KR20210137959A - Light emitting device and gas sensor using the same - Google Patents

Abstract

The present invention relates to an ultraviolet light emitting element. According to the present invention, the light emitting element includes a substrate, a first conductivity type semiconductor layer disposed on the substrate, a second conductivity type semiconductor layer disposed on the first conductivity type semiconductor layer, and an active layer emitting an ultraviolet wavelength disposed between the first conductivity type semiconductor layer and the two conductive semiconductor layer. The active layer has a quantum well structure including a well layer and a barrier layer, the well layer and the barrier layer are semiconductor layers having a composition formula of AlxGa1-xN (0 <= x <= 1), and the Al composition ratio of the well layer to the barrier layer may be 1:13 to 1:1.20.

Description

Light emitting device and gas sensor using the same

The embodiment relates to a light emitting device and a gas sensor using the same, and more particularly, to a light emitting device emitting ultraviolet rays and a gas sensor using the same.

A semiconductor device containing a compound such as GaN or AlGaN has many advantages, such as having a wide and easily adjustable band gap energy, and thus can be used in various ways as a light emitting device, a light receiving device, and various diodes.

Nitride semiconductors are receiving great attention in the field of developing optical devices and high-power electronic devices due to their high thermal stability and wide bandgap energy. In particular, ultraviolet (UV) light-emitting devices, blue light-emitting devices, green light-emitting devices, and red light-emitting devices using nitride semiconductors have been commercialized and widely used.

On the other hand, such a light emitting device is used in various fields, and recently, research for detecting harmful gas using the light emitting device is in progress.

The conventional harmful gas detector can detect carbon dioxide, but has a problem in that it cannot detect nitrogen oxides such as automobile exhaust gas.

An embodiment is to provide an ultraviolet light emitting device capable of detecting nitrogen oxide and a gas sensor using the same.

A light emitting device according to an embodiment includes a substrate; a first conductivity-type semiconductor layer disposed on the substrate; a second conductivity type semiconductor layer disposed on the first conductivity type semiconductor layer; and an active layer emitting an ultraviolet wavelength disposed between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer, wherein the active layer has a quantum well structure including a well layer and a barrier layer, the well layer and the barrier layer The layer is _{a semiconductor layer having a composition formula of Al x} Ga _1-x N (0≤x≤1), and the Al composition ratio of the well layer to the Al composition ratio of the barrier layer may be 1:13 to 1:1.20.

In an embodiment, the Al composition ratio of the well layer may be 72% to 78%.

In an embodiment, the first conductivity type semiconductor layer includes an AlGaN-based semiconductor, and the first conductivity type semiconductor layer is a 1-1 conductivity type semiconductor layer adjacent to the active layer, and below the 1-1 conductivity type semiconductor layer A 1-2 conductivity type semiconductor layer disposed on and a 1-3 conductivity type semiconductor layer disposed under the 1-2 conductivity type semiconductor layer, wherein the Al composition ratio of the 1-1 conductivity type semiconductor layer is the above. The Al composition ratio of the barrier layer is equal to or higher than the Al composition ratio of the 1-2 conductivity type semiconductor layer, and the Al composition ratio of the 1-1 conductivity type semiconductor layer is equal to or lower than the aluminum composition ratio of the 1-3 conductivity type semiconductor layer. The Al composition ratio may be equal to or higher than the aluminum composition ratio of the 1-1 conductive type semiconductor layer.

In an embodiment, the Al composition ratio of the well layer and the 1-1 conductivity type semiconductor layer is 1:1.16 to 1:1.23, and the Al composition ratio of the well layer and the 1-2 conductivity type semiconductor layer is 1 : 1.09 to 1:1.17, and the Al composition ratio of the well layer and the 1-3 conductivity-type semiconductor layer may be 1:1.16 to 1:1.24.

In an embodiment, the Al composition ratio of the 1-1 conductivity type semiconductor layer is 87% to 92%, the Al composition ratio of the 1-2 conductivity type semiconductor layer is 82% to 98%, and the 1-3 conductivity type semiconductor layer The Al composition ratio of the type semiconductor layer may be 87% to 92%.

In an embodiment, a hole injection layer adjacent to the active layer between the active layer and the second conductivity-type semiconductor layer; and an electron barrier layer disposed on the hole injection layer, wherein the hole injection layer includes an AlGaN-based semiconductor, and the Al composition ratio may be higher than the Al composition ratio of the 1-1 conductivity type semiconductor layer.

In an embodiment, a difference in Al content between the hole injection layer and the barrier layer may be twice or more than a difference in Al content between the 1-1 conductivity-type semiconductor layer and the barrier layer.

In an embodiment, the electron blocking layer may include an AlGaN-based semiconductor, and the composition ratio of Al may be lower than that of the hole injection layer.

In an embodiment, the Al composition ratio of the well layer and the hole injection layer may be 1:1.20 to 1:1.27.

In an embodiment, the Al composition ratio of the well layer and the electron blocking layer may be 1:1.16 to 1:1.23.

In an embodiment, the Al composition ratio of the hole injection layer may be 90% to 95%, and the Al composition ratio of the electron blocking layer may be 87% to 92%.

