TWI842560B - Light emitting element and display device - Google Patents

Abstract

A light-emitting element includes a buffer layer, microstructures, a first type semiconductor layer, an active layer, a second type semiconductor layer, a first electrode and a second electrode. The microstructures are disposed on the buffer layer. The first type semiconductor layer is disposed on the buffer layer. The active layer is disposed on the first type semiconductor layer. The second type semiconductor layer is disposed on the active layer. The first electrode is electrically connected to the first type semiconductor layer. The second electrode is electrically connected to the second type semiconductor layer. A material of the buffer layer is different from a material of the microstructures. In addition, a display device including the light-emitting element is also provided.

Description

Light emitting element and display device

The present invention relates to an optoelectronic element and an optoelectronic device, and in particular to a light-emitting element and a display device.

The LED display panel includes a driving backplane and LED elements transferred to the driving backplane. Inheriting the characteristics of LEDs, LED display panels have advantages such as power saving, high efficiency, high brightness and fast response time. In addition, compared with organic LED display panels, LED display panels also have advantages such as easy color adjustment, long luminous life and no image burn-in. Therefore, LED display panels are regarded as the next generation of display technology.

However, the top surface of the LED element is uneven, which causes the ambient light to pass through the circular polarizer and be reflected by the uneven top surface of the LED element. It cannot be completely blocked by the circular polarized light and transmitted to the outside world, causing depolarization. When the LED display panel is not enabled, the reflectivity is too high and it is bright. In addition, due to the uneven top surface of the LED element, the LED display panel will also have rainbow pattern problems under strong light, affecting the optical performance of the LED display panel.

The present invention provides a light-emitting element with good optical performance.

The present invention provides a display device with good optical performance.

The light-emitting element of the present invention includes a buffer layer, a plurality of microstructures, a first type semiconductor layer, an active layer, a second type semiconductor layer, a first electrode and a second electrode. The plurality of microstructures are arranged on the buffer layer. The first type semiconductor layer is arranged on the buffer layer. The active layer is arranged on the first type semiconductor layer. The second type semiconductor layer is arranged on the active layer. The first electrode is electrically connected to the first type semiconductor layer. The second electrode is electrically connected to the second type semiconductor layer. The material of the buffer layer is different from the material of the microstructure.

The display device of the present invention comprises the above-mentioned light-emitting element and a driving backplane, wherein the light-emitting element is electrically connected to the driving backplane, and the buffer layer of the light-emitting element has a light-emitting surface.

Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and description to represent the same or similar parts.

It should be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "connected to" another element, it may be directly on or connected to another element, or an intermediate element may also exist. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element, there are no intermediate elements. As used herein, "connected" may refer to physical and/or electrical connections. Furthermore, "electrically connected" or "coupled" may mean that there are other elements between two elements.

As used herein, "about," "approximately," or "substantially" includes the stated value and the average value within an acceptable deviation range of a particular value determined by a person of ordinary skill in the art, taking into account the measurement in question and the particular amount of error associated with the measurement (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations of the stated value, or within ±30%, ±20%, ±10%, ±5%. Furthermore, as used herein, "about," "approximately," or "substantially" can select a more acceptable deviation range or standard deviation depending on the optical property, etching property, or other property, and can apply to all properties without using a single standard deviation.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by ordinary technicians in the field to which the present invention belongs. It will be further understood that those terms as defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology and the present invention, and will not be interpreted as an idealized or overly formal meaning unless expressly defined as such in this document.

1A to 1F are cross-sectional schematic diagrams of a manufacturing process of a display device according to an embodiment of the present invention.

1A , first, a buffer layer 120 is formed on a growth substrate 110 . The growth substrate 110 is used to deposit the buffer layer 120 . The buffer layer 120 is used to be separated from the growth substrate 110 . In this embodiment, the buffer layer 120 is also used for growing an undoped epitaxial layer 140 (shown in FIG. 1C ). For example, in this embodiment, the material of the growth substrate 110 may include sapphire, and the material of the buffer layer 120 may include aluminum nitride (AlN), gallium nitride (GaN), zinc oxide (ZnO), indium gallium nitride (GaInN), indium nitride (InN) or aluminum gallium nitride (AlGaN), but the present invention is not limited thereto.

