CN102104097A - Multi-quantum well structure, light-emitting diode and light-emitting diode package - Google Patents
Multi-quantum well structure, light-emitting diode and light-emitting diode package Download PDFInfo
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- CN102104097A CN102104097A CN 201110008901 CN201110008901A CN102104097A CN 102104097 A CN102104097 A CN 102104097A CN 201110008901 CN201110008901 CN 201110008901 CN 201110008901 A CN201110008901 A CN 201110008901A CN 102104097 A CN102104097 A CN 102104097A
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Abstract
The invention discloses a multi-quantum well structure, a light-emitting diode comprising the multi-quantum well structure, and a light-emitting diode package comprising the light-emitting diode. The multi-quantum well structure is arranged between a first conductive type semiconductor layer and a second conductive type semiconductor layer. The multi-quantum well structure comprises a plurality of barrier layers and a plurality of active layers isolated by the barrier layers. The energy band gaps of the active layers are smaller than those of the adjacent barrier layers. The energy band gaps of the barrier layers are smaller than those of the first conductive type semiconductor layer and the second conductive type semiconductor layer. Moreover, the energy band gaps of the plurality of barrier layers are reduced gradually from both sides to the centre, and the energy band gaps of the plurality of active layers are also reduced gradually from both sides to the centre. The invention can effectively prevent a current carrier from escaping, improve the probability of compounding electrons and holes, and further improve the internal quantum efficiency of the light-emitting diode.
Description
Technical field
The present invention relates to the semiconductor light emitting field, particularly relate to a kind of multi-quantum pit structure and manufacture method thereof, comprise the light-emitting diode and the light emission diode package member of described multi-quantum pit structure.
Background technology
Light-emitting diode (LED, Light Emitting Diode) is applied to various fields owing to have long, advantage such as power consumption is low of life-span, especially day by day significantly improves along with its illumination performance index, and LED is commonly used for light-emitting device at lighting field.Wherein, be the III-V compound semiconductor of representative with gallium nitride (GaN) because have that band gap is wide, luminous efficiency is high, characteristics such as electronics saturation drift velocity height, chemical property are stable, in field of optoelectronic devices such as high brightness blue light-emitting diode, blue lasers huge application potential is arranged, caused people's extensive concern.
The researcher obtains the gallium nitrate based blue LED electro-optical efficiency of indium recently about 60%, yet, still lower by the internal quantum efficiency of electronics and the compound generation light of holoe carrier.What is worse, internal quantum efficiency reaches peak value usually when current density is significantly less than operating current, and is accompanied by the increase of electric current and dull the reduction.This phenomenon is commonly referred to " sagging (droop) ".For reaching the peak efficiency of indium gallium nitride based LED, it is vital understanding and reducing " sagging ".People have proposed the various possibility mechanism that cause this " sagging " effect, comprise the charge carrier escape, loss that dislocation causes and auger effect.
Specifically please refer to Fig. 1, it is the generalized section of existing a kind of light-emitting diode, the gallium nitrate based light-emitting diode of indium that described light-emitting diode 10 is a L type structure, and described light-emitting diode 10 is the light-emitting diode of Sapphire Substrate.Described light-emitting diode 10 comprises: Sapphire Substrate 100; Be positioned at n type semiconductor layer 120, multi-quantum pit structure (MQW) 130 and p type semiconductor layer 140 on the Sapphire Substrate 100 successively.Because Sapphire Substrate 100 is non-conductive, therefore, light-emitting diode also needs to form the opening that the degree of depth extends to n type semiconductor layer 120, wherein, n type electrode 160 is positioned at described opening, be used to connect a n type semiconductor layer 120 and a power cathode, p type electrode 170 is positioned at p type semiconductor layer 140 tops, is used to connect a p type semiconductor layer 140 and a positive source.Wherein, n type semiconductor layer 120 is made of n-GaN usually, and p type semiconductor layer 140 is made of p-GaN usually.
Please refer to Fig. 2 and Fig. 3, wherein, Fig. 2 is the generalized section of multi-quantum pit structure shown in Figure 1, and Fig. 3 is the energy band diagram of multi-quantum pit structure shown in Figure 2.A plurality of active layers 132 that described multi-quantum pit structure 130 generally includes a plurality of barrier layers 131 and separated by barrier layer 131, described active layer is also referred to as potential well layer or active layer, energy bandgaps between the conduction band energy of described active layer 132 and the valence band energy is less than the energy bandgaps of barrier layer 131, and described active layer 132 and barrier layer 131 constitute by the III-V semiconducting compound.General, described active layer 132 is by In
1-xGa
xThe N material constitutes, and described barrier layer 131 is made of GaN.And the energy gap of a plurality of active layers 132 is all identical, and the energy bandgaps Eg of promptly a plurality of active layers 132 is all identical, that is to say, the degree of depth of each trap all is identical.
