CN112289901A - Micro light emitting element and micro light emitting element display device - Google Patents
Micro light emitting element and micro light emitting element display device Download PDFInfo
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- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/20—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate
- H01L33/24—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate of the light emitting region, e.g. non-planar junction
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- H01L27/153—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission in a repetitive configuration, e.g. LED bars
- H01L27/156—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components having potential barriers, specially adapted for light emission in a repetitive configuration, e.g. LED bars two-dimensional arrays
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- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/14—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
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Abstract
The invention provides a micro light-emitting element and a micro light-emitting element display device. The micro light-emitting device includes an epitaxial structure, a first electrode and a second electrode. The epitaxial structure includes a first type semiconductor layer, a light emitting layer and a second type semiconductor layer. The light emitting layer is located between the first type semiconductor layer and the second type semiconductor layer. The first-type semiconductor layer includes a first portion and a second portion connected to each other. The edge of the first portion is spaced from the edge of the second portion. The bottom area of the first portion is smaller than the top area of the second portion. The first electrode is configured on the epitaxial structure and is positioned on the first part of the first type semiconductor layer. The second electrode is configured on the epitaxial structure. The micro light-emitting element can improve the quantum efficiency, and the micro light-emitting element display device adopting the micro light-emitting element can have better display quality.
Description
Technical Field
The present invention relates to a semiconductor device, and more particularly, to a micro light emitting device and a micro light emitting device display apparatus.
Background
A Light Emitting element such as a Light Emitting Diode (LED) can emit Light by driving a Light Emitting layer of the LED with an electron current. The current stage of led still faces many technical challenges, and the Efficiency degradation (Efficiency Droop) effect of the led is one of them. Specifically, the led has a peak External Quantum Efficiency (EQE) when the led is in an operating range of current density. As the current density of the led is continuously increased, the external quantum efficiency is decreased, which is the efficiency degradation effect of the led.
Currently, in the fabrication of micro light emitting diodes (micro LEDs), an etching process is used to perform a mesa (mesa) and an isolation (isolation) process. However, during the etching process, the sidewall (sidewall) of the micro light emitting diode may be damaged. When the size of the micro light emitting diode is smaller than 50 micrometers, the ratio of carriers flowing through the side wall is increased as the ratio of the surface area of the side wall surface to the surface area of the whole epitaxial structure is larger, thereby affecting the micro light emitting diode and causing the great reduction of the external quantum efficiency.
Disclosure of Invention
The present invention is directed to a micro light emitting device that can improve quantum efficiency (EQE).
The invention is directed to a micro light-emitting device display device, which comprises the micro light-emitting device and has better display quality.
According to an embodiment of the present invention, a micro light emitting device includes an epitaxial structure, a first electrode, and a second electrode. The epitaxial structure includes a first type semiconductor layer, a light emitting layer and a second type semiconductor layer. The light emitting layer is located between the first type semiconductor layer and the second type semiconductor layer. The first-type semiconductor layer includes a first portion and a second portion connected to each other. The edge of the first portion is spaced from the edge of the second portion. The bottom area of the first portion is smaller than the top area of the second portion. The first electrode is configured on the epitaxial structure and is positioned on the first part of the first type semiconductor layer. The second electrode is configured on the epitaxial structure.
In the micro light-emitting element according to the embodiment of the invention, the resistance value of the first portion of the first type semiconductor layer is larger than the resistance value of the second portion.
In the micro light-emitting element according to the embodiment of the invention, the resistance value of the region where the second portion overlaps the first portion is smaller than the resistance value of the region where the second portion does not overlap the first portion.
In the micro light emitting device according to the embodiment of the invention, the first portion of the first type semiconductor layer has a first thickness, the second portion has a second thickness, and a ratio of the second thickness to the first thickness is between 0.1 and 0.5.
In the micro light emitting device according to the embodiment of the invention, the second thickness of the second portion is between 0.1 micron and 0.5 micron.
In the micro light emitting device according to the embodiment of the invention, a ratio of the first bottom area of the first portion to the bottom area of the first type semiconductor layer is between 0.8 and 0.98.
In the micro light emitting device according to the embodiment of the invention, the pitch is between 0.5 micrometers and 5 micrometers.
In the micro light emitting device according to the embodiment of the invention, the length of the epitaxial structure is less than or equal to 50 micrometers.
