KR20220140143A - Ultraviolet semiconductor light emitting device and method of manufacturing the same - Google Patents

Abstract

Disclosed are an ultraviolet semiconductor light emitting device capable of forming an ohmic contact between a p-type AlGaN layer and a p-side electrode and at the same time preventing deterioration in light emitting characteristics, and a manufacturing method thereof. The ultraviolet semiconductor light emitting device according to the present invention comprises: a substrate; an n-type AlGaN layer formed on the substrate; an active layer formed on the n-type AlGaN layer; a p-type AlGaN layer formed on the active layer; a p-side electrode formed on the p-type AlGaN layer; and an n-side electrode electrically connected to the n-type AlGaN layer. An AlGaN contact layer containing an n-type impurity is formed between the p-type AlGaN layer and the p-side electrode.

Description

Ultraviolet semiconductor light emitting device and manufacturing method thereof

The present invention relates to an ultraviolet semiconductor light emitting device. More particularly, the present invention relates to an ultraviolet semiconductor light emitting device having excellent ohmic contact characteristics and ultraviolet light emission efficiency between a p-type semiconductor layer and an electrode.

Further, the present invention relates to a method for manufacturing an ultraviolet semiconductor light emitting device.

The ultraviolet semiconductor light emitting device emits ultraviolet rays with a wavelength of about 220 to 320 nm by recombination of electrons provided from the n-type semiconductor layer and holes provided from the p-type semiconductor layer in the active layer. It is a semiconductor light emitting device.

Ultraviolet rays emitted from the ultraviolet semiconductor light emitting device have high energy, and thus may provide a sterilization effect. Accordingly, ultraviolet semiconductor light emitting devices are being applied in various fields requiring sterilization.

1A is a cross-sectional view schematically illustrating an example of a conventional ultraviolet semiconductor light emitting device.

Referring to FIG. 1A , a conventional ultraviolet semiconductor light emitting device has a structure including a substrate 101, a buffer layer 105, an n-type semiconductor layer 110, an active layer 120, and a p-type semiconductor layer 130 from the bottom. have In the ultraviolet semiconductor light emitting device, the buffer layer 105 is generally formed of AlN, and the n-type semiconductor layer 110 and the p-type semiconductor layer 130 are generally formed of AlGaN. In general, the n-type semiconductor layer 110 is doped with Si as an n-type impurity, and the p-type semiconductor layer 130 is doped with Mg as a p-type impurity. In addition, the p-side electrode 140 is formed on the p-type semiconductor layer 130 , and the n-side electrode 150 is formed on the n-type semiconductor layer 110 .

In general, the contact between the p-type semiconductor layer 130 and the p-side electrode 140 is difficult to form an ohmic contact. This is due to the fact that p-AlGaN used as a p-type semiconductor layer has a high bandgap energy. The absence of an ohmic contact between the p-type semiconductor layer 130 and the p-side electrode 140 results in an increase in driving voltage, so an ohmic contact is formed between the p-type semiconductor layer 130 and the p-side electrode 140 . Needs to be.

1B is a cross-sectional view schematically illustrating another example of a conventional ultraviolet semiconductor light emitting device.

The UV light emitting device shown in FIG. 1B has a substrate 101, a buffer layer 105, an n-type semiconductor layer 110, an active layer 120, and a p-type semiconductor layer 130, similarly to the UV light emitting device shown in FIG. 1A. has a structure comprising In the ultraviolet semiconductor light emitting device, the buffer layer 105 is generally formed of AlN, and the n-type semiconductor layer 110 and the p-type semiconductor layer 130 are generally formed of AlGaN. In general, the n-type semiconductor layer 110 is doped with Si as an n-type impurity, and the p-type semiconductor layer 130 is doped with Mg as a p-type impurity. In addition, an n-side electrode 150 is formed on the n-type semiconductor layer 110 .

However, in the semiconductor light emitting device illustrated in FIG. 1B , the contact layer 160 is additionally formed on the p-type semiconductor layer 130 , and the p-side electrode 140 is formed on the contact layer 160 . The contact layer 160 is a semiconductor layer having a smaller bandgap energy than p-AlGaN, and is generally formed of p-GaN. The thickness of the p-GaN-based contact layer 160 is about 5 to 300 nm.

However, p-GaN has a high absorption rate for ultraviolet rays. Therefore, an ultraviolet light emitting device to which a p-GaN-based contact layer is applied can exhibit a low driving voltage, but has a disadvantage in that the ultraviolet light emitting efficiency is low due to a high absorption rate for ultraviolet rays.

Korean Patent Publication No. 10-1697462 (2017.01.18. Announcement)

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultraviolet semiconductor light emitting device capable of forming an ohmic contact between a p-type AlGaN layer and a p-side electrode and at the same time preventing deterioration of ultraviolet light emission characteristics.

Another object of the present invention is to provide a method of manufacturing an ultraviolet semiconductor light emitting device capable of forming an ohmic contact between a p-type AlGaN layer and a p-side electrode.

An ultraviolet semiconductor light emitting device according to an embodiment of the present invention for solving the above problems includes a substrate, an AlN layer formed on the substrate, an n-type AlGaN layer formed on the AlN layer, an active layer formed on the n-type AlGaN layer, and the and a p-type AlGaN layer formed on the active layer, a p-side electrode formed on the p-type AlGaN layer, and an n-side electrode electrically connected to the n-type AlGaN layer. Characteristically, in the ultraviolet semiconductor light emitting device according to an embodiment of the present invention, an AlGaN contact layer including an n-type impurity is formed between the p-type AlGaN layer and the p-side electrode.