In an embodiment, the second conductivity type semiconductor layer includes an AlGaN-based semiconductor, and a second conductivity type semiconductor layer disposed adjacent to the active layer and a second conductivity type semiconductor layer disposed on the 2-1 conductivity type semiconductor layer -2 conductivity type semiconductor layer and a 2-3 conductivity type semiconductor layer disposed on the 2-2 conductivity type semiconductor layer, wherein the 2-1 conductivity type semiconductor layer and the 2-2 conductivity type semiconductor layer and the Al composition ratio of the second-third conductivity type semiconductor layer may decrease upward.

In an embodiment, the Al composition ratio of the well layer and the 2-1 conductivity-type semiconductor layer is 1:1.03 to 1:1.09, and the Al composition ratio of the well layer and the 2-2 conductivity-type semiconductor layer is 1:0.96 to 1 : 1.04, and the Al composition ratio of the well layer and the second-third conductivity type semiconductor layer may be 1:0.83 to 1:0.91.

In an embodiment, a contact layer may be disposed on the second conductivity type semiconductor layer, and the Al composition ratio of the contact layer may be 50% or less.

In an embodiment, the Al composition ratio of the 2-1 conductivity-type semiconductor layer is 77% to 82%, the Al composition ratio of the 2-2 conductivity-type semiconductor layer is 72% to 78%, and the 2-3 conductivity The Al composition ratio of the type semiconductor layer may be 62% to 68%.

In an embodiment, the thickness of the well layer may be 0.1 nm to 3 nm, and the thickness of the barrier layer may be 1 nm to 20 nm.

In addition, the gas sensor according to an embodiment of the present invention includes a housing having a gas inlet and an exhaust port; a light emitting device disposed on one side of the housing to emit ultraviolet light;

a light receiving element spaced apart from the light emitting element to sense the ultraviolet light emitted from the light emitting element; and a calculation unit for calculating a gas concentration by comparing the amount of ultraviolet light sensed by the light receiving element with a reference value.

In an embodiment, a first reflective part may be formed on one side of the housing, and the first reflective part may reflect the ultraviolet rays emitted from the light emitting device to the light receiving device.

In an embodiment, a second reflector may be formed on the other side of the housing, and the second reflector may receive the ultraviolet light reflected from the first reflector and reflect it to the light receiving element.

In an embodiment, the light emitting device comprises: a substrate; a first conductivity-type semiconductor layer disposed on the substrate; a second conductivity type semiconductor layer disposed on the first conductivity type semiconductor layer; and an active layer emitting an ultraviolet wavelength disposed between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer, wherein the active layer has a quantum well structure including a well layer and a barrier layer, the well layer and the barrier layer The layer is _{a semiconductor layer having a composition formula of Al x} Ga _1-x N (0≤x≤1), and the Al composition ratio of the well layer to the Al composition ratio of the barrier layer may be 1:13 to 1:1.20.

According to the embodiment, it is possible to provide an ultraviolet light emitting device by changing only the Al composition ratio of the nitride-based semiconductor layer without changing the structure of the conventional light emitting device.

In addition, according to the Example, NO. Noxious gases such as NO ₂ and SO can be detected.

1 is a cross-sectional view of an ultraviolet light emitting device according to an embodiment of the present invention.
2 is a cross-sectional view showing the structure of an active layer according to an embodiment of the present invention.
3 is a cross-sectional view of a first conductivity type semiconductor layer according to an embodiment of the present invention.
4 is a cross-sectional view of a second conductivity type semiconductor layer according to an embodiment of the present invention.
5 is a cross-sectional view of a light emitting device package according to an embodiment of the present invention.
6 to 9 are diagrams showing the configuration of a gas sensor to which a light emitting device according to an embodiment of the present invention is applied.

The present embodiments may be modified in other forms or various embodiments may be combined with each other, and the scope of the present invention is not limited to each of the embodiments described below.

Even if a matter described in a specific embodiment is not described in another embodiment, it may be understood as a description related to another embodiment unless a description contradicts or contradicts the matter in another embodiment.

For example, if a specific embodiment describes a feature for configuration A and another embodiment describes a feature for configuration B, the opposite or contradictory description is not explicitly described in an embodiment in which configuration A and configuration B are combined. Unless otherwise indicated, it should be understood as belonging to the scope of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention that can specifically realize the above objects will be described with reference to the accompanying drawings.

In the description of the embodiment according to the present invention, in the case of being described as being formed on "on or under" of each element, above (above) or below (on) or under) includes both elements in which two elements are in direct contact with each other or one or more other elements are disposed between the two elements indirectly. In addition, when expressed as "up (up) or down (on or under)", it may include the meaning of not only an upward direction but also a downward direction based on one element.

The semiconductor device may include various electronic devices such as a light emitting device and a light receiving device, and both the light emitting device and the light receiving device may include a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer.

The semiconductor device according to the present embodiment may be a light emitting device.

The light emitting device emits light by recombination of electrons and holes, and the wavelength of this light is determined by the material's inherent energy bandgap. Accordingly, the emitted light may vary depending on the composition of the material.

1 shows a conceptual diagram of an ultraviolet light emitting device 100 according to an embodiment of the present invention.

