A light emitting diode with a photonic crystal reflective layer structure

Abstract

The present invention discloses a light emitting diode with a photonic crystal reflective layer structure, comprising a photonic crystal reflective layer, a substrate, a nitride buffer layer, an n-type nitride layer, a multi-quantum well structure, an electron blocking layer, a p-type nitride layer, a transparent conductive layer, an n-type electrode arranged on the n-type nitride layer, and a p-type electrode arranged on the p-type nitride layer, which are arranged in sequence from bottom to top. The photonic crystal reflective layer is composed of two metal layers and two oxide layers inserted alternately. The present invention can modulate the photonic bandgap of the photonic crystal reflective layer by introducing a photonic crystal reflective layer structure formed by two metal layers and two oxide layers inserted alternately, and can flexibly and greatly change the reflectivity and applicable band of the photonic crystal reflective layer, so as to achieve high reflectivity for the emission light of a wider continuous band of the LED, thereby effectively improving the luminous efficiency of the LED.

Description

Technical Field

[0001] The present invention provides a light emitting diode with a photonic crystal reflective layer structure, belonging to the technical field of semiconductor optoelectronic materials and devices. Background Art

[0002] Light-Emitting Diode (LED) is a semiconductor electronic component that emits light. This electronic component appeared as early as 1962. Today, the light it can emit covers the visible light, infrared and ultraviolet bands, and the brightness has reached a very high level. LED has attracted much attention due to its advantages such as high efficiency, energy saving, small size and long life, and has begun to gradually replace traditional lighting methods such as fluorescent lamps and incandescent lamps. Although due to the introduction of epitaxial growth technologies such as MOCVD and multi-quantum well active regions, the internal quantum efficiency has reached a maximum of more than 80%, and there is limited room for improvement, but the light extraction efficiency of LED chips is still not high, which seriously affects the external quantum efficiency and the final luminous efficiency of LED devices. Therefore, it is very important to develop a reflective layer structure that helps to improve the light extraction efficiency to improve the performance of LED devices.

[0003] Photonic crystals, as an artificial optical material whose refractive index changes periodically in different dimensions, have a unique photonic bandgap structure. People can use the photonic bandgap effect to modulate the transmission characteristics of photons, which is of great significance in photonics. One-dimensional photonic crystals usually have a photonic bandgap only in one direction, while two-dimensional photonic crystals and three-dimensional photonic crystals can achieve more complex photonic bandgap structures and functions compared to one-dimensional photonic crystals. However, due to the rather complex structure of two-dimensional photonic crystals, especially three-dimensional photonic crystals, they are very difficult to design and manufacture. The structural design and preparation of one-dimensional photonic crystals are relatively simple, and they are expected to play an important role in replacing two-dimensional and three-dimensional photonic crystals in some photonic devices. Therefore, exploring the application of one-dimensional photonic crystals in the field of LED manufacturing is still of great value for improving the performance of LEDs. Summary of the invention

[0004] Purpose of the invention: By providing a one-dimensional photonic crystal reflective layer structure formed by alternating insertion of two metal layers and two oxide layers, the photonic bandgap of the photonic crystal reflective layer is modulated so as to flexibly and greatly change the reflectivity and applicable light band of the photonic crystal reflective layer, thereby achieving high reflectivity for LED emitted light in a wider continuous band and effectively improving the luminous efficiency of the LED.

[0005] Technical solution: To achieve the above purpose, the present invention adopts the following technical solution:

[0006] like Figure 1As shown, the present invention provides a light-emitting diode with a photonic crystal reflective layer structure, comprising a photonic crystal reflective layer, a substrate, a nitride buffer layer, an n-type nitride layer, a multi-quantum well structure, an electron blocking layer, a p-type nitride layer and a transparent conductive layer arranged in sequence from bottom to top; the light-emitting diode also includes an n-type electrode and a p-type electrode, the n-type electrode is arranged on the upper surface of the n-type nitride layer, and the p-type electrode is arranged on the upper surface of the transparent conductive layer.

