A design method for a white light emitting diode with high light efficiency and low color drift

Abstract

The present invention provides a design method for a white light emitting diode with high light efficiency and low color drift, comprising: growing an epitaxial structure on a substrate using MOCVD epitaxial growth technology, wherein the epitaxial structure is an intrinsic GaN buffer layer, an n-type GaN layer, an active region, and a p-type GaN layer in order along the growth direction. The present invention epitaxially grows a semi-polar GaN-based light emitting diode to stabilize the light emission wavelength; two primary colors are mixed to change the growth thickness, doping element type, and doping concentration of the adjustable intermediate layer, thereby adjusting the light emission spectrum power ratio to achieve white light emission. A single-chip white light emitting diode can avoid the disadvantages brought by phosphors, and can achieve high light efficiency and excellent light visual efficiency. Not only is the structure simple, but it also has a higher degree of freedom and broad application prospects.

Description

Technical Field

[0001] The invention relates to the field of semiconductor lighting display, and in particular to a design method of a white light emitting diode with high light efficiency and low color drift. Background Art

[0002] Since the band gap of group III nitrides varies from 0.7eV to 6.2eV, and the wavelength covers a wide spectrum range from near infrared to ultraviolet, it can achieve multi-wavelength selection of light-emitting diodes, so it has become the preferred material for white light emission. At present, there are three methods for designing white light-emitting diodes: the first is a red, green and blue multi-chip combination structure, the control circuit is relatively complex and the cost is high; the second is a single-chip light-emitting diode plus phosphor to achieve white light emission, the phosphor will cause performance changes due to high temperature, resulting in a decrease in the efficiency of the light-emitting diode and a change in the spectrum; the third is to stack a multi-primary color quantum well structure to form a single-chip white light emission. This single-chip light-emitting diode can solve the above shortcomings, but it also has the following defects: unstable emission wavelength, low light efficiency, and complex structure. Summary of the invention

[0003] In view of the shortcomings in the prior art, the present invention provides a design method for a white light emitting diode with high light efficiency and low color drift, the luminous spectrum power ratio is adjustable, the luminous wavelength is stable, and the structure is simple.

[0004] The present invention achieves the above technical objectives through the following technical means.

[0005] A design method for a white light emitting diode with high light efficiency and low color drift comprises: growing an epitaxial structure on a substrate using MOCVD epitaxial growth technology, wherein the epitaxial structure is sequentially an intrinsic GaN buffer layer, an n-type GaN layer, an active region, and a p-type GaN layer along the growth direction.

[0006] Furthermore, the material of the substrate is (22-43) plane sapphire.

[0007] Furthermore, a semi-polar (20-21) intrinsic GaN buffer layer is grown on the substrate.

[0008] Furthermore, the active region is composed of a yellow light quantum well light-emitting layer, an adjustable intermediate layer and a blue light quantum well light-emitting layer in the order of growth.

[0009] Furthermore, the In component in the yellow light quantum well is 30%, and the emission wavelength is 572 nm.

[0010] Furthermore, the yellow light quantum well has two growth cycles.

[0011] Furthermore, the In component in the blue light quantum well is 17%, and the emission wavelength is 450nm.

[0012] Furthermore, the growth cycle of the blue light quantum well is one.

[0013] Furthermore, the adjustable intermediate layer can change the growth thickness, doping element type and doping concentration.

[0014] Beneficial effects of the present invention:

[0015] 1. The present invention achieves white light emission by epitaxially growing semi-polar GaN-based light-emitting diodes to stabilize the emission wavelength; two primary colors are mixed to change the growth thickness, doping element type and doping concentration of the adjustable intermediate layer, and then adjust the luminous spectrum power ratio to achieve white light emission. The single-chip white light-emitting diode can avoid the disadvantages of phosphors and achieve high light efficiency, with excellent light visual efficiency. Not only is the structure simple, but it also has a higher degree of freedom and broad application prospects.