Referring to FIG. 1B , a plurality of microstructures 130 are then formed on the buffer layer 120. The plurality of microstructures 130 are disposed on the buffer layer 120. The material of the microstructures 130 is different from the material of the buffer layer 120. The microstructures 130 are used to reduce the defect density when the epitaxial layer 140 (shown in FIG. 1C ) is grown. In the present embodiment, the plurality of microstructures 130 are separated from each other, but the present invention is not limited thereto. For example, in the present embodiment, the material of the microstructures 130 may include aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), silicon nitride (SiN) or zinc oxide (ZnO), but the present invention is not limited thereto.

Referring to FIG. 1C , an epitaxial layer 140, a first type semiconductor layer 150, an active layer 160, and a second type semiconductor layer 170 are then formed on the buffer layer 120 and the plurality of microstructures 130. The first type semiconductor layer 150 is disposed on the buffer layer 120. The active layer 160 is disposed on the first type semiconductor layer 150. The second type semiconductor layer 170 is disposed on the active layer 160. In this embodiment, the epitaxial layer 140 may be disposed between the first type semiconductor layer 150 and the buffer layer 120. The epitaxial layer 140 has a surface 142 facing away from the active layer 160. The surface 142 has a plurality of micro-recesses 142a. The plurality of microstructures 130 are disposed in the plurality of micro recesses 142a of the epitaxial layer 140. In this embodiment, the material of the epitaxial layer 140 and the material of the microstructures 130 may be different.

For example, in this embodiment, the material of the epitaxial layer 140 may include undoped gallium nitride (GaN), the material of the first type semiconductor layer 150 may include n-type gallium nitride (GaN), the active layer 160 may be a multiple quantum well, the material of the multiple quantum well may include gallium nitride (GaN) and indium gallium nitride (InGaN), and the material of the second type semiconductor layer 170 may include p-type gallium nitride (GaN), but the present invention is not limited thereto.

1D , a first electrode 180 and a second electrode 190 are then formed, wherein the first electrode 180 is electrically connected to the first type semiconductor layer 150, and the second electrode 190 is electrically connected to the second type semiconductor layer 170. For example, in this embodiment, the first electrode 180 and the second electrode 190 can be selectively disposed on the same side of the active layer 160, but the present invention is not limited thereto.

1E , the growth substrate 110 is then removed from the buffer layer 120 to form a light-emitting element LED. In this embodiment, the light-emitting element LED includes a buffer layer 120, a plurality of microstructures 130, an epitaxial layer 140, a first type semiconductor layer 150, an active layer 160, a second type semiconductor layer 170, a first electrode 180, and a second electrode 190. For example, in this embodiment, a laser lift-off process may be used to separate the growth substrate 110 and the buffer layer 120, but the present invention is not limited thereto. In this embodiment, the wavelength of the laser L used in the laser stripping process may be between 100 nm and 600 nm, and the intensity of the laser L used in the laser stripping process may be between 0.1 J/cm ² and 1 J/cm ² , but the present invention is not limited thereto.

For example, in one embodiment, the material of the buffer layer 120 is gallium nitride (GaN), and the central wavelength of the laser L used in the laser stripping process may be 248nm; in another embodiment, the material of the buffer layer 120 is aluminum nitride (AlN), and the central wavelength of the laser L used in the laser stripping process may be 193nm; in another embodiment In an embodiment, the material of the buffer layer 120 is indium gallium nitride (GaInN), and the center wavelength of the laser L used in the laser stripping process can be 532nm; in another embodiment, the material of the buffer layer 120 is zinc oxide (ZnO), and the center wavelength of the laser L used in the laser stripping process can be 248nm; but the present invention is not limited thereto.

1F, the light-emitting element LED is then transferred to the driving backplane 200, and the light-emitting element LED is electrically connected to the driving backplane 200. For example, in this embodiment, the driving backplane 200 includes a pixel driving circuit (not shown) and a plurality of pads (not shown) electrically connected to the pixel driving circuit, and the first electrode 180 and the second electrode 190 of the light-emitting element LED can be electrically connected to the plurality of pads, respectively. In the present embodiment, the pixel driving circuit may include a data line (not shown), a scan line (not shown), a power line (not shown), a common line (not shown), a first transistor (not shown), a second transistor (not shown) and a capacitor (not shown), wherein a first end of the first transistor is electrically connected to the data line, a control end of the first transistor is electrically connected to the scan line, a second end of the first transistor is electrically connected to a control end of the second transistor, a first end of the second transistor is electrically connected to the power line, the capacitor is electrically connected to a second end of the first transistor and a first end of the second transistor, a second end of the second transistor is electrically connected to a pad, and the common line is electrically connected to another pad, but the present invention is not limited thereto.