Referring to FIG. 1 , the light emitting device 100 includes a substrate 110 , a first conductivity type semiconductor layer 130 disposed on the substrate, an active layer 140 disposed on the first conductivity type semiconductor layer, and the It includes a second conductivity type semiconductor layer 170 disposed on the active layer, a buffer layer 120 may be disposed between the substrate and the first conductivity type semiconductor layer, and the active layer 140 and the second conductivity type semiconductor layer A hole injection layer 150 and an electron barrier layer 160 may be disposed between the layers 170 .

The substrate 110 may be formed of a material having excellent thermal conductivity, and may be a conductive substrate or an insulating substrate. For example, the substrate 110 may include at least one _{of sapphire (Al 2} O ₃ ), SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge, and Ga ₂ 0 _{3 .} The substrate 110 may be, for example, an AlN template. A plurality of protrusions (not shown) may be formed on the upper and/or lower surfaces of the substrate 110 , and each of the plurality of protrusions includes at least one of a hemispherical shape, a polygonal shape, and an elliptical shape and has a side cross-section. It may be arranged in a form or a matrix form. The protrusion may improve light extraction efficiency.

A plurality of compound semiconductor layers may be grown on the substrate 110 , and equipment for growing the plurality of compound semiconductor layers is an electron beam evaporator, physical vapor deposition (PVD), chemical vapor deposition (CVD), or plasma laser deposition (PLD). , a dual-type thermal evaporator may be formed by sputtering, metal organic chemical vapor deposition (MOCVD), or the like, but is not limited thereto.

A buffer layer 120 may be disposed on the substrate 110 .

The buffer layer 120 relieves a lattice mismatch between the substrate 110 and the first conductivity-type semiconductor layer 130 and allows the conductivity-type semiconductors to be easily grown. The buffer layer 120 may be a semiconductor layer including a composition formula _{of Al x} Ga _{1-x N (0≤x≤1).} Therefore, when the Al composition ratio is 100%, the buffer layer 120 may be an AlN layer.

A first conductivity type semiconductor layer 130 and a second conductivity type semiconductor layer 170 may be disposed on the buffer layer 120 , and are disposed between the first conductivity type semiconductor layer 130 and the second conductivity type semiconductor layer. An active layer 140 may be disposed.

The active layer 140 is a layer in which electrons (or holes) injected through the first conductivity type semiconductor layer 130 and holes (or electrons) injected through the second conductivity type semiconductor layer 170 meet. The active layer 140 may transition to a low energy level as electrons and holes recombine, and may generate light having an ultraviolet wavelength.

The active layer 140 may have any one of a single well structure, a multi-well structure, a single quantum well structure, a multi-quantum well (MQW) structure, a quantum dot structure, or a quantum wire structure, and the active layer 140 . The structure is not limited thereto.

The active layer 140 may be implemented with a compound semiconductor. The active layer 140 may be embodied as at least one of a group II-VI group and a group III-V compound semiconductor, for example.

When the active layer 140 is implemented as a multi-well structure, the active layer 140 includes a plurality of well layers and a plurality of barrier layers. In the active layer 140 , well layers and barrier layers are alternately disposed. A pair of the well layer and the barrier layer may be formed in 2 to 30 cycles. Preferably, the number of pairs of the well layer and the barrier layer may be 4 pairs.

The well layer may be formed of, for example, a semiconductor material having a composition formula of _{Al x} Ga _{1-x N (0≤x≤1).} The barrier layer may be formed of, for example, a semiconductor material having a composition formula of _{Al x} Ga _{1-x N (0≤x≤1).}

2 is a cross-sectional view showing the structure of the active layer.

Referring to FIG. 2 , it can be seen that the well layer 142 and the barrier layer 144 are repeatedly disposed.

The wavelength of light generated from the active layer 140 is determined by the energy bandgap of the well layer 142 and the barrier layer 144 .

The energy bandgap may be adjusted by adjusting the aluminum content of the well layer 142 and the barrier layer 144 , and light in the ultraviolet C (UVC) band may be generated using this.

* The relationship between wavelength and energy bandgap is established as eV=1240/λ(nm).

When the energy bandgap is adjusted to 5.39 eV by the above equation, light having a wavelength of 230 nm can be output.

The energy bandgap can be adjusted by adjusting the aluminum composition ratio of the well layer 142 and the barrier layer 144 .

When the aluminum adjustment ratio of the well layer 142 and the barrier layer 144 is in the range of 1:1.3 to 1:1.20, the energy bandgap between the well layer and the barrier layer becomes approximately 5.39eV, and light in the 230nm wavelength band is output. can That is, the aluminum composition ratio of the barrier layer may be determined within the range of 1.13 times to 1.20 times the aluminum composition ratio of the well layer.

The specific gravity of aluminum of the well layer 142 may be 72% to 78%, and the specific gravity of aluminum of the barrier layer 144 may be determined by the ratio of 1:1.3 to 1:1.20 according to the specific gravity of aluminum of the well layer 142 . . For example, when the proportion of aluminum of the well layer 142 is 75%, the proportion of aluminum of the barrier layer 144 may be 85% to 90%. In addition, the thickness T of the well layer 142 may be 0.1 nm to 3 nm, and the thickness T2 of the barrier layer may be 1 nm to 20 nm.