Described light-emitting diode 10 is used for when luminous, with first electrode 160 be electrically connected to power cathode, second electrode 170 is electrically connected to positive source, because n type semiconductor layer 120 is opposite with the doping type of p type semiconductor layer 140, the gallium nitride that the n type mixes drives by external voltage and makes electron drift, the gallium nitride that the p type mixes drives by external voltage and makes hole drift, under the PN junction forward bias, near the PN junction district or in the trap, after high-octane electronics was fallen valence band and hole-recombination in the conduction band, unnecessary energy discharged with the form of light and heat.By adjusting the band structure and the energy bandgaps of material, can change light wavelength that light-emitting diode sends, just spectrum or color; By adjusting the flow through size of led current, the just intensity of scalable light emitting diode light.Be understandable that although in described light-emitting diode 10, owing to adopted multi-quantum pit structure, it is than traditional single quantum, charge carrier is not easy to escape more,, this still can not satisfy the demands.How can further prevent the charge carrier escape, thereby improve the internal quantum efficiency of light-emitting diode, become those skilled in the art's problem demanding prompt solution.
In order to solve the problem that charge carrier is escaped, another kind of multi-quantum pit structure is also disclosed in the prior art.As shown in Figure 4, the mode of described multi-quantum pit structure by the barrier layer at two ends is increased reaches the purpose that stops that charge carrier is escaped.Yet the energy bandgaps Eg of the active layer of described multi-quantum pit structure is all identical, only relies on and increases barrier layer, still can not reach the effect that preferable inhibition charge carrier is escaped.
CN 1518137A discloses a kind of optics with quantum well, this optics with quantum well has predetermined linear tilt by conduction band energy and the valence band energy that makes quantum well, perhaps, have the band gap hierarchic structure of using a plurality of active layers, improved the recombination rate in electronics and hole thus.Yet this patent only is that electronics and hole can be distributed uniformly, but can not stop the charge carrier escape very effectively.
CN 1567607A discloses a kind of light-emitting diode of the GaN of having based multiple quantum well, the quantum well region of this light-emitting diode undopes, the growth of quantum well region both sides has plain GaN separator, thickness by reasonable adjustment GaN separator, can adjust the position of p-N knot effectively, improve the recombination probability in electronics and hole.Yet this patent also only makes electronics and the hole in the quantum well spatially coincide together, and still can not stop the charge carrier escape very effectively.
Summary of the invention
The objective of the invention is to, a kind of multi-quantum pit structure and manufacture method thereof are provided, to solve the fugacious problem of existing multi-quantum pit structure charge carrier.
Another object of the present invention is to, a kind of light-emitting diode is provided, escape, improve the internal quantum efficiency of light-emitting diode to prevent charge carrier.
Another purpose of the present invention is, a kind of light emission diode package member is provided, and with when preventing that charge carrier from escaping, provides the light of predetermined color.
For solving the problems of the technologies described above, the invention provides a kind of multi-quantum pit structure, described multi-quantum pit structure is arranged between first conductive type semiconductor layer and second conductive type semiconductor layer, described multi-quantum pit structure comprises a plurality of barrier layers and a plurality of active layers that separated by barrier layer, the energy bandgaps of described active layer is less than the energy bandgaps of adjacent barrier layer, the energy bandgaps of described barrier layer is less than the energy bandgaps of described first conductive type semiconductor layer and second conductive type semiconductor layer, and, the energy bandgaps of described a plurality of barrier layers reduces in the middle of two side direction gradually, and the energy bandgaps of a plurality of active layers also reduces in the middle of two side direction gradually.
Optionally, in described multi-quantum pit structure, the energy bandgaps of described a plurality of barrier layers reduces from two side direction mid lines.The energy bandgaps of described active layer is 2.63eV～3.41eV.
Optionally, in described multi-quantum pit structure, described barrier layer and active layer constitute by the III-V compounds of group.Described first conductive type semiconductor layer and second conductive type semiconductor layer are made of GaN, and described barrier layer is by In
1-yGa
yN constitutes, and described active layer is by In
1-xGa
xN constitutes, wherein, and 0.7＜x＜1, x＜y＜1.
Optionally, in described multi-quantum pit structure, described multi-quantum pit structure comprises 2～10 active layers.The thickness of described a plurality of active layers is all identical.The thickness of described a plurality of barrier layers is all identical.
Accordingly, the present invention also provides a kind of manufacture method of multi-quantum pit structure, comprising: alternately form a plurality of barrier layers and active layer between first conductive type semiconductor layer and second conductive type semiconductor layer; Wherein, when forming described barrier layer, make the energy bandgaps of the energy bandgaps of described barrier layer, and the energy bandgaps of described a plurality of barrier layers is reduced in the middle of two side direction gradually less than described first conductive type semiconductor layer and second conductive type semiconductor layer; When forming described active layer, the energy bandgaps of a plurality of active layers is reduced gradually in the middle of two side direction.
