This application claims priority to Chinese Invention Patent Application No. 202210418925.2, filed on Apr. 20, 2022, which is incorporated herein by reference in its entirety.
The disclosure relates to a semiconductor light-emitting device, and more particularly to a light-emitting diode (LED) and a light-emitting device including the same.
A light-emitting diode (LED) is a semiconductor light-emitting device typically made of a semiconductor material such as GaN, GaAs, GaP, GaAsP, AlGalnP, etc., and includes a PN junction for light emitting. In forward bias, electrons in the semiconductor may travel from an N-region into a P region, and holes may travel from the P region into the N region, such that a portion of minority carriers having entered the opposite region (e.g., the electrons in the P region) may recombine with majority carriers (e.g., the holes in the P region) to emit light. LEDs offer advantages such as high light-emission intensity, fast response, small size, long lifespan, etc., and are thus considered to be one of the most promising light sources currently.
A conventional LED includes a substrate, an epitaxial structure, and an electrode structure which generally includes a pad layer and an ohmic contact layer. The ohmic contact layer is configured to form electrical connection, i.e., ohmic contacts, between the electrode structure and a semiconductor layer of the epitaxial structure. The pad layer serves as a wire-bonding pad for subsequent packaging and wire-bonding procedures, and for providing protection to underlying elements of the LED. The pad layer is generally made of gold. However, problems such as wire-bonding abnormalities or layer crack/peeling occur frequently during the wire bonding procedure.
Therefore, an object of the disclosure is to provide a light-emitting diode and a light-emitting device that can alleviate at least one of the drawbacks of the prior art.
According to one aspect of the disclosure, the light-emitting diode includes a semiconductor epitaxial structure and an electrode structure. The semiconductor epitaxial structure includes a first semiconductor layer, an active layer and a second semiconductor layer arranged in such order. The electrode structure is disposed on the semiconductor epitaxial structure and includes an ohmic contact layered unit disposed on the semiconductor epitaxial structure, and a wire bonding layered unit disposed on the ohmic contact layered unit. The wire bonding layered unit includes at least one stress buffer portion and a pad portion disposed on the at least one stress buffer portion. The at least one stress buffer portion includes a first stress buffer layer, a first electrode metal layer and a second stress buffer layer which are stacked on one another in such order on the ohmic contact layered unit. Each of the first and second stress buffer layers has a hardness greater than that of the pad portion.
According to another aspect of the disclosure, the light-emitting device includes at least one aforementioned light-emitting diode.
Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment(s) with reference to the accompanying drawings. It is noted that various features may not be drawn to scale.
Before the disclosure is described in greater detail, it should be noted that where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics.
It should be noted herein that for clarity of description, spatially relative terms such as “horizontal,” “vertical,” “transverse,” “center,” “top,” “bottom,” “upper,” “lower,” “left,” “right,” “inner,” “outer,” “on,” “above,” “over,” “downwardly,” “upwardly” and the like may be used throughout the disclosure while making reference to the features as illustrated in the drawings. The features may be oriented differently (e.g., rotated 90 degrees or at other orientations) and the spatially relative terms used herein may be interpreted accordingly. In addition, the terms “first,” “second,” “third,” etc., are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or as implicitly specifying the number of elements. Thus, for an element with one of these terms preceding it, the disclosure encompasses the possibility that there may be one or more such elements. In this disclosure, unless otherwise specified, “a plurality of,” “plural” or the like means two or more. In addition, the terms “includes,” “comprises” or the like or any variation thereof does not exclude the presence of additional elements not specifically disclosed.
In this disclosure, it is to be noted that, unless otherwise expressly specified, the terms “mount,” “connect,” “couple,” “install,” etc., are to be interpreted in a broad sense, e.g., as encompassing fixed connection, removable connection, or integrated connection (e.g., one-piece formation), as encompassing mechanical connection or electrical or signal connection, and as encompassing direct connection or indirect connection through an intermediary.