When outputting light of a different wavelength band, the energy bandgap can be adjusted by adjusting the specific gravity of aluminum.

For example, if you want to output light with a wavelength of 220 nm, adjust the specific gravity of aluminum so that the energy band gap is 5.63 eV, and if you want to output light with a wavelength of 240 nm, adjust the specific gravity of aluminum so that the energy band gap is 5.17 eV can

Specifically, when the aluminum composition ratio of the well layer is 60% and the aluminum composition ratio of the barrier layer is 68% to 72%, it is possible to output light having a wavelength of 220 nm, the aluminum composition ratio of the well layer is 90%, and the aluminum composition ratio of the barrier layer is When the aluminum composition ratio is 95% to 98%, light having a wavelength of 240 nm may be output.

The aluminum specific gravity of the other layers 130 , 150 , 160 , and 170 is adjusted according to the aluminum specific gravity of the well layer 142 and the barrier layer 144 .

The first conductivity-type semiconductor layer 130 may be implemented with a compound semiconductor of group III-V or group II-VI, and may be doped with a first dopant. The first conductivity type semiconductor layer 130 may be implemented with a semiconductor material having a composition formula _{of Al x} Ga _{1-x N (0≤x≤1).} The aluminum composition ratio of the first conductivity type semiconductor layer 130 may be higher than that of the barrier layer 144 . In addition, the first dopant may be an n-type dopant such as Si, Ge, Sn, Se, or Te. When the first dopant is an n-type dopant, the first conductivity-type semiconductor layer 130 may be an n-type semiconductor layer.

The first conductivity type semiconductor layer 130 may be divided into a plurality of layers according to the Al composition ratio.

3 is a cross-sectional view of the first conductivity type semiconductor layer 130 .

Referring to FIG. 2 , the first conductivity type semiconductor layer 130 is a 1-1 conductivity type semiconductor layer 132 adjacent to the active layer and a first conductivity type semiconductor layer disposed under the 1-1 conductivity type semiconductor layer. It may include a -2 conductivity type semiconductor layer 134 and a 1-3 conductivity type semiconductor layer 136 disposed under the 1-2 conductivity type semiconductor layer.

The first-first conductivity type semiconductor layer 132 may be equal to or higher than the aluminum composition ratio of the barrier layer 144 . When the aluminum composition ratio of the well layer 142 is 75%, the aluminum composition ratio of the 1-1 conductive type semiconductor layer 132 may be 87% to 92%. The aluminum composition ratio of the well layer 142 and the 1-1 conductive type semiconductor layer 132 may be 1:1.15 to 1:1.23. In addition, the thickness of the 1-1 conductive type semiconductor layer 132 may be 1 nm to 500 nm.

The aluminum composition of the 1-2 conductivity type semiconductor layer 134 is lower than the aluminum composition of the 1-1 conductivity type semiconductor layer 132 . When the aluminum composition ratio of the well layer 142 is 75%, the aluminum composition ratio of the 1-2 conductivity type semiconductor layer 134 may be 82% to 88%. The aluminum composition ratio of the well layer 142 and the 1-2th conductivity type semiconductor layer 132 may be 1:1.09 to 1:1.17.

The aluminum composition of the 1-3 conductivity-type semiconductor layer 136 may be the same as the aluminum composition of the 1-1 conductivity-type semiconductor layer 132 . When the aluminum composition ratio of the well layer 142 is 75%, the aluminum composition ratio of the 1-3 conductivity type semiconductor layer 136 may be 87% to 92%. The aluminum composition ratio of the well layer 142 and the 1-3 conductivity-type semiconductor layer 136 may be 1:1.15 to 1:1.23.

In addition, the aluminum composition ratio of the 1-3 conductivity type semiconductor layer 136 is lower than that of the buffer layer 120 and higher than that of the 1-2 conductivity type semiconductor layer 134 . The aluminum composition ratio of the buffer layer is 100%. If the aluminum composition ratio changes rapidly, the crystallinity is not good, so the 1-3 conductivity type semiconductor layer 136 is formed between the n-contact layer 134 and the buffer layer 120 so that the aluminum composition is rapidly changed. prevent this from changing.

A hole injection layer 150 may be disposed on the active layer 140 .

The hole injection layer 150 may effectively move holes to the center of the active layer to increase luminous efficiency. The hole injection layer 150 may include a first hole injection layer and a second hole injection layer. The first hole injection layer may be an undoped layer. The second hole injection layer may be a layer doped with a p-type dopant.

The aluminum composition ratio of the hole injection layer 150 should be higher than the aluminum composition ratio of the 1-3th conductivity type semiconductor layer 136 . The aluminum composition ratio of the hole injection layer may be the highest except for the buffer layer.

When the aluminum composition ratio of the well layer 142 is 75%, the aluminum composition ratio of the hole injection layer 150 may be 90% to 95%. The aluminum composition ratio of the hole injection layer of the well layer 142 may be 1:1.2 to 1: 1.27.

