TWI557945B - Light-emitting diode (led) chip with a bragg reflector - Google Patents

Description

LED chip with Bragg mirror

The present invention relates to a light-emitting diode wafer, and more particularly to a light-emitting diode wafer having a Bragg mirror.

A light-emitting diode (hereinafter referred to as LED) wafer is a core component (LED light) of a semiconductor light-emitting device LED, and the principle of LED light-emitting is mainly the P-N junction of the LED chip.

A gallium nitride-based LED chip that emits light of a blue or ultraviolet wavelength is mainly formed by forming a Bragg reflector on a bottom surface of a transparent substrate such as a sapphire substrate. The technique of DBR) is used for reflection. In addition to this, the Bragg mirror can also be used to reflect the green wavelength and the red wavelength.

However, referring to Figure 1, a Bragg mirror of a conventional LED wafer is shown as a function of wavelengths of visible light and reflectivity. Once the LED using the Bragg mirror, it will be in the blue wavelength range (for example, in the wavelength range of 400 nm (nm) to 500 nm), in the green wavelength range (for example, in the wavelength range of 500 nm to 600 nm), and in the red wavelength range. The reflectance of light emitted in a medium (for example, a wavelength range of 600 nm to 780 nm) is not the same or the same, and even when the reflectance is as high as 100%, the white light (ie, brightness) generated by the LED chip is high, but the blue light is The lower the wavelength, generally 450~455nm or 455~460nm, which belongs to the section with the strongest radiation damage, the light source emitted will be horrible, which is not conducive to long-term viewing of the human eye. In addition, when the LED chip generates the light source The longer the interval, the faster the fluorescent powder in the light source decays, and the light in the blue light band that is in contact with the human eye becomes more and more intense, thereby causing damage to the human eye.

Therefore, how to develop a light-emitting diode wafer having a Bragg mirror, which solves the above problem is the creative motive of the present invention.

It is an object of the present invention to provide a light-emitting diode wafer having a Bragg mirror which mainly causes the Bragg mirror to have a light reflectance for wavelengths in the blue wavelength range smaller than in the green wavelength range and the red wavelength range. The light reflectance of the wavelength to reduce the reflectivity of the blue light.

In order to achieve the foregoing objective, a light emitting diode chip having a Bragg mirror according to the present invention includes: a substrate having a first surface and a second surface opposite to the first surface; a light emitting unit disposed on the first surface of the substrate; a Bragg mirror disposed on the second surface of the substrate for reflecting light emitted by the light emitting unit; and a metal layer disposed on the Bragg mirror; In that: the Bragg mirror has a light reflectance for a wavelength in a blue wavelength range smaller than a wavelength in a green wavelength range and a red wavelength range, and the Bragg mirror has a wavelength in the blue wavelength range The light has a reflectance of no more than 96%.

Preferably, the Bragg mirror has a reflectivity of 95% for light of a wavelength in the blue wavelength range.

Preferably, the Bragg mirror has a reflectivity of 95% for light having a wavelength of 420 nm to 500 nm in the blue wavelength range.

Preferably, the Bragg mirror has a reflectivity of 95% for light having a wavelength of 460 ± 10 nm in the blue wavelength range.

Preferably, the Bragg mirror is 420 nm for the blue wavelength range In the wavelength of up to 500 nm, the light reflectance near the wavelength of 460 ± 10 nm is lower.

Preferably, the metal layer comprises aluminum or gold.

Preferably, the metal layer is further provided with a protective layer.

Preferably, the Bragg mirror is formed by alternately stacking a plurality of high refractive index layers and a plurality of low refractive index layers.

Preferably, the high refractive index layer of the Bragg mirror is titanium dioxide, and the low refractive index layer is cerium oxide.

Preferably, the Bragg mirror has a reflectance of 90% to 96% for light of a wavelength in the blue wavelength range.

The present invention has been described with reference to the preferred embodiments of the present invention in accordance with the accompanying drawings.

10‧‧‧Substrate

11‧‧‧ first surface

12‧‧‧ second surface

20‧‧‧Lighting unit

21‧‧‧First Conductive Semiconductor Layer

22‧‧‧Active layer

22‧‧‧Second conductive semiconductor layer

30‧‧‧Brazil mirror

31‧‧‧High refractive index layer

32‧‧‧Low refractive index layer

40‧‧‧metal layer

51‧‧‧Transparent shock layer

52‧‧‧p electrode pad

53‧‧‧n electrode pad

56‧‧‧Protective layer

Figure 1 is a graph of a Bragg mirror of a conventional light-emitting diode wafer as a function of wavelength and reflectance for each visible light.

Figure 2A is a schematic view of a first embodiment of the present invention.

2B is a partial enlarged view of FIG. 2A.

Figure 3 is a graph of the Bragg mirror of the first embodiment of the present invention as a function of wavelength and reflectance for each visible light.

Figure 4 is a graph of the Bragg mirror of the second embodiment of the present invention as a function of wavelength and reflectance for each visible light.

Referring to FIG. 2A, FIG. 2B and FIG. 3, a first embodiment of the present invention provides a light-emitting diode chip having a Bragg mirror, which is mainly composed of a substrate 10 and a light-emitting unit. 20. A Bragg mirror 30 and a metal layer 40, wherein:

The substrate 10 has a first surface 11 and a second surface 12 opposite to the first surface 11; in this embodiment, the substrate 10 is a transparent substrate, such as sapphire or tantalum carbide (SiC). ).