Please refer to Figure 1F, then, a packaging layer 210 is formed on the light-emitting element LED. The packaging layer 210 is disposed on the light-emitting element LED. The dielectric layer 220 is disposed between the packaging layer 210 and the light-emitting element LED. At this point, the display device 10 of the present embodiment is completed. In one embodiment, the packaging layer 210 may include a light-transmitting substrate, a color filter layer, a circular polarizer or a combination thereof, but the present invention is not limited thereto. In one embodiment, the dielectric layer 220 may be an organic flat layer or air, but the present invention is not limited thereto. In this embodiment, the light-emitting element LED is, for example, a micro light-emitting diode (μLED), and the display device 10 is, for example, a micro light-emitting diode display panel, but the present invention is not limited thereto.

In this embodiment, the buffer layer 120 has a first surface 122 and a second surface 124. The first surface 122 of the buffer layer 120 contacts the plurality of microstructures 130. The second surface 124 of the buffer layer 120 is disposed opposite to the first surface 122 of the buffer layer 120, and the second surface 124 of the buffer layer 120 is substantially a plane. The second surface 124 of the buffer layer 120 is a light emitting surface of the light emitting element LED. In one embodiment, if the encapsulation layer 210 includes a circular polarizer, the outward surface of the light emitting element LED (i.e., the second surface 124 of the buffer layer 120) is a flat surface, which can improve the depolarization phenomenon caused by the uneven surface and the rainbow pattern phenomenon under strong light irradiation.

In this embodiment, the light emitting element LED is used to emit a light beam (not shown), the light beam has a central wavelength λ, and the buffer layer 120 has a thickness T and a refractive index n, and T=λ/4n. In this way, constructive interference can be formed to increase the light output of the light emitting element LED and reduce the reflection of ambient light. For example, in one embodiment, the central wavelength λ of the light beam emitted by the light emitting element LED is about 460nm, and the thickness T of the buffer layer 120 is about 60nm. At this time, the transmittance of the buffer layer 120 can be increased to 89.70%, and the reflectivity of the buffer layer 120 can be reduced to 10.3%, but the present invention is not limited thereto.

It should be noted that the following embodiments use the same component numbers and some contents of the previous embodiments, wherein the same number is used to represent the same or similar components, and the description of the same technical contents is omitted. The description of the omitted parts can be referred to the previous embodiments, and the following embodiments will not be repeated.

2A to 2F are cross-sectional schematic diagrams of a manufacturing process of a display device according to another embodiment of the present invention.

The display device 10A and its manufacturing process in FIG. 2F are similar to the display device 10 and its manufacturing process in FIG. 1F . The difference between the two is that the first electrode 180 and the second electrode 190 are formed at different times and positions.

2C , in detail, in this embodiment, a first type semiconductor layer 150, an active layer 160, and a second type semiconductor layer 170 may be sequentially formed on the buffer layer 120 and the plurality of microstructures 130. In this embodiment, the first type semiconductor layer 150 has a surface 152 facing away from the active layer 160, the surface 152 may have a plurality of micro-recesses 152a, and the plurality of microstructures 130 may be disposed in the plurality of micro-recesses 152a of the first type semiconductor layer 150.

Referring to FIG. 2D , a second electrode 190 is then formed on the second type semiconductor layer 170. Referring to FIG. 2E , the growth substrate 110 is then removed to expose the buffer layer 120. Referring to FIG. 2F , the buffer layer 120 is then etched to form an opening 126 of the buffer layer 120, wherein the opening 126 at least exposes a portion of the first type semiconductor layer 150. Referring to FIG. 2F , a first electrode 180 is then formed on the buffer layer 120, wherein the first electrode 180 is electrically connected to the first type semiconductor layer 150 through the opening 126 of the buffer layer 120.

In this embodiment, the light-emitting element LED-A includes a buffer layer 120, a plurality of microstructures 130, a first type semiconductor layer 150, an active layer 160, a second type semiconductor layer 170, a first electrode 180 and a second electrode 190, and the first electrode 180 and the second electrode 190 are respectively disposed on opposite sides of the active layer 160.