Optionally,, utilize the mode of metallo-organic compound chemical vapour deposition (CVD), alternately form a plurality of barrier layers and active layer in described multi-quantum pit structure manufacture method.Described barrier layer and active layer constitute by the III-V compounds of group, and the variation of the predetermined component content by adjusting described active layer reduces the energy bandgaps of described a plurality of active layers gradually in the middle of two side direction; The variation of the predetermined component content by adjusting described barrier layer reduces the energy bandgaps of described a plurality of barrier layers gradually in the middle of two side direction.
Described first conductive type semiconductor layer and second conductive type semiconductor layer are made of GaN, and described barrier layer is by In
1-yGa
yN constitutes, and described active layer is by In
1-xGa
xN constitutes, wherein, 0.7＜x＜1, x＜y＜1, the predetermined composition of described active layer and barrier layer is In.
Accordingly, the present invention also provides a kind of light-emitting diode, comprising: first conductive type semiconductor layer and second conductive type semiconductor layer; And described multi-quantum pit structure.
Optionally, in described light-emitting diode, also comprise substrate, resilient coating and transparency conducting layer, wherein, described resilient coating is between the described substrate and first conductive type semiconductor layer; Described transparency conducting layer is positioned on described second conductive type semiconductor layer.Described first conduction type is the n type, and described second conduction type is the p type.
Optionally, in described light-emitting diode, comprise that also first electrode, second electrode and the degree of depth extend to the opening of first conductive type semiconductor layer, wherein, described first electrode is positioned at opening, is used to connect first conductive type semiconductor layer and power cathode; Described second electrode is positioned at the transparency conducting layer top, is used to connect transparency conducting layer and positive source.
Optionally, in described light-emitting diode, described light-emitting diode also comprises first electrode and second electrode, wherein, described first electrode is positioned on the surface of described substrate away from first conductive type semiconductor layer, is used to connect first conductive type semiconductor layer and power cathode; Described second electrode is positioned at the transparency conducting layer top, is used to connect transparency conducting layer and positive source.
Accordingly, the present invention also provides a kind of light emission diode package member, comprising: described light-emitting diode; And the fluorescent material that is arranged on described light emitting surface of light emitting diode, so that the light of predetermined color to be provided.
Optionally, in described light emission diode package member, also comprise the epoxy resin that covers described light emitting surface of light emitting diode, described fluorescent material is coated in described epoxy resin surface.
Optionally, in described light emission diode package member, also comprise the epoxy resin that covers described light emitting surface of light emitting diode, described fluorescent material is incorporated in the described epoxy resin.
Optionally, in described light emission diode package member, described fluorescent material and fluorescent material are modulated into fluorescent glue with glue, more described fluorescent glue are coated in light emitting surface of light emitting diode.
Optionally, in described light emission diode package member, the optical source wavelength of described light-emitting diode emission is between 370nm to 480nm, and described fluorescent material is made up of purple light excited fluorescent material and blue-light excited fluorescent material, so that white light to be provided.
Owing to adopted above technical scheme, compared with prior art, the present invention has the following advantages:
Multi-quantum pit structure provided by the invention, the energy bandgaps of a plurality of barrier layers is all less than the energy bandgaps of first conductive type semiconductor layer and second conductive type semiconductor layer, and, the energy bandgaps of a plurality of barrier layers reduces in the middle of two side direction gradually, the energy bandgaps of a plurality of active layers also reduces in the middle of two side direction gradually, promptly, keep the degree of depth of trap constant, but active layer energy bandgaps reduce gradually in the middle of two side direction, can prevent the charge carrier escape effectively, improve the compound probability in electronics and hole, and then improve the internal quantum efficiency of light-emitting diode.
Light emission diode package member provided by the invention is provided with fluorescent material by the exiting surface at light-emitting diode, to reach the purpose that predetermined color light is provided.Especially, the optical source wavelength of described light-emitting diode emission is provided with purple light excited fluorescent material and blue-light excited fluorescent material by the exiting surface at light-emitting diode between 370nm to 480nm, to produce white light.
Description of drawings
Fig. 1 is the generalized section of existing a kind of light-emitting diode;
Fig. 2 is the generalized section of multi-quantum pit structure shown in Figure 1;
Fig. 3 is the energy band diagram of multi-quantum pit structure shown in Figure 2;
Fig. 4 is the energy band diagram of existing another kind of multi-quantum pit structure;
Fig. 5 is the generalized section of the multi-quantum pit structure of the embodiment of the invention;
Fig. 6 is the energy band diagram of multi-quantum pit structure shown in Figure 5;
Fig. 7 is the generalized section of the light-emitting diode of the embodiment of the invention;
Fig. 8 is the generalized section of the light emission diode package member of the embodiment of the invention.
Embodiment
Core concept of the present invention is, a kind of multi-quantum pit structure is provided, comprise described multi-quantum pit structure light-emitting diode, and the light emission diode package member that comprises described light-emitting diode, in described multi-quantum pit structure, the energy bandgaps of a plurality of barrier layers is all less than the energy bandgaps of first conductive type semiconductor layer and second conductive type semiconductor layer, and, the energy bandgaps of a plurality of barrier layers reduces in the middle of two side direction gradually, the energy bandgaps of a plurality of active layers also reduces in the middle of two side direction gradually, promptly, keep the degree of depth of trap constant, but active layer energy bandgaps reduce gradually in the middle of two side direction, can prevent the charge carrier escape effectively, improve the compound probability in electronics and hole, and then improve the internal quantum efficiency of light-emitting diode.
Please refer to Fig. 5 and Fig. 6, wherein, Fig. 5 is the generalized section of the multi-quantum pit structure of the embodiment of the invention, and Fig. 6 is the energy band diagram of multi-quantum pit structure shown in Figure 5.
As shown in Figure 5 and Figure 6, multi-quantum pit structure 230 is arranged between first conductive type semiconductor layer 220 and second conductive type semiconductor layer 230, described multi-quantum pit structure 230 comprises a plurality of barrier layers 231 and a plurality of active layers 232 that separated by barrier layer 231, the energy bandgaps of described active layer 232 is less than the energy bandgaps of adjacent barrier layer 231, the energy bandgaps of described barrier layer 231 is less than the energy bandgaps of first conductive type semiconductor layer 220 and second conductive type semiconductor layer 230, and, the energy bandgaps of a plurality of barrier layers 231 reduces in the middle of two side direction gradually, the energy bandgaps of a plurality of active layers 232 also reduces in the middle of two side direction gradually, that is to say, under the constant prerequisite of the degree of depth of trap, 232 energy bandgaps of active layer reduces in the middle of two side direction gradually, can prevent the charge carrier escape effectively, improve the compound probability in electronics and hole, and then the internal quantum efficiency of raising light-emitting diode, the luminous efficiency and the reliability of raising light-emitting diode.
In the present embodiment, the energy bandgaps of described a plurality of barrier layer 231 is from middle the reducing with certain slope linearity of two side direction.Need to prove that in other embodiment of the present invention, the energy bandgaps of described a plurality of barrier layers 231 also can nonlinearly reduce.
Preferably, the energy bandgaps Eg of described active layer 232 all between 2.63eV to 3.41eV, can prevent the charge carrier escape very effectively, and may command is launched the light of expection wavelength.Be understandable that above-mentioned numerical value also is not used in qualification the present invention, the energy bandgaps of active layer 232 can be adjusted accordingly.
Wherein, described barrier layer 231 and active layer 232 constitute by the III-V semiconducting compound.Preferable, described first conductive type semiconductor layer 220 and second conductive type semiconductor layer 230 constitute by GaN, and described barrier layer 231 is by In
1-yGa
yN constitutes, and described active layer 232 is by In
1-xGa
xN constitutes, wherein, and 0.7＜x＜1, x＜y＜1.In the present embodiment, first conduction type is the n type, and second conduction type is the p type, and therefore, described first conductive type semiconductor layer 220 is made of n-GaN, and 230 of described second conductive type semiconductor layers are made of p-GaN.
Further, the material component difference between a plurality of active layers 232, thus make the energy bandgaps between a plurality of active layers 232 have nothing in common with each other; Equally, the material component between a plurality of barrier layers 231 is also inequality, thereby makes the energy bandgaps between a plurality of barrier layers 231 have nothing in common with each other.Can control its energy bandgaps width by the numerical value of the x in the control active layer material, thereby make the energy bandgaps of a plurality of active layers 232 reduce gradually; And by controlling the numerical value of the y in the barrier layer material, make the energy bandgaps of barrier layer 231 all less than the energy bandgaps of first conductive type semiconductor layer 220 and second conductive type semiconductor layer 230, and make the energy bandgaps between a plurality of barrier layers 231 have nothing in common with each other.
Need to prove that foregoing description also is not used in qualification the present invention, described active layer 232 also can be by removing In
1-xGa
xOther material outside the N constitutes, as long as by being scheduled to the content of composition in the control active layer material, make the energy bandgaps of a plurality of active layers 232 reduce successively to get final product in the middle of two side direction.In addition, described barrier layer 231 also can be by removing In
1-yGa
yOther material outside the N constitutes, as long as make the energy bandgaps of the energy bandgaps of active layer 232 less than adjacent barrier layer 231, make the energy bandgaps of the energy bandgaps of described barrier layer 231, and make the energy bandgaps between a plurality of barrier layers 231 in the middle of two side direction, reduce successively to get final product less than described first conductive type semiconductor layer 220 and second conductive type semiconductor layer 230.
