KR20170103163A - Semiconductor device - Google Patents

Abstract

According to an embodiment, provided is a semiconductor device which comprises: a first conductive semiconductor layer; a stress reducing layer arranged on the first conductive semiconductor layer; an active layer of a multiple quantum well structure arranged on the stress reducing layer wherein the active layer is a blocking layer of a first quantum wall and/or a second quantum wall; and a second conductive semiconductor layer on the active layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor device having excellent light efficiency.

Semiconductor devices including compounds such as GaN and AlGaN have many advantages such as having a wide and easily adjustable band gap energy, and are used in various applications such as light emitting devices and light receiving devices.

Particularly, a light emitting device such as a light emitting diode or a laser diode using a semiconductor material of Group 3-5 or 2-6 group semiconductors can be applied to various devices such as a red, Blue, and ultraviolet rays. By using fluorescent materials or combining colors, it is possible to realize a white light beam with high efficiency. Also, compared to conventional light sources such as fluorescent lamps and incandescent lamps, low power consumption, , Safety, and environmental friendliness.

Therefore, a transmission module of the optical communication means, a light emitting diode backlight replacing a cold cathode fluorescent lamp (CCFL) constituting a backlight of an LCD (Liquid Crystal Display) display device, a white light emitting element capable of replacing a fluorescent lamp or an incandescent lamp Diode lighting, automotive headlights, and traffic lights.

1A and 1B are views showing a conventional light emitting device.

The light emitting device 100 includes a buffer layer 120 and a light emitting structure 130 including a first conductive semiconductor layer 132, an active layer 134, and a second conductive semiconductor layer 136 on a substrate 110 And a first electrode 182 and a second electrode 186 are disposed on the first conductivity type semiconductor layer 132 and the second conductivity type semiconductor layer 136, respectively.

A stress relieving layer 140 having an InGaN / GaN structure may be disposed between the first conductive semiconductor layer 132 and the active layer 134, and the stress relaxation layer 140 may be disposed between the active layer 134 and the second conductive semiconductor layer 136 An electron blocking layer (EBL) 160 may be disposed between the anode and the cathode.

The stress relieving layer 140 may have a superlattice (SLs) structure in which a plurality of InGaN 141 and GaN 142 are alternately arranged as shown in FIG. 1B. The InGaN layer 141 and the GaN layer 142 (T ₁ , t ₂ ) may be different from each other.

The stress relieving layer 140 can relieve the stress applied to the active layer 134 from the first conductivity type semiconductor layer 132, but has the following problems.

FIGS. 2A and 2B are diagrams showing an energy band gap and an electron overflow of a conventional light emitting device, and FIGS. 2A and 2B are diagrams showing an energy band gap and an electron overflow of a conventional light emitting device.

2B, the energy band gap of the quantum wall in the active layer 140 gradually increases due to the piezoelectric field at the interface between InGaN and GaN, Electrons traveling in the direction of the active layer 140 through overflow or tunneling increase.

The increase in electrons in the direction of the active layer causes an unbalance in the number of electrons and holes, thereby reducing the light efficiency of the light emitting element.

The embodiment attempts to provide a semiconductor device having excellent light efficiency.

The embodiment includes a first conductivity type semiconductor layer; A stress relieving layer disposed on the first conductive type semiconductor layer; An active layer of a multiple quantum well structure disposed on the stress relieving layer and having a first quantum wall and / or a second quantum wall as a blocking layer; And a second conductive semiconductor layer on the active layer.

The barrier layer may comprise AlGaN / InGaN / GaN.

The thickness of the barrier layer may be from 1 nanometer to 20 nanometers.

The composition ratio of Al (aluminum) in AlGaN may be 1% to 20%.

The composition ratio of In (indium) in InGaN may be 1% to 20%.

The stress relieving layer may have a plurality of InGaN / GaN or a plurality of GaN / InGaN structures.

The thickness of GaN may be greater than the thickness of the InGaN.

The thicknesses of the plurality of GaNs or the thicknesses of the plurality of InGaNs may be constant.

In the light emitting device according to the embodiment, a barrier layer of an AlGaN / InGaN / GaN structure is disposed between the stress relaxation layer (SLs) and the active layer (MQW), and a lattice mismatch between AlN, InN and GaN, A piezoelectric field is generated at the interface between the InGaN layer and the GaN layer, which causes energy band bending, so that the energy levels of the AlGaN layer and the GaN layer are similar to each other, So that the electrons are evenly distributed in the entire region of the active layer of the multiple quantum well structure, so that the light efficiency can be improved.