In the micro light emitting device according to the embodiment of the invention, a ratio of a surface area of the side surface of the epitaxial structure to a surface area of the epitaxial structure is greater than or equal to 0.01.
In the micro light-emitting device according to the embodiment of the invention, the cross-sectional shape of the first portion of the first type semiconductor layer is a trapezoid. The cross-sectional shapes of the second part of the stacked first-type semiconductor layer, the light emitting layer and the second-type semiconductor layer are trapezoidal.
In the micro light-emitting element according to the embodiment of the invention, the side surface of the light-emitting layer is coplanar with the side surface of the second portion of the first-type semiconductor layer.
In the micro light emitting device according to the embodiment of the invention, the first type semiconductor layer has a connection surface between the first portion and the second portion. The angle between the connecting surface and the side surface of the first portion is between 30 and 80 degrees.
In the micro light emitting device according to an embodiment of the invention, the second type semiconductor layer has a bottom surface far from the light emitting layer, and an included angle between the bottom surface and a side surface of the second type semiconductor layer is between 30 degrees and 80 degrees.
In the micro light emitting device according to the embodiment of the invention, a ratio of the thickness of the first portion of the first type semiconductor layer to the thickness of the epitaxial structure is between 0.05 and 0.4. The ratio of the side surface area of the first portion to the side surface area of the epitaxial structure is between 0.2 and 0.8.
In the micro light emitting device according to the embodiment of the invention, the orthographic projection of the first electrode on the first type semiconductor layer is located in the first portion.
In the micro light emitting device according to the embodiment of the invention, the first type semiconductor layer is a P-type semiconductor layer, and the second type semiconductor layer is an N-type semiconductor layer.
In the micro light emitting device according to the embodiment of the invention, the first electrode and the second electrode are respectively located on two opposite sides of the epitaxial structure.
In the micro light emitting device according to the embodiment of the invention, the second type semiconductor layer includes a third portion and a fourth portion connected to each other. The cross-sectional shape of the first portion of the first-type semiconductor layer is trapezoidal. The cross-sectional shapes of the second part of the stacked first-type semiconductor layer, the light emitting layer and the third part of the second-type semiconductor layer are trapezoidal. The cross-sectional shape of the fourth portion of the second-type semiconductor layer is trapezoidal.
In the micro light emitting device according to the embodiment of the invention, the micro light emitting device further includes an insulating layer extending to cover the peripheral surface of the first type semiconductor layer and the peripheral surface of the light emitting layer. The second electrode is connected with the second type semiconductor layer, extends and is distributed along the side surface of the epitaxial structure from the second type semiconductor layer to cover the insulating layer, and one end of the second electrode and the first electrode are positioned on the same side of the epitaxial structure.
In the micro light emitting device according to an embodiment of the invention, the epitaxial structure further includes a via hole, and the via hole penetrates through the first type semiconductor layer, the light emitting layer and a portion of the second type semiconductor layer. The micro light-emitting element further comprises an insulating layer and a first electrode which are arranged on the first part of the first type semiconductor layer and extend to cover the inner wall of the through hole and the peripheral surface of the epitaxial structure. The first electrode and the second electrode are positioned on the first part of the first type semiconductor layer, and the second electrode extends into the through hole and is electrically connected with the second type semiconductor layer.
In the micro light emitting device according to the embodiment of the invention, the micro light emitting device further includes a current adjusting layer disposed in the second portion of the first type semiconductor layer, and the current adjusting layer extends from the peripheral surface of the second portion toward the inside of the first type semiconductor layer.
In the micro light emitting device according to the embodiment of the invention, the micro light emitting device further includes an ohmic contact layer disposed between the first portion of the first type semiconductor layer and the first electrode.
In an embodiment of the invention, the micro light emitting device further includes an insulating layer and a first electrode disposed on the first portion of the first type semiconductor layer, exposing a portion of the first portion, and extending to cover a peripheral surface of the epitaxial structure.
According to an embodiment of the present invention, a micro light emitting device display apparatus includes a driving substrate and a plurality of micro light emitting devices. The micro light-emitting elements are separately arranged on the driving substrate and electrically connected to the driving substrate. The micro light-emitting device includes an epitaxial structure, a first electrode and a second electrode. The epitaxial structure includes a first type semiconductor layer, a light emitting layer and a second type semiconductor layer. The light emitting layer is located between the first type semiconductor layer and the second type semiconductor layer. The first-type semiconductor layer includes a first portion and a second portion connected to each other. The edge of the first portion is spaced from the edge of the second portion. The second portion is located between the first portion and the light emitting layer. The first electrode is configured on the epitaxial structure and is positioned on the first part of the first type semiconductor layer. The second electrode is configured on the epitaxial structure.