As a result of forming an AlGaN contact layer including an n-type impurity between the p-type AlGaN layer and the p-side electrode, a low forward driving voltage can be exhibited and high luminous efficiency can be exhibited.

The AlGaN contact layer is preferably formed to have a thickness of 1.5 nm to 4 nm. In this case, the ultraviolet semiconductor light emitting device may exhibit a forward voltage of 6.5 V to 6.7 V under a forward current of 60 mA.

In the AlGaN contact layer, the doping concentration of the n-type impurity may be 1×10 ¹⁹ particles/cm ³ or more, preferably 1×10 ¹⁹ to 4×10 ²⁰ particles/cm ³ .

In at least a portion of the AlGaN contact layer, the concentration of the n-type impurity may be higher than the concentration of the p-type impurity.

At least a portion of the AlGaN contact layer may include only n-type impurities.

In the AlGaN contact layer, the Al molar ratio, [Al]/([Al]+[Ga]) may be 0.1 to 0.55 (here, [Al] and [Ga] are mol% of Al and Ga).

At least one layer of a current spreading layer formed between the AlGaN contact layer and the p-side electrode and an electron blocking layer formed between the active layer and the p-type AlGaN layer may be further included.

An ultraviolet semiconductor light emitting device according to another embodiment of the present invention for solving the above problems is a p-type AlGaN layer, a p-side electrode formed under the p-type AlGaN layer, an active layer formed on the p-type AlGaN layer, and on the active layer An n-type AlGaN layer is formed, and an n-side electrode is formed on the n-type AlGaN layer, and an AlGaN contact layer including an n-type impurity is formed between the p-type electrode and the p-type AlGaN layer.

The AlGaN contact layer is preferably formed to have a thickness of 1.5 nm to 4 nm. In this case, the ultraviolet semiconductor light emitting device may exhibit a forward voltage of 6.5 V to 6.7 V under a forward current of 60 mA.

In the AlGaN contact layer, the doping concentration of the n-type impurity may be 1×10 ¹⁹ particles/cm ³ or more, preferably 1×10 ¹⁹ to 4×10 ²⁰ particles/cm ³ .

In at least a portion of the AlGaN contact layer, the concentration of the n-type impurity may be higher than the concentration of the p-type impurity.

At least a portion of the AlGaN contact layer may include only n-type impurities.

In the AlGaN contact layer, [Al]/([Al]+[Ga]) may be 0.1 to 0.55 (here, [Al] and [Ga] are mol% of Al and Ga).

At least one layer of a current spreading layer formed between the AlGaN contact layer and the p-side electrode and an electron blocking layer formed between the active layer and the p-type AlGaN layer may be further included.

The method for manufacturing an ultraviolet semiconductor light emitting device according to an embodiment of the present invention for solving the above problems comprises the steps of sequentially forming an AlN layer, an n-type AlGaN layer, an active layer, and a p-type AlGaN layer on a substrate, on the p-type AlGaN layer forming an AlGaN contact layer doped with an n-type impurity, exposing a portion of the n-type AlGaN layer through etching, and forming a p-side electrode on the AlGaN contact layer doped with the n-type impurity; and forming an n-side electrode to be electrically connected to the n-type AlGaN layer.

The AlGaN contact layer may be formed to a thickness of 1.5 nm to 4 nm.

When forming the AlGaN contact layer, the doping concentration of the n-type impurity is adjusted to 1×10 ¹⁹ to 4×10 ²⁰ pieces/cm ³ , and [Al]/([Al]+[Ga]) from 0.1 to 0.55 (here, [Al] and [Ga] are mol% of Al and Ga).

When forming the AlGaN contact layer, p-type impurities may be doped together with n-type impurities.

By further forming a current dispersing layer on the AlGaN contact layer to form a p-side electrode on the current dispersing layer, or by additionally forming an electron blocking layer on the active layer, the p-type electrode is formed on the electron blocking layer An AlGaN layer can be formed.

The method for manufacturing an ultraviolet semiconductor light emitting device according to another embodiment of the present invention for solving the above problems includes sequentially forming an AlN layer, an n-type AlGaN layer, an active layer, and a p-type AlGaN layer on a substrate, the p-type AlGaN layer forming an AlGaN contact layer doped with an n-type impurity thereon, forming a p-side electrode on the AlGaN contact layer doped with an n-type impurity, the substrate using a laser lift-off process or a wet etching process; and exposing the n-type AlGaN layer by removing the AlN layer, and forming an n-side electrode on the n-type AlGaN layer.

The AlGaN contact layer may be formed to a thickness of 1.5 nm to 4 nm.

When forming the AlGaN contact layer, the doping concentration of the n-type impurity is adjusted to 1×10 ¹⁹ to 4×10 ²⁰ pieces/cm ³ , and [Al]/([Al]+[Ga]) from 0.1 to 0.55 (here, [Al] and [Ga] are mol% of Al and Ga).

When forming the AlGaN contact layer, p-type impurities may be doped together with n-type impurities.

