CN102820398B - Distributed Bragg reflection and small area metal contact composite three-dimensional electrode - Google Patents
Distributed Bragg reflection and small area metal contact composite three-dimensional electrode Download PDFInfo
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- CN102820398B CN102820398B CN201210319019.3A CN201210319019A CN102820398B CN 102820398 B CN102820398 B CN 102820398B CN 201210319019 A CN201210319019 A CN 201210319019A CN 102820398 B CN102820398 B CN 102820398B
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Abstract
A distributed Bragg reflection and small area metal contact composite three-dimensional electrode relates to an electrode and can restrain strong negative effects of a light emitting diode metal electrode in light absorbing and improve transverse current expanding uniformity of a light emitting diode. The distributed Bragg reflection and small area metal contact composite three-dimensional electrode is provided with a distributed Bragg reflection structure, a small area metal ohmic contact array and a semiconductor substrate, the distributed Bragg reflection structure is arranged on the semiconductor substrate, and the distributed Bragg reflection structure is a multilayer medium which is a membrane stack being composed of at least one high refractive index medium layer and at least one low refractive index medium layer. The small area metal ohmic contact array is compounded with and penetrates through the distributed Bragg reflection structure to be in ohmic contact with the semiconductor substrate to form the composite three-dimensional electrode.
Description
Technical field
The present invention relates to a kind of electrode, especially relate to Distributed Bragg Reflection and small size Metal Contact complex three-dimensional electrode that one is applicable to light-emitting diode (LED).
Background technology
Current, in the face of global non-renewable resources are on the verge of exhausted present situation, energy savings has become the core topic of 21 century.Illumination is very important in world energy sources wastage in bulk or weight, and therefore, the research of energy-conserving light source of new generation receives increasing concern.Light-emitting diode (LED), as new and effective solid state light emitter, has the remarkable advantages such as long-life, energy-conserving and environment-protective, rich color, becomes the desirable third generation light source after incandescent lamp and fluorescent lamp.In recent years, along with the development of semiconductor fabrication, large-power light-emitting diodes is increasingly extensive in the application in the fields such as traffic, illumination, military affairs.
But, for large-power light-emitting diodes, the contact area also corresponding increase of its metal electrode and semiconductor base, this light that part LED is sent block by electrode and absorb, cause optical output power heavy losses, thus constrain the further raising of LED light extraction efficiency.So, people are for the low problem of LED light extraction efficiency, concrete solution is proposed from device architecture aspect, as make flip chip structure, array structure electrode etc. (1, Chih-Feng Lu et.al., " InGaN/GaNquantum well interconnected microdisk light emitting diodes ", Applied Physics Letters, 77 (2000) 3236; 2, Chih-Feng Lu et.al., " Reduction in the efficiency droop effect of a light-emitting diodethrough surface plasmon coupling ", Applied Physics Letters, 96 (2010) 261104.).In flip chip structure, utilize Sapphire Substrate face for light-emitting window, thus reduce blocking of electrode pair light, luminous efficiency is increased; But it is to sacrifice the emergent light in sapphire side current expansion uniformity and opposite side GaN face for cost.In array electrode structure, by appropriate design array distribution, the relative contact that effectively can reduce metal and semiconductor base amasss, and improves the uniformity of current expansion, but faced by GaN, the absorption of light is still serious.
Therefore, how to improve the light extraction efficiency of large-power light-emitting diodes, and improve the uniformity of its lateral current, become problem demanding prompt solution in light-emitting diode research field now.
Summary of the invention
The present invention aims to provide a kind of light emitting diode metal electrode that suppresses and absorbs the stronger negative effect of light, improves Distributed Bragg Reflection and the small size Metal Contact complex three-dimensional electrode of light-emitting diode lateral current uniformity.
The present invention is provided with Distributed Bragg Reflection (DBR) structure, small size metal ohmic contact array and semiconductor base; Described Distributed Bragg Reflection (DBR) structure is established on a semiconductor substrate, described Distributed Bragg Reflection (DBR) structure is multilayer dielectricity, the membrane stack that described multilayer dielectricity is alternately made up of at least 1 floor height index dielectric layer and at least 1 layer of low refractive index dielectric layer; Described small size metal ohmic contact array and Distributed Bragg Reflection (DBR) structure composite also run through Distributed Bragg Reflection (DBR) structure and form complex three-dimensional electrode with semiconductor base ohmic contact again.
Described multilayer dielectricity can be provided with GaN/AlN multilayer dielectric film and the HfO in 10 cycles in 20 cycles
2/ SiO
2multilayer dielectricity membrane structure, can record the reflectivity of this dbr structure up to 98%.
Described small size metal ohmic contact array is interconnected amongst one another by deposition layer of metal film, and metallic film and electrod-array close contact, contribute to the even diffusion of electric current, improve the performance of device.Described metallic film can adopt Au film or Ag film etc.
The present invention is Distributed Bragg Reflection and small size Metal Contact complex three-dimensional electrode, i.e. the three-diemsnional electrode of semiconductor photoelectronic device that is combined into of Distributed Bragg Reflection (DBR) structure and small size metal ohmic contact array.
The optical thickness of every layer material of described multilayer thin film stack is 1/4th of LED active area emission wavelength, thus the high reflection mirror defined for LED luminescence band, the light of directive three-diemsnional electrode can be reflected back, and then eliminate metal extension layer to greatest extent to the absorption of light.
The key property of Distributed Bragg Reflection (DBR) structure is most high reflectance and the reflection bandwidth of its design wavelength.Reflectivity can increase along with the increase of film periodicity, in theory can close to 100%; Reflection bandwidth then depends on the refractive index difference of different materials, and difference more large bandwidth is wider, and this outer film periodicity increase also can make zone of reflections band edge more precipitous.The dbr structure being the most often applied to GaN base blue-ray LED and deep ultraviolet LED is GaN/AlN, Al
xga
1-xn/AlN or HfO
2/ SiO
2material.The present invention grows GaN/AlN multilayer film and the HfO in 10 cycles in 20 cycles
2/ SiO
2multilayer dielectricity membrane structure, can record the reflectivity of this dbr structure up to 98%.
Small size metal array of the present invention and semiconductor base ohmic contact, it runs through Distributed Bragg Reflection (DBR) structure, thus forms complex three-dimensional electrode:
1) spacing of metal array depends on the size of contact area and prospective current density.Adopting is that the relative contact that the metal array of diameter can reduce metal and semiconductor base effectively amasss with sub-wavelength dimensions, and then the blocking and absorb of reduction electrode pair light; Electrod-array (can be even or non-uniform Distribution) is separated by a determining deviation while meeting small area of contact, avoiding causing electrode local current densities too large, evenly expanding to realizing transverse current.
2) surface plasma excimer can be propagated in smooth or coarse metal surface, and kind and the diameter of its generation and metal material are closely related.Different metal and the resonance energy needed for semiconductor material interface system, namely corresponding LED emission wavelength, different.The SPPs resonance energy at Al and GaN interface is about 5eV(250nm), make Al become the optimal selection of deep ultraviolet region generation SPPs, and Ag, Au etc. are used for visible light wave range.
3) when enough hour of the diameter (sub-wavelength) of contacting metal, periodically the free electron of the metallic nanostructured surface of concavo-convex change is by by the interaction with photon, inspire SPPs and with incident light generation coupled resonance, make electronics, hole again radiation recombination occurs at metal and semiconductor contact interface, reduce light loss; On the other hand, when small size metal contact and LED active area distance enough nearly (tens nanometers) time, at the energy of SPPs resonance frequency with in quantum well, the energy of dipole is consistent, dipole generation radiation recombination in direct capture active area is discharged photon, improve the radiation recombination probability that electronics, hole are right, the final external quantum efficiency improving device.
Small size array of the present invention is interconnected amongst one another by deposition layer of metal film (Au or Ag etc.), and metallic film and electrod-array close contact, contribute to the even diffusion of electric current, improve the performance of device.
The present invention is intended to utilize metal micro-nano structure easily to form this characteristic of surface plasma excimer, absorbed luminous energy is launched again in the form of light, meanwhile, utilize being coupled of surface plasma excimer (SPPs) and active area charge carrier, improve the radioluminescence efficiency of light-emitting diode.
Accompanying drawing explanation
Fig. 1 is the cross-sectional view of the embodiment of the present invention.
Fig. 2 is electrod-array (M × N, M >=2, N >=2) distribution map that the embodiment of the present invention is overlooked from semiconductor base side.In fig. 2, structure is 10 × 10 arrays.
In fig 1 and 2, respectively be labeled as: 1-Distributed Bragg Reflection (DBR) structure, 2-small size metal array, 3-semiconductor base, the high refractive index medium layer of 4-Distributed Bragg Reflection (DBR) structure, the low refractive index dielectric layer of 5-Distributed Bragg Reflection (DBR) structure, 6-metallic film.
Embodiment
Below in conjunction with Fig. 1 and 2, the concrete structure introducing the embodiment of the present invention in detail and the conventional fabrication process adopted thereof and equipment.
Embodiment 1
First utilizing gas phase epitaxy of metal organic compound (MOVPE) technology to prepare the semiconductor base that diameter is 5.08cm on a sapphire substrate, by regulating and controlling the component of quantum well, the deep ultraviolet LED structure that emission wavelength is 280nm can be realized.Meanwhile, the GaN/AlN multilayer film dbr structure in 20 cycles of growth in situ, the optical thickness of every layer dielectric is 70nm.It forms according to the sequencing alternating deposit of high index of refraction (refractive index of the GaN that 280nm wavelength is corresponding is about 2.51) dielectric layer 4 and low-refraction (refractive index of the AlN that 280nm wavelength is corresponding is about 2.32) dielectric layer 5, then use spectrophotometer to test its reflectivity, this dbr structure reflectivity can reach 98%.
After semiconductor base mask lithography, inductively coupled plasma (ICP) technology is adopted to etch.After removing mask layer by chemical cleaning, (for p-type group III-nitride, the metal of ohmic contact is other combinations such as Ni/Au or Ni/Pt/Au to adopt high vacuum thermal evaporation or sputtering method plated metal; For N-shaped group III-nitride, the metal of ohmic contact is the combinations such as Ti/Al/Ti).In nitrogen atmosphere, short annealing makes metal array (M × N, M >=2, N >=2) and semiconductor base 3 form ohmic contact for tens seconds.
Recycling high vacuum thermal evaporation or sputtering method deposit layer of metal film 6, as Au, Ag etc., to form electrode on small size metal array.
Embodiment 2
First utilizing gas phase epitaxy of metal organic compound (MOVPE) technology to prepare the semiconductor base that diameter is 5.08cm on a sapphire substrate, by regulating and controlling the component of quantum well, the blue light LED structure that emission wavelength is 460nm can be realized.
After semiconductor base mask lithography, inductively coupled plasma (ICP) technology is adopted to etch.By high vacuum thermal evaporation or sputtering method plated metal, (for p-type group III-nitride, the metal of ohmic contact is other combinations such as Ni/Au or Ni/Pt/Au again; For N-shaped group III-nitride, the metal of ohmic contact is the combinations such as Ti/Al/Ti).Short annealing makes metal array (M × N, M >=2, N >=2) and semiconductor base 3 form ohmic contact for tens seconds under nitrogen atmosphere.Remove mask layer by chemical cleaning, make metal array and semiconductor base directly contact to be connected to and be integrated, in column.
Utilize high vacuum thermal evaporation or sputtering method at the HfO in 10 cycles of gap deposition of metal array
2/ SiO
2multilayer film dbr structure, it is according to the high index of refraction (HfO that 460nm wavelength is corresponding
2refractive index be about 1.89) dielectric layer 4 and the low-refraction (SiO that 460nm wavelength is corresponding
2refractive index be about 1.46) the sequencing alternating deposit of dielectric layer 5 forms, the optical thickness of every layer of dielectric material is 115nm.Thus make small size metal array 2 run through Distributed Bragg Reflection (DBR) structure 1, form complex three-dimensional electrode.
ICP technology etching is adopted to remove the HfO that columnar metal array covers
2and SiO
2retained material, then on small size metal array, deposit layer of metal film 6 by high vacuum thermal evaporation or sputtering method, as Au or Ag etc., to form electrode.
Claims (3)
1. Distributed Bragg Reflection and small size Metal Contact complex three-dimensional electrode, is characterized in that being provided with Distributed Bragg Reflection structure, small size metal ohmic contact array and semiconductor base; Described Distributed Bragg Reflection structure is established on a semiconductor substrate, and described Distributed Bragg Reflection structure is multilayer dielectricity, the membrane stack that described multilayer dielectricity is alternately made up of at least 1 floor height index dielectric layer and at least 1 layer of low refractive index dielectric layer; Described small size metal ohmic contact array and Distributed Bragg Reflection structure composite also run through Distributed Bragg Reflection structure and form complex three-dimensional electrode with semiconductor base ohmic contact again;
Described small size metal ohmic contact array is interconnected amongst one another by deposition layer of metal film, metallic film and electrod-array close contact;
Described small size refers to that the metal electrode area in complex three-dimensional electrode is enough little, describedly enough littlely refers to that diameter reaches sub-wavelength dimensions.
2. Distributed Bragg Reflection and small size Metal Contact complex three-dimensional electrode as claimed in claim 1, is characterized in that described multilayer dielectricity is provided with GaN/AlN multilayer dielectric film or the HfO in 10 cycles in 20 cycles
2/ SiO
2multilayer dielectricity membrane structure.
3. Distributed Bragg Reflection as claimed in claim 1 and small size Metal Contact complex three-dimensional electrode, is characterized in that described metallic film adopts Au film or Ag film.
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| US11024767B2 (en) * | 2017-10-17 | 2021-06-01 | Lumileds Llc | Nano-photonics reflector for LED emitters |
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| KR101106151B1 (en) * | 2009-12-31 | 2012-01-20 | 서울옵토디바이스주식회사 | Light emitting device and method of fabricating the same |
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