In view of the above, in the design of the micro light emitting device of the present invention, the first type semiconductor layer includes a first portion and a second portion connected to each other, wherein a gap is formed between an edge of the first portion and an edge of the second portion, and a first bottom area of the first portion is smaller than a second bottom area of the second portion. By this design, the thickness of the peripheral edge of the first type semiconductor layer can be reduced to increase the sheet resistance around part of the first type semiconductor layer, thereby reducing the proportion of the first type semiconductor carrier to the side wall. Therefore, the micro light-emitting element can improve the quantum efficiency, and the micro light-emitting element display device adopting the micro light-emitting element can have better display quality.
Drawings
FIG. 1A is a schematic top view of a micro light-emitting device display apparatus according to an embodiment of the present invention;
FIG. 1B is a schematic perspective view of a micro light-emitting device of the micro light-emitting device display apparatus of FIG. 1A;
FIG. 1C is a schematic cross-sectional view of a micro light-emitting device of the micro light-emitting device display apparatus of FIG. 1A;
fig. 2A is a schematic cross-sectional view of a micro light-emitting device according to another embodiment of the invention;
fig. 2B is a schematic cross-sectional view of a micro light-emitting device according to another embodiment of the invention;
fig. 3 is a schematic cross-sectional view of a micro light-emitting device according to another embodiment of the invention;
fig. 4A is a schematic cross-sectional view of a micro light-emitting device according to another embodiment of the invention;
fig. 4B is a schematic cross-sectional view of a micro light-emitting device according to another embodiment of the invention;
fig. 4C is a schematic cross-sectional view of a micro light-emitting device according to another embodiment of the invention;
FIG. 5A is a graph of current density versus quantum efficiency for a plurality of micro light-emitting devices having different etch depths;
fig. 5B is a graph of current density versus quantum efficiency for a plurality of micro-light emitting devices having different etch widths.
Description of the reference numerals
A micro light emitting element display device;
100a, 100 b', 100c, 100d, 100e, 100f a micro light emitting element;
110a, 110b, 110c are epitaxial structures;
112a first type semiconductor layer;
113 a first part;
114, a light emitting layer;
115: a second portion;
116. 116b a second type semiconductor layer;
117: a third portion;
118, a through hole;
119, the fourth part;
119a top surface;
120 a first electrode;
130. 130b, 130c a second electrode;
140 ohmic contact layer;
150a, 150 b', 150c insulating layers;
160a, 160b, 160c a current regulation layer;
200, a driving substrate;
a1 and A2 are included angles;
b1, bottom surface;
b2, C2, P lateral surface;
c1, connecting surface;
D. d1, D2, D3, L, L1, L2, L3;
e1, bottom area;
e2, top area;
e3, bottom area;
g1, spacing;
g2, another spacing;
s is a side surface;
t is the thickness;
t1: first thickness;
t2: second thickness.
Detailed Description
Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the description to refer to the same or like parts.
Fig. 1A is a schematic top view of a micro light emitting device display apparatus according to an embodiment of the invention. Fig. 1B is a schematic perspective view of a micro light emitting device of the micro light emitting device display apparatus of fig. 1A. Fig. 1C is a schematic cross-sectional view of a micro light-emitting device of the micro light-emitting device display apparatus of fig. 1A.
Referring to fig. 1A, in the present embodiment, a micro light emitting device display apparatus 10 includes a plurality of micro light emitting devices 100a and a driving substrate 200. The micro light emitting devices 100a are disposed on the driving substrate 200 separately from each other and electrically connected to the driving substrate 200. Here, the driving substrate 200 is, for example, a Complementary Metal-Oxide-Semiconductor (CMOS) substrate, a Liquid Crystal On Silicon (LCOS) substrate, a Thin Film Transistor (TFT) substrate, or another substrate having an operating circuit, and is not limited thereto. A Micro light emitting element 100a, such as a Micro light emitting diode (Micro LED) or microchip, as used herein, "Micro" element means that it can have a size of 1 micron to 100 microns. In some embodiments, the microelements may have a maximum width of 20 microns, 10 microns, or 5 microns. In some embodiments, the microelements may have a maximum height of less than 20 microns, 10 microns, or 5 microns. It should be understood, however, that embodiments of the present invention are not necessarily limited thereto, and that implementation of certain embodiments may be applied to larger and perhaps smaller dimensions.