By further forming a current dispersing layer on the AlGaN contact layer to form a p-side electrode on the current dispersing layer, or by additionally forming an electron blocking layer on the active layer, the p-type electrode is formed on the electron blocking layer An AlGaN layer can be formed.

According to the method for manufacturing an ultraviolet semiconductor light emitting device according to the present invention, an AlGaN contact layer including an n-type impurity is formed on the p-type AlGaN layer, and then a p-side electrode is formed. Through this, the ultraviolet semiconductor light emitting device according to the present invention can form a good ohmic contact between the AlGaN contact layer and the p-side electrode, and as a result, a low forward driving voltage can be exhibited.

In addition, the ultraviolet semiconductor light emitting device according to the present invention can exhibit a low forward driving voltage, and can exhibit relatively high luminous efficiency compared to the case where a conventional p-GaN contact layer is applied.

Effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the detailed description below.

1A schematically shows an example of a conventional ultraviolet semiconductor light emitting device.
1B schematically shows another example of a conventional ultraviolet semiconductor light emitting device.
2A schematically shows an ultraviolet semiconductor light emitting device according to a first embodiment of the present invention.
2B schematically shows an ultraviolet semiconductor light emitting device according to a second embodiment of the present invention.
3A schematically shows an ultraviolet semiconductor light emitting device according to a third embodiment of the present invention.
3B schematically shows an ultraviolet semiconductor light emitting device according to a fourth embodiment of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be embodied in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout. The sizes and relative sizes of layers and regions in the drawings may be exaggerated for clarity of description.

References to an element or layer as being “on” or “on” another element or layer include both those directly on top of the other element or layer as well as intervening other layers or other elements. On the other hand, reference to an element "directly on" or "directly on" indicates that there are no intervening elements or layers intervening. In addition, when it is described that a component is "connected", "coupled" or "connected" to another component, the components may be directly connected or connected to each other, but other components are "connected" between each component. It should be understood that each component may be “interposed” or “connected”, “coupled” or “connected” through another component.

Spatially relative terms "below", "lower", "above", "upper", etc. facilitate the correlation between one element or components and another element or components as shown in the drawings. can be used to describe Spatially relative terms should be understood as terms including different orientations of the device during use or operation in addition to the orientation shown in the drawings. For example, when an element shown in the figures is turned over, an element described as "below" another element may be placed "above" the other element. Accordingly, the exemplary term “below” may include both directions below and above.

The terminology used herein is for the purpose of describing the embodiments, and thus is not intended to limit the present invention. In this specification, the singular also includes the plural, unless specifically stated otherwise in the phrase. As used herein, “comprises” and/or “comprising” does not exclude the presence or addition of one or more other components, steps, acts and/or elements in a recited element, step, operation and/or element. .

Hereinafter, an ultraviolet semiconductor light emitting device and a manufacturing method thereof according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2A schematically shows an ultraviolet semiconductor light emitting device according to a first embodiment of the present invention.

Referring to FIG. 2A , the ultraviolet semiconductor light emitting device according to the first embodiment includes a substrate 201 , an AlN layer 205 , an n-type AlGaN layer 210 , an active layer 220 , a p-type AlGaN layer 230 , and p It includes a side electrode 250 and an n-side electrode 260 . An AlGaN contact layer 240 is formed between the p-type AlGaN layer and the p-side electrode.

The substrate 201 may be, for example, a growth substrate such as a sapphire substrate. In addition, the substrate 201 may be a silicon substrate, a GaN substrate, an AlN substrate, or the like. In addition, the substrate 201 may use a patterned substrate such as PSS (Patterned Sapphire Substrate).

An AlN layer 205 is formed on the substrate 201 . The AlN layer 205 serves as a base layer for forming AlGaN semiconductor layers. The AlN layer 205 may be formed of a single crystal or a polycrystal. The thickness of the AlN layer 205 may be about 1 to 3 μm, but is not limited thereto. Preferably, the AlN layer 205 may be formed of a single crystal in order to improve the crystal quality of the semiconductor layers thereon.

In addition, on the AlN layer 205, more specifically, between the AlN layer 205 and the n-type AlGaN layer 210, for the purpose of improving the crystal quality of the light emitting device, an un-doped AlGaN layer (not shown) ) may be further formed.

An n-type AlGaN layer 210 is formed on the AlN layer 205 . The n-type AlGaN layer 210 is formed as a single layer or multiple layers of AlGaN, and is doped with an n-type impurity such as Si or Ge.

The active layer 220 is formed on the n-type AlGaN layer 210 . The active layer 220 may be formed in a multi-quantum wells (MQWs) structure in which well layers and barrier layers are alternately stacked. As electrons provided from the n-type AlGaN layer 210 and holes provided from the p-type AlGaN layer 230 recombine in the well layers of the active layer 220 , ultraviolet light may be emitted. The active layer 220 has, for example, an Al molar ratio ([Al]/([Al]+[Ga]), where [Al] and [Ga] are Al and Ga mol%) with an Al content such as 0.35 to 0.45. The low AlGaN well layer and the AlGaN barrier layer having a relatively high Al content compared to the well layer such as 0.55 to 0.65 in Al molar ratio may be alternately stacked, but the present invention is not limited thereto. As long as it can emit ultraviolet light through recombination of electrons provided in 210 and holes provided in the p-type AlGaN layer 230 , it may be applied without limitation.