The difference in the aluminum composition ratio between the hole injection layer 150 and the barrier layer 144 may be twice or more than the difference in the aluminum composition ratio between the 1-1 conductivity type semiconductor layer 132 and the barrier layer. That is, the following expression holds:

(Hole injection layer Al composition ratio - barrier layer Al composition ratio) ≥ 2 (1-1 conductivity type semiconductor layer Al composition ratio - barrier layer Al composition ratio)

For example, when the aluminum composition ratio of the barrier layer is 88% and the aluminum composition ratio of the 1-1 conductivity type semiconductor layer 132 is 90%, the aluminum composition ratio of the hole injection layer 150 should be 92% or more.

The hole injection layer 150 may have a thickness of 1 nm to 10 nm.

An electron blocking layer 160 may be disposed on the hole injection layer 150 .

The electron blocking layer 160 serves as electron blocking and cladding (MQW cladding) of the active layer, thereby improving luminous efficiency. The electron blocking layer 160 may be formed of an Al _x Ga _(1-x) N (0≤x≤1) based semiconductor, and may have a higher energy band gap than that of the active layer 140 . The aluminum composition ratio of the electron blocking layer 160 may be lower than the aluminum composition ratio of the hole injection layer 150 . When the aluminum composition ratio of the well layer 142 is 75%, the aluminum composition ratio of the electron blocking layer 160 may be 87% to 92%. The aluminum composition ratio of the well layer 142 and the electron blocking layer 160 may be 1:1.16 to 1:1.23.

The electron blocking layer 160 may have a thickness of 1 nm to 100 nm.

A second conductivity type semiconductor layer 170 may be disposed on the electron blocking layer 160 .

The second conductivity type semiconductor layer 170 is formed on the active layer 140 , and may be implemented as a compound semiconductor such as group III-V or group II-VI, and is formed on the second conductivity type semiconductor layer 127 . Two dopants may be doped. The second conductivity type semiconductor layer 170 may be a semiconductor material having a composition formula _{of Al x} Ga _{1-x N (0≤x≤1).} When the second dopant is a p-type dopant such as Mg, Zn, Ca, Sr, or Ba, the second conductivity-type semiconductor layer 170 doped with the second dopant may be a p-type semiconductor layer.

The second conductivity type semiconductor layer 170 may be divided into a plurality of layers according to the aluminum composition ratio.

4 is a cross-sectional view of the second conductivity type semiconductor layer 170 .

* Referring to FIG. 4 , the second conductivity type semiconductor layer 170 includes a 2-1 conductivity type semiconductor layer 172 and a 2-1 conductivity type semiconductor layer disposed on the electron blocking layer 160 . It may include a 2-2 conductivity type semiconductor layer 174 disposed thereon and a 2-3 conductivity type semiconductor layer 176 disposed on the 2-2 conductivity type semiconductor layer.

The aluminum composition ratio of the 2-1-th conductivity-type semiconductor layer 172 , the 2-2 conductivity-type semiconductor layer 174 , and the 2-3th conductivity-type semiconductor layer 176 may be sequentially lowered upward. When the aluminum composition ratio of the well layer 142 is 75%, the aluminum composition ratio of the 2-1 conductivity type semiconductor layer 172 may be 77% to 82%, and the aluminum composition ratio of the 2-2 conductivity type semiconductor layer 174 is 77% to 82%. The aluminum composition ratio may be 72% to 77%, and the aluminum composition ratio of the second-third conductivity type semiconductor layer 176 may be 62% to 68%.

The aluminum composition ratio of the well layer 142 and the 2-1 th conductivity type semiconductor layer 172 may be 1:1.03 to 1: 1.09. The aluminum composition ratio of the well layer 142 and the second-second conductivity type semiconductor layer 174 may be 1:0.96 to 1:1.04. The aluminum composition ratio of the well layer 142 and the second-third conductivity type semiconductor layer 176 may be 1:0.83 to 1:0.91.

The thickness of the 2-1-th conductivity type semiconductor layer 172 , the 2-2 conductivity type semiconductor layer 174 , and the 2-3 conductivity type semiconductor layer 176 may all be 1 nm to 100 nm.

In addition, the 1-2 conductivity type semiconductor layer 134 may be a first contact layer, and a first electrode 192 may be disposed thereon.

A second contact layer 180 may be disposed on the second conductivity-type semiconductor layer 170 , and a second electrode 194 may be disposed on the second contact layer 180 .

The aluminum composition ratio of the second contact layer 180 should be lower than the aluminum composition ratio of the well layer, and specifically, it may be less than 50%. The second contact layer 180 has a smaller bandgap than the second conductivity-type semiconductor layer, thereby reducing contact resistance, thereby reducing power consumption.

The second contact layer 180 may have a thickness of 1 nm to 10 nm.

When the first electrode 192 is electrically connected to the first conductivity-type semiconductor layer 130 , the second electrode 194 is electrically connected to the second conductivity-type semiconductor layer 170 .

The first electrode 192 and the second electrode 194 may be formed of a non-transmissive metal having characteristics of an ohmic contact, an adhesive layer, and a bonding layer, but is not limited thereto. The first electrode 192 and the second electrode 194 include Ti, Ru, Rh, Ir, Mg, Zn, Al, In, Ta, Pd, Co, Ni, Si, Ge, Ag and Au, and their selections. alloys can be selected.