In detail, referring to fig. 1A, fig. 1B and fig. 1C, the micro light emitting device 100a includes an epitaxial structure 110a, a first electrode 120 and a second electrode 130. The epitaxial structure 110a includes a first-type semiconductor layer 112a, a light-emitting layer 114 and a second-type semiconductor layer 116. The light emitting layer 114 is located between the first-type semiconductor layer 112a and the second-type semiconductor layer 116. The first-type semiconductor layer 112a includes a first portion 113 and a second portion 115 connected to each other. The edge of the first portion 113 and the edge of the second portion 115 have a distance G1 therebetween, i.e. the width of the first portion 113 is different from the width of the second portion 115, and the distance G1 is the difference between the widths of the first portion 113 and the second portion 115. The second portion 115 is located between the first portion 113 and the light emitting layer 114, where the first portion 113 and the second portion 115 are formed at the same time and are made of the same material, and a bottom area E1 of the first portion 113 is smaller than a top area E2 of the second portion 115. The first electrode 120 is disposed on the epitaxial structure 110a and on the first portion 113 of the first-type semiconductor layer 112 a. In particular, the orthographic projection of the first electrode 120 on the first-type semiconductor layer 112a is located within the first portion 113. The second electrode 130 is disposed on the epitaxial structure 110 a. In this embodiment, the first electrode 120 and the second electrode 130 are respectively located on two opposite sides of the epitaxial structure 110a, i.e. the micro light emitting device 100a is embodied as a vertical micro light emitting diode. The first type semiconductor layer 112a is, for example, a P-type semiconductor layer, and the second type semiconductor layer 116 is, for example, an N-type semiconductor layer, but not limited thereto.
In detail, in the present embodiment, the resistance value of the first portion 113 of the first-type semiconductor layer 112a is greater than the resistance value of the second portion 115. The resistance value of the region where the second portion 115 overlaps the first portion 113 is smaller than the resistance value of the region where the second portion 115 does not overlap the first portion 113. That is, as shown in fig. 1B and 1C, the resistance values of the two sides of the second portion 115 (i.e., the area not covered by the first portion 113) are greater than the resistance value of the middle (i.e., the area covered by the first portion 113). Therefore, the first type semiconductor carriers of the first type semiconductor layer 112a move toward the middle of the second portion 115, thereby reducing the ratio of the first type semiconductor carriers toward the sidewall of the epitaxial structure 110 a. Thus, the quantum efficiency of the micro light-emitting device 100a of the present embodiment can be improved.
Referring to fig. 1C, in the present embodiment, the first portion 113 of the first type semiconductor layer 112a has a first thickness T1, and the second portion 115 has a second thickness T2, and a ratio of the second thickness T2 to the first thickness T1 is, for example, between 0.1 and 0.5. Here, the second thickness T2 of the second portion 115 is, for example, between 0.1 micron and 0.5 micron. If the second thickness T2 of the second portion 115 is too thin (i.e., the ratio is less than 0.1), the process yield is not good; on the contrary, if the second thickness T2 of the second portion 115 is too thick (i.e. the above ratio is greater than 0.5), the movement of the first type semiconductor carriers to the sidewalls cannot be reduced.