When the active layer 220 is formed based on the AlGaN layer to emit ultraviolet light, the n-type semiconductor layer and the p-type semiconductor layer on the upper and lower portions of the active layer 220 are also formed of an AlGaN layer in terms of lowering light absorption. preferred in For example, when the active layer is formed on the basis of the AlGaN layer, if the n-type semiconductor layer and the p-type semiconductor layer are formed of n-type GaN and p-type GaN, a large amount of ultraviolet rays formed in the active layer and the n-type semiconductor layer By absorption in the p-type semiconductor layer, the luminous efficiency may be reduced. For this reason, in the present invention, the n-type semiconductor layer is formed of n-type AlGaN and the p-type semiconductor layer is formed of p-type AlGaN.

The p-type AlGaN layer 230 is formed on the active layer 220 . The p-type AlGaN layer 230 is formed of AlGaN in a single layer or in multiple layers. The p-type AlGaN layer 230 is doped with a p-type impurity such as Mg.

In order to prevent electrons provided from the n-type AlGaN layer 210 from overflowing the p-type AlGaN layer 230 beyond the active layer 220 , an electron blocking layer is disposed between the active layer 220 and the p-type AlGaN layer 230 . An Electron Blocking Layer (EBL) 225 may be additionally formed. The electron blocking layer 225 may be formed to have a higher bandgap energy than the barrier layer of the active layer. For example, the electron blocking layer 225 may be formed of AlGaN having a higher Al content than the barrier layer of the active layer.

A p-side electrode 250 is formed on the p-type AlGaN layer 230 . In addition, an n-side electrode 260 is formed on the n-type AlGaN layer 210 . FIG. 2A shows an example in which a portion of the n-type AlGaN layer 210 is exposed and an n-side electrode 260 is formed on the exposed n-type AlGaN layer 210 . However, the present invention is not limited thereto, and for example, the n-side electrode may be formed on the same plane as the p-side electrode through a via hole. Each of the p-side electrode 250 and the n-side electrode 260 may be formed of a metal having excellent electrical conductivity, such as Cr, Mo, Cu, Al, or graphene.

Meanwhile, referring to FIG. 2A , in the ultraviolet semiconductor light emitting device according to the first embodiment, an AlGaN contact layer 240 is formed between the p-type AlGaN layer 230 and the p-side electrode 250 . In the present invention, an n-type impurity is included in the AlGaN contact layer 240 . Preferably, the AlGaN contact layer 240 may be formed of an n-type AlGaN layer 240 .

As described above, in the case of an ultraviolet semiconductor light emitting device to which a conventional p-GaN contact layer is applied, the p-GaN bandgap energy is lower than that of p-AlGaN, so that the p-side electrode and the ohmic contact are well formed. Therefore, it can represent a low forward voltage. However, due to the inherent UV absorption characteristics of p-GaN, the UV semiconductor light emitting device to which the p-GaN contact layer is applied has a disadvantage in that the UV light emission efficiency is low.

In contrast, in the ultraviolet semiconductor light emitting device according to the present invention, an AlGaN contact layer 240 containing n-type impurities is formed between the p-type AlGaN layer 230 and the p-side electrode 250 . The AlGaN contact layer 240 including the n-type impurity may have a smaller work function than the undoped AlGaN layer or the p-type AlGaN layer due to doping of the n-type impurity, and thus the AlGaN contact layer ( A good ohmic contact may be formed between the 240 ) and the p-side electrode 250 to indicate a low forward voltage.

Furthermore, in the case of the AlGaN semiconductor, which is the basis of the ultraviolet semiconductor light emitting device, since the ultraviolet absorption rate is lower than that of the GaN semiconductor, the deterioration of the ultraviolet light emitting efficiency can be reduced or prevented.

Meanwhile, an n-type GaN contact layer may be considered between the p-type AlGaN layer 230 and the p-side electrode 250 . However, in the case of the n-type GaN contact layer, the forward voltage characteristic can be improved, but it is difficult to achieve high UV light emission efficiency due to the high UV absorption rate of GaN itself. Therefore, considering both the forward voltage characteristic and the ultraviolet light emission efficiency, it can be considered that the AlGaN contact layer 240 including the n-type impurity is preferably disposed between the p-type AlGaN layer 230 and the p-side electrode 250 . have.

The AlGaN contact layer 240 may be formed of, for example, an AlGaN layer doped with only n-type impurities. As another example, the AlGaN contact layer 240 may be formed of an AlGaN layer doped with both n-type impurities and p-type impurities. The p-type impurity may be intentionally included in the AlGaN contact layer 240 or may be included unintentionally due to a so-called memory effect.

As another example, in at least a portion of the AlGaN contact layer 240 , the concentration of the n-type impurity may be higher than the concentration of the p-type impurity. For example, in the AlGaN contact layer 240, the concentration of the n-type impurity is lower than that of the p-type impurity in the portion adjacent to the p-type AlGaN layer 230 (for example, the lower half in the thickness direction), and the p-type electrode ( 250), the concentration of the n-type impurity may be higher than the concentration of the p-type impurity in the portion (eg, the upper half in the thickness direction).

As another example, at least a portion of the AlGaN contact layer 240 may include only n-type impurities. For example, the AlGaN contact layer 240 includes both n-type impurities and p-type impurities in the portion adjacent to the p-type AlGaN layer 230 (eg, the lower half in the thickness direction), and is formed on the p-side electrode 250 . The adjacent portion (eg, the upper half in the thickness direction) may include only n-type impurities.