A light emitting device emitting an ultraviolet wavelength may be manufactured by the aluminum composition as described above.

In particular, according to this embodiment, the aluminum composition ratio and thickness of the well layer are appropriately adjusted through bandgap engineering without significantly changing the stack structure of the conventional light emitting device, and accordingly, the aluminum composition ratio of the other layers is appropriately adjusted. A light emitting device emitting an ultraviolet wavelength can be more easily manufactured.

5 is a cross-sectional view illustrating a light emitting device package including a light emitting device according to an embodiment of the present invention.

Referring to FIG. 5 , the light emitting device package 10 includes a package body 1 , a first lead electrode 2 and a second lead front 3 installed on the package body 1 , and the first lead A light emitting device 100 electrically connected to the electrode 2 and the second lead front 3 , and a molding member 4 surrounding the light emitting device 100 are included.

The package body 1 may be formed of a silicon material, a synthetic resin material, or a metal material, and an inclined surface may be formed on the main portion of the light emitting device 100 .

The first lead electrode 2 and the second lead electrode 3 are electrically isolated from each other, and serve to provide power to the light emitting device 100 . In addition, the third lead front (2) and the second lead electrode (3) may serve to increase the light efficiency by reflecting the light generated by the light emitting device 100, the light emitting device (100) It can also serve to dissipate the generated heat to the outside.

The light emitting device 100 may be disposed on the package body 1 or on the third lead electrode 2 or the second electrode layer 3 .

The light emitting device 100 may be electrically connected to the first lead electrode 2 and the second lead electrode 3 by any one of a wire method, a flip chip method, or a die bonding method. In the embodiment, it is illustrated that the light emitting device 100 is electrically connected to the first lead electrode 2 and the second lead electrode 3 through a wire, but is not limited thereto.

The molding member 4 may surround the light emitting device 100 to protect the light emitting device 100 . In addition, the molding member 4 may include a phosphor 5 to change the wavelength of light emitted from the light emitting device 100 .

6 to 9 are diagrams showing the configuration of a gas sensor to which a light emitting device according to an embodiment of the present invention is applied. 6 to 9 show only the schematic structure, and the circuit configuration for calculating the gas concentration is omitted. Although not shown in FIGS. 6 to 9 , the gas sensor according to the embodiment may include a calculator for calculating the gas concentration by comparing the amount of ultraviolet light detected by the light receiving element with a reference value.

Referring to FIG. 6 , the gas sensor 200 includes a housing 210 having an inlet and an exhaust port formed therein, a light emitting device 220 disposed on one side of the housing, and a light emitting device spaced apart from the light emitting device and emitted from the light emitting device. It may include a light receiving element 230 for detecting the gas concentration by sensing ultraviolet rays.

An inlet 212 and an exhaust port 214 may be formed in the housing, and the inlet 212 and the exhaust port 214 may be formed on surfaces facing each other. The position of the inlet 212 and the exhaust port is not limited, but as shown, the inlet 212 and the exhaust port 214 are not arranged in a straight line but are arranged in a diagonal direction to each other to ensure the time for the gas to stay in the housing. It can improve the accuracy of gas detection.

The housing 210 may have a cylindrical elongated shape, but is not limited thereto.

When the longer side of the housing 210 is referred to as a transverse direction, the inlet 212 may be formed in the upper portion of the housing, and the exhaust port 214 may be formed in the lower portion of the housing.

A light emitting device 220 and a light receiving device 230 may be disposed inside the housing 210 .

The light emitting device 220 is a light emitting device that emits ultraviolet light, and the light emitting device shown in FIG. 1 may be used.

The light emitting device 220 may be disposed at an outer portion of the housing in a horizontal direction, and the light receiving device 230 may be disposed opposite to the light emitting device 220 . That is, the light emitting device 220 and the light receiving device 230 are preferably disposed to be spaced apart as much as possible. This is because the accuracy of the detection sensor is improved as the flight distance increases before the light emitted from the light emitting device is received by the light receiving device 230 .

In this case, the light emitting unit 222 of the light emitting device 220 and the light receiving unit 232 of the light receiving device 230 may be disposed to face each other.

A photodiode may be used as the light receiving device 220 , and may receive ultraviolet light emitted from the light emitting device 220 and compare it with a reference value to detect a gas concentration. The reference value may be preset as the amount of ultraviolet light received from the light receiving element when there is no gas in the housing. That is, the gas concentration can be detected by comparing the amount of UV light received when there is no gas in the housing with the amount of UV light received when gas is introduced. Since UV rays emitted from the light emitting device are refracted and scattered by gas particles, the amount of UV light received by the light receiving device 230 is different from the reference value when gas is present.

The gas includes NO, NO ₂ , and noxious automobile gases such as _{So x .}

7 shows another embodiment of the gas sensor, in which a reflector is added to one surface of the housing.

Referring to FIG. 7 , the gas sensor 300 includes a housing 210 having an inlet and an exhaust port formed therein, a light emitting device 220 disposed on one side of the housing, and an ultraviolet light emitted from the light emitting device spaced apart from the light emitting device. It can be seen that the light receiving element 230 for sensing the gas concentration is included, and the reflective part 216 is formed on one surface of the housing.