The present disclosure provides a light-emitting diode (LED) and a light-emitting device including the same.
Each of the first semiconductor layers 91, the active layer 92, and the second semiconductor layer 93 may include a lll-V compound semiconductor material, such as GaP, GaAs, or GaN, etc. A wavelength of light emitted from the LED 1 is determined by a material composition and a thickness of the well layers of the active layer 92. In certain embodiments, the active layer 92 includes AlGalnP and emits red light, and therefore, the LED 1 is a red LED. In certain embodiments, the active layer 92 includes AlGaAs, InGaAs, etc, and thus emits infrared light, and thus, the LED 1 is an infrared LED. In some embodiments, the LED 1 may be configured to emit light having a wavelength ranging from 550 nm to 950 nm. The first semiconductor layer 91, the active layer 92, and the second semiconductor layer 93 may be manufactured by a conventional epitaxy process, such as organic metal chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or a hydride vapor phase epitaxy (HVPE).
In the LED 1, the first semiconductor layer 91 has a portion (S1) that is not covered by the active layer 92 and the second semiconductor layer 93. The first electrode 94 is disposed on the portion (S1), and the second electrode 95 is disposed on the second semiconductor layer 93.
Referring to
In addition, the first electrode 94 and/or the second electrode 95 according to the present disclosure are designed to include an electrode structure described below so as to diminish abnormalities in a wire-bonding procedure.
The wire bonding layered unit 20 includes at least one stress buffer portion 21 and a pad portion 22 disposed on the at least one stress buffer portion 21. A thickness of the wire bonding layered unit 20 may vary based on the size of the LED 1, 2 and a force that the LED needs to withstand during the wire bonding process. The thickness of the wire bonding layered unit 20 of the electrode structure 3 may be more than 0.5 times a total thickness of the electrode structure 3. In certain embodiments, the thickness of the wire bonding layered unit 20 of the electrode structure 3 is 0.55 to 0.97 times the total thickness of the electrode structure 3, for example, 0.55 to 0.8 times, 0.8 to 0.9 times, or 0.9 to 0.97 times. In certain embodiments, the thickness of the wire bonding layered unit 20 ranges from 10,000 angstroms (Å) to 40,000 Å, e.g., from 12,000 Å to 40,000 Å. The wire bonding layered unit 20 is the main structure in the electrode structure 3 that bears the force and pressure encountered during the wire bonding process e.g., a soldering process.
The pad portion 22 is an outermost layer of the electrode structure 3, and is directly subjected to external force and serves as an external contact for the electrode structure 3. In certain embodiments, the pad portion 22 has a thickness which is of more than 50% of the total thickness of the wire bonding layered unit 20, for example, 75% to 80%. The thickness of the pad portion 22 may range from 10,000 Å to 30,000 Å. The pad portion 22 provides both physical and chemical protections for the electrode structure 3. The pad portion 22 may be made of a material exhibiting good stability and ductility, including, for example, Au, Al, Cu or alloys (e.g., AlCu) thereof.
The stress buffer portion 21 is provided between the pad portion 22 and the barrier layer 40 for enhancing the connections between the wire bonding layered unit 20 and the barrier layer 40. As shown in
In certain embodiments, the hardness of each of the first stress buffer layer 24a and the second stress buffer layer 24b is greater than that of the first electrode metal layer 23. During the wire bonding procedure, the bonding force or pressure exerted on the pad portion 22 transmits to the stress buffer portion 21, and is distributed by the first stress buffer layer 24a, and then, is absorbed by the first electrode metal layer 23 (which is thus deformed). Such deformation energy will be further reduced by the second stress buffer layer 24b, so that the bonding performance of the electrode structure 3 may be improved by the stress buffer portion 21. The first stress buffer layer 24a has a thickness that may be the same as or different from that of the second stress buffer layer 24b, and includes a metallic material which may be the same as or different from that of the second stress buffer layer 24b. In addition, the first electrode metal layer 23 includes a metallic material which may be the same as or different from that of the pad portion 22. In certain embodiments, the first electrode metal layer 23 includes the metallic material the same as that of the pad portion 22. In certain embodiments, the first stress buffer layer 24a includes the metallic material the same as that of the second stress buffer layer 24b, and has the thickness the same as that of the second stress buffer layer 24b.