Wherein, described multi-quantum pit structure 230 can comprise 2～10 active layers 232.Preferably, the quantity of active layer 232 is 2～6, and the active layer number of multi-quantum pit structure 230 is set to above-mentioned numerical value, can be under the prerequisite that obtains comparatively desirable internal quantum efficiency, simplify the structure of multi-quantum pit structure 230 as much as possible, thereby reduce the complexity of manufacturing process.Certainly, the number of described barrier layer 231 and active layer 232 is not limited to the numerical value of foregoing description.
In the multi-quantum pit structure 230 that present embodiment provides, the bottom of each trap all is levels, and promptly the energy bandgaps of single active layer is a uniformity, and the energy bandgaps between a plurality of active layer has nothing in common with each other.Yet will be appreciated that described multi-quantum pit structure 230 also can be the trap of other shape, for example, the bottom of each trap also can tilt.
In the multi-quantum pit structure 230 that present embodiment provides, the thickness of a plurality of barrier layers 231 all is identical, and the thickness of a plurality of active layers 232 also is identical, so that processing and fabricating.For example, the thickness of each barrier layer 231 is 0.1～10nm, and the thickness of each active layer 232 is similarly 0.1～10nm.Yet will be appreciated that, thickness between described a plurality of barrier layer 231 also can be inequality, equally, the thickness between described a plurality of active layers 232 also can be inequality, and those skilled in the art can reach the purpose of emission predetermined wavelength light by the thickness of adjusting barrier layer 231 and active layer 232.
The embodiment of the invention also provides a kind of multi-quantum pit structure manufacture method, and described multi-quantum pit structure manufacture method comprises: alternately form a plurality of barrier layers 231 and a plurality of active layer 232 between first conductive type semiconductor layer 220 and second conductive type semiconductor layer 230; Wherein, when forming described barrier layer 231, make the energy bandgaps of the energy bandgaps of barrier layer 231, and the energy bandgaps of described a plurality of barrier layer 231 is reduced in the middle of two side direction gradually less than first conductive type semiconductor layer 220 and second conductive type semiconductor layer 230; When forming active layer 232, the energy bandgaps of a plurality of active layers 232 is reduced gradually in the middle of two side direction.That is, keep the degree of depth of trap constant, but the energy bandgaps between a plurality of active layer reduces gradually in the middle of two side direction, can prevent more effectively that charge carrier from escaping, improve the compound probability in electronics and hole.
The mode of metallo-organic compound chemical vapour deposition (CVD) (MOCVD) be can utilize, a plurality of barrier layers 231 and a plurality of active layer 232 alternately formed.Described barrier layer 231 and active layer 232 constitute by the III-V compounds of group, and the variation of the predetermined component content by adjusting described active layer 232 materials reduces the energy bandgaps of described a plurality of active layer 232 gradually in the middle of two side direction; And the variation of the predetermined component content by adjusting described barrier layer 231, the energy bandgaps of described a plurality of barrier layer 231 is reduced in the middle of two side direction gradually.
In the present embodiment, the technological temperature of described metallo-organic compound chemical vapor deposition method for example is 540～800 ℃, and chamber pressure for example is 50～400Torr, and the Ga source for example is TMGa or TEGa, and the In source for example is TMIn or TEIn, and the N source for example is NH
3, carrier gas for example is N2, H2 or other inert gas.Wherein, the flow in In source for example is 100～500 μ mol/min, and Ga source and In source ratio for example are 0.1～0.4, NH
3Flow for example be 0.3～0.5slpm, the flow of carrier gas for example is 0.3～0.5slpm.Can in same chamber, finish above-mentioned technology, only need to change different programs (controlling different flows), can realize above-mentioned purpose.Certainly, foregoing description also is not used in qualification the present invention, and those skilled in the art can adjust reacting gas and every technological parameter accordingly according to the actual conditions of metallo-organic compound chemical vapour deposition (CVD) board.
In the multi-quantum pit structure manufacture method that present embodiment provides, described barrier layer 231 is by In
1-yGa
yN constitutes, and described active layer 232 is by In
1-xGa
xN constitutes, wherein, 0.7＜x＜1, x＜y＜1, described barrier layer 231 and active layer 232 predetermined compositions are In.Can be by adjusting described In
1-xGa
xThe numerical value of x among the N promptly reduces the energy bandgaps of a plurality of active layers 232 by the content of adjusting In gradually in the middle of two side direction, perhaps by the content of adjusting Ga the energy bandgaps of a plurality of active layers 232 is reduced gradually in the middle of two side direction.In like manner, can be by adjusting described In
1-yGa
yThe numerical value of y among the N promptly reduces the energy bandgaps of a plurality of barrier layers 231 by the content of adjusting In gradually in the middle of two side direction, perhaps by the content of adjusting Ga the energy bandgaps of a plurality of barrier layers 231 is reduced gradually in the middle of two side direction.