In some examples, the concentration of the n-type impurity in the AlGaN contact layer 240 may be substantially constant in the thickness direction. In some other examples, the concentration of the n-type impurity in the AlGaN contact layer 240 may gradually increase from the bottom to the top.

Meanwhile, the AlGaN contact layer 240 is preferably formed to a thickness of 1.5 to 4 nm, and more preferably formed to a thickness of 1.5 to 3 nm. When the thickness of the AlGaN contact layer 240 exceeds 4 nm, the forward voltage characteristic may be deteriorated. Conversely, in order to set the thickness of the AlGaN contact layer 240 to 1.5 nm, very high process accuracy may be required.

As a result of the experiment, when the AlGaN contact layer 240 had a thickness of 1.5 to 4 nm, more preferably 1.5 to 3 nm, the UV semiconductor light emitting device could exhibit a forward voltage of 6.5 to 6.7 V under a forward current of 60 mA.

Also, in the AlGaN contact layer 240 , the doping concentration of the n-type impurity may be 1×10 ¹⁹ particles/cm ³ or more, and preferably 1×10 ¹⁹ to 4×10 ²⁰ particles/cm ³ . The doping concentration of the n-type impurity means an average doping concentration. The doping concentration of 1×10 ¹⁹ pieces/cm ³ or more of the n-type impurity goes beyond the unavoidable doping of the n-type impurity due to contamination and the like, and can be viewed as a result of intentionally adding the n-type impurity. When the doping concentration of the n-type impurity is less than 1×10 ¹⁹ pieces/cm ³ , a sufficient ohmic contact with the p-side electrode 250 may not be formed, so that forward voltage characteristics may be deteriorated. Conversely, when the doping concentration of the n-type impurity exceeds 4×10 ²⁰ pieces/cm ³ , an n-type AlGaN layer having an excessively high doping concentration of the n-type impurity is formed on the p-type AlGaN layer 230 , so that the ultraviolet light emitting device may not work properly.

In addition, in the AlGaN contact layer 240 , the Al molar ratio, [Al]/([Al]+[Ga]) may be 0.1 to 0.55 (here, [Al] and [Ga] are mol% of Al and Ga). have. When [Al]/([Al]+[Ga]) is less than 0.1, the composition of the AlGaN contact layer becomes similar to that of GaN due to insufficient Al content, and the UV absorption rate may be increased. Conversely, when [Al]/([Al]+[Ga]) exceeds 0.55, the resistance and bandgap energy may become excessively high and the forward voltage characteristic may be deteriorated.

The n-type AlGaN layer 210 , the active layer 220 , the p-type AlGaN layer 230 , and the AlGaN contact layer 240 constituting the ultraviolet semiconductor light emitting device according to the first embodiment of the present invention are MOCVD (Metal Organic Chemical Vapor). Deposition) may be formed at a deposition temperature of about 900 ~ 1200 ℃ by a known method such as.

More specifically, the ultraviolet semiconductor light emitting device according to the first embodiment of the present invention may be manufactured by the following process.

First, an AlN layer 205 , an n-type AlGaN layer 210 , an active layer 220 , and a p-type AlGaN layer 230 are sequentially formed on a substrate 201 by a method such as MOCVD.

Next, an AlGaN contact layer 240 doped with an n-type impurity such as Si is formed on the p-type AlGaN layer 230 . In this case, as described above, the AlGaN contact layer 240 is preferably formed to a thickness of 1.5 nm to 4 nm, and more preferably formed to a thickness of 1.5 nm to 3 nm.

In addition, when forming the AlGaN contact layer 240 , the doping concentration of the n-type impurity is adjusted to 1×10 ¹⁹ to 4×10 ²⁰ pieces/cm ³ , and [Al]/([Al]+[Ga]) can be adjusted to 0.1 to 0.55 (here, [Al] and [Ga] are mol% of Al and Ga).

In addition, when forming the AlGaN contact layer 240 , p-type impurities may be intentionally or unintentionally doped together with n-type impurities.

Thereafter, a portion of the n-type AlGaN layer 210 is exposed in the form shown in FIG. 2A through, for example, mesa etching. Thereafter, the p-side electrode 250 is formed on the AlGaN contact layer 240 , and the n-side electrode 260 is formed to be electrically connected to the exposed n-type AlGaN layer 210 . For example, the n-side electrode 260 may be formed on the exposed n-type AlGaN layer 210 as shown in FIG. 2A . As another example, a via hole is formed so that the n-type AlGaN layer is exposed from the p-type AlGaN layer, an insulator is formed on the wall surface of the via hole and a part of the p-type AlGaN layer to prevent short circuit, and then an insulating layer inside the via hole and on the p-type AlGaN layer. An n-side electrode may be formed by forming a metal layer thereon.

2B schematically shows an ultraviolet semiconductor light emitting device according to a second embodiment of the present invention.

Referring to FIG. 2B , the UV semiconductor light emitting device according to the second embodiment has a substrate 201 , an AlN layer 205 , an n-type AlGaN layer 210 , and an active layer, like the UV semiconductor light emitting device according to the first embodiment. 220 , a p-type AlGaN layer 230 , a p-side electrode 250 , and an n-side electrode 260 .