In terms of area ratio, the ratio of the bottom area E1 of the first portion 113 of the first type semiconductor layer 112a to the bottom area E3 of the first type semiconductor layer 112a (also the bottom area of the second portion 115) is, for example, between 0.8 and 0.98. More specifically, a ratio of a surface area of the side surface S of the epitaxial structure 110a to a surface area of the epitaxial structure 110a is, for example, greater than or equal to 0.01. Here, the length of the epitaxial structure 110a is, for example, 50 μm or less. Furthermore, the distance G1 between the edge of the first portion 113 and the edge of the second portion 115 is, for example, between 0.5 microns and 5 microns. If the distance G1 is too large (i.e., greater than 5 μm), the light emitting area of the light emitting layer 114 is affected. In addition, a ratio of the first thickness T1 of the first portion 113 of the first-type semiconductor layer 112a to the thickness T of the epitaxial structure 110a is, for example, between 0.05 and 0.4. The ratio range enables the thickness of the first portion 113 to be controlled within a proper range, which can reduce the probability of carrier escape from the sidewall of the first portion 113 due to too long sidewall, or increase the difficulty or failure rate of the process due to too thin sidewall. In one embodiment, the thickness T of the epitaxial structure 110a is, for example, 3 to 8 microns, and the thickness of the first-type semiconductor layer 112a (i.e., the first thickness T1 plus the second thickness T2) is, for example, 0.5 to 1 micron. The ratio of the side surface area of the first portion 113 of the first-type semiconductor layer 112a to the side surface area of the epitaxial structure 110a is, for example, between 0.2 and 0.8. The area of the side surface of the first portion 113 is within the above ratio range, which can balance the light emitting area of the first type semiconductor layer 112a and the thin film resistance effect. That is, the carrier passing through the light emitting layer 114 can be ensured to have a larger area, and the gap G1 between the first portion 113 and the second portion 115 can be maintained, so that the difference in resistance between the layers is not reduced due to the too short gap G1.
Referring to fig. 1C, the cross-sectional shape of the first portion 113 of the first-type semiconductor layer 112a of the present embodiment is a trapezoid. The cross-sectional shapes of the second portion 115 of the stacked first-type semiconductor layer 112a, the light emitting layer 114, and the second-type semiconductor layer 116 are trapezoidal. That is, the epitaxial structure 110a of the present embodiment has two trapezoidal structures, so as to increase the light-emitting efficiency. More specifically, the side surface of the light emitting layer 114 is coplanar with the side surface of the second portion 115 of the first-type semiconductor layer 112a, wherein the plane is a slope. The edge of the first portion 113 of the first-type semiconductor layer 112a and the edge of the light emitting layer 114 have another distance G2, wherein the another distance G2 may be slightly larger than or equal to the distance G1, which is not limited herein.
Furthermore, the first-type semiconductor layer 112a has a connection surface C1 between the first portion 113 and the second portion 115, and an included angle a1 between the connection surface C1 and a side surface C2 of the first portion 113 is, for example, between 30 degrees and 80 degrees. On the other hand, the second-type semiconductor layer 116 has a bottom surface B1 far away from the light emitting layer 114, and an included angle a2 between the bottom surface B1 and a side surface B2 of the second-type semiconductor layer 116 is, for example, between 30 degrees and 80 degrees. That is, the angle of the trapezoid is, for example, between 30 degrees and 80 degrees.
In addition, referring to fig. 1C, the micro light emitting device 100a of the present embodiment further includes an ohmic contact layer 140, wherein the ohmic contact layer 140 is disposed between the first portion 113 of the first type semiconductor layer 112a and the first electrode 120. Since the area of the micro light emitting device 100a is small, the hole injection efficiency and the current distribution can be improved by the ohmic contact layer 140. In addition, the micro light emitting device 100a of the present embodiment further includes an insulating layer 150a, wherein the insulating layer 150a and the first electrode 120 are disposed on the first portion 113 of the first type semiconductor layer 112a, and expose a portion of the first portion 113, and extend to cover the peripheral surface S of the epitaxial structure 110 a.
In short, since the distance G1 is formed between the edge of the first portion 113 and the edge of the second portion 115 of the first type semiconductor layer 112a in the present embodiment, the thickness of the peripheral edge of the first type semiconductor layer 112a can be reduced to increase the sheet resistance around a portion of the first type semiconductor layer 112a, thereby reducing the ratio of the first type semiconductor carriers to the sidewall. In this way, the micro light emitting device 100a of the present embodiment can improve the quantum efficiency, and the micro light emitting device display apparatus 10 using the micro light emitting device 100a of the present embodiment can have better display quality.
It should be noted that the following embodiments follow the reference numerals and parts of the contents of the foregoing embodiments, wherein the same reference numerals are used to indicate the same or similar elements, and the description of the same technical contents is omitted. For the description of the omitted parts, reference may be made to the foregoing embodiments, and the following embodiments will not be repeated.
