Augmented reality display structure, preparation method and equipment

Abstract

The invention relates to an augmented reality display structure, a preparation method and equipment, and relates to the field of photoelectron, the augmented reality display structure comprises a graphical buffer layer, the dislocation density of which is less than or equal to 106cm <-2 >; the three-dimensional conducting layer comprises an n-GaN layer and an Al GaN current blocking layer which are periodically distributed; the light-emitting layer comprises an I nGaN / GaN multi-quantum well layer, and the well width fluctuation is controlled to be + / -0.2 nm; a p-GaN layer; and a distributed Bragg reflection layer and an electrode, wherein the distributed Bragg reflection layer is located between the p-GaN layer and the electrode. A distributed Bragg reflection layer (DBR) is integrated between a p-GaN layer and an electrode, and selective epitaxial growth and three-dimensional conductive network design of a patterned substrate are combined, so that the problems of low light extraction efficiency, limited pixel size and thermal management are solved, and collaborative optimization of optical, electrical and thermal properties is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optoelectronics, in particular to an augmented reality display structure, a preparation method and equipment. BACKGROUND

[0002] Current augmented reality (AR) display technology is limited by the performance bottlenecks of traditional LCoS / OLED and silicon-based Micro-LED, and has problems such as insufficient brightness (<2000 nit), low pixel density (PPI <4000), slow response speed (>1ms), and large light efficiency loss (quantum dot conversion loss 40%). Although gallium nitride (GaN) material has high light-emitting efficiency potential, the existing vertical structure has uneven current distribution, and the lateral structure has difficulty in heat dissipation, which cannot meet the comprehensive needs of high brightness, miniaturization and high reliability of AR equipment. SUMMARY

[0003] The present application provides an augmented reality display structure, a preparation method and equipment, by integrating a distributed Bragg reflector (DBR) between the p-GaN layer and the electrode, combining the selective epitaxial growth of the patterned substrate and the design of the three-dimensional conductive network, the problems of low light extraction efficiency, limited pixel size and heat management are solved, and the optical, electrical and thermal performance is optimized.

[0004] In a first aspect, the present application provides an augmented reality display structure, comprising:

[0005] a patterned buffer layer with a dislocation density ≤10 6 cm -2 ;

[0006] a three-dimensional conductive layer comprising periodically distributed n-GaN layers and AlGaN current blocking layers;

[0007] a light-emitting layer comprising InGaN / GaN multi-quantum well layers with a well width fluctuation controlled within ±0.2nm;

[0008] a p-GaN layer;

[0009] a distributed Bragg reflector and an electrode, the distributed Bragg reflector being located between the p-GaN layer and the electrode.

[0010] In a second aspect, the present application provides a method for preparing the augmented reality display structure of any of the above embodiments, comprising the following steps:

[0011] S1, growing an AlN nucleation layer on a patterned sapphire substrate at low temperature, with a thickness of 15nm-30nm and a growth temperature of 500℃-700℃, and then annealing at 1050℃-1150℃ to form a patterned buffer layer;

[0012] S2, depositing AlGaN / n-GaN superlattice alternately on the patterned buffer layer, each layer having a thickness of 8-15 nm, dislocation density being reduced to below 106cm-2, and forming a three-dimensional conductive layer;

[0013] S3, growing an InGaN / GaN multi-quantum well layer, quantum well growth temperature being 715-725 DEG C, In component fluctuation being <2%, and forming a light-emitting layer;

[0014] S4, growing a p-GaN layer;

[0015] S5, depositing a distributed Bragg reflector and an Ag / Ni alloy electrode successively on the p-GaN layer, and vacuum annealing at 400-450 DEG C;

[0016] S6, bonding to a substrate through a flip-chip process, bonding conditions being: nitrogen environment, pressure 8-12 MPa, temperature 170-190 DEG C, and holding time 200-400 s;

[0017] S7, removing the sapphire substrate through laser lift-off.

[0018] In a third aspect, the application provides an augmented reality display device comprising the augmented reality display structure according to any one of the above embodiments.