In this embodiment, the light emitting unit 220 and the light receiving unit 232 of the light receiving device 230 other than the light emitting device 220 may be disposed in the same direction.

That is, the light emitting unit 222 of the light emitting device 220 may be disposed to face the reflecting unit 216 of the housing 210 . The light emitted from the light emitting unit 222 is reflected by the reflecting unit 216 and is incident on the light receiving element 230 .

An aluminum layer may be coated on the reflective part 216 . The reflectance of ultraviolet light can be increased by coating the reflector with aluminum.

According to the embodiment of FIG. 6 , the light emitting device 220 may be disposed to be somewhat spaced apart from the reflecting unit 216 . In the embodiment of FIG. 5, the light emitting element is disposed on the side of the housing to secure a distance between the light emitting element and the light receiving element, but in the embodiment of FIG. This can make the light path longer.

7 shows another embodiment of the gas sensor, in which a reflector is further added to the other surface of the housing.

Referring to FIG. 7 , the gas sensor 400 includes a housing 210 having an inlet and an exhaust port formed therein, a light emitting device 220 disposed on one side of the housing, and an ultraviolet light emitted from the light emitting device spaced apart from the light emitting device. It can be confirmed that the light receiving element 230 for detecting the gas concentration by detecting have.

7 is a form in which the second reflection unit 218 is further added. The second reflection unit 218 may be disposed on one side of the first reflection unit 216 in the opposite direction.

In this case, the light emitting device 220 and the light receiving device 230 may be disposed such that the light emitting unit 222 and the light receiving unit 232 face in opposite directions. With this structure, the light emitted from the light emitting unit 222 may be incident on the light receiving unit 232 by adding the first reflecting unit 216 and the second reflecting unit 218 .

Since the light receiving element 230 receives the light reflected from the second reflecting unit 218 , it may be disposed to be somewhat spaced apart from the second reflecting unit 218 . That is, in the embodiment of FIGS. 2 and 3 , the light receiving element 230 is disposed on the outer portion of the housing as much as possible in order to secure an optical path, but in the embodiment of FIG. ) to receive the reflected light, so it may be disposed to be spaced apart from the second reflecting unit 218 .

As described above, according to the embodiment of the present invention, harmful gases such as automobile exhaust gas can be detected by using the ultraviolet light emitting device and the light receiving device.

In addition, the accuracy of gas detection can be improved by providing a reflector in the housing to lengthen the light path.

8 shows another embodiment of the gas sensor, in which the housing is formed in a circular shape.

Referring to FIG. 9 , the light emitting device 220 and the light receiving device 230 are disposed on the bottom surface, and a reflective surface 516 is formed on the housing 510 . The ultraviolet light emitted from the light emitting device 220 is reflected by the reflective surface 516 and is incident on the light receiving device 230 .

.

The light emitting device includes a laser diode in addition to the light emitting diode described above.

The laser diode may include a first conductivity-type semiconductor layer, an active layer, and a second conductivity-type semiconductor layer having the above-described structure in the same manner as the light emitting device. In addition, an electro-luminescence phenomenon in which light is emitted when a current flows after bonding a p-type first conductivity type semiconductor and an n-type second conductivity type semiconductor is used, but the directionality of the emitted light and there is a difference in phase. That is, the laser diode uses a phenomenon called stimulated emission and constructive interference, so that light having one specific wavelength (monochromatic beam) can be emitted with the same phase and in the same direction. Therefore, it can be used for optical communication, medical equipment, and semiconductor processing equipment.

As the light receiving element, a photodetector, which is a kind of transducer that detects light and converts its intensity into an electrical signal, may be exemplified. As such a photodetector, a photovoltaic cell (silicon, selenium), a photoconductive device (cadmium sulfide, cadmium selenide), a photodiode (for example, a PD having a peak wavelength in a visible blind spectral region or a true blind spectral region), a phototransistor , a photomultiplier tube, a phototube (vacuum, gas-filled), an IR (Infra-Red) detector, etc., but the embodiment is not limited thereto.

In addition, a semiconductor device such as a photodetector may be generally manufactured using a direct bandgap semiconductor having excellent light conversion efficiency. Alternatively, the photodetector has various structures, and the most common structures include a pin-type photodetector using a pn junction, a Schottky-type photodetector using a Schottky junction, and a Metal Semiconductor Metal (MSM) photodetector. have.

A photodiode may include a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer having the above-described structure in the same way as the light emitting device, and has a pn junction or pin structure. The photodiode operates by applying a reverse bias or zero bias, and when light is incident on the photodiode, electrons and holes are generated and a current flows. In this case, the magnitude of the current may be substantially proportional to the intensity of light incident on the photodiode.

A photovoltaic cell or solar cell is a type of photodiode, and may convert light into electric current. The solar cell may include a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer having the above-described structure in the same manner as the light emitting device.

In addition, it may be used as a rectifier of an electronic circuit through the rectification characteristic of a general diode using a p-n junction, and may be applied to an oscillation circuit by being applied to a very high frequency circuit.