Also, in the ultraviolet semiconductor light emitting device according to the second embodiment, an AlGaN contact layer 240 including n-type impurities is formed between the p-type AlGaN layer 230 and the p-side electrode 250 . Preferably, the AlGaN contact layer 240 may be formed of an n-type AlGaN layer 240 .

The AlGaN contact layer 240 may be formed of an AlGaN layer doped with only n-type impurities or an AlGaN layer doped with both n-type impurities and p-type impurities. As another example, in at least a portion of the AlGaN contact layer 240 , the concentration of the n-type impurity may be higher than the concentration of the p-type impurity. As another example, at least a portion of the AlGaN contact layer 240 may include only n-type impurities.

Also, the concentration of the n-type impurity in the AlGaN contact layer 240 may be substantially constant in the thickness direction. Alternatively, the concentration of the n-type impurity in the AlGaN contact layer 240 may gradually increase from the bottom to the top.

The AlGaN contact layer 240 is preferably formed to a thickness of 1.5 to 4 nm, and more preferably formed to a thickness of 1.5 to 3 nm. When the above thickness condition is satisfied, the ultraviolet semiconductor light emitting device may exhibit a forward voltage of 6.5 V to 6.7 V under the condition of a forward current of 60 mA.

Also, in the AlGaN contact layer 240 , the doping concentration of the n-type impurity may be 1×10 ¹⁹ particles/cm ³ or more, preferably 1×10 ¹⁹ to 4×10 ²⁰ particles/cm ³ .

Also, in the AlGaN contact layer 240 , [Al]/([Al]+[Ga]) may be 0.1 to 0.55 (here, [Al] and [Ga] are mol% of Al and Ga).

Meanwhile, referring to FIG. 2B , in the ultraviolet semiconductor light emitting device according to the second embodiment, a current spreading layer 270 is additionally formed between the AlGaN contact layer 240 and the p-side electrode 250 .

The current spreading layer 270 may improve the current dispersion characteristics of the p-type AlGaN layer 230 and the AlGaN contact layer 240 to contribute to uniform light emission throughout the active layer.

The current spreading layer 270 may be formed of a transparent conductive oxide (TCO), such as indium tin oxide (ITO) or fluorine-doped tin oxide (FTO). However, the current dispersing layer 270 is not necessarily formed of a transparent conductive oxide, and the current dispersing layer 270 may be formed of graphene, and PEDOT:PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) It may be formed of a conductive polymer such as

3A schematically shows an ultraviolet semiconductor light emitting device according to a third embodiment of the present invention.

Referring to FIG. 3A , the ultraviolet semiconductor light emitting device according to the third embodiment includes an n-type AlGaN layer 310 , an active layer 320 , and a p-type AlGaN layer 330 , and a p-type AlGaN layer 330 from below. , an active layer 320 and an n-type AlGaN layer 310 are formed. A p-side electrode 350 is formed below the p-type AlGaN layer 330 , and an n-side electrode 360 is formed above the n-type AlGaN layer 310 . Also, an electron blocking layer 325 may be additionally formed between the active layer 320 and the p-type AlGaN layer 330 .

Meanwhile, also in the case of the ultraviolet semiconductor light emitting device according to the third embodiment, the AlGaN contact layer 340 including the n-type impurity is formed between the p-side electrode 350 and the p-type AlGaN layer 330 . Preferably, the AlGaN contact layer 340 may be formed of an n-type AlGaN layer 340 .

The AlGaN contact layer 340 may be formed of an AlGaN layer doped with only n-type impurities or an AlGaN layer doped with both n-type impurities and p-type impurities. As another example, in at least a portion of the AlGaN contact layer 340 , the concentration of the n-type impurity may be higher than the concentration of the p-type impurity. As another example, at least a portion of the AlGaN contact layer 340 may include only n-type impurities.

Also, the concentration of the n-type impurity in the AlGaN contact layer 340 may be substantially constant in the thickness direction. Alternatively, the concentration of the n-type impurity in the AlGaN contact layer 340 may gradually increase from the bottom to the top.

The AlGaN contact layer 340 is preferably formed to a thickness of 1.5 to 4 nm, and more preferably formed to a thickness of 1.5 to 3 nm. When the above thickness condition is satisfied, the ultraviolet semiconductor light emitting device may exhibit a forward voltage of 6.5 V to 6.7 V under the condition of a forward current of 60 mA.

In addition, in the AlGaN contact layer 340 , the doping concentration of the n-type impurity may be 1×10 ¹⁹ particles/cm ³ or more, preferably 1×10 ¹⁹ to 4×10 ²⁰ particles/cm ³ .

Also, in the AlGaN contact layer 340 , [Al]/([Al]+[Ga]) may be 0.1 to 0.55 (here, [Al] and [Ga] are mol% of Al and Ga).

The ultraviolet semiconductor light emitting device shown in FIG. 3A has a so-called vertical structure. The ultraviolet semiconductor light emitting device shown in FIG. 3A may be manufactured, for example, by the following method.

First, an AlN layer, an n-type AlGaN layer 310, an active layer 320, a p-type AlGaN layer 330, and an AlGaN contact layer 340 doped with n-type impurities are formed on a growth substrate such as a sapphire substrate by MOCVD. After sequentially forming, the p-side electrode 350 is formed.

Thereafter, the growth substrate and the AlN layer are removed using a laser lift off (LLO) process, a wet etching process, etc. to form the n-side electrode 360 .

