CN101226980A - A light-emitting diode device that uses photonic crystal structure to suppress side light emission - Google Patents

Abstract

The invention discloses a light-emitting diode device that uses a photonic crystal structure to suppress lateral light output, which includes a substrate and a semiconductor epitaxial layer stacked on the substrate, and the semiconductor epitaxial stack includes an N-type layer, a light-emitting layer and a P-type layer. layer, the P-type layer is provided with a P-type electrode, part of the semiconductor epitaxial stack is etched to the N-type layer, and the exposed part of the N-type layer is provided with an N-type electrode, wherein the edge of the light-emitting diode chip is provided with a penetrating A two-dimensional photonic crystal structure of semiconductor epitaxial stacks, the photonic crystal is composed of dielectric columns whose dielectric constants change periodically. The invention can suppress the light output from the side of the light emitting diode, and effectively improve the light output efficiency of the front side. In addition, the invention also provides a manufacturing method of a light-emitting diode device using a photonic crystal structure to suppress side light emission.

Description

A light-emitting diode device that uses photonic crystal structure to suppress side light emission

technical field

The invention relates to a semiconductor light-emitting device and a manufacturing method thereof, in particular to a light-emitting diode device that uses a photonic crystal structure to suppress side light emission and a manufacturing method thereof.

Background technique

III-V compound semiconductor materials are widely used in light-emitting diodes, semiconductor lasers, detectors, and electronic devices. The light-emitting diode chip is obtained by growing an N-type layer, a single quantum well/multi-quantum well light-emitting layer, and a P-type layer on an epitaxial wafer substrate. In addition, a buffer layer and a current spreading layer can also be selectively grown. The difference in dielectric constant between different layers and between the device and the external medium makes the light-emitting diode chip form a change in refractive index in a direction perpendicular to the layer structure. The light emitted from the light-emitting layer of the chip will undergo a change in the refractive index between the layer structures during the process of exiting the device, and a part of the light will be reflected back, especially when entering the optically thinner medium from the optically denser medium. The light with an angle greater than the critical angle will be totally reflected at the interface, and as a result, a part of the light will be reflected back and go out from the side after multiple reflections, which reduces the light output from the front of the chip. In order to collect the light coming out from the side, methods such as reflective cups and bowls and highly reflective layers evaporated on the cups and bowls are used in the design of the chip packaging structure. Cause uneven light color, appear yellow circle phenomenon.

In order to improve the efficiency of front light output, materials with similar dielectric constants are used to reduce the refractive index difference between layers, the surface of the light output surface is roughened or a two-dimensional photonic crystal structure is made to destroy the total reflection interface, and the size of the chip is increased to increase the light from the surface. Opportunities to go out frontally and other means. Although the above method can improve the front light emission to a certain extent, according to the light emitting mechanism of the light emitting diode, it is spontaneous emission, and the light emitted by the light emitting layer is isotropic, and the side light emission is inevitable under normal circumstances.

Photonic crystal is a structure whose dielectric constant changes periodically. Its main feature is that it has a complete photonic band gap. When the photon energy is within the complete photonic band gap, photons will be reflected. Therefore, using the photonic crystal structure, it is possible to make The interface with very good reflectivity, even a fully reflective interface with all angles. At present, the two-dimensional photonic crystals used in light-emitting diodes are mainly made of periodic air columns or dielectric columns on the light-emitting surface to improve the light-emitting efficiency of the surface. However, the photonic bandgap of this photonic crystal structure only has an effect on the photons emitted from the side, and has no direct effect on the photons emitted from the surface. In fact, it is equivalent to a regular surface roughening effect. How to directly use the bandgap effect of two-dimensional photonic crystals in light-emitting diode devices without increasing the complexity of the process is an important issue to improve the light-emitting efficiency of light-emitting diodes.

Contents of the invention

The invention proposes a light-emitting diode device that uses a two-dimensional photonic crystal structure to suppress side light output, and the structure can effectively improve front light output efficiency. In addition, the invention also provides a method for manufacturing a light emitting diode device that uses a photonic crystal structure to suppress side light emission.

In order to achieve the above object, the present invention adopts the following technical solutions:

A light-emitting diode device that uses a photonic crystal structure to suppress lateral light emission, which includes a substrate and a semiconductor epitaxial layer stacked on the substrate. The semiconductor epitaxial stack includes an N-type layer, a light-emitting layer, and a P-type layer. The P-type A P-type electrode is set on the layer, and part of the semiconductor epitaxial stack is etched to the N-type layer, and an N-type electrode is set on the exposed part of the N-type layer. The two-dimensional photonic crystal structure, the photonic crystal is composed of dielectric pillars whose dielectric constant changes periodically.

Wherein, the medium filled in the above-mentioned dielectric column may be a dielectric material or air having a refractive index different from that of the semiconductor epitaxial stack material.

The size of the dielectric pillars and the period of the lattice formed by them are in the same order of magnitude as the wavelength of light radiated by the light-emitting layer, specifically 50nm to 900nm; the radiation frequency of the photonic crystal formed by the dielectric pillars relative to the light-emitting layer is a two-dimensional photonic bandgap ; The lattice of the photonic crystal formed by the dielectric pillar is a rectangular lattice, a triangular lattice, a hexagonal lattice or a superlattice structure.

The dielectric pillars also penetrate part or all of the substrate.

The light-emitting area of the light-emitting diode chip has a circular or square structure, the N-type electrode has a ring-shaped or fan-shaped structure, and the P-type electrode has a circular or square structure.

The substrate is sapphire, silicon, zinc oxide, aluminum nitride or gallium nitride, and the semiconductor epitaxial stack is made of indium gallium aluminum nitrogen (In _x Ga _y Al _1-xy N, 0<=x<=1, 0<= y<=1) Material composition.

The substrate is gallium arsenide or gallium phosphide material, and the semiconductor epitaxial stack is made of indium gallium aluminum phosphide (In _x Ga _y A _1-xy P, 0<=x<=1, 0<=y<=1) or aluminum Made of gallium arsenide (Al _x Ga _1-x As, 0<=x<=1) material.

A buffer layer is also arranged between the semiconductor epitaxy stack and the substrate, and a transparent electrode is also arranged between the P-type layer and the P-type electrode.

In addition, the present invention also provides a method for manufacturing a light-emitting diode device that uses a photonic crystal structure to suppress side light emission, the steps of which include:

a. Depositing a semiconductor epitaxial stack on the substrate, the semiconductor epitaxial stack includes an N-type layer, a light-emitting layer and a P-type layer from bottom to top;

b. Etching part of the semiconductor epitaxial stack to the N-type layer through a dry etching process;

c. Evaporating an N-type electrode on the exposed N-type layer, and evaporating a transparent electrode and a P-type electrode on the P-type layer;

d. By means of electron beam lithography and dry etching, a two-dimensional photonic crystal structure that runs through the semiconductor epitaxial stack is etched on the edge of the light-emitting diode chip. The photonic crystal is a medium whose dielectric constant changes periodically column composition.

In step d, a photonic crystal mask is made first, and then the pattern of the mask is transferred to the semiconductor epitaxial stack by photolithography and dry etching.

By means of electron beam lithography and dry etching, the edge of the light-emitting diode chip is etched to the inside of the substrate or to the bottom of the substrate to form a dielectric column penetrating part or all of the substrate.

The invention utilizes the photonic crystal structure to suppress the light-emitting diode device and the manufacturing method thereof, and makes a dielectric column whose dielectric constant changes periodically around the light-emitting area, forming a two-dimensional photonic crystal band gap, so that the side of the light-emitting layer The directional light is reflected back into the device, and after multiple reflections, absorption, and re-emission processes, the photons will finally be emitted from the front of the light-emitting device, thereby increasing the amount of light emitted from the surface and improving the light-emitting efficiency of the light-emitting device. The technology of the light emitting diode device is simple to manufacture, and the application of the white light diode packaged by the light emitting diode device can effectively reduce the phenomenon of uneven light color such as yellow circles.

The present invention can also be applied to light-emitting devices such as organic light-emitting diodes (OLEDs) and polymer light-emitting diodes (PLEDs).

Description of drawings:

1 is a schematic cross-sectional view of the structure center of a semiconductor light emitting device according to Embodiment 1 of the present invention;

2 is a schematic front view of the structure of the semiconductor light emitting device according to Embodiment 1 of the present invention;

3 is a schematic front view of the structure of a semiconductor light emitting device according to Embodiment 2 of the present invention;

4 is a schematic cross-sectional view of the structure center of the semiconductor light emitting device according to Embodiment 3 of the present invention.

Fig. 5 is a schematic cross-sectional view of the structure center of the semiconductor light emitting device according to Embodiment 4 of the present invention.

In the above figure, 1 is the substrate, 2 is the buffer layer, 3 is the N-type layer, 4 is the light-emitting layer, 5 is the P-type layer, 6 is the dielectric column, 7 is the light-emitting surface, 8 is the P-type electrode, and 9 is the N-type electrode. Type electrode, 10 is the lower electrode, 11 is the transparent electrode, 12 is the upper electrode

Detailed ways

Example 1

Referring to FIG. 1 and FIG. 2, a light-emitting diode device that utilizes a photonic crystal structure to suppress lateral light emission includes a substrate 1 and a semiconductor epitaxial layer stacked on the substrate 1, and the semiconductor epitaxial stack includes an N-type layer 3 , the light-emitting layer 4 and the P-type layer 5, the P-type layer 5 is provided with a P-type electrode 8, part of the semiconductor epitaxial stack is etched to the N-type layer 3, and the exposed part of the N-type layer 3 is provided with an N-type electrode 9 , wherein a two-dimensional photonic crystal structure penetrating through the semiconductor epitaxial stack is provided at the edge of the light emitting diode chip, and the photonic crystal is composed of dielectric pillars 6 whose dielectric constants vary periodically.

Wherein, the medium filled in the above-mentioned dielectric column 6 may be a dielectric material having a refractive index different from that of the semiconductor epitaxial stack material, and of course it may also be air. The number of rows of the dielectric columns 6 can be determined according to the process operation and the expected reflectivity, the more the rows, the better the reflection effect.

The size of the dielectric column 6 is in the same order of magnitude as the wavelength of light radiated by the light emitting layer 4 . Specifically, it is 50 nm to 900 nm. In order to make the material structure formed by the dielectric pillars have a good reflection effect, the frequency radiated by the crystal lattice formed by the dielectric pillars 6 relative to the light-emitting layer 4 needs to be a two-dimensional photonic band gap, so that the energy is within the two-dimensional photonic band gap Photons cannot be emitted from the side of the light-emitting layer 4, so that the light is emitted from the light-emitting surface 7 after being reflected from the side, which greatly improves the light-emitting rate of the light-emitting diode device. Therefore, the photonic crystal can be used to make an interface with very good reflection properties. Even an interface with total reflection at all angles.

The shape of the dielectric pillar 6 and the shape of the lattice formed therefrom can be selected as rectangular lattice, triangular lattice, hexagonal lattice or superlattice as required.

In order to solve the problem of cracks in the semiconductor epitaxial stack or lattice mismatch with the substrate 1, a buffer layer 2 is also provided between the semiconductor epitaxial stack and the substrate 1. At the same time, in order to solve the problem that the semiconductor current injection can be uniformly diffused to The P-type layer 5 is further provided with a transparent electrode 11 between the P-type layer 5 and the P-type electrode 8 .