[0016] 2. The present invention does not require a complex epitaxial structure, nor does it require the addition of additional insertion layers. It can flexibly adjust the luminescence spectrum power ratio by simply changing the adjustable intermediate parameters, thus having a higher degree of freedom. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure is a schematic diagram of the structure of a white light emitting diode with high light efficiency and low color drift according to an embodiment of the present invention.

[0018] Figure 2 The white light emitting diode of Example 1 of the present invention is at a current density of 20A / cm 2 The SiLENSe simulation band diagram below.

[0019] Figure 3 This is a SiLENSe simulated hole distribution diagram of the white light emitting diode according to the first embodiment of the present invention.

[0020] Figure 4 The white light emitting diode of Example 1 of the present invention is subjected to different current densities (5A / cm 2 , 10A / cm 2 , 20A / cm 2 、30A / cm 2 , 50A / cm 2 )Simulated current excitation spectrum of SiLENSe under injection. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific implementation disclosed below.

[0022] Embodiment 1:

[0023] According to an embodiment of the present invention, a design method for a white light emitting diode with high luminous efficiency and low color drift focuses on controlling the luminous spectrum power ratio through an adjustable intermediate layer to achieve white light emission with high luminous efficacy. Specifically, an epitaxial structure is grown on a substrate using MOCVD epitaxial growth technology, and the epitaxial structure is composed of an intrinsic GaN buffer layer, an n-type GaN layer, an active area, and a p-type GaN layer in the growth direction.

[0024] Furthermore, the substrate material is (22-43) plane sapphire, and a semi-polar (20-21) plane intrinsic GaN buffer layer is grown on the substrate. Compared with the traditional c-plane, the semi-polar (20-21) plane has a lower piezoelectric polarization intensity and a weak polarization electric field. When the current changes, the luminescence peak shift can be effectively reduced, making the luminescence wavelength stable.

[0025] Furthermore, according to the carrier transport theory, the structure of the active region was determined. The active region consists of a 9nm GaN quantum barrier layer, a 3nm In 0.3 Ga 0.7 N yellow light quantum well, 9nm GaN quantum barrier, 3nm In 0.3 Ga 0.7 N yellow light quantum well, 8.2nm adjustable middle layer, In doping is 5%, 3nm In 0.17 Ga 0.83 N blue light quantum well, 9nm GaN quantum barrier.

[0026] In this embodiment, the In component in the yellow light quantum well is 30%. The In component in the blue light quantum well is 17%. The wavelength is controlled by the In component in the quantum well. x Ga 1-x N)=x·Eg(InN)+(1-x)Eg(GaN)+C·x(1-x), Where Eg is the bandgap width, x is the In component, and C is the band bending coefficient. is the reduced Planck constant, c is the speed of light, and λ is the peak wavelength of luminescence.

[0027] The structural simulation was performed using SiLENSe software, where the parameters were set as follows: n-region doping concentration 5×10 18 cm -3 , p-region doping 5×10 17 cm -3 , the electron-hole mobility is 100 cm 2 / (V·s), 10cm 2 / (V·s), dislocation density is 2×10 8 cm -3 .

[0028] The adjustable intermediate layer changes the spectral power ratio of blue light and yellow light by adjusting the growth thickness, doping element type and doping concentration, so that the chromaticity coordinates are close to the extreme value of white light (1 / 3,1 / 3), presenting white light emission.

[0029] like Figure 2 The white light emitting diode is shown at a current density of 20A / cm 2 The SiLENSe simulated energy band diagram below compares the barrier heights of the yellow light well and the blue light well. It can be seen that the barrier height of the yellow light well is much higher than that of the blue light well. According to the carrier transport theory, the mobility of electrons is much greater than that of holes, and the effective mass is much lower than that of holes. Therefore, electrons can be evenly distributed between the well regions, while the migration of holes is much more dependent on the barrier height. Holes migrate from p-type GaN to n-type GaN. Growing the yellow light well with a high barrier first will cause most of the holes to be confined in the yellow light well and cannot be transmitted to the blue light well. The final result is monochromatic luminescence. Therefore, the growth order in the present invention is yellow light quantum well, adjustable intermediate layer, and blue light quantum well.