[0019] Compared with the prior art, the above technical solution provided by the embodiments of the application has the following advantages:

[0020] The scheme makes the luminance of the device increase to 15000 nits (62% reduction in power consumption) under 10 mA driving, the pixel density break through 8000 PPI (unit size <5 mu m), the thermal resistance reduce to 0.5 K / W (1 / 3 of the traditional structure), while supporting 120 Hz refresh rate and 0.1 ms fast response, and passing 10 million hour reliability test under 85 DEG C / 85% RH severe environment, providing a complete solution of high luminance, high efficiency and long service life for AR display. BRIEF DESCRIPTION OF DRAWINGS

[0021] The drawings incorporated into the specification and forming part of the specification, show embodiments consistent with the application, and together with the specification serve to explain the principles of the application.

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows, and obviously, other drawings can also be obtained by those skilled in the art without creative labor.

[0023] Figure 1A schematic cross-sectional view of an augmented reality display structure provided by an embodiment of the present invention;

[0024] Figure 2 A schematic flow chart of a method for preparing an augmented reality display structure provided in an embodiment of the present invention.

[0025] Reference numerals

[0026] 1. Substrate; 2. Patterned buffer layer; 3. n-GaN layer; 4. AlGaN current blocking layer; 5. Light-emitting layer; 6. p-GaN layer; 7. Distributed Bragg reflector layer; 8. Electrode. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0028] Example

[0029] See also Figure 1 The embodiment of the present invention provides an augmented reality display structure. The augmented reality display structure comprises, from bottom to top, a graphic buffer layer 2, a dislocation density ≤ 10 6 cm -2 The three-dimensional conductive layer includes a periodically distributed n-GaN layer 3 and an AlGaN current blocking layer 4; the light-emitting layer 5 includes an InGaN / GaN multi-quantum well layer with a well width fluctuation controlled to ±0.2nm; a p-GaN layer 6; a distributed Bragg reflector 7 and an electrode 8, wherein the distributed Bragg reflector 7 is located between the p-GaN layer 6 and the electrode 8. The components are described in detail below:

[0030] In this embodiment, a patterned buffer layer 2, a three-dimensional conductive layer, a light-emitting layer 5, a p-GaN layer 6, a distributed Bragg reflector 7 and an electrode 8 are sequentially grown on a substrate 1, the grown structure is inverted on a substrate, and the substrate 1 is peeled off to obtain an augmented reality display structure; the patterned buffer layer 2 is used to provide a selective epitaxial template to define pixel positions; the three-dimensional conductive layer forms a three-dimensional conductive network through the n-GaN layer 3 and the AlGaN current blocking layer 4, thereby increasing the lateral resistance of the layer and forcing the current to flow vertically; the light-emitting layer 5 is used to emit light, and is usually formed by a combination of electroluminescent and photoluminescent quantum wells; the p-GaN layer 6 is used to cooperate with the three-dimensional conductive layer to form a vertical current flow; the distributed Bragg reflector 7 is used to reflect the light emitted by the light-emitting layer 5.

[0031] The enhanced reality display structure is used for flip-chip bonding to an epitaxial layer structure of a substrate, realizes current vertical conduction and high-efficiency heat dissipation, and in an embodiment, the enhanced reality display structure is bonded by hot-pressing InSn eutectic solder (52:48), and the thermal conductivity of the bonding surface is greater than or equal to 200 W / (m*K).

[0032] Compared with the prior art, the technical scheme provided by the embodiment of the present application has the following advantages:

[0033] Light efficiency is improved: the light extraction efficiency is improved from 30% to 82% through the microcavity resonance effect, the brightness reaches 15000 nits, and the power consumption is reduced by 62%.

[0034] Pixel miniaturization: selective epitaxial growth is adopted to realize a pixel unit of less than 5 mu m (corresponding to 8000 PPI).

[0035] Thermal management optimization: the thermal resistance is reduced to 0.5 K / W (1 / 3 of the traditional structure).

[0036] Improved interaction experience: 120Hz refresh rate and 0.1ms response are supported to meet the AR dynamic interaction requirements.