The substrate 1 is made of Si, sapphire or GaN-based substrate material, and the semiconductor epitaxial stack is made of indium gallium aluminum nitride (In _x Ga _y Al _1-xy N, 0<=x<=1, 0<=y<=1 ) material formation. Of course, in addition to this, the substrate 1 can be formed of gallium arsenide or gallium phosphide (GaP)-based substrate materials, and the semiconductor epitaxial stack is made of indium gallium aluminum phosphide (In _x Ga _y Al _1-xy P, 0<=x<=1,0<=y<=1) or aluminum gallium arsenic (Al _x Ga _1-x As, 0<=x<=1) material. The transparent electrode can adopt nickel-gold alloy oxide (Oxidzed-Ni/Au), indium tin oxide (ITO), zinc aluminum oxide (AZO), zinc oxide, and their composition (such as Ni/AZO, NiO/AZO, Ni /ZnO, NiO/Zn0, etc.).

The light-emitting diode chip can also adopt a circular light-emitting region structure, and adopt a corresponding ring-shaped N-type electrode and a circular P-type electrode.

In addition, the present invention also provides a method for manufacturing a light-emitting diode device with total side reflection, which includes the following steps:

a. Clean the substrate 1 first, and deposit the buffer layer 2 and the semiconductor epitaxial stack structure sequentially on the substrate 1 by metal-organic chemical vapor deposition. The semiconductor epitaxial stack includes at least an N-type layer from bottom to top 3. Single quantum/multiple quantum well light-emitting layer 4 and P-type layer 5.

b. After the deposition of the semiconductor epitaxial stack is completed, the P-type layer 5 is partially etched on the semiconductor epitaxial stack through a dry etching process until the N-type layer 3 is exposed to form an N-type electrode region.

c. An N-type electrode 9 is formed by vapor deposition in the N-type electrode region, and a transparent electrode layer 11 and a P-type electrode 8 are formed on the P-type layer 5 .

d. According to the required crystal lattice and its size, use electron beam lithography and dry etching methods to make a two-dimensional photonic crystal structure that runs through the semiconductor epitaxial stack at the edge of the light-emitting diode chip. The photonic crystal is composed of It is composed of dielectric columns 6 whose dielectric constant changes periodically.

In the above step of making the dielectric pillar, the photonic crystal structure can also be made into a mask, and then the pattern of the mask can be transferred to the semiconductor epitaxial stack by photolithography and dry etching.

c, d two-step process can change the order according to the actual situation.

The dielectric pillar 6 is etched to a depth of several micrometers, such as 3-6 micrometers, vertically penetrating from the top of the semiconductor epitaxial stack to the upper surface of the substrate 1 .

Example 2

As shown in Figure 3, this embodiment is similar to Embodiment 1, the difference is that: in order to further improve the total reflection effect of the side and make it easier to make a closed periodic dielectric column, the light-emitting diode chip adopts a circular light-emitting area structure, and adopts Corresponding ring-shaped N-type electrodes and circular P-type electrodes.

Example 3

As shown in Figure 4, this embodiment is similar to Embodiment 1 and Embodiment 2, the difference is that in order to further improve the effect of total reflection on the side, the etching of the dielectric pillar 6 penetrates deeply from the P-type layer 5 to the inside of the substrate 1 , or throughout the entire substrate 1 .

This embodiment includes the structure of the light-emitting area of the light-emitting diode chip in embodiment 1 and embodiment 2 using square, circular and other arbitrary patterns.

Example 4

As shown in Figure 5, this embodiment is different from Embodiment 1 and Embodiment 2 in that the substrate 1 is a conductive substrate, such as Si, SiC, GaAs, GaP or metal, and the epitaxial stack material includes GaN base, GaAs base and other materials. The P and N electrodes of the light-emitting diode are made into an up-and-down structure, forming the upper electrode 12 and the lower electrode 10 respectively, and a two-dimensional photonic crystal structure penetrating through the semiconductor epitaxial stack is made on the edge of the light-emitting diode chip. This embodiment includes the light-emitting diode device structures with square, circular and other arbitrary shapes on the front side used in embodiment 1 and embodiment 2. It also includes the case that part of the dielectric column 6 constituting the photonic crystal structure goes deep into the substrate 1 , or runs through the entire substrate 1 .