Fig. 2A is a schematic cross-sectional view of a micro light-emitting device according to another embodiment of the invention. Referring to fig. 1C and fig. 2A, the micro light-emitting device 100b of the present embodiment is similar to the micro light-emitting device 100a of fig. 1C, and the difference between the two devices is: in the present embodiment, the second-type semiconductor layer 116b of the epitaxial structure 110b includes a third portion 117 and a fourth portion 119 connected to each other. The cross-sectional shape of the first portion 113 of the first-type semiconductor layer 112a is trapezoidal. The second portion 115 of the first-type semiconductor layer 112a, the light emitting layer 114, and the third portion 117 of the second-type semiconductor layer 116b are stacked to have a trapezoidal cross-sectional shape. The fourth portion 119 of the second-type semiconductor layer 116b has a trapezoidal cross-sectional shape. That is, the epitaxial structure 110b of the present embodiment has three trapezoidal structures. Furthermore, the insulating layer 150b of the present embodiment extends to cover the peripheral surface of the first type semiconductor layer 112a and the peripheral surface of the light emitting layer 114. In detail, the insulating layer 150b and the first electrode 120 are disposed on the first portion 113 of the first type semiconductor layer 112a and extend to cover the peripheral surface of the first type semiconductor layer 112a, the peripheral surface of the light emitting layer 114, the peripheral surface of the third portion 117 of the second type semiconductor layer 116b, and a portion of the peripheral surface of the fourth portion 119. That is, the insulating layer 150b exposes a portion of the fourth portion 119 of the second-type semiconductor layer 116 b. As shown in the micro light emitting device 100B 'of fig. 2B, the insulating layer 150B' may also completely cover the side surface of the fourth portion 119, exposing only a portion of the top surface 119a of the fourth portion 119 for contacting the second electrode 130B. The first electrode 120 and the second electrode 130b may be located on the same side of the epitaxial structure 110b, i.e., the micro light emitting device 100b may be a flip-chip type or a horizontal type light emitting diode. In fig. 2A and 2B, the second electrode 130B is connected to the second type semiconductor layer 116B, and extends from the second type semiconductor layer 116B along the side surface P of the epitaxial structure 110B to cover the insulating layer 150B, and one end of the second electrode 130B and the first electrode 120 are located on the same side of the epitaxial structure 110B. Further, the second electrode 130b extends from the first portion 113 of the first-type semiconductor layer 112a to a region of the fourth portion 119 of the second-type semiconductor layer 116b not covered by the insulating layer 150b along the side surface P of the epitaxial structure 110b, and is electrically connected to the fourth portion 119. Due to the structural design of the epitaxial structure 110b of the present embodiment, the first electrode 120 and the second electrode 130b have the same height, and thus, the configuration yield can be better.
Fig. 3 is a schematic cross-sectional view of a micro light-emitting device according to another embodiment of the invention. Referring to fig. 1C and fig. 3, the micro light-emitting device 100C of the present embodiment is similar to the micro light-emitting device 100a of fig. 1C, and the difference between the two devices is: in the present embodiment, the epitaxial structure 110c further includes a via 118, wherein the via 118 penetrates the first-type semiconductor layer 112a, the light-emitting layer 114 and a portion of the second-type semiconductor layer 116. The insulating layer 150c and the first electrode 120 of the micro light emitting device 100c are disposed on the first portion 113 of the first type semiconductor layer 112a, and extend to cover the inner wall of the via 118 and the peripheral surface S of the epitaxial structure 110 c. The first electrode 120 and the second electrode 130c are disposed on the first portion 113 of the first type semiconductor layer 112a, and the second electrode 130c extends into the through hole 118 and is electrically connected to the second type semiconductor layer 116.
Fig. 4A is a schematic cross-sectional view of a micro light-emitting device according to an embodiment of the invention. Referring to fig. 1C and fig. 4A, the micro light-emitting device 100d of the present embodiment is similar to the micro light-emitting device 100a of fig. 1C, and the difference between the two devices is: in the present embodiment, the micro light emitting device 100d further includes a current adjusting layer 160a, wherein the current adjusting layer 160a is disposed in the second portion 115 of the first type semiconductor layer 113. As shown in fig. 4A, the current regulation layer 160a is extended from the peripheral surface of the second portion 115 toward the inside of the first type semiconductor layer 113, and the current regulation layer 160a is positioned relatively adjacent to the first portion 113 of the first type semiconductor layer 112 a. Here, the material of the current adjustment layer 160a is, for example, a non-conductive insulating material such as silicon dioxide (SiO2) or aluminum nitride (AlN).