1A and 1B are diagrams showing a conventional light emitting device,
FIGS. 2A and 2B are diagrams showing an energy band gap and an electron overflow of a conventional light emitting device,
3A to 3C are views showing a light emitting device according to an embodiment,
FIGS. 4A and 4B are views showing the action of the electron blocking layer of the light emitting device according to the embodiment,
5A and 5B are diagrams showing the distribution of electrons of the conventional light emitting device and the light emitting device according to the embodiment,
6 is a view illustrating a light emitting device package in which a light emitting device according to an embodiment is disposed.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: FIG.

In the description of the embodiment according to the present invention, in the case of being described as being formed "on or under" of each element, the upper (upper) or lower (lower) or under are all such that two elements are in direct contact with each other or one or more other elements are indirectly formed between the two elements. Also, when expressed as "on or under", it may include not only an upward direction but also a downward direction with respect to one element.

A semiconductor device according to the present invention includes: a first conductivity type semiconductor layer; a stress relieving layer disposed on the first conductivity type semiconductor layer; and a second quantum barrier layer disposed on the stress relieving layer, An active layer of a multi quantum well structure and a second conductivity type semiconductor layer on the active layer.

The semiconductor device may include a light emitting element, a light receiving element, and the like. The light emitting element and the light receiving element may include the first conductivity type semiconductor layer, the active layer, and the second conductivity type semiconductor layer. Hereinafter, a light emitting device will be described as one example of a semiconductor device.

3A to 3C are views showing a light emitting device according to an embodiment.

The light emitting device 200 includes a buffer layer 220 and a light emitting structure 230 including a first conductive semiconductor layer 232, an active layer 234, and a second conductive semiconductor layer 236 on a substrate 210 And a first electrode 282 and a second electrode 286 are disposed on the first conductivity type semiconductor layer 232 and the second conductivity type semiconductor layer 236, respectively.

A stress relieving layer 240 having an InGaN / GaN structure may be disposed between the first conductivity type semiconductor layer 232 and the active layer 234 and an AlGaN / GaN structure may be disposed between the stress relieving layer 240 and the active layer 234. [ A blocking layer 250 of InGaN / GaN structure may be disposed. The blocking layer 250 may be the first or second quantum wall of the active layer 234 of the multiple quantum well structure.

An electron blocking layer (EBL) 260 may be disposed between the active layer 234 and the second conductivity type semiconductor layer 236 and a light transmitting conductive layer 270 May be disposed.

The substrate 210 may be formed of a material suitable for semiconductor material growth or a carrier wafer, may be formed of a material having excellent thermal conductivity, and may include a conductive substrate or an insulating substrate. For example, at least one of sapphire (Al ₂ O ₃ ), SiO ₂ , SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge and Ga ₂ O ₃ can be used.

A pattern is disposed on the surface of the substrate 210 to reflect or scatter light traveling in the direction of the substrate 210 emitted from the active layer 234 to improve the light efficiency of the entire light emitting device 200 .

Since the substrate 210 and the light emitting structure 230 are different materials, the lattice mismatch is very large and the difference in thermal expansion coefficient between them is very large. Therefore, dislocations that deteriorate the crystallinity, the buffer layer 220 may be disposed between the substrate 210 and the light emitting structure because the light emitting layer may have melt-back, crack, pit, and surface morphology defects.

The first conductive semiconductor layer 232 may be formed of a compound semiconductor such as Group III-IV or II-V, and may be doped with a first conductive dopant. The first conductive semiconductor layer 232 is a semiconductor material having a composition formula of Al _x In _y Ga _(1-xy) N (0? X? 1, 0? _Y? 1, 0? _X + y? , GaN, InAlGaN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP.

When the first conductivity type semiconductor layer 232 is an n-type semiconductor layer, the first conductivity type dopant may include n-type dopants such as Si, Ge, Sn, Se, and Te. The first conductive semiconductor layer 232 may be formed as a single layer or a multilayer, but is not limited thereto.

The stress relieving layer 240 may have a superlattice (SLs) structure in which a plurality of InGaN 241 and GaN 242 are alternately arranged and the InGaN layer 241 and the GaN layer 242 may have a thickness t ₃ , t ₄ ) may be different from each other. 3B, the stress relieving layer 240 is disposed in the order of the InGaN layer 241 and the GaN layer 242 from the lower substrate direction, or alternatively the GaN layer 242 and InGaN Layer 241 in that order.

The thicknesses of the respective InGaN layers 241 may be equal to each other, and the thicknesses of the respective GaN layers 242 may be equal to each other.

At this time, the thicknesses t ₃ and t _{4 of the} InGaN layer 141 and the GaN layer 142 may be different from each other. More specifically, the thickness t ₃ of the InGaN layer 141 may be greater than the thickness t ₃ of the InGaN layer 141. may be a 2-nm thickness (t ₄₎ that may be greater, for example, the thickness of the InGaN layer (141) (t ₃₎ is 1.5 can be a nano-meter thickness (t ₄₎ of the GaN layer 142 .

The barrier layer 250 disposed on the stress relieving layer 240 may be a first quantum wall and / or a second quantum wall in the active layer 234 of a multiple quantum well structure, which will be described later. A part of electrons traveling in the direction of the active layer 234 can be blocked.

The AlGaN layer 251, the InGaN layer 252, and the GaN layer 253 may be sequentially disposed from the direction adjacent to the stress relieving layer 240. The AlGaN layer 252 may be formed of AlGaN / InGaN / .

The thickness of the entire barrier layer 250 may be the sum of the thicknesses t ₅ , t ₆ and t _{7 of the} AlGaN layer 251, the InGaN layer 252 and the GaN layer 253. For example, Meter to 20 nanometers.

The total thickness of the AlGaN, InGaN, and GaN may be 1 nm or more even if the lattice constant of each of the AlGaN, InGaN, and GaN is about 3 to 4 ohm Strong (A). In a multi-quantum well structure, if the thickness of the quantum wall exceeds 20 nanometers, the resistance may become too large, so that the total thickness can be 20 nanometers or less.

The composition ratio of Al (aluminum) in the AlGaN layer 251 may be 1% to 20%, and the composition ratio of In (indium) in the InGaN layer 252 may be 1% to 20%.

Since Al and In are included in the AlGaN layer 251 and the InGaN layer 252 and the energy band gap is different from that of the GaN layer 253, at least 1% or more of Al and In can be contained, and in the case of the active layer emitting blue light Al and In can be included within 15%, but up to 20% for UV LED and Green LED. If Al and In are contained in an amount exceeding 20%, the lattice mismatch of each layer in the barrier layer may become large and the crystal quality may deteriorate.

The active layer 234 may include a multi quantum well (MQW) structure.

InGaN / InGaN, InGaN / InGaN, InGaN / GaN, InAlGaN / GaN, GaAs (InGaAs), and AlGaN / AlGaN / InGaN / GaN, , / AlGaAs, GaP (InGaP) / AlGaP, but the present invention is not limited thereto. The well layer may be formed of a material having an energy band gap smaller than the energy band gap of the barrier layer.

Electrons injected through the first conductivity type semiconductor layer 232 and holes injected through the second conductivity type semiconductor layer 236 meet each other to have energy determined by the energy band inherent to the active layer 234 Emits light. The light emitted from the active layer 234 may be different depending on the composition of the material of the active layer and may be blue light, ultraviolet (UV) light or deep ultraviolet (UV) light.

An electron blocking layer 260 may be disposed between the active layer 234 and the second conductive semiconductor layer 236. Since electrons have greater mobility than holes, the electron blocking layer 260 can prevent electrons from overflowing into the second conductivity type semiconductor layer 236 and distinguish it from the blocking layer 240, Layer 260 as shown in FIG.

Electron blocking layer 260 is _{Al x In y Ga 1 -x- y} N can be formed of (0≤x≤1,0≤y≤1) based semiconductor, for example may be made of AlGaN, an active layer ( 234, and may be formed to have a thickness of, for example, about 100 Å to about 600 Å, but are not limited thereto.

The second conductive type semiconductor layer 236 may be formed of a semiconductor compound, and the source may be, for example, gallium (Ga) or ammonia (NH ₃ ). The second conductive semiconductor layer 236 may be formed of a compound semiconductor such as Group III-IV or II-V, and may be doped with a second conductive dopant. The second conductivity type semiconductor layer 236 is formed of a semiconductor material having a composition formula of In _x Al _y Ga _{1 -x- y} N (0? X? 1, 0? _Y? 1, 0? _X + , AlGaN, GaN AlInN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP.

When the second conductivity type semiconductor layer 236 is a p-type semiconductor layer, the second conductivity type dopant may be a p-type dopant such as Mg, Zn, Ca, Sr, and Ba. The second conductivity type semiconductor layer 236 may be formed as a single layer or a multilayer, but is not limited thereto.

