CN103715339A - GaN-based light emitting diode and preparation method thereof - Google Patents

Abstract

The invention discloses a gallium nitride-based light emitting diode and a preparation method thereof. The gallium nitride-based light emitting diode comprises an X-type gallium nitride layer and an X-type electrode arranged on the X-type gallium nitride layer; the X A current blocking region is formed on the X-type GaN layer at the bottom of the X-type electrode; the area of the current blocking region is smaller than that of the X-type electrode; the X-type GaN layer is an N-type GaN layer or a P-type GaN layer layer, and the X-type electrode corresponds to the X-type gallium nitride layer as an N-type electrode or a P-type electrode. The invention utilizes photolithography and plasma dry etching technology to form a high-resistance area on the treated surface, finally realizes the purpose of current splitting and guiding, and greatly reduces the invalid light emission of the LED electrode area.

Description

A gallium nitride-based light-emitting diode and its preparation method

Technical field:

The invention belongs to the technical field of gallium nitride-based light-emitting diode manufacturing technology, and specifically relates to a gallium nitride-based light-emitting diode and a preparation method thereof.

Background technique:

Light Emitting Diode (LED for short) has been developed for decades, and has been widely used in the fields of signal display, backlight and solid-state lighting, bringing various conveniences to human life. LED devices based on III-V compound gallium nitride (GaN) materials (including various alloy material systems obtained by doping its congeners In and Al elements) can cover most of the wavelength bands from deep ultraviolet to visible light. Most LED devices are manufactured by epitaxial growth to form P-type and N-type layer thin film materials, and grow periodic multilayer materials with different energy band structures between the P-type and N-type layers to form the carrier recombination zone. Luminous area. The epitaxial growth substrate mostly uses materials such as sapphire (Al ₂ O ₃ ) or silicon carbide (SiC), and then uses semiconductor processing technology to complete the steps of chip working area definition, electrode fabrication, and surface texturing to form light-emitting devices. After being packaged, a forward voltage is added to make it emit light. In the device design work, according to the energy band design theory and actual process control, the optical output of different wavelengths can be realized, and a wide range of practical applications can be obtained.

The horizontal structure LED device places the N-type and P-type electrodes on the same side of the LED film, and the bottom layer of the film is an insulating sapphire material substrate. The P-type and N-type electrodes are manufactured by photolithography, partial dry etching, physical vapor deposition and other processes, and are distributed on different positions on the same surface of the chip, and the injected working current flows through the light-emitting area of the LED from the horizontal direction. . Due to the uneven electron lateral injection and lateral diffusion of this device, the uneven current injection from the P-type electrode area to the N-type electrode area limits the maximum chip size of a single LED and the luminous efficiency of the overall device. At the same time, due to the large difference in refractive index between gallium nitride material and air or packaging material, its total reflection angle is large, resulting in low light extraction efficiency. Another device is to use the chip upside-down method. The chip is pressed together with a conductive material such as a silicon substrate through a thick metal solder layer. Get higher luminous efficiency, but P and N poles are still in the same layer. The third method is to completely change the structure of LED devices, using substrate removal and transfer methods such as ultraviolet laser lift-off, and using the strong light absorption of ultraviolet laser at the interface between sapphire material and GaN material to generate local thermal decomposition of GaN to realize LED thin film and Separation of sapphire substrates. Make the N-type and P-type electrodes change from a horizontal structure to a vertical structure, that is, the injection current mainly flows through the LED device structure in a manner perpendicular to the surface of the film to realize a vertical structure LED device, which not only greatly improves the operating current, but also because At the same time, the heat dissipation effect is improved, and the reliability of the device is also greatly improved.

However, in the LED chip structures with various structures above, since the area under the electrode pad is the area where the current injection is the most concentrated, the luminous effect in this area is the most obvious. After multiple reflections, it is absorbed by the material to form a thermal effect), so insulating materials have been widely used in the LED chip process to prepare the current blocking layer (CBL–current blocking layer), so that the injected current can be reduced or avoided in this area, reducing ineffective luminescence. This process requires the use of chemical vapor deposition, photolithography, and wet etching to prepare a dielectric material layer with a certain thickness on the surface of gallium nitride under the electrode, such as silicon nitride or silