LIGHT-EMITTING DEVICE AND MANUFACTURING METHOD THEREOF
A light-emitting device comprises a carrier; a first semiconductor element formed on the carrier and comprising a first semiconductor structure and a second semiconductor structure, wherein the second semiconductor structure is closer to the carrier than the first semiconductor structure is, the first semiconductor structure comprises a first active layer emitting a first light having a first dominant wavelength during a normal operation, and the second semiconductor structure comprises a second active layer; and a bridge on a side surface of the second active layer of the second semiconductor structure.
This application is a continuation application of a previously filed U.S. patent application Ser. No. 14/808,295 filed on Jul. 24, 2015, entitled as “LIGHT-EMITTING DEVICE AND MANUFACTURING METHOD THEREOF”. The disclosure of the reference cited herein is incorporated by reference.
TECHNICAL FIELDThe disclosure relates to a light-emitting device, and more particularly, to a light-emitting device emitting multiple dominant wavelengths.
DESCRIPTION OF BACKGROUND ARTLight-emitting diode (LED) is widely used as a solid-state lighting source. Light-emitting diode (LED) generally comprises a p-type semiconductor layer, an n-type semiconductor layer, and an active layer between the p-type semiconductor layer and the n-type semiconductor layer for emitting light. The principle of LED is to transform electrical energy to optical energy by applying electrical current to LED and injecting electrons and holes to the active layer. The combination of electrons and holes in the active layer emits light accordingly.
SUMMARY OF THE DISCLOSUREA light-emitting device comprises a carrier; a first semiconductor element formed on the carrier and comprising a first semiconductor structure and a second semiconductor structure, wherein the second semiconductor structure is closer to the carrier than the first semiconductor structure is, the first semiconductor structure comprises a first active layer emitting a first light having a first dominant wavelength during a normal operation, and the second semiconductor structure comprises a second active layer; and a bridge on a side surface of the second active layer of the second semiconductor structure.
Next, the method comprises a step of epitaxially growing a reflective layer 13 on the first semiconductor stack 11. The reflective layer 13 comprises a DBR structure and group III-V semiconductor material. The reflective layer 13 comprises a conductivity-type same as that of the second semiconductor layer 113 of the first semiconductor stack 11. Next, a tunnel junction 14 comprising group III-V semiconductor material is epitaxially grown on the first semiconductor stack 11. The tunnel junction 14 comprises a p-n junction formed by a first heavily-doped layer of a first conductivity-type, for example an n-type conductive semiconductor layer, and a second heavily-doped layer of a second conductivity-type, for example a p-type semiconductor layer. The heavily-doped n-type conductive semiconductor layer and the heavily-doped p-type layer have a doping concentration at least one order higher than that of the semiconductor layer of the first semiconductor stack 11. These heavily-doped layers of the tunnel junction 14 are preferable doped with a doping concentration greater than 1018/cm3, thus providing a low electrical junction resistance during operation. The tunnel junction 14 having low resistance is provided to be an electrical junction between the first semiconductor structure 11a and another semiconductor structure deposited thereon in the following process. A side of the tunnel junction 14, which is adjacent to the second semiconductor layer 113 or the reflective layer 13, comprises a conductivity-type same as that of the second semiconductor layer 113 or the reflective layer 13. An opposite side of the tunnel junction 14, which is away from the second semiconductor layer 113 or the reflective layer 13, comprises a conductivity-type opposite to that of the second semiconductor layer 113 or the reflective layer 13.