Fig. 4B is a schematic cross-sectional view of a micro light-emitting device according to an embodiment of the invention. Referring to fig. 4A and fig. 4B, the micro light-emitting device 100e of the present embodiment is similar to the micro light-emitting device 100d of fig. 4A, and the difference therebetween is: in the present embodiment, the current adjustment layer 160b is positioned in the middle of the second portion 115 of the first-type semiconductor layer 112 a.
Fig. 4C is a schematic cross-sectional view of a micro light-emitting device according to an embodiment of the invention. Referring to fig. 4A and fig. 4C, the micro light-emitting device 100f of the present embodiment is similar to the micro light-emitting device 100d of fig. 4A, and the difference therebetween is: in the present embodiment, the current adjusting layer 160c is located in the second portion 115 of the first type semiconductor layer 113 and is relatively adjacent to the light emitting layer 114, so as to prevent the first type semiconductor carriers from going to the sidewall of the light emitting layer 114.
Fig. 5A is a graph of current density versus quantum efficiency for a plurality of micro light emitting devices having different etch depths. Fig. 5B is a graph of current density versus quantum efficiency for a plurality of micro-light emitting devices having different etch widths. It should be noted that the etching depth described herein is, for example, the second thickness T2 of the second portion 115 of the first type semiconductor layer 112a divided by the thickness of the first type semiconductor layer 112a (i.e., the first thickness T1 plus T2) in fig. 1C. The etching width described herein is, for example, a distance from the edge of the first electrode 120 to the edge of the first portion 113 of the first-type semiconductor layer 112a divided by a distance from the edge of the first electrode 120 to the edge of the second portion 115 of the first-type semiconductor layer 112a in fig. 1C.
Referring to FIG. 5A, a curve L shows an ideal state without considering surface recombination (surface recombination). The curves L1 and L2 both include the surface recombination effect and represent the states of 0 and 0.12 etching depth ratio, respectively, while the curve L3 includes the surface recombination effect but the first-type semiconductor layer is not patterned, so the etching depth ratio is 1. As is clear from fig. 5A, the deeper the etching depth (i.e., the curve L1), the more the quantum efficiency of the micro light-emitting device can be improved.
Referring to FIG. 5B, curve D shows an ideal state without considering surface recombination (surface recombination). The curves D1 and D2 both include the surface recombination effect and represent the states of 0.33 and 0.7 etching width ratio, respectively, while the curve D3 includes the surface recombination effect but the first-type semiconductor layer is not patterned, so the etching width ratio is 1. As is clear from fig. 5B, the wider the etching width (i.e., the curve D2), the more the quantum efficiency of the micro light-emitting device can be improved. In short, the above design is suitable for small current densities, e.g., current densities of 10A/cm or less2The effect is more obvious.
In summary, in the design of the micro light emitting device of the present invention, the first type semiconductor layer includes a first portion and a second portion connected to each other, wherein a gap is formed between an edge of the first portion and an edge of the second portion. By this design, the thickness of the peripheral edge of the first type semiconductor layer can be reduced to increase the sheet resistance around part of the first type semiconductor layer, thereby reducing the proportion of the first type semiconductor carrier to the side wall. Therefore, the micro light-emitting element can improve the quantum efficiency, and the micro light-emitting element display device adopting the micro light-emitting element can have better display quality.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (20)
1. A micro light-emitting device, comprising:
the epitaxial structure comprises a first type semiconductor layer, a light emitting layer and a second type semiconductor layer, wherein the light emitting layer is positioned between the first type semiconductor layer and the second type semiconductor layer, the first type semiconductor layer comprises a first part and a second part which are connected with each other, a distance is arranged between the edge of the first part and the edge of the second part, and the bottom area of the first part is smaller than the top area of the second part;
a first electrode disposed on the epitaxial structure and on the first portion of the first-type semiconductor layer; and
the second electrode is configured on the epitaxial structure.
2. The micro light-emitting element according to claim 1, wherein a resistance value of the first portion of the first-type semiconductor layer is larger than a resistance value of the second portion.
3. A micro light-emitting element according to claim 2, wherein a resistance value of a region where the second portion overlaps with the first portion is smaller than a resistance value of a region where the second portion does not overlap with the first portion.
4. The micro light-emitting device of claim 1, wherein the first portion of the first type semiconductor layer has a first thickness, the second portion has a second thickness, and a ratio of the second thickness to the first thickness is between 0.1 and 0.5.