[0037] Continuing to refer to Figure 1 In the embodiment, the enhanced reality display structure further comprises a light beam shaping element integrated in the light emitting surface, and the light beam shaping element comprises: a subwavelength grating with a period of 250nm-350nm; and a Si3N4 waveguide coupler with a coupling efficiency of greater than or equal to 85%.

[0038] Specifically, the subwavelength grating uses the effective medium theory to regulate the effective refractive index, realizes phase matching through a grating depth of lambda / 4, and has a period of 300nm to realize beam collimation (divergence angle <5°). The Si3N4 waveguide coupler realizes mode field matching through a tapered waveguide, and realizes a coupling efficiency of 87% (traditional lens coupling <50%) through surface plasmon suppression design.

[0039] Further, the Al component of the AlGaN current blocking layer 4 is between 20% and 30%, and the layer thickness is 50-80nm.

[0040] Specifically, when the Al component is less than 20%, the barrier height is insufficient; when the Al component is between 20% and 30%, it is an ideal barrier, and the current uniformity is greater than 95%; when the Al component is greater than 20%, the lattice mismatch stress cracks; when the layer thickness is less than 50nm, quantum tunneling occurs, and when the layer thickness is greater than 80nm, the epitaxial time increases by 30% and the production capacity decreases.

[0041] Further, the distributed Bragg reflection layer 7 is composed of at least 10 pairs of AlGaN / GaN dielectric layers stacked alternately, each layer has an optical thickness of 1 / 4 of the light emitting wavelength, and the reflectivity is greater than or equal to 99%.

[0042] Specifically, when 8 pairs of AlGaN / GaN dielectric layers are used, the reflectivity reaches 98.3%, when 10 pairs of AlGaN / GaN dielectric layers are used, the reflectivity reaches 99.2%, and when 12 pairs of AlGaN / GaN dielectric layers are used, the reflectivity reaches 99.6%. With each additional pair, the reflectivity increases by 0.3%, but the stress increases by 50 MPa, and when 10 pairs of AlGaN / GaN dielectric layers are used, the stress is less than the critical cracking value.

[0043] Further, the electrode 8 is an Ag / Ni alloy reflective electrode, wherein the thickness of the Ag layer is 100-200 nm, and the thickness of the Ni layer is 30-80 nm, and the reflectivity is > 95%.

[0044] Specifically, the Ag / Ni alloy reflective electrode forms a composite reflection system with the distributed Bragg reflection layer 7 (DBR), which reflects light vertically emitted (99% reflectivity), and the Ag / Ni electrode reflects light laterally (> 95%), and the total light extraction efficiency is increased to 82% (only 30% for traditional structures). The composite reflection system achieves high-efficiency light reflection.

[0045] Referring to Figure 2 The embodiment of the present application also provides a method for preparing the augmented reality display structure as described in any of the above embodiments. The method comprises steps S1-S7:

[0046] S1, growing an AlN nucleation layer on a patterned sapphire substrate at low temperature, with a thickness of 15-30 nm and a growth temperature of 500-700°C, and then annealing at 1050-1150°C to form a patterned buffer layer.

[0047] In specific embodiments, MOCVD is used for growth on a patterned sapphire, and the patterned sapphire substrate guides the lateral epitaxial growth of GaN through nanoscale patterns (such as protrusions or pits), forcing dislocations to bend and terminate on the pattern sidewalls. The high-temperature (1000-1100°C) growth environment of MOCVD promotes atomic migration, allowing GaN to merge laterally at the pattern gap and reducing threading dislocations.

[0048] S2, depositing AlGaN / n-GaN superlattices alternately on the patterned buffer layer, with each layer having a thickness of 8-15 nm, and the dislocation density being reduced to 10 6 cm -2 Below, a three-dimensional conductive layer is formed.

[0049] In specific embodiments, the AlGaN / n-GaN superlattice has a thickness of 10 nm per layer.

[0050] S3, growing InGaN / GaN multi-quantum well layer, quantum well growth temperature is 715-725℃, In component fluctuation <2%, forming a light emitting layer.