[0007] The substrate can be made of polar, semi-polar or non-polar oriented sapphire, silicon carbide, silicon, zinc oxide, gallium nitride, aluminum nitride and other materials.

[0008] Furthermore, the photonic crystal reflective layer includes 3 to 5 periodic structural units stacked together, each periodic structural unit includes a TiO2 layer, an Ag layer, a SiO2 layer and a Pt layer sequentially arranged from top to bottom, and the thickness of the photonic crystal reflective layer is 450 to 750 nm.

[0009] The thickness of the TiO2 layer in the periodic structure unit is 25-35 nm, the thickness of the Ag layer is 60-75 nm, the thickness of the SiO2 layer is 30-40 nm, and the thickness of the Pt layer is 30-45 nm.

[0010] The thickness of the p-type nitride layer is 20 to 1000 nm; the p-type nitride layer can be a p-type binary nitride with uniform composition, a p-type ternary nitride with uniform composition, a p-type quaternary nitride with uniform composition, a p-type ternary nitride with gradient composition, or a p-type quaternary nitride with gradient composition; the p-type nitride layer is p-doped with Mg element, and the hole concentration formed by doping is 1x10 16 ~1x10 19 cm -3 ; The p-type binary nitride is InN, GaN or AlN; the p-type ternary nitride is AlGaN or InGaN; the p-type quaternary nitride is AlInGaN.

[0011] Furthermore, the electron blocking layer is AlN or BN nitride, and its thickness is 2 to 20 nm.

[0012] Furthermore, the potential wells and potential barriers of the multi-quantum well structure are periodically arranged with a period number of 3 to 15, and the length of each period is 4 to 15 nm. The potential wells and potential barriers are made of different materials. Both the potential wells and potential barriers can be made of binary nitrides with uniform composition, ternary nitrides with uniform composition, quaternary nitrides with uniform composition, ternary nitrides with gradient composition, or quaternary nitrides with gradient composition.

[0013] Furthermore, the thickness of the n-type nitride layer (102) is 0.5-5 μm; the n-type nitride layer may be made of n-type binary nitride, n-type ternary nitride or n-type quaternary nitride with uniform composition; the n-type nitride layer may also be made of n-type ternary nitride or n-type quaternary nitride with gradient composition;

[0014] Among them, the n-type binary nitride is InN, GaN or AlN; the n-type ternary nitride is AlGaN or InGaN; the n-type quaternary nitride is AlInGaN;

[0015] The n-type nitride layer is n-doped with Si element, and the electron concentration formed by doping is 1x10 17 ~1x10 21 cm -3 .

[0016] Furthermore, the nitride buffer layer uses binary or ternary nitrides with uniform composition; the nitride buffer layer may also use ternary nitrides with gradient composition; wherein the binary nitride is InN, GaN or AlN; and the ternary nitride is AlGaN or InGaN.

[0017] Beneficial effects: By adjusting the materials, thickness and structure of the one-dimensional photonic crystal, the photon bandgap can be modulated to achieve the purpose of obtaining high reflectivity in a longer continuous band. The present invention can greatly change the absorption and scattering characteristics of the one-dimensional photonic crystal by introducing a photonic crystal reflective layer structure formed by alternating insertion of two metal layers and two oxide layers in the one-dimensional photonic crystal, and can flexibly and significantly change the reflectivity and applicable band of the photonic crystal reflective layer, and can stably obtain high reflectivity in a continuous wide band ranging from ultraviolet light to visible light to near-infrared light, thereby effectively improving the luminous efficiency of LEDs. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the cross-sectional layer structure of an LED with a photonic crystal reflective layer structure provided by the present invention.

[0019] Figure 2 This is a schematic diagram of the cross-sectional layer structure of an LED prepared using prior art.

[0020] Figure 3 This is a detailed structural schematic diagram of the photonic crystal reflective layer provided by the present invention.