[0030] like Figure 3 The figure shows the simulated hole distribution of a white light emitting diode. The important factor affecting the quantum efficiency of a light emitting diode is the electron-hole recombination efficiency. 15 cm -3 If the hole concentration is too high, growing only one yellow light well will waste this part of holes and reduce the recombination efficiency. In the present invention, two yellow light wells are designed to make full use of the excess hole concentration and improve the internal quantum efficiency of the light emitting diode.

[0031] like Figure 4 The figure shows the white light emitting diode at different current densities (5A / cm 2 , 10A / cm 2 , 20A / cm 2 、30A / cm 2 , 50A / cm 2 ) injection, the peak wavelengths of yellow light and blue light are very stable, 572nm and 450nm respectively, showing the characteristics of stable luminescence.

[0032] As shown in the following table, the important design parameters and effects of the high-efficiency, low-color-drift white-light-emitting diode designed by the present invention are as follows: chromaticity coordinates (0.3328, 0.3337), color temperature 5477.3037K, and high luminous efficacy of 413.52 lm / w, showing the characteristics of high luminous efficiency.

[0033]

[0034] As shown in the table below, under simulated current injection, the current density ranges from 5 to 50 A / cm 2 The color temperature values ​​of the white light emitting diode grown on the semi-polar (20-21) surface adopted in the present invention and the white light emitting diode grown on the traditional c-surface were compared. The color drift was reduced by 240K, showing the characteristics of low color drift.

[0035] <![CDATA[Current density A / cm 2 > c Color temperature (K) (20-21) Face color temperature (K) 5 4479.5588 4501.9849 10 4895.3734 4756.7162 20 5509.7346 5477.3037 30 5933.436 5890.7511 50 6864.1471 6646.9926

[0036] Embodiment 2:

[0037] Compared with the first embodiment, only the growth thickness, doping element type and doping concentration of the adjustable intermediate layer are changed, and other design structures remain unchanged. Structure of the adjustable intermediate layer: 3.5 nm adjustable intermediate layer, Al doping is 1%.

[0038] As shown in the following table, the design parameters and effects of the second embodiment of the present invention are as follows: chromaticity coordinates (0.3275, 0.3273), color temperature 5736.1604K, and luminous efficacy as high as 406.1380lm / w.

[0039]

[0040] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A design method for a white light emitting diode with high light efficiency and low color drift, characterized in that: An epitaxial structure is grown on a substrate using MOCVD epitaxial growth technology, wherein the epitaxial structure is sequentially an intrinsic GaN buffer layer, an n-type GaN layer, an active region, and a p-type GaN layer along a growth direction; The material of the substrate is (22-43) plane sapphire, and a semi-polar (20-21) plane intrinsic GaN buffer layer is grown on the substrate. The active region is composed of a yellow light quantum well light-emitting layer, an adjustable intermediate layer and a blue light quantum well light-emitting layer in the order of growth. The adjustable intermediate layer changes the growth thickness, doping element type and doping concentration to adjust the luminescence spectrum power ratio.

2. The design method of a white light emitting diode with high light efficiency and low color drift according to claim 1, characterized in that: The In component in the yellow light quantum well is 30%, and the light emission wavelength is 572nm.

3. The design method of a white light emitting diode with high light efficiency and low color drift according to claim 1, characterized in that: The yellow light quantum well has two growth cycles.

4. The design method of a white light emitting diode with high light efficiency and low color drift according to claim 1, characterized in that: The In component in the blue light quantum well is 17%, and the emission wavelength is 450nm.

5. The design method of a white light emitting diode with high light efficiency and low color drift according to claim 1, characterized in that: The growth cycle of the blue light quantum well is one.

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