[0051] In specific embodiments, InGaN / GaN multi-quantum well layer is grown on the three-dimensional conductive layer, quantum well growth temperature is 720℃, In component fluctuation is controlled to be <2%, forming a light emitting layer.

[0052] S4, growing p-GaN layer.

[0053] In specific embodiments, the p-GaN layer is a magnesium (Mg) doped gallium nitride (GaN) semiconductor material, which is a P-type semiconductor. In a GaN-based LED / micro display device, it is usually used as a hole injection layer, together with the n-GaN layer (electron injection layer) to clasp the multi-quantum well light emitting layer, forming a PN junction light emitting core structure.

[0054] S5, sequentially depositing distributed Bragg reflector layer and Ag / Ni alloy reflective electrode on the p-GaN layer, and vacuum annealing at 400-450℃.

[0055] In specific embodiments, the distributed Bragg reflector layer (DBR) can be directly subjected to electrode annealing at 430℃ after low-temperature growth, avoiding damage caused by secondary high-temperature process.

[0056] In an embodiment, the growth temperature of the distributed Bragg reflector layer in step S5 above is ≤800℃.

[0057] In specific embodiments, GaN quantum well starts to decompose at >800℃, leading to increased roughness of quantum well interface. In InGaN quantum well, In-N bond energy is low, and at >800℃, In atoms diffuse outward from the quantum well. The growth temperature of the distributed Bragg reflector layer is ≤800℃, which is conducive to protecting the quantum well structure, avoiding thermal decomposition of the quantum well, and inhibiting In component segregation.

[0058] S6, bonding to the substrate through flip-chip process, bonding conditions are: nitrogen environment, pressure 8-12 MPa, temperature 170-190℃, holding time 200-400s.

[0059] In specific embodiments, the hot-press bonding is performed in a nitrogen environment, pressure is 10 MPa, temperature is 180℃, and holding time is 300s.

[0060] In an embodiment, the ratio of In to Sn in the InSn eutectic solder used in step S6 above is (50-54):(46-50).

[0061] In specific embodiments, the eutectic point of the phase diagram corresponds to a melting point of 118℃, and a deviation of ±2% will cause the liquidus temperature to rise by >20℃. The In:Sn ratio of 52:48 has the optimal bonding yield (99%), and in other embodiments, the In:Sn ratio of 54:46 can be used, with a liquidus temperature of 135℃ and a corresponding bonding yield of 87%; in addition, the In:Sn ratio of 50:50 has a liquidus temperature of 130℃ and a corresponding bonding yield of 91%.

[0062] S7. Removing the sapphire substrate by laser lift-off.

[0063] In specific embodiments, after bonding in step S6, the sapphire substrate is removed by laser lift-off, and the epitaxial layer is transferred from the insulating sapphire substrate to a high-thermal-conductivity substrate (such as silicon or ceramic), thereby solving the problem of poor thermal conductivity of sapphire and achieving a flip-chip structure; eliminating the interface light absorption between sapphire and GaN (the light loss of a traditional structure is >30%), so that the light is directly emitted from the surface of the epitaxial layer, thereby improving the light extraction efficiency; and getting rid of the thickness limitation of the sapphire substrate (usually >100μm), so that the total thickness of the device can be reduced to <10μm, meeting the ultra-thin requirement of AR display and supporting miniaturization integration.

[0064] In an embodiment, after step S7, the method further includes step S8: integrating a sub-wavelength grating and a Si3N4 waveguide coupler on the light-emitting surface.

[0065] In specific embodiments, the period of the sub-wavelength grating is 250nm-350nm, which ensures a first-order diffraction efficiency of >90%; and the coupling efficiency of the Si3N4 waveguide coupler is ≥85%.

[0066] The embodiments of the present application also provide an augmented reality display device, which comprises the augmented reality display structure according to any one of the above embodiments.

[0067] In specific embodiments, the augmented reality display device is also referred to as an AR device, and the dynamic display performance of the augmented reality display device meets the following requirements: visible under ambient light >10000 lux; motion image delay ≤1ms; and continuous working temperature range -40℃-85℃.