[0021] Figure 4 It is a reflectivity simulation curve diagram of the photonic crystal reflection layer of the present invention. DETAILED DESCRIPTION

[0022] Figure 1The LED with a photonic crystal reflective layer structure provided by the present invention is shown, and the LED includes, arranged from bottom to top, a photonic crystal reflective layer 101, an m-plane sapphire substrate 102, a nitride buffer layer 103, an n-type nitride layer 104, a multi-quantum well structure 105, an electron blocking layer 106, a p-type nitride layer 107 and a transparent conductive layer 108, wherein an n-type electrode 109 is further arranged on the upper surface of the n-type nitride layer 104, and a p-type electrode 110 is arranged on the upper surface of the transparent conductive layer 108. The nitride buffer layer 103 is made of GaN, the electron blocking layer 106 is made of AlN, and the transparent conductive layer 108 is made of ITO conductive film.

[0023] The photonic crystal reflective layer 101 includes a stacked periodic structural unit, each periodic structural unit includes a 30nm thick TiO2 layer 1011, a 60nm thick Ag layer 1012, a 30nm thick SiO2 layer 1013 and a 30nm thick Pt layer 1014 arranged in order from top to bottom, the period length is 150nm, the number of repeated periods is 5, and the total layer thickness of the photonic crystal reflective layer 101 is 750nm. The thickness of the GaN buffer layer 103 is 30nm. The thickness of the n-type GaN layer 104 is 3μm, and the layer is n-type doped with Si element, and the electron concentration obtained by doping is 1x10 18 cm -3 .

[0024] The multi-quantum well structure 105 adopts an AlGaN / AlN periodic structure, wherein the AlGaN well layer has an Al component of 40% and a thickness of 3 nm, the AlN barrier has a thickness of 5 nm, the number of periods is 10, and the length of each period is 8 nm.

[0025] The p-type nitride layer 107 is made of p-type GaN with a thickness of 200 nm. The layer is doped with Mg element, and the hole concentration obtained by doping is 1x10 18 cm -3 .

[0026] The n-type nitride layer 104 is made of n-type GaN, the n-type electrode 109 disposed thereon is a Ti metal layer, and the p-type electrode 110 disposed on the p-type GaN layer 107 is a Ni / Ag alloy layer.

[0027] like Figure 2 As shown, it is an LED prepared by the prior art, including a substrate 102, a nitride buffer layer 103, an n-type nitride layer 104, a multi-quantum well structure 105, an electron blocking layer 106, a p-type nitride layer 107 and a transparent conductive layer 108 arranged in sequence from bottom to top, an n-type electrode 109 is also arranged on the upper surface of the n-type nitride layer 104, and a p-type electrode 110 is arranged on the upper surface of the transparent conductive layer 108.

[0028] Compared with the LED prepared by the prior art, the photonic crystal reflective layer 101 in the LED with the photonic crystal reflective layer structure provided by the present invention is an asymmetric periodic structure formed by alternating insertion of two metal layers and two oxide layers. When the electromagnetic wave (light wave) propagates in the photonic crystal material, it is modulated due to the existence of Bragg scattering, and the electromagnetic wave energy is affected by the periodic structure to form an energy band structure. The band gap between energy bands is the photonic band gap. Electromagnetic waves (photons) with energy within the photonic band gap cannot enter the photonic crystal and propagate.

[0029] The photonic crystal reflective layer 101 provided by the present invention greatly changes the absorption and scattering characteristics of the LED structure by introducing a photonic crystal reflective layer structure formed by alternating insertion of two metal layers and two oxide layers. Figure 4 From the curve of reflectivity versus luminous wavelength calculated based on the theoretical simulation of photonic crystals, it can be seen that the photonic crystal reflective layer provided by the present invention can flexibly and greatly change the reflectivity and applicable band of the photonic crystal reflective layer, so that it can stably have a high reflectivity from the ultraviolet band of 300nm, to the entire visible light band, and up to the near-infrared band of 900nm, thereby significantly improving the luminous efficiency of the LED.

[0030] like Figure 4 The figure shows the reflectivity curve of the photonic crystal reflective layer of the present invention in various luminous wavebands, obtained by simulation calculation based on the photonic crystal theory. It can be seen from the figure that in the wide waveband range of 300-900nm, its reflectivity is greater than 90%.

[0031] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention.