To adjust described In
1-xGa
xThe numerical value of x is example among the N, can adjust the flow in In source separately when carrying out the metallo-organic compound chemical vapor deposition method, perhaps, adjusts the flow in Ga source separately, perhaps, adjusts the flow in In source and Ga source simultaneously and adjusts In accordingly
1-xGa
xThe value of x among the N, thus reach the purpose that the energy bandgaps that makes a plurality of active layers 232 reduces in the middle of two side direction gradually.More specifically, at described In
1-xGa
xThe x value is big more among the N, and then the energy bandgaps of active layer reduces accordingly.That is, at described In
1-xGa
xIn the N material, the content of In is few more, and the energy bandgaps of corresponding active layer is big more.If the content of In is reduced, only need the In source flux to be reduced or the flow in Ga source is reduced.Certainly, the present invention is not limited to foregoing description, can also realize purpose of the present invention by the mode that improves or reduce epitaxial growth temperature.
The embodiment of the invention also provides a kind of light-emitting diode that comprises described multi-quantum pit structure.Specifically please refer to Fig. 7, it is the generalized section of the light-emitting diode of the embodiment of the invention.
As shown in Figure 7, described light-emitting diode 20 comprises: substrate 200; Be formed at first conductive type semiconductor layer 220, second conductive type semiconductor layer 240 and multi-quantum pit structure 230 on the substrate 200, described multi-quantum pit structure 230 is arranged between described first conductive type semiconductor layer 220 and second conductive type semiconductor layer 230.Because the energy bandgaps of a plurality of active layers 232 of multi-quantum pit structure 230 reduces in the middle of two side direction gradually, and, the energy bandgaps of barrier layer is less than the energy bandgaps of first conductive type semiconductor layer 220 and second conductive type semiconductor layer 230, the energy bandgaps of described a plurality of barrier layer 231 also reduces in the middle of two side direction gradually, promptly, keep the degree of depth of trap constant, but active layer 232 energy bandgaps reduce gradually in the middle of two side direction, can prevent the charge carrier escape effectively, improve the compound probability in electronics and hole, and then improve the internal quantum efficiency of light-emitting diode.
Preferably, in the light-emitting diode 20 that provides in the present embodiment, also comprise resilient coating 210, described resilient coating 210 is between the substrate 200 and first conductive type semiconductor layer 220, described resilient coating 210 can improve lattice constant mismatch and the stress problem between substrate 200 and the gallium nitride material, the material of described resilient coating 210 is preferably n type indium nitride or n type carborundum, to obtain preferable conductive effect.
Preferably, in the light-emitting diode 20 that provides in the present embodiment, also comprise transparency conducting layer 250, described transparency conducting layer 250 is positioned on described second conductive type semiconductor layer 240, because the conductivity of p type gallium nitride is smaller, therefore at the current-diffusion layer of second conductive type semiconductor layer, 240 surface deposition layer of metal, help to improve conductivity, the material of described transparency conducting layer 250 for example is the Ni/Au material.
In the light-emitting diode 20 that provides in the present embodiment, described first conduction type is the n type, and described second conduction type is the p type.Described light-emitting diode 200 comprises that also first electrode 260, second electrode 270 and the degree of depth extend to the opening of first conductive type semiconductor layer 220, wherein, first electrode 260 is positioned at described opening, be used to connect first conductive type semiconductor layer 220 and the power cathode, second electrode 270 is positioned at transparency conducting layer 250 tops, be used to connect transparency conducting layer 250 and positive source, thereby form the light emitting diode construction (being also referred to as L type structure) of level.In the light emitting diode construction of level, whether conduct electricity and no requirement (NR) for substrate 200, therefore, described substrate 200 promptly can be silicon substrate, silicon carbide substrates or the gallium nitride substrate that can conduct electricity, and also can be the Sapphire Substrate that can not conduct electricity.
Need to prove that in another specific embodiment of the present invention, described first electrode 260 also can be positioned on the surface of substrate 200 away from first conductive type semiconductor layer 220, is used to connect first conductive type semiconductor layer 220 and the power cathode; Second electrode 270 is positioned at the transparency conducting layer top, is used to connect transparency conducting layer 250 and positive source, thereby forms vertical light emitting diode construction (being also referred to as V-structure).Described light-emitting diode is used for when luminous, and LED core links to each other with positive source by the second conduction type electrode 260, links to each other with power cathode by the first conduction type electrode 270.Than the light emitting diode construction of level, vertical light emitting diode construction radiating effect is better, and helps saving chip area, improves the chip utilance.Be understandable that if form vertical light emitting diode construction, substrate 200 must be the substrate that can conduct electricity, for example, silicon substrate, silicon carbide substrates or gallium nitride substrate.