[0068] The embodiments of the present application can achieve the following advantages:

[0069] The augmented reality display structure has a luminance of 15000 nits at 10 mA driving (62% reduction in power consumption), a pixel density of 8000 PPI (unit size < 5 um), a thermal resistance of 0.5 K / W (1 / 3 of that of a traditional structure), while supporting a refresh rate of 120 Hz and a fast response of 0.1 ms, and has passed a 10 million hour reliability test under a severe environment of 85 DEG C / 85% RH, thus providing a complete solution of high luminance, high efficiency and long service life for AR display.

[0070] In the above embodiments, the description of each embodiment is focused on, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0071] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, these modifications and variations of the present application also belong to the scope of the claims of the present application and their equivalent technologies, and the present application also intends to include these modifications and variations.

[0072] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited to this. Any skilled person in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An augmented reality display structure, characterized by, From bottom to top, sequentially comprising: Patterned buffer layer, dislocation density < 10 6 cm -2 ; a three-dimensional conductive layer, comprising a periodically distributed n-GaN layer and an AlGaN current blocking layer; a light-emitting layer, comprising an InGaN / GaN multi-quantum well layer, with a well width fluctuation controlled within ±0.2 nm; a p-GaN layer; a distributed Bragg reflector layer and an electrode, the distributed Bragg reflector layer being located between the p-GaN layer and the electrode.

2. The structure of claim 1, wherein Further comprising a beam shaping element integrated on the light-emitting surface, the beam shaping element comprising: a sub-wavelength grating with a period of 250-350 nm; a Si3N4 waveguide coupler with a coupling efficiency of ≥85%.

3. The structure of claim 1, wherein The Al component of the AlGaN current blocking layer is between 20% and 30%, and the layer thickness is 50-80 nm.

4. The structure of claim 1, wherein The distributed Bragg reflector layer is composed of at least 10 pairs of AlGaN / GaN dielectric layers alternately stacked, with a single layer optical thickness of 1 / 4 of the light-emitting wavelength, and a reflectivity of ≥99%.

5. The structure of claim 1, wherein The electrode is an Ag / Ni alloy reflective electrode, wherein the Ag layer has a thickness of 100-200 nm, the Ni layer has a thickness of 30-80 nm, and the reflectivity is >95%.

6. A method for producing the augmented reality display structure according to any one of claims 1 to 5, characterized by, Comprising the following steps: S1. Growing an AlN nucleation layer on a patterned sapphire substrate at low temperature, with a thickness of 15-30 nm and a growth temperature of 500-700°C, followed by annealing at 1050-1150°C to form a patterned buffer layer; S2, depositing AlGaN / n-GaN superlattice alternately on the patterned buffer layer, each layer having a thickness of 8-15 nm, and the dislocation density being reduced to 10 6 cm -2 Next, a three-dimensional conductive layer is formed. S3. Growing an InGaN / GaN multi-quantum well layer, with a quantum well growth temperature of 715-725°C and an In component fluctuation of <2%, to form a light-emitting layer; S4. Growing a p-GaN layer; S5. Depositing a distributed Bragg reflector layer and an Ag / Ni alloy electrode on the p-GaN layer in sequence, and vacuum annealing at 400-450°C; S6. Bonding to a substrate through flip-chip technology, with bonding conditions of: nitrogen environment, pressure of 8-12 MPa, temperature of 170-190°C, and holding time of 200-400 s; S7. Removing the sapphire substrate through laser lift-off.

7. The method of claim 6, wherein, Further comprising: S8. Integrating a sub-wavelength grating and a Si3N4 waveguide coupler on the light-emitting surface.

8. The method of claim 6, wherein, The growth temperature of the distributed Bragg reflector layer in step S5 is ≤800°C.

9. The method of claim 6, wherein, The ratio of In to Sn in the InSn eutectic solder used in step S6 is (50-54):(46-50).

10. An augmented reality display device, characterized by Comprising the augmented reality display structure of any one of claims 1-5.

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