5. The micro light-emitting element of claim 4, wherein the second thickness of the second portion is between 0.1 microns and 0.5 microns.
6. The micro light-emitting device of claim 1, wherein a ratio of the bottom area of the first portion to a bottom area of the first type semiconductor layer is between 0.8 and 0.98.
7. The micro light-emitting device of claim 1, wherein the pitch is between 0.5 microns and 5 microns.
8. The micro light-emitting device as claimed in claim 1, wherein a ratio of a surface area of a side surface of the epitaxial structure to a surface area of the epitaxial structure is 0.01 or greater.
9. A micro light-emitting device according to claim 1, wherein the first portion of the first type semiconductor layer has a trapezoidal cross-sectional shape, and the second portion of the first type semiconductor layer, the light-emitting layer and the second type semiconductor layer are stacked has a trapezoidal cross-sectional shape.
10. A micro light-emitting element according to claim 9, wherein a side surface of the light-emitting layer is coplanar with a side surface of the second portion of the first-type semiconductor layer.
11. The micro light-emitting device of claim 9, wherein the first type semiconductor layer has a connection surface between the first portion and the second portion, and an included angle between the connection surface and a side surface of the first portion is between 30 degrees and 80 degrees.
12. A micro light-emitting device according to claim 9, wherein the second type semiconductor layer has a bottom surface opposite to the bottom surface far from the light-emitting layer, and an included angle between the bottom surface and a side surface of the second type semiconductor layer is between 30 degrees and 80 degrees.
13. The micro light-emitting device as claimed in claim 1, wherein a ratio of a thickness of the first portion of the first type semiconductor layer to a thickness of the epitaxial structure is 0.05 to 0.4, and a ratio of a side surface area of the first portion to a side surface area of the epitaxial structure is 0.2 to 0.8.
14. A micro-light emitting device as claimed in claim 1, wherein an orthographic projection of the first electrode on the first type semiconductor layer is located within the first portion.
15. The micro light-emitting device as claimed in claim 1, wherein the first and second electrodes are respectively located on opposite sides of the epitaxial structure.
16. A micro light-emitting device according to claim 1, wherein the second type semiconductor layer comprises a third portion and a fourth portion connected to each other, the first portion of the first type semiconductor layer has a trapezoidal cross-sectional shape, and the second portion of the first type semiconductor layer, the light-emitting layer and the third portion of the second type semiconductor layer are stacked to have a trapezoidal cross-sectional shape, and the fourth portion of the second type semiconductor layer has a trapezoidal cross-sectional shape.
17. The micro light-emitting element according to claim 16, further comprising:
and the insulating layer extends to cover the peripheral surface of the first type semiconductor layer and the peripheral surface of the light-emitting layer, wherein the second electrode is connected with the second type semiconductor layer and extends and distributes from the second type semiconductor layer along the side surface of the epitaxial structure to cover the insulating layer, and one end of the second electrode and the first electrode are positioned on the same side of the epitaxial structure.
18. The micro light-emitting device as claimed in claim 1, wherein the epitaxial structure further comprises a via hole penetrating the first type semiconductor layer, the light-emitting layer and a portion of the second type semiconductor layer, the micro light-emitting device further comprising:
and an insulating layer and the first electrode are arranged on the first part of the first type semiconductor layer and extend to cover the inner wall of the through hole and the peripheral surface of the epitaxial structure, wherein the first electrode and the second electrode are positioned on the first part of the first type semiconductor layer, and the second electrode extends into the through hole and is electrically connected with the second type semiconductor layer.
19. The micro light-emitting element according to claim 1, further comprising:
and the current regulation layer is configured in the second part of the first type semiconductor layer, and extends and distributes from the peripheral surface of the second part to the inner part of the first type semiconductor layer.
20. A micro light-emitting element display device, comprising:
a drive substrate; and
the micro light-emitting devices of claim 1, wherein the micro light-emitting devices are disposed on the driving substrate separately from each other and electrically connected to the driving substrate.
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| CN202011176558.7A CN112289901A (en) | 2020-10-28 | 2020-10-28 | Micro light emitting element and micro light emitting element display device |
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| CN202011176558.7A CN112289901A (en) | 2020-10-28 | 2020-10-28 | Micro light emitting element and micro light emitting element display device |
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