3B schematically shows an example of an ultraviolet semiconductor light emitting device according to a fourth embodiment of the present invention.

Referring to FIG. 3B , the ultraviolet semiconductor light emitting device according to the fourth embodiment includes an n-type AlGaN layer 310 , an active layer 320 , and a p-type AlGaN layer 330 , and a p-type AlGaN layer 330 from below. , an active layer 320 and an n-type AlGaN layer 310 are formed. A p-side electrode 350 is formed below the p-type AlGaN layer 330 , and an n-side electrode 360 is formed above the n-type AlGaN layer 310 . Also, an electron blocking layer 325 may be additionally formed between the active layer 320 and the p-type AlGaN layer 330 .

An AlGaN contact layer 340 including n-type impurities is formed between the p-side electrode 350 and the p-type AlGaN layer 330 . Preferably, the AlGaN contact layer 340 may be formed of an n-type AlGaN layer 340 .

The AlGaN contact layer 340 may be formed of an AlGaN layer doped with only n-type impurities or an AlGaN layer doped with both n-type impurities and p-type impurities. As another example, in at least a portion of the AlGaN contact layer 340 , the concentration of the n-type impurity may be higher than the concentration of the p-type impurity. As another example, at least a portion of the AlGaN contact layer 340 may include only n-type impurities.

Also, the concentration of the n-type impurity in the AlGaN contact layer 340 may be substantially constant in the thickness direction. Alternatively, the concentration of the n-type impurity in the AlGaN contact layer 340 may gradually increase from the bottom to the top.

The AlGaN contact layer 340 is preferably formed to a thickness of 1.5 to 4 nm, and more preferably formed to a thickness of 1.5 to 3 nm. When the above thickness condition is satisfied, the ultraviolet semiconductor light emitting device may exhibit a forward voltage of 6.5 V to 6.7 V under the condition of a forward current of 60 mA.

In addition, in the AlGaN contact layer 340 , the doping concentration of the n-type impurity may be 1×10 ¹⁹ particles/cm ³ or more, preferably 1×10 ¹⁹ to 4×10 ²⁰ particles/cm ³ .

Also, in the AlGaN contact layer 340 , [Al]/([Al]+[Ga]) may be 0.1 to 0.55 (here, [Al] and [Ga] are mol% of Al and Ga).

Meanwhile, referring to FIG. 3B , in the ultraviolet semiconductor light emitting device according to the fourth embodiment, in order to improve the current dissipation characteristics of the p-type AlGaN layer 330 and the AlGaN contact layer 340 , the AlGaN contact layer 340 and A current spreading layer 370 is additionally formed between the p-side electrodes 350 .

The current spreading layer 370 may be formed of a transparent conductive oxide, graphene, a conductive polymer, or the like.

Example

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is presented as a preferred example of the present invention and cannot be construed as limiting the present invention in any sense. Content not described here will be omitted because it can be technically inferred sufficiently by a person skilled in the art.

An ultraviolet semiconductor light emitting device specimen according to Comparative Example 1 and a UV semiconductor light emitting device specimen according to Example 1 were prepared. The UV semiconductor light emitting device specimen according to Comparative Example 1 and the UV semiconductor specimen according to Example 1 were prepared in the same manner except that the chip size and the composition of the contact layer were different.

In the case of the ultraviolet semiconductor light emitting device according to Comparative Example 1, the contact layer between the p-type AlGaN layer and the p-side electrode was formed of p-type GaN having an average Mg doping concentration of 1x10 ²⁰ pieces/cm ³ , and the ultraviolet light according to Example 1 In the case of the semiconductor light emitting device, the contact layer between the p-type AlGaN layer and the p-side electrode was formed of n-type AlGaN (Al molar ratio: 0.4) having an average Si doping concentration of 1× ^{10 20} pieces/cm ³ at 950°C.

The UV luminous efficiency was evaluated by Wall Plug Efficiency (WPE), which means the ratio of the input power of the electric energy applied to the light emitting device to the output power of the emitted UV light.

[Table 1]

Referring to Table 1, it can be seen that the UV semiconductor light emitting device specimen according to Comparative Example 1 showed a relatively low forward voltage, but the WPE luminous efficiency was only about 2.3%. In contrast, in the case of the ultraviolet semiconductor light emitting device specimen according to Example 1, the forward voltage was slightly higher than that of Comparative Example 1, but the WPE luminous efficiency was about 5%, which was about twice higher than that of Comparative Example 1.

An ultraviolet semiconductor light emitting device was manufactured under the same conditions as in Example 1 except for the thickness of the AlGaN contact layer between the p-type AlGaN layer and the p-side electrode, and the forward voltage was measured, as shown in Table 2.

In the UV semiconductor light emitting device specimens according to Examples 2 and 3, as in the UV semiconductor light emitting device specimen according to Example 1, the AlGaN contact layer had an average Si doping concentration of 1× ^{10 20} pieces/cm ³ n-type AlGaN ( Al molar ratio: 0.4).

[Table 2]

Comparing Example 1 and Example 2 in Table 2, it can be seen that the forward voltage (Vf) decreases as the thickness of the AlGaN contact layer including the n-type impurity increases from 1.5 nm to 3 nm. However, it can be seen that the forward voltage Vf rather increases as the thickness of the AlGaN contact layer including the n-type impurity increases from 3 nm to 4.5 nm. From the results according to Table 2, it can be seen that the thickness of the AlGaN contact layer containing the n-type impurity is preferably less than 4.5 nm, more preferably 1.5 to 4 nm, and most preferably 1.5 to 3 nm.