Since the contact characteristics between the second electrode 286 and the second conductivity type semiconductor layer 236 are poor, the light-transmitting conductive layer 270 may be formed on the light-emitting structure 230. Therefore, the ITO (Indium Tin Oxide) The conductivity characteristics with the second electrode 286 are excellent and the current injection characteristics into the second conductivity type semiconductor layer 236 can be improved.

The second conductivity type semiconductor layer 236, the electron blocking layer 260, the active layer 234, the barrier layer 250, and the stress relieving layer 240 from the transmissive conductive layer 270, The first electrode 282 is disposed on the exposed portion of the first conductivity type semiconductor layer 232 and the exposed portion of the first conductivity type semiconductor layer 232 is exposed, The second electrode 286 may be disposed on the second electrode 270.

The first electrode 282 and the second electrode 286 may include at least one of aluminum (Al), titanium (Ti), chrome (Cr), nickel (Ni), copper (Cu) Or a multi-layer structure.

Although the lateral light emitting device is shown in FIG. 3A and the like, a structure such as the blocking layer 250 described above may be applied to a vertical light emitting device or a flip chip light emitting device.

4A and 4B are views illustrating the operation of the electron blocking layer of the light emitting device according to the embodiment.

The energy band gap of each layer is shown, and a box indicated by a red dotted line corresponds to the blocking layer. If the barrier layer of AlGaN / InGaN / GaN structure is disposed between the stress relaxation layer (SLs) and the active layer (MQW), the AlGaN layer, the InGaN layer, and the GaN layer, due to the lattice mismatch between AlN, InN and GaN The energy level of the AlGaN layer and the GaN layer are similar to each other as shown in FIG. 4B, so that the energy of the electrons Overflow can be reduced.

5A and 5B are diagrams showing the distribution of electrons in the conventional light emitting device and the light emitting device according to the embodiment.

In contrast to the conventional light emitting device of FIG. 5A, in the case of the light emitting device according to the embodiment of FIG. 5B, electrons are uniformly distributed throughout the active layer of the multiple quantum well structure, thereby improving the light efficiency.

6 is a view illustrating a light emitting device package in which a light emitting device according to an embodiment is disposed.

The light emitting device package 300 according to the embodiment may include a body 310, a cavity formed on the body 310 and a light emitting device 200 disposed in the cavity. The body 310 ) May include lead frames 321 and 322 for electrical connection with the light emitting device 200.

The light emitting device 200 may be disposed on the bottom surface of the cavity and the molding portion 355 may be disposed in the cavity so as to surround the light emitting device 200. The fluorescent material 350 may be included in the molding portion 355 And can emit light in the second wavelength range by being excited by the light in the first wavelength range emitted from the light emitting device 200.

The resin that can be mixed with the phosphor in the molding part 350 may be any one of a silicone resin, an epoxy resin, and an acrylic resin or a mixture thereof. The phosphor 350 may be a YAG fluorescent material, a nitride fluorescent material, a silicate, or a combination thereof, but is not limited thereto.

The body 310 may be formed of a silicon material, a synthetic resin material, or a metal material. The body 310 may have a cavity with an open top and side and bottom surfaces.

The cavity may be formed in a cup shape, a concave container shape or the like, and the side surface of the cavity may be formed perpendicular or inclined with respect to the bottom surface, and may vary in size and shape.

The shape of the cavity viewed from the top may be circular, polygonal, elliptical, or the like, but may be a curved edge shape, but is not limited thereto.

The body 310 may include a first lead frame 321 and a second lead frame 322 and may be electrically connected to the light emitting device 200 through a wire 340. When the body portion 310 is made of a conductive material such as a metal material, although not shown, an insulating layer is coated on the surface of the body portion 310 to prevent an electrical short between the first and second lead frames 321 and 322 have.

The first lead frame 321 and the second lead frame 322 are electrically separated from each other and can supply current to the light emitting device 200. [ The first lead frame 321 and the second lead frame 322 may reflect the light generated from the light emitting device 200 to increase the light efficiency, It may be discharged.

6, the light emitting device 200 may be connected to the first lead frame 321 and the second lead frame 322 through a wire 340. However, in addition to the wire bonding method, Or may be connected by a bonding method.

The above-described light emitting device is constituted by a light emitting device package and can be used as a light source of an illumination system, for example, as a light source of an image display device or a light source of an illumination device.

When used as a backlight unit of a video display device, it can be used as an edge-type backlight unit or as a direct-type backlight unit. When used as a light source of a lighting device, it can be used as a regulator or bulb type. It is possible.