10, 10A: Display device 110: Growth substrate 120: Buffer layer 122: First surface 124: Second surface 126: Opening 130: Microstructure 140: Epitaxial layer 142, 152: Surface 142a, 152a: Micro-depression 150: First type semiconductor layer 160: Active layer 170: Second type semiconductor layer 180: First electrode 190: Second electrode 200: Driving backplane 210: Encapsulation layer 220: Dielectric layer L: Laser LED, LED-A: Light-emitting element T: Thickness

Figures 1A to 1F are schematic cross-sectional views of a manufacturing process of a display device according to one embodiment of the present invention. Figures 2A to 2F are schematic cross-sectional views of a manufacturing process of a display device according to another embodiment of the present invention.

10: Display device

120: Buffer layer

122: First surface

124: Second surface

130: Microstructure

140: Epitaxial layer

142: Surface

142a: Slightly concave

150: Type I semiconductor layer

160: Active layer

170: Type II semiconductor layer

180: First electrode

190: Second electrode

200: Drive backplane

210: Packaging layer

220: Dielectric layer

LED: light-emitting element

T:Thickness

Claims (11)

A light-emitting element includes: a buffer layer; a plurality of microstructures disposed on the buffer layer; a first type semiconductor layer disposed on the buffer layer; an active layer disposed on the first type semiconductor layer; a second type semiconductor layer disposed on the active layer; a first electrode electrically connected to the first type semiconductor layer; and a second electrode electrically connected to the second type semiconductor layer, wherein the material of the buffer layer is different from that of the microstructures, and the light-emitting element is used to emit a light beam having a central wavelength (λ), and the buffer layer has a thickness (T) and a refractive index (n), and T=λ/4n. The light-emitting element as described in claim 1 further comprises: an epitaxial layer disposed between the first type semiconductor layer and the buffer layer, wherein a surface of the epitaxial layer facing away from the active layer has a plurality of micro-recesses, and the microstructures are disposed in the micro-recesses of the epitaxial layer. A light-emitting element as described in claim 2, wherein the material of the epitaxial layer is different from the material of the microstructure. The light-emitting element as described in claim 1, wherein a surface of the first type semiconductor layer facing away from the active layer has a plurality of micro-recesses, and the microstructures are disposed in the micro-recesses of the first type semiconductor layer. The light-emitting element as described in claim 1, wherein the buffer layer has a first surface and a second surface, the first surface of the buffer layer contacts the microstructures, the second surface of the buffer layer is disposed opposite to the first surface of the buffer layer, and the second surface of the buffer layer is substantially a plane. A display device includes: at least one light-emitting element, wherein each light-emitting element includes: a buffer layer; a plurality of microstructures disposed on the buffer layer; a first type semiconductor layer disposed on the buffer layer; an active layer disposed on the first type semiconductor layer; a second type semiconductor layer disposed on the active layer; a first electrode electrically connected to the first type semiconductor layer; and a second electrode electrically connected to the second type semiconductor layer, wherein each of the light emitting elements is used to emit a light beam having a central wavelength (λ), the buffer layer having a thickness (T) and a refractive index (n), and T=λ/4n; and a driving backplane, wherein the at least one light emitting element is electrically connected to the driving backplane, and the buffer layer has a light emitting surface. A display device as described in claim 6, wherein the material of the buffer layer is different from the material of the microstructures. The display device as described in claim 6, wherein each of the light-emitting elements further comprises: An epitaxial layer disposed between the first type semiconductor layer and the buffer layer, wherein a surface of the epitaxial layer facing away from the active layer has a plurality of micro-recesses, and the microstructures are disposed in the micro-recesses of the epitaxial layer. A display device as described in claim 8, wherein the material of the epitaxial layer is different from the material of the microstructures. A display device as described in claim 6, wherein a surface of the first type semiconductor layer facing away from the active layer has a plurality of micro-recesses, and the microstructures are disposed in the micro-recesses of the first type semiconductor layer. A display device as described in claim 6, wherein the buffer layer has a first surface and a second surface, the first surface of the buffer layer contacts the microstructures, the second surface of the buffer layer is disposed opposite to the first surface of the buffer layer, and the second surface of the buffer layer is substantially a plane.

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