As described above, the ultraviolet semiconductor light emitting device according to the present invention includes an AlGaN contact layer including an n-type impurity between the p-type AlGaN layer and the p-side electrode, thereby exhibiting a low forward driving voltage and high luminous efficiency. can

Although the above description has been focused on the embodiments of the present invention, various changes or modifications may be made at the level of those skilled in the art. Such changes and modifications can be said to belong to the present invention without departing from the scope of the present invention. Accordingly, the scope of the present invention should be judged by the claims described below.

201: substrate 205: AlN layer
210, 310: n-type AlGaN layer 220, 320: active layer
225, 325: electron blocking layer 230, 330: p-type AlGaN layer
240, 340: AlGaN contact layer 250, 350: p-side electrode
260, 360: n-side electrode 270, 370: current distribution layer

Claims (15)

Board;
an AlN layer formed on the substrate;
an n-type AlGaN layer formed on the AlN layer;
an active layer formed on the n-type AlGaN layer;
a p-type AlGaN layer formed on the active layer;
a p-side electrode formed on the p-type AlGaN layer; and
an n-side electrode electrically connected to the n-type AlGaN layer;
An AlGaN contact layer including an n-type impurity is formed between the p-type AlGaN layer and the p-side electrode.
p-type AlGaN layer;
a p-side electrode formed under the p-type AlGaN layer;
an active layer formed on the p-type AlGaN layer;
an n-type AlGaN layer formed on the active layer;
an n-side electrode formed on the n-type AlGaN layer;
An ultraviolet semiconductor light emitting device, characterized in that an AlGaN contact layer including an n-type impurity is formed between the p-side electrode and the p-type AlGaN layer.
3. The method of claim 1 or 2,
The AlGaN contact layer is an ultraviolet semiconductor light emitting device, characterized in that formed to a thickness of 1.5nm to 4nm.
4. The method of claim 3,
The ultraviolet semiconductor light emitting device, characterized in that it exhibits a forward voltage of 6.5 ~ 6.7V under the forward current 60mA condition.
3. The method of claim 1 or 2,
In the AlGaN contact layer, the doping concentration of the n-type impurity is 1×10 ¹⁹ to 4×10 ²⁰ pieces/cm ³ An ultraviolet semiconductor light emitting device, characterized in that.
3. The method of claim 1 or 2,
In the AlGaN contact layer, the concentration of the n-type impurity is higher than the concentration of the p-type impurity in at least part of the UV semiconductor light emitting device.
3. The method of claim 1 or 2,
The AlGaN contact layer is an ultraviolet semiconductor light emitting device, characterized in that at least a portion includes only n-type impurities.
3. The method of claim 1 or 2,
In the AlGaN contact layer, [Al]/([Al] + [Ga]) is 0.1 to 0.55 (here, [Al], [Ga] is Al, Ga mol%) UV semiconductor light emitting device, characterized in that .
3. The method of claim 1 or 2,
a current spreading layer formed between the AlGaN contact layer and the p-side electrode; and
an electron blocking layer formed between the active layer and the p-type AlGaN layer;
Ultraviolet semiconductor light emitting device, characterized in that it further comprises at least one layer.
sequentially forming an AlN layer, an n-type AlGaN layer, an active layer, and a p-type AlGaN layer on a substrate;
forming an AlGaN contact layer doped with n-type impurities on the p-type AlGaN layer;
exposing a portion of the n-type AlGaN layer through etching; and
and forming a p-side electrode on the AlGaN contact layer doped with the n-type impurity, and forming an n-side electrode to be electrically connected to the n-type AlGaN layer.
sequentially forming an AlN layer, an n-type AlGaN layer, an active layer, and a p-type AlGaN layer on a substrate;
forming an AlGaN contact layer doped with n-type impurities on the p-type AlGaN layer;
forming a p-side electrode on the AlGaN contact layer doped with the n-type impurity;
exposing the n-type AlGaN layer by removing the substrate and the AlN layer using a laser lift-off process or a wet etching process; and
and forming an n-side electrode on the n-type AlGaN layer.
12. The method of claim 10 or 11,
When the AlGaN contact layer is formed, the method for manufacturing an ultraviolet semiconductor light emitting device, characterized in that it is formed to a thickness of 1.5 nm to 4 nm.
12. The method of claim 10 or 11,
When forming the AlGaN contact layer, the doping concentration of the n-type impurity is adjusted to 1×10 ¹⁹ to 4×10 ²⁰ pieces/cm ³ , and [Al]/([Al]+[Ga]) from 0.1 to 0.55 (Here, [Al] and [Ga] are Al and Ga mol%), characterized in that the UV semiconductor light emitting device manufacturing method.
12. The method of claim 10 or 11,
When the AlGaN contact layer is formed, a p-type impurity is doped together with an n-type impurity.
12. The method of claim 10 or 11,
By further forming a current dispersing layer on the AlGaN contact layer to form a p-side electrode on the current dispersing layer,
An electron blocking layer is additionally formed on the active layer to form the p-type AlGaN layer on the electron blocking layer.

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