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

The light emitted from the light emitting device is mixed with light in a plurality of wavelength ranges, and light can be radiated around the light emitting device.

The laser diode may include the first conductivity type semiconductor layer, the active layer and the second conductivity type semiconductor layer having the above-described structure, like the light emitting element. Then, electro-luminescence (electroluminescence) phenomenon in which light is emitted from the active layer when electric current is applied after bonding the p-type first conductivity type semiconductor and the n-type second conductivity type semiconductor is used, There is a difference between the directionality of light and the wavelength band. That is, the laser diode can emit light having one specific wavelength (monochromatic beam) with the same phase and in the same direction by using a phenomenon called stimulated emission and a constructive interference phenomenon. It can be used for optical communication.

The light receiving element may refer to a photodetector, which is a kind of transducer that detects light and converts its intensity into an electric signal. As such a photodetector, a photodiode (e.g., a PD with a peak wavelength in a visible blind spectral region or a true blind spectral region), a photodiode (e.g., a photodiode such as a photodiode (silicon, selenium), a photoconductive element (cadmium sulfide, cadmium selenide) , Photomultiplier tube, phototube (vacuum, gas-filled), IR (Infra-Red) detector, and the like.

In addition, a semiconductor device such as a photodetector may be fabricated using a direct bandgap semiconductor, which is generally excellent in photo-conversion efficiency. Alternatively, the photodetector has a variety of structures, and the most general structure includes a pinned photodetector using a pn junction, a Schottky photodetector using a Schottky junction, and a metal-semiconductor metal (MSM) photodetector have. Among them, the pin type photodetector and the Schottky type photodetector can be implemented using a nitride semiconductor material.

The photodiode may include a first conductivity type semiconductor layer having the above-described structure, an active layer, and a second conductivity type semiconductor layer in the same manner as the light emitting device. The laser diode has a pn junction or a pin structure. When a reverse bias is applied to the photodiode, the resistance becomes very high and a minute current flows. However, when light is incident on the photodiode, electrons and holes are generated and a current flows. At this time, the magnitude of the voltage is almost proportional to the intensity of light incident on the photodiode.

A photovoltaic cell or a solar cell is a type of photodiode that can convert light into current using a photoelectric effect. The solar cell, like the light emitting device, may include the first conductivity type semiconductor layer, the active layer and the second conductivity type semiconductor layer having the above-described structure. Electrons and holes are generated in the n-type first conductivity type semiconductor layer and the p-type second conductivity type semiconductor layer when solar light or the like is incident from the outside, Type electrode and the p-type electrode. When the n-type electrode and the p-type electrode are connected to each other, electrons move from the n-type electrode to the p-type electrode and current flows.

The solar cell can be divided into a crystalline solar cell and a thin film solar cell. The thin film solar cell can be divided into an inorganic thin film solar cell and an organic thin film solar cell.

In addition, the above-described semiconductor element is not necessarily implemented as a semiconductor, and may further include a metal material as the case may be. 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, or As and may be doped with a p- And may be implemented using a semiconductor material or an intrinsic semiconductor material.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

100, 200: light emitting device 110, 210:
120, 220: substrate 230: light emitting structure
140, 240: stress relaxation layer 250: barrier layer
260: Electron barrier layer 270: Transparent conductive layer
282, 286: first and second electrodes 300: light emitting device package
310: package body 321: first lead frame
322: second lead frame

Claims (8)

A first conductive semiconductor layer;
A stress relieving layer disposed on the first conductive type semiconductor layer;
An active layer of a multiple quantum well structure disposed on the stress relieving layer and having a first quantum wall and / or a second quantum wall as a blocking layer; And
And a second conductivity type semiconductor layer on the active layer. The method of claim 1,
Wherein the barrier layer comprises AlGaN / InGaN / GaN. The method according to claim 1,
Wherein the thickness of the blocking layer is from 1 nanometer to 20 nanometers. 3. The method of claim 2,
And the composition ratio of Al (aluminum) in the AlGaN is 1% to 20%. 3. The method of claim 2,
Wherein a composition ratio of In (indium) in the InGaN is 1% to 20%. The method according to claim 1,
Wherein the stress relieving layer has a plurality of InGaN / GaN or a plurality of GaN / InGaN structures. The method according to claim 6,
Wherein a thickness of the GaN is greater than a thickness of the InGaN. The method according to claim 6,
Wherein the thicknesses of the plurality of GaNs or the thicknesses of the plurality of InGaNs are constant.

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