Then, an etching stop layer 23 is epitaxially grown on the first semiconductor stack 11. Next, a second semiconductor stack 15 is epitaxially grown on the etching stop layer 23 by epitaxy method, such as metallic-organic chemical vapor deposition (MOCVD) method, molecular beam epitaxy (MBE) method, or hydride vapor phase epitaxy (HVPE) method. The second semiconductor stack 15 comprises a third semiconductor layer 151 having a first conductivity-type, a fourth semiconductor layer 153 having a second-conductivity type different from the first conductivity-type, and an second active layer 152 formed between the third semiconductor layer 151 and the fourth semiconductor layer 153. The second active layer 152 comprises a single heterostructure (SH), a double heterostructure (DH), or a multi-quantum well (MQW) structure. In one embodiment, the third semiconductor layer 151 is an n-type semiconductor layer for providing electrons, the fourth semiconductor layer 153 is a p-type semiconductor layer for providing holes, and holes and electrons combine in the second active layer 152 to emit light under a driving current. Alternatively, the third semiconductor layer 151 can be a p-type semiconductor layer, and the fourth semiconductor layer 153 can be an n-type semiconductor layer. The material of the second active layer 152 comprises InxGayAl(1−x−y)N for emitting light having a dominant wavelength in the ultraviolet to green spectral regions, InxGayAl(1−x−y)P for emitting light having a dominant wavelength in the yellow to red spectral regions, or InxGayAl(1−x−y)As for emitting light having a dominant wavelength in the infrared spectral region.
The first semiconductor stack 11, the reflective layer 13, the tunnel junction 14, the etching stop layer 23, and the second semiconductor stack 15 are deposited on the growth substrate continuously in an epitaxy chamber to prevent from being contaminated and to ensure a high quality of the semiconductor layers that staked.
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Next, alternate examples of the method of manufacturing the light-emitting device 1 are respectively shown in
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The first top electrode 17, the second top electrode 18, the bottom electrode 22, and the third top electrode 16 comprise metal material having low electrical resistance, such as Au, Al, Pt, Cr, Ti, Ni, W, or the combination thereof, and can be formed of a monolayer or multiple layers. A thickness of the first top electrode 17, the second top electrode 18, the bottom electrode 22, or the third top electrode 16 is about 0.1 to 10 microns. The first top electrode 17 and the second top electrode 18 each has a shape such as rectangular, polygon, circle, or ellipse from a top view of the light-emitting device 1. The first top electrode 17, the second top electrode 18, the bottom electrode 22, and the third top electrode 16 can be formed by sputtering, vapor deposition, or plating.
The third top electrode 16 is formed on the surface 15s of the second semiconductor structure 15a. The first top electrode 17 and the bottom electrode 22 provide first electrical current to forward bias the first MQW structure of the first active layer 112 of the first semiconductor structure 11a to emit light having a first dominant wavelength λ1. The second top electrode 18 and the bottom electrode 22 provide second electrical current to forward bias the third MQW structure of the second active layer 152 of the third semiconductor structure 15b to emit light having a second dominant wavelength λ2, wherein λ1 is different from λ2. More specifically, the first light-emitting element 1a only emit the first dominant wavelength generated in the first MQW structure under an electrical current 100 flowing in series through the first MQW structure and the second MQW structure, wherein the second MQW structure of the second active layer 152 of the second semiconductor structure 15a is non-luminous even when forward-biasing the second semiconductor structure 15a.
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Furthermore, the diode character of the second semiconductor structure 15a of the first light-emitting element 1a may not completely be broken down in the first embodiment or the short circuit formed by the third top electrode 16 (contact 161 and bridge 162) may not completely block electrical current flowing through the second active layer 152 of the second semiconductor structure 15a of the first light-emitting element 1a in the second embodiment. Some dim light with weak optical output power may be generated and emitted from the second active layer 152 of the second semiconductor structure 15a of the first light-emitting element 1a. Accordingly, the reflective layer 13 is formed between the first semiconductor layer 151 of the second semiconductor structure 15a of the first light-emitting element 1a and the second semiconductor layer 113 of the first semiconductor structure 11a of the first light-emitting element 1a as shown in
It will be apparent to those having ordinary skill in the art that various modifications and variations can be made in accordance with the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.