In addition, the above-described semiconductor device is not necessarily implemented only as a semiconductor, and may further include a metal material in some cases. For example, a semiconductor device such as a light-receiving device may be implemented using at least one of Ag, Al, Au, In, Ga, N, Zn, Se, P, or As, and may be formed using a p-type or n-type dopant. It may be implemented using a doped semiconductor material or an intrinsic semiconductor material. In the above, the embodiment has been mainly described, but this is only an example and does not limit the present invention, and those of ordinary skill in the art to which the present invention pertains are not exemplified above in the range that does not depart from the essential characteristics of the present embodiment. It will be appreciated that various modifications and applications are possible. For example, each component specifically shown in the embodiment can be implemented by modification. And differences related to such modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

110: substrate 120: buffer layer
130: first conductivity type semiconductor layer 140: active layer
150: hole injection layer 160: electron blocking layer
170: second conductivity type semiconductor layer 180: contact layer

Claims (8)

Board;
a first conductivity-type semiconductor layer disposed on the substrate;
a second conductivity type semiconductor layer disposed on the first conductivity type semiconductor layer; and
An active layer emitting an ultraviolet wavelength disposed between the first conductivity-type semiconductor layer and the second conductivity-type semiconductor layer,
The active layer has a quantum well structure including a well layer and a barrier layer,
The well layer and the barrier layer are semiconductor layers having a composition formula _{of Al x} Ga _{1-x N (0≤x≤1),}
The ratio of the Al composition of the well layer to the Al composition of the barrier layer is 1:13 to 1:1.20,
The Al composition ratio of the well layer is 72% to 78%.
According to claim 1,
Between the active layer and the second conductivity type semiconductor layer further comprises a hole injection layer adjacent to the active layer,
The Al composition ratio of the well layer and the hole injection layer is 1:1.20 to 1:1.27.
3. The method of claim 2,
Further comprising an electron blocking layer disposed on the hole injection layer,
The Al composition ratio of the well layer and the electron blocking layer is 1:1.16 to 1:1.23.
According to claim 1,
The first conductivity type semiconductor layer includes a 1-1 conductivity type semiconductor layer adjacent to the active layer, a 1-2 conductivity type semiconductor layer disposed under the 1-1 conductivity type semiconductor layer, and the 1-2 conductivity type semiconductor layer. It includes a 1-3 conductivity type semiconductor layer disposed under the type semiconductor layer,
The 1-1 conductivity type semiconductor layer is equal to or higher than the Al composition ratio of the barrier layer,
The Al composition of the 1-2 conductivity type semiconductor layer is lower than the Al composition of the 1-1 conductivity type semiconductor layer,
The Al composition of the 1-3 conductivity type semiconductor layer is the same as the Al composition of the 1-1 conductivity type semiconductor layer, a light emitting device.
According to claim 1,
The first conductivity type semiconductor layer includes a 1-1 conductivity type semiconductor layer adjacent to the active layer, a 1-2 conductivity type semiconductor layer disposed under the 1-1 conductivity type semiconductor layer, and the 1-2 conductivity type semiconductor layer. It includes a 1-3 conductivity type semiconductor layer disposed under the type semiconductor layer,
Further comprising a buffer layer disposed between the substrate and the first conductivity-type semiconductor layer,
The aluminum composition ratio of the 1-3 conductivity type semiconductor layer is lower than that of the buffer layer and higher than that of the 1-2 conductivity type semiconductor layer, a light emitting device.
According to claim 1,
Further comprising; an electron blocking layer disposed on the second conductivity type semiconductor layer;
The second conductivity type semiconductor layer includes a 2-1 conductivity type semiconductor layer disposed on the electron blocking layer, a 2-2 conductivity type semiconductor layer disposed on the 2-1 conductivity type semiconductor layer, and the second conductivity type semiconductor layer. - Containing a 2-3th conductivity type semiconductor layer disposed on the -2 conductivity type semiconductor layer,
The Al composition ratio of the 2-1 conductivity type semiconductor layer, the 2-2 conductivity type semiconductor layer, and the 2-3 conductivity type semiconductor layer is decreased in the order of the semiconductor layer, the light emitting device.
According to claim 1,
Further comprising; an electron blocking layer disposed on the second conductivity type semiconductor layer;
The second conductivity type semiconductor layer includes a 2-1 conductivity type semiconductor layer disposed on the electron blocking layer, a 2-2 conductivity type semiconductor layer disposed on the 2-1 conductivity type semiconductor layer, and the second conductivity type semiconductor layer. - Containing a 2-3th conductivity type semiconductor layer disposed on the -2 conductivity type semiconductor layer,
The Al composition ratio of the well layer and the 2-1 conductivity type semiconductor layer is 1: 1.03 to 1: 1.09,
The Al composition ratio of the well layer and the 2-2 conductivity type semiconductor layer is 1: 0.96 to 1: 1.04,
The Al composition ratio of the well layer and the second-third conductivity type semiconductor layer is 1:0.83 to 1:0.91.
According to claim 1,
a second contact layer disposed on the second conductivity type semiconductor layer; and a second electrode disposed on the second contact layer;
The Al composition ratio of the second contact layer is 50% or less of the Al composition ratio of the well layer.

Images