The light emitting unit 20 is disposed on the first surface 11 of the substrate 10; in the embodiment, the light emitting unit 20 includes a first conductive type semiconductor layer 21 disposed on the first surface 11 of the substrate 10, and a first conductive type disposed on the first conductive layer The active layer 22 of the semiconductor layer 21 and the second conductive semiconductor layer 23 disposed on the active layer 22 opposite to the first conductive semiconductor layer 21, and the second conductive semiconductor layer 23 A transparent electric shock layer 51 (indium tin oxide, ITO) is disposed thereon, and a p-electrode pad 52 is further disposed on the transparent electric shock layer 51, and an n-electrode pad 53 is disposed on the first conductive semiconductor layer 21.

The Bragg mirror 30 is disposed on the second surface 12 of the substrate 10 for reflecting the light emitted by the light emitting unit 20; in this embodiment, the Bragg mirror 30 is composed of a plurality of high refractive index layers 31 and a plurality of low refractive indices. interaction of push layer 32 are laminated, should the high refractive index layer 31 is titanium dioxide (TiO _2), the low refractive index layer 32 of silicon dioxide (SiO _2).

The metal layer 40 is disposed on the Bragg mirror 30. In this embodiment, the metal layer 40 comprises aluminum or gold, and a protective layer 56 is further disposed on the metal layer 40.

Since the substrate 10, the light-emitting unit 20, the Bragg mirror 30, the metal layer 40, and the protective layer 56 are all of the conventional structures, and the configuration and the operation manner thereof are the same as those of the prior art, and are not the focus of the present invention. Therefore, the detailed composition and operation of these structures will not be described in detail.

The present invention is characterized in that, based on the above-described configuration, the Bragg mirror 30 has a light reflectance for a wavelength in a blue light wavelength range smaller than a light reflectance at a wavelength in a green light wavelength range and a red light wavelength range. In the example, the Bragg mirror 30 is close to 100% for a wavelength range of green light (for example, a wavelength range of 500 nm to 600 nm) and a wavelength range of red light (for example, a wavelength range of 600 nm to 780 nm), and the Bragg mirror 30 for the blue wavelength range The light of the wavelength has a reflectance of not more than 96%, and in this embodiment, the Bragg mirror 30 has a reflectance of 90% to 96% for light of a wavelength in the blue wavelength range. Further, the Bragg mirror has a reflectance of 95% for light having a wavelength of 460 ± 10 nm in the blue wavelength range, and the Bragg mirror 30 is for a wavelength of 420 nm to 500 nm in the blue wavelength range In the rice wavelength, the closer to the wavelength of 460 ± 10 nm, the lower the light reflectance.

The above is the structure and configuration description of each main component of the first embodiment of the present invention. Thereby, the present invention at least achieves the following effects.

The light source emitted by the LED of the present invention can be softened and glare-free, which is advantageous for long-term viewing by the human eye, and at the same time, the longer the light source of the light-emitting diode wafer of the present invention generates light source, although the fluorescent powder in the light source is attenuated. The faster, but the present invention causes the Bragg mirror 30 to have a light reflectance for a wavelength in the blue wavelength range smaller than a wavelength in the green wavelength range and the red wavelength range, and the Bragg mirror 30 is The light of the wavelength in the blue wavelength range has a reflectance of 90% to 96%, thereby reducing the reflectance of the blue light, and also reducing the strong sense of illumination of the blue light band that is in contact with the human eye, thereby reducing damage to the human eye. .

Referring to FIG. 4, which is a graph of a Bragg mirror according to a second embodiment of the present invention as a function of visible light wavelength and reflectance, the second embodiment of the present invention differs from the first embodiment in that.

The Bragg mirror has a reflectance of 95% for light having a wavelength of 420 nm to 500 nm in the blue wavelength range.

In the above, the above embodiments and drawings are only the preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, that is, the equivalent changes and modifications made by the scope of the present invention are all It should be within the scope of the patent of the present invention.

Claims (9)

A light emitting diode chip having a Bragg mirror, comprising: a substrate having a first surface and a second surface opposite to the first surface; a light emitting unit disposed on the first surface of the substrate; a Bragg mirror disposed on the second surface of the substrate for reflecting light emitted by the light emitting unit; and a metal layer disposed on the Bragg mirror; wherein the Bragg mirror is in a blue wavelength range The light reflectance of the wavelength is smaller than the light reflectance of the wavelength in the green wavelength range and the red light wavelength range, and the Bragg mirror has a reflectance of no more than 96% for the light of the wavelength in the blue wavelength range, the Bragg The mirror has a lower light reflectance for a wavelength of 420 nm to 500 nm in the wavelength range of 420 nm to 500 nm in the blue wavelength range. A light-emitting diode wafer having a Bragg mirror as claimed in claim 1, wherein the Bragg mirror has a reflectance of 95% for light of a wavelength in the blue wavelength range. A light-emitting diode wafer having a Bragg mirror as claimed in claim 2, wherein the Bragg mirror has a reflectance of 95% for light having a wavelength of 420 nm to 500 nm in a blue wavelength range. A light-emitting diode wafer having a Bragg mirror as claimed in claim 2, wherein the Bragg mirror has a reflectance of 95% for light having a wavelength of 460 ± 10 nm in a blue wavelength range. A light-emitting diode wafer having a Bragg mirror as claimed in claim 1, wherein the metal layer comprises aluminum or gold. A light-emitting diode chip having a Bragg mirror according to claim 1, wherein the metal layer is further provided with a protective layer. A light-emitting diode wafer having a Bragg mirror as claimed in claim 1, wherein the Bragg inverse The mirror is formed by alternately stacking a plurality of high refractive index layers and a plurality of low refractive index layers. A light-emitting diode wafer having a Bragg mirror according to claim 7, wherein the high refractive index layer of the Bragg mirror is titanium dioxide and the low refractive index layer is germanium dioxide. A light-emitting diode wafer having a Bragg mirror as claimed in claim 1, wherein the Bragg mirror has a reflectance of 90% to 96% for light of a wavelength in a blue wavelength range.