Claims
1. A light-emitting device, comprising:
- a carrier;
- a first semiconductor element formed on the carrier and comprising a first semiconductor structure and a second semiconductor structure, wherein the second semiconductor structure is closer to the carrier than the first semiconductor structure is, the first semiconductor structure comprises a first active layer emitting a first light having a first dominant wavelength during a normal operation, and the second semiconductor structure comprises a second active layer; and
- a bridge on a side surface of the second active layer of the second semiconductor structure.
2. The light-emitting device of claim 1, further comprising a tunnel junction between the first semiconductor structure and the second semiconductor structure, wherein the tunnel junction comprises a p-n junction.
3. The light-emitting device of claim 2, wherein the tunnel junction comprises a first layer of a first conductivity-type and a second layer of a second conductivity-type, and the first conductivity-type is different from the second conductivity-type.
4. The light-emitting device of claim 3, wherein the first semiconductor element comprises a semiconductor layer on the first active layer and having a doping concentration, and the first layer of the first conductivity-type and/or the second layer of the second conductivity-type has a doping concentration at least one order higher than the doping concentration of the semiconductor layer of the first semiconductor element.
5. The light-emitting device of claim 1, wherein the carrier comprises a side face, the first semiconductor structure comprises a side face, and the side surface of the second active layer is between the side face of the first semiconductor structure and the side face of the carrier.
6. The light-emitting device of claim 1, further comprising a second semiconductor element on the carrier, wherein the first semiconductor element is physically spaced apart from the second semiconductor element.
7. The light-emitting device of claim 6, wherein the second semiconductor element comprises a third semiconductor structure emitting a second dominant wavelength during a normal operation.
8. The light-emitting device of claim 7, wherein the first dominant wavelength is different from the second dominant wavelength.
9. The light-emitting device of claim 1, wherein the second semiconductor structure comprises a top surface, and the light-emitting device further comprises a contact on the top surface of the second semiconductor structure.
10. The light-emitting device of claim 9, wherein the bridge is in contact with the contact.
11. The light-emitting device of claim 9, wherein the second semiconductor structure comprises a third semiconductor layer, a fourth semiconductor layer, and the second active layer is between the third semiconductor layer and the fourth semiconductor layer; and wherein the bridge extends from the contact, and covers a side surface of the third semiconductor layer and a side surface of the fourth semiconductor layer.
12. The light-emitting device of claim 1, wherein the second semiconductor structure comprises a third semiconductor layer, a fourth semiconductor layer, and the second active layer is between the third semiconductor layer and the fourth semiconductor layer; and wherein the bridge covers a side surface of the third semiconductor layer and a side surface of the fourth semiconductor layer.
13. The light-emitting device of claim 1, further comprising a first top electrode and a bottom electrode, wherein the first top electrode is on the first semiconductor structure, and the bottom electrode is on a side of the carrier opposite to the first semiconductor structure.
14. The light-emitting device of claim 13, further comprising a second semiconductor element on the carrier, wherein the first semiconductor element is physically spaced apart from the second semiconductor element, and the second semiconductor element comprises a third semiconductor structure.
15. The light-emitting device of claim 14, further comprising a second top electrode on the third semiconductor structure.
16. The light-emitting device of claim 15, wherein the bottom electrode is vertically overlapped with the first top electrode, the second top electrode and the bridge.
17. The light-emitting device of claim 15, wherein the second top electrode is closer to the carrier than the first top electrode is.
18. The light-emitting device of claim 1, further comprising an etching stop layer formed between the first semiconductor structure and the second semiconductor structure.
19. The light-emitting device of claim 1, wherein the second active layer does not emit light during the normal operation.
20. The light-emitting device of claim 1, further comprising an adhesive layer between the second semiconductor structure and the carrier.
Type: Application
Filed: Sep 21, 2017
Publication Date: Jan 11, 2018
Inventors: Shao-Ping LU (Hsinchu), Yi-Ming CHEN (Hsinchu), Yu-Ren PENG (Hsinchu), Chun-Yu LIN (Hsinchu), Chun-Fu TSAI (Hsinchu), Tzu-Chieh HSU (Hsinchu)
Application Number: 15/711,737