Claims (10)

1. LED device of utilizing photon crystal structure to suppress the side direction bright dipping, it comprises substrate (1) and is laminated in semiconductor epitaxial layers on the substrate (1), this semiconductor epitaxial lamination comprises N type layer (3), luminescent layer (4) and P type layer (5), P type layer (5) is provided with P type electrode (8), the part semiconductor extension lamination is etched to N type layer (3), the part N type layer (3) that exposes is provided with N type electrode (9), it is characterized in that: be provided with through the two-dimensional photon crystal structure of semiconductor epitaxial lamination at the edge of light-emitting diode chip for backlight unit, this photonic crystal is to be periodically variable medium post (6) by electric medium constant to constitute.

2. LED device as claimed in claim 1 is characterized in that: the optical wavelength of the size of medium post (6) and the cycle of formed lattice thereof and luminescent layer (4) radiation is in the same order of magnitude, is 50nm～900nm; Radiation frequency by the relative luminescent layer of the formed photonic crystal of medium post (6) (4) is the two-dimensional photon band gap; Lattice by the formed photonic crystal of medium post (6) is rectangular lattice, triangular crystal lattice, hexagonal lattice or superlattice structure.

3. LED device as claimed in claim 1 is characterized in that: medium post (6) also runs through part or all of substrate (1).

4. LED device as claimed in claim 1 is characterized in that: the light-emitting zone of this light-emitting diode chip for backlight unit is circle or square structure, N type electrode (9) in the form of a ring or sector structure, the rounded or square structure of P type electrode (8).

5. as each described LED device of claim 1 to 4, it is characterized in that: substrate (1) is sapphire, silicon, zinc oxide, aluminium nitride or gallium nitride material, and the semiconductor epitaxial lamination is by indium-gallium-aluminum-nitrogen (In _xGa _yAl _1-x-yN, 0＜=x＜=1,0＜=y＜=1) the material formation.

6. as each described LED device of claim 1 to 4, it is characterized in that: substrate (1) is GaAs or gallium phosphide material, and the semiconductor epitaxial lamination is by indium gallium aluminium phosphorus (In _xGa _yAl _1-x-yP, 0＜=x＜=1,0＜=y＜=1) or gallium aluminium arsenic (Al _xGa _1-xAs, 0＜=x＜=1) the material formation.

7. as each described LED device of claim 1 to 4, it is characterized in that: also be provided with a resilient coating (2) between semiconductor epitaxial lamination and the substrate (1), also be provided with transparency electrode between P type layer (5) and the P type electrode (8).

8. manufacture method of utilizing photon crystal structure to suppress the LED device of side direction bright dipping, its step comprises:

A, go up the deposited semiconductor extension lamination at substrate (1), this semiconductor epitaxial lamination comprises N type layer (3), luminescent layer (4) and P type layer (5) from lower to upper;

B, by dry etch process, the part semiconductor extension lamination is etched into N type layer;

C, on the N type layer that exposes evaporation N type electrode (9), go up evaporation transparency electrode (7) and P type electrode (8) at P type layer (5);

D, by the method for electron beam lithography and dry etching, etch through the two-dimensional photon crystal structure of semiconductor epitaxial lamination at the edge of light-emitting diode chip for backlight unit, this photonic crystal is to be periodically variable medium post (6) by electric medium constant to constitute.

9. LED device as claimed in claim 8 is characterized in that: in steps d, make the photonic crystal mask plate earlier, by photoetching and dry etch process the mask plate decorative pattern is forwarded on the semiconductor epitaxial lamination.

10. LED device as claimed in claim 8 or 9, it is characterized in that: by the method for electron beam lithography and dry etching, the edge of light-emitting diode chip for backlight unit is continued to be etched to substrate interior or until the substrate bottom, forms the medium post (6) that runs through part or all of substrate (1).

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