Claims

1. A light emitting diode having a photonic crystal reflective layer structure, characterized in that: It comprises a photonic crystal reflection layer (101), a substrate (102), a nitride buffer layer (103), an n-type nitride layer (104), a multi-quantum well structure (105), an electron blocking layer (106), a p-type nitride layer (107) and a transparent conductive layer (108) which are arranged in sequence from bottom to top; The light-emitting diode further comprises an n-type electrode (109) and a p-type electrode (110), wherein the n-type electrode (109) is arranged on the surface of the n-type nitride layer (104), and the p-type electrode (110) is arranged on the upper surface of the transparent conductive layer (108); The thickness of the p-type nitride layer (107) is 20 to 1000 nm; The p-type nitride layer (107) may be a p-type binary nitride with uniform composition, a p-type ternary nitride with uniform composition, a p-type quaternary nitride with uniform composition, a p-type ternary nitride with gradient composition, or a p-type quaternary nitride with gradient composition; The p-type nitride layer (107) is p-doped with Mg element, and the hole concentration formed by doping is 1x10 16 ~1x10 19 cm -3 ; The p-type binary nitride is InN, GaN or AlN; the p-type ternary nitride is AlGaN or InGaN; the p-type quaternary nitride is AlInGaN; The thickness of the n-type nitride layer (102) is 0.5 to 5 μm; The n-type nitride layer (102) may be made of n-type binary nitride with uniform composition, n-type ternary nitride with uniform composition, n-type quaternary nitride with uniform composition, n-type ternary nitride with gradient composition, or n-type quaternary nitride with gradient composition; Among them, the n-type binary nitride is InN, GaN or AlN; the n-type ternary nitride is AlGaN or InGaN; the n-type quaternary nitride is AlInGaN; The n-type nitride layer (102) is n-doped with Si element, and the electron concentration formed by doping is 1x10 17 ~1x10 21 cm -3 .

2. The light emitting diode having a photonic crystal reflective layer structure according to claim 1, characterized in that: The photonic crystal reflection layer (101) comprises 3 to 5 periodic structural units arranged in a stacked manner, each periodic structural unit comprises a TiO2 layer (1011), an Ag layer (1012), a SiO2 layer (1013) and a Pt layer (1014) arranged in sequence from top to bottom, and the layer thickness of the photonic crystal reflection layer (101) is 450 to 750 nm.

3. The light emitting diode having a photonic crystal reflective layer structure according to claim 2, characterized in that: The thickness of the TiO2 layer (1011) in the periodic structural unit is 25 to 35 nm, the thickness of the Ag layer (1012) is 60 to 75 nm, the thickness of the SiO2 layer (1013) is 30 to 40 nm, and the thickness of the Pt layer (1014) is 30 to 45 nm.

4. The light emitting diode having a photonic crystal reflective layer structure according to claim 2, characterized in that: The electron blocking layer (106) is AlN or BN nitride, and its thickness is 2-20 nm.

5. The light emitting diode having a photonic crystal reflective layer structure according to claim 2, characterized in that: The potential wells and potential barriers of the multi-quantum well structure (105) are arranged periodically, the number of periods is 3 to 15, the length of each period is 4 to 15 nm, the potential wells and potential barriers are made of different materials, and both the potential wells and potential barriers can be made of binary nitrides with uniform composition, ternary nitrides with uniform composition, quaternary nitrides with uniform composition, ternary nitrides with gradually changing composition, or quaternary nitrides with gradually changing composition.

6. The light emitting diode having a photonic crystal reflective layer structure according to claim 2, characterized in that: The nitride buffer layer (103) is made of binary or ternary nitride with uniform composition; Alternatively, the nitride buffer layer (103) is made of a ternary nitride with a gradient composition; Among them, the binary nitride is InN, GaN or AlN; the ternary nitride is AlGaN or InGaN.

7. The light emitting diode having a photonic crystal reflective layer structure according to claim 2, characterized in that: The substrate (102) may be made of polar, semi-polar or non-polar oriented sapphire, silicon carbide, silicon, zinc oxide, gallium nitride or aluminum nitride.

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