A total thickness of the stress buffer portion 21 is 0.05 to 0.5 times the total thickness of the wire bonding layered unit 20, for example, 0.05 to 0.2 times, 0.2 to 0.25 times, or 0.25 to 0.5 times. In certain embodiments, the total thickness of the stress buffer portion 21 is 0.2 to 0.25 times the total thickness of the wire bonding layered unit 20. The thickness of each of the first stress buffer layer 24a and the second stress buffer layer 24b independently may range from 300 Å and 2000 Å. The first electrode metal layer 23 has a thickness of 1 to 20 times the thickness of the first stress buffer layer 24a or the thickness of the second stress buffer layer 24b, e.g., 1 to 3 times, 3 to 7 times or 7 to 20 times. In some embodiments, the thickness of the first electrode metal layer 23 is 3 to 7 times the thickness of the first stress buffer layer 24a or the thickness of the second stress buffer layer 24b. Since the material included in the first stress buffer layer 24a or the second stress buffer layer 24b is relatively active, the thickness of the first and second stress buffer layers 24a and 24b is designed to be only a small portion of the total thickness of the wire bonding layered unit 20, so as to obtain a good overall stability of the electrode structure 3. Each of the first and second stress buffer layers 24a, 24b may independently include a harder metallic material, such as Ti, Ni, W or Cr. Thus, the stress buffer portion 21 may include e.g., Ti/Au/Ti, Ti/Al/Ti, Ti/Cu/Ti, Ti/AICu/Ti, Ni/Au/Ni, Ni/Al/Ni, Ni/Cu/Ni, Ni/AICu/Ni, W/Au/W, W/Al/W, W/AICu/W, W/Cu/W, Cr/Au/Cr, Cr/Al/Cr, Cr/Cu/Cr, Cr/AICu/Cr, Ti/Au/Ni, Ti/Al/W, Ti/Cu/Cr, Ti/AICu/Cr, Ni/Au/ Ti, Ni/Al/W, Ni/Cu/Cr or Ni/AICu/Cr.
In certain embodiments, the ohmic contact layered unit 10 includes, for example, Au, Ge, Ni, Cr, or alloys thereof, and has a thickness ranging from 500 Å to 2,000 Å.
The barrier layer 40 includes a first barrier metal layer 41 and a second barrier metal layer 42 disposed on the first barrier metal layer 41. The first barrier metal layer 41 includes a material different from that of the second barrier metal layer 42. In certain embodiments, the first barrier metal layer 41 has a thickness of 1 to 3 times a thickness of the second barrier metal layer 42. In certain embodiments, the thickness of the first barrier metal layer 41 ranges from 500 Å to 5000 Å, and the thickness of the second barrier metal layer 42 ranges from 500 Å and 2000 Å. Each of the first barrier metal layer 41 and the second barrier metal layer 42 independently includes a material such as Cr, Pt, Ti, Al, Cu, Ni, W, Au, or combinations thereof. Thus, the barrier layer 40 includes a composite material having at least two metal materials, for example, Cr/Pt, Cr/Ti, Cr/Al, Cr/Cu, Cr/Ni, Cr/W, Cr/Au, Pt/Ti, Pt/Al, Pt/Cu, Pt/Ni, Pt/W, Pt/Au, Au/Cr, Au/Ti, Au/Cu, Au/Pt, Au/Al or Au/Ni.
The adhesion layer 30 is a layer that is, in the electrode structure 3, closest to the semiconductor epitaxial structure 90 for providing an enhanced adhesion between the ohmic contact layered unit 10 and the semiconductor epitaxial structure 90. In certain embodiments, the adhesion layer 30 has a thickness ranging from 100 Å to 500 Å, and includes a material such as Au, Cr, or Rh.
