgap width of the fourth multi-quantum well layer is Eg4. The wavelength corresponding to the fourth multi-quantum well layer is 435 nm. The material used is InGaN.

[0070] Step six: sequentially grow a second conductive layer on top of the fourth quantum well layer.

[0071] Step 7: Complete the preparation of the transparent contact layer, P electrode, N electrode and transparent insulating layer through chip process to prepare a completed LED chip.

[0072] Through processes such as grinding, cutting, testing, and sorting, the final preparation of the chip is completed to form an independent LED composite light-emitting diode.

[0073] The luminescence spectrum after the test is shown in Figure 3 (the spectral morphology is not limited to the test results; Figure 3 (a) shows the test results at 10mA, Figure 3 (b) shows the test results at 40mA, Figure 3 (c) shows the test results at 60mA, and Figure 3 (d) shows the test results at 150mA). Under different currents, the spectrum can change with the input of current. This change is due to the difference caused by the change in the ratio of electroluminescence to photoluminescence.

[0074] Comparative Example 1:

[0075] Implementing a traditional blue-ray chip manufacturing method: The substrate material of the present invention can be a sapphire substrate material or other substrate material that can be used to grow an epitaxial layer.

[0076] The substrate material is a sapphire substrate. A buffer layer and a first conductive layer are sequentially grown on the substrate material.

[0077] A second multi-quantum well layer is grown on the first conductive layer, and the quantum well has a bandgap width Eg2. The wavelength corresponding to the second multi-quantum well layer is 470nm. The material used is InGaN.

[0078] A second conductive layer is sequentially grown on the second multi-quantum well.

[0079] The transparent contact layer, P electrode, N electrode and transparent insulating layer are prepared through chip process to prepare a completed LED chip.

[0080] Through processes such as grinding, cutting, testing, and sorting, the final preparation of the chip is completed to form an independent LED composite light-emitting diode.

[0081] The luminous spectrum after the test is shown in Figure 4 (Figure 4 (a) shows the test result at 60mA, and Figure 4 (b) shows the test result at 150mA). The spectral morphology does not change with the current because traditional LEDs use electroluminescence.

[0082] Comparative Example 2:

[0083] Traditional green LED growth method:

[0084] The substrate material is a sapphire substrate. A buffer layer and a first conductive layer are sequentially grown on the substrate material.

[0085] A second multi-quantum well layer is grown on the first conductive layer, the bandgap width of the second multi-quantum well layer is Eg2, the wavelength corresponding to the second multi-quantum well layer is 535 nm, and the material used is InGaN.

[0086] A second conductive layer is sequentially grown on the second multi-quantum well layer.

[0087] The transparent contact layer, P electrode, N electrode and transparent insulating layer are prepared through chip process to prepare a completed LED chip.

[0088] Through processes such as grinding, cutting, testing, and sorting, the final preparation of the chip is completed to form an independent LED composite light-emitting diode.

[0089] The luminous spectrum after the test is shown in Figure 5 (Figure 5 (a) shows the test results at 10mA, Figure 5 (b) shows the test results at 40mA, Figure 5 (c) shows the test results at 60mA, and Figure 5 (d) shows the test results at 150mA). The spectral morphology does not change with the current because traditional LEDs use electroluminescence.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A composite multi-spectrum light emitting diode structure, characterized in that: It comprises a substrate material layer (1); A buffer layer (2) is provided on the substrate material layer (1); A first conductive layer (3) is provided on the buffer layer (2); A quantum well structure layer (4) is provided on the first conductive layer (3); A second conductive layer (5) is provided on the quantum well structure layer (4); A transparent contact layer (6) is provided on the second conductive layer (5); Along the direction from the substrate material layer (1) to the transparent contact layer (6), the quantum well structure layer (4) comprises a quantum well unit, the quantum well unit comprises a first multi-quantum well layer (4.1), a second multi-quantum well layer (4.2), a third multi-quantum well layer (4.3) and a fourth multi-quantum well layer (4.4) arranged in sequence, the first multi-quantum well layer (4.1) has a bandgap width of Eg1, the second multi-quantum well layer (4.2) has a bandgap width of Eg2, the third multi-quantum well layer (4.3) has a bandgap width of Eg3, the fourth multi-quantum well layer (4.4) has a bandgap width of Eg4, and Eg2 <Eg1<Eg3<Eg4; The output light corresponding to Eg2 is 500-550nm green light or 470-500nm blue light; The emission wavelength of the emission light of Eg1 is 440-470nm; The emission wavelength of the emission light of Eg3 is 255-440nm, the emission wavelength of the emission light of Eg4 is 250-435nm, and the wavelength difference between Eg4 and Eg3 is between 5-30nm; While Eg1, Eg2, Eg3 and Eg4 can independently realize electroluminescence, Eg3 and / or Eg4 can realize photoluminescence of Eg2.

2. The composite multi-spectrum light emitting diode structure according to claim 1, characterized in that: The quantum well structure layer (4) comprises 2 to 20 quantum well units which are overlapped.

3. The composite multi-spectrum light emitting diode structure according to claim 2, characterized in that: The materials of the first multi-quantum well layer (4.1), the second multi-quantum well layer (4.2), the third multi-quantum well layer (4.3) and the fourth multi-quantum well layer (4.4) are all AlGaN and / or InGaN.

4. A method for preparing a composite multi-spectrum light-emitting diode structure according to any one of claims 1 to 3, characterized in that: The steps include: Step 1: sequentially growing a buffer layer (2) and a first conductive layer (3) on the substrate material layer (1); Step 2: growing a quantum well structure layer (4) on the first conductive layer (3), specifically comprising: Firstly, a first multi-quantum well layer (4.1) is grown on the first conductive layer (3), wherein the emission wavelength corresponding to the forbidden band width Eg1 of the first multi-quantum well layer (4.1) is 440-470 nm; A second multi-quantum well layer (4.2) is grown on the first multi-quantum well layer (4.1), wherein the emission wavelength corresponding to the bandgap width Eg2 of the second multi-quantum well layer (4.2) is 500-550nm or 470-500nm; A third multi-quantum well layer (4.3) is grown on the second multi-quantum well layer (4.2), wherein the emission wavelength corresponding to the bandgap width Eg3 of the third multi-quantum well layer (4.3) is 255-440 nm; A fourth multi-quantum well layer (4.4) is grown on the third multi-quantum well layer (4.3), wherein the fourth multi-quantum well layer (4.4) has a bandgap width Eg4 corresponding to an emission wavelength of 250-435 nm; Step 3: growing a second conductive layer (5) on the fourth multi-quantum well layer (4.4); Step 4: growing a transparent contact layer (6) on the second conductive layer (5).

5. The preparation method according to claim 4, characterized in that: It also includes the preparation of P-electrode, N-electrode and transparent insulating layer through chip process.

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