The present invention also provides a kind of light emission diode package member that comprises described light-emitting diode.Specifically please refer to Fig. 8, it is the generalized section of the light emission diode package member of the embodiment of the invention.
Described light emission diode package member 20 ' comprising: light-emitting diode 20; And the fluorescent material (not shown among Fig. 8) that is arranged on described light-emitting diode 20 exiting surfaces, so that the light of predetermined color to be provided.In light emission diode package member 20 ', multi-quantum pit structure 230 comprises a plurality of barrier layers 231 and a plurality of active layers 232 that separated by barrier layer 231, the energy bandgaps of described active layer 232 is less than the energy bandgaps of adjacent barrier layer 231, and, the energy bandgaps of described a plurality of active layer 232 reduces in the middle of two side direction gradually, the energy bandgaps of described a plurality of barrier layer 231 also reduces in the middle of two side direction gradually, that is to say, under the constant prerequisite of the degree of depth of trap, make active layer 232 energy bandgaps reduce gradually in the middle of two side direction, can prevent the charge carrier escape effectively, improve the compound probability in electronics and hole, and then improve the internal quantum efficiency of light-emitting diode.
Yet,, can cause described light-emitting diode to launch the light of the wavelength of not expecting (light that wavelength is relatively short) because the energy bandgaps of active layer changes, at this moment, can to produce the light of required predetermined color, improve light utilization efficiency by fluorescent material being set at light-emitting diode 20 exiting surfaces.
In the present embodiment, described light emission diode package member 20 ' also comprises the epoxy resin 30 that covers described light-emitting diode 20 exiting surfaces, and described fluorescent material can be coated in epoxy resin 30 surfaces.Can pass through known method for packing, apply epoxy resin, not repeat them here at LED surface.
Need to prove, fluorescent material set-up mode of the present invention is not limited to foregoing description, also can in the process of preparation epoxy resin, directly mix fluorescent material, the epoxy resin that will mix fluorescent material again covers light emitting surface of light emitting diode, also can be indirect reach the purpose that fluorescent material is arranged on light emitting surface of light emitting diode.
Perhaps, described fluorescent material and fluorescent material are modulated with glue, made fluorescent glue, more described fluorescent glue is coated on the light emitting surface of light emitting diode, also can reach same purpose.Utilisation point glue machine is coated in described fluorescent glue on the light emitting surface of light emitting diode, and then reaches indirectly fluorescent material is arranged on purpose on the exiting surface of light-emitting diode.
Further, in described light emission diode package member 20 ', the optical source wavelength that described light-emitting diode is launched is between 370nm to 480nm, and corresponding, described fluorescent material is made up of purple light excited fluorescent material and blue-light excited fluorescent material, so that white light to be provided.
More specifically, can perhaps apply purple light excited fluorescent material and blue-light excited fluorescent material, thereby produce white light more with practical value by in epoxy resin, mixing purple light excited fluorescent material and blue-light excited fluorescent material at epoxy resin surface.And, can realize controlling in a big way the color developing of white light by the mixed proportion of purple light excited fluorescent material of control and blue-light excited fluorescent material.For example, the weight ratio of each composition is in the described fluorescent material: purple light excited fluorescent material: 50%～75%, and blue-light excited fluorescent material: 25%～50%.Certainly, above-mentioned numerical value also is not used in qualification the present invention, can obtain the light of needed color accordingly by adjusting the composition of fluorescent material.In addition, can adopt known purple light excited fluorescent material and blue-light excited fluorescent material, not give unnecessary details the concrete composition of fluorescent material at this.
Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.
Claims (23)
1. multi-quantum pit structure, described multi-quantum pit structure is arranged between first conductive type semiconductor layer and second conductive type semiconductor layer, described multi-quantum pit structure comprises a plurality of barrier layers and a plurality of active layers that separated by barrier layer, the energy bandgaps of described active layer is less than the energy bandgaps of adjacent barrier layer, the energy bandgaps of described barrier layer is less than the energy bandgaps of described first conductive type semiconductor layer and second conductive type semiconductor layer, and, the energy bandgaps of described a plurality of barrier layers reduces in the middle of two side direction gradually, and the energy bandgaps of described a plurality of active layers also reduces in the middle of two side direction gradually.
2. multi-quantum pit structure as claimed in claim 1 is characterized in that the energy bandgaps of described a plurality of barrier layers reduces from two side direction mid lines.
3. multi-quantum pit structure as claimed in claim 2 is characterized in that, the energy bandgaps of described active layer is 2.63eV～3.41eV.
4. multi-quantum pit structure as claimed in claim 3 is characterized in that, described barrier layer and active layer constitute by the III-V compounds of group.
5. multi-quantum pit structure as claimed in claim 4 is characterized in that, described first conductive type semiconductor layer and second conductive type semiconductor layer are made of GaN, and described barrier layer is by In
1-yGa
yN constitutes, and described active layer is by In
1-xGa
xN constitutes, wherein, and 0.7＜x＜1, x＜y＜1.
6. multi-quantum pit structure as claimed in claim 1 is characterized in that, described multi-quantum pit structure comprises 2～10 active layers.
7. as any described multi-quantum pit structure in the claim 1 to 6, it is characterized in that the thickness of described a plurality of active layers is all identical.
8. as any described multi-quantum pit structure in the claim 1 to 6, it is characterized in that the thickness of described a plurality of barrier layers is all identical.
9. the manufacture method of a multi-quantum pit structure as claimed in claim 1 comprises:
Between first conductive type semiconductor layer and second conductive type semiconductor layer, alternately form a plurality of barrier layers and a plurality of active layer;
Wherein, when forming described barrier layer, make the energy bandgaps of the energy bandgaps of described barrier layer, and the energy bandgaps of described a plurality of barrier layers is reduced in the middle of two side direction gradually less than described first conductive type semiconductor layer and second conductive type semiconductor layer; When forming described active layer, the energy bandgaps of a plurality of active layers is reduced gradually in the middle of two side direction.
10. manufacture method as claimed in claim 9 is characterized in that, utilizes the mode of metallo-organic compound chemical vapour deposition (CVD), alternately forms a plurality of barrier layers and a plurality of active layer.
11., it is characterized in that described barrier layer and active layer constitute by the III-V compounds of group as claim 9 or 10 described manufacture methods; The variation of the predetermined component content by adjusting described barrier layer reduces the energy bandgaps of described a plurality of barrier layers gradually in the middle of two side direction; The variation of the predetermined component content by adjusting described active layer reduces the energy bandgaps of described a plurality of active layers gradually in the middle of two side direction.
12. manufacture method as claimed in claim 11 is characterized in that, described first conductive type semiconductor layer and second conductive type semiconductor layer are made of GaN, and described barrier layer is by In
1-yGa
yN constitutes, and described active layer is by In
1-xGa
xN constitutes, wherein, 0.7＜x＜1, x＜y＜1, the predetermined composition of described active layer and barrier layer is In.
13. a light-emitting diode comprises:
First conductive type semiconductor layer and second conductive type semiconductor layer; And
As any described multi-quantum pit structure in the claim 1～8.
14. light-emitting diode as claimed in claim 13 is characterized in that, described light-emitting diode also comprises substrate, resilient coating and transparency conducting layer, wherein,
Described resilient coating is between the described substrate and first conductive type semiconductor layer;
Described transparency conducting layer is positioned on described second conductive type semiconductor layer.
15. light-emitting diode as claimed in claim 14 is characterized in that, described first conduction type is the n type, and described second conduction type is the p type.
16. light-emitting diode as claimed in claim 15 is characterized in that, described light-emitting diode comprises that also first electrode, second electrode and the degree of depth extend to the opening of described first conductive type semiconductor layer, wherein,
Described first electrode is positioned at opening, is used to connect first conductive type semiconductor layer and a power cathode;
Described second electrode is positioned at the transparency conducting layer top, is used to connect a transparency conducting layer and a positive source.
17. light-emitting diode as claimed in claim 16 is characterized in that, described light-emitting diode also comprises first electrode and second electrode, wherein,
Described first electrode is positioned on the surface of described substrate away from first conductive type semiconductor layer, is used to connect first conductive type semiconductor layer and a power cathode;
Described second electrode is positioned at the transparency conducting layer top, is used to connect a transparency conducting layer and a positive source.
18. a light emission diode package member comprises:
As any described light-emitting diode in the claim 13～17; And
Be arranged on the fluorescent material of described light emitting surface of light emitting diode, so that the light of predetermined color to be provided.
19. light emission diode package member as claimed in claim 18 is characterized in that, also comprises the epoxy resin that covers described light emitting surface of light emitting diode, described fluorescent material is coated in described epoxy resin surface.
20. light emission diode package member as claimed in claim 18 is characterized in that, also comprises the epoxy resin that covers described light emitting surface of light emitting diode, described fluorescent material is incorporated in the described epoxy resin.
21. light emission diode package member as claimed in claim 18 is characterized in that, described fluorescent material and fluorescent material are modulated into fluorescent glue with glue, more described fluorescent glue are coated in light emitting surface of light emitting diode.
22., it is characterized in that the optical source wavelength of described light-emitting diode emission is between 370nm to 480nm as any described light emission diode package member in the claim 18 to 21.
23. light emission diode package member as claimed in claim 22 is characterized in that, described fluorescent material is made up of purple light excited fluorescent material and blue-light excited fluorescent material, so that white light to be provided.
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