LED products X1 each having a structure as shown in
Referring to Table 1, under the same experimental conditions, the abnormality rate of the LED product X1 according to the present disclosure was significantly reduced. In other words, since the stress buffer portion 21 was included in the wire bonding layered unit 20, the bonding performance of the LED product was greatly improved.
The hardness of each of the first, second and third stress buffer layers 24a, 24b and 24c is greater than that of each of the first electrode metal layer 23 and the second electrode metal layer 25. In this embodiment, a structure containing the first stress buffer layer 24a, the first electrode metal layer 23, the second stress buffer layer 24b, the second electrode metal layer 25, and the third stress buffer layer 24c that are stacked on one another in such order may effectively absorb bonding energy and diminish possible deformation during wire bonding, so as to improve the reliability of the wire bonds in LEDs. The first stress buffer layer 24a, the second stress buffer layer 24b, and the third stress buffer layer 24c are identical to or different from each other in thickness and/or material. Each of the first electrode metal layer 23 and the second electrode metal layer 25 includes a metallic material which may be the same as or different from that of the pad portion 22. In certain embodiments, the material of the first electrode metal layer 23 is the same as that of the second electrode metal layer 25. In certain embodiments, the first electrode metal layer 23 has a thickness that is the same as that of the second electrode metal layer 25. In certain embodiments, the first stress buffer layer 24a, the second stress buffer layer 24b, and the third stress buffer layer 24c are made of the same material and have the same thickness.
The first stress buffer layer 24a, the second stress buffer layer 24b, and the third stress buffer layer 24c each includes a harder metallic material such as Ti, Ni, W, or Cr. Therefore, the stress buffer portion 21 may have a composite material, such as a Ti/Au/Ti/Au/Ti, Ti/Al/Ti/Al/Ti, Ti/Cu/Ti/Cu/Ti, Ti/AICu/Ti/AICu/Ti, Ni/Au/Ni/Au/Ni, Ni/Al/Ni/Al/Ni, Ni/Cu/Ni/Cu/Ni, Ni/AICu/Ni/AICu/Ni, W/Au/W/Au/W, W/Al/W/Al/W, W/AICu/W/AICu/W, W/Cu/W/Cu/W, Cr/Au/Cr/Au/Cr, Cr/Al/Cr/Al/Cr, Cr/Cu/Cr/Cu/Cr, Cr/AICu/Cr/AICu/Cr, Ti/Au/Ni/Al/Ni, Ti/Al/W/Cu/Cr, Ti/Cu/Cr/AICu/W, Ti/AICu/Cr/Cu/W, Ni/Au/Ti/Al/Ni, Ni/Al/W/Al/Cr, Ni/Cu/Cr/Cu/Cr or Ni/AICu/Cr/Au/Ti.
The present disclosure also provides a light-emitting device including the light-emitting diode as described above.
In conclusion, compared to the prior art, the LED according to the present disclosure is capable of successfully withstanding the bonding force or pressure exerted on the electrode structure during the wire bonding procedure by means of the stress buffer portion 21 provided in the electrode structure. Accordingly, the electrode structure of the LED according to the present disclosure provides an improved performance in resisting against crack/peeling and reducing abnormalities of the LED.
In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment(s). It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects; such does not mean that every one of these features needs to be practiced with the presence of all the other features. In other words, in any described embodiment, when implementation of one or more features or specific details does not affect implementation of another one or more features or specific details, said one or more features may be singled out and practiced alone without said another one or more features or specific details. It should be further noted that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure.
While the disclosure has been described in connection with what is(are) considered the exemplary embodiment(s), it is understood that this disclosure is not limited to the disclosed embodiment(s) but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.
Number | Date | Country | Kind |
---|---|---|---|
202210418925.2 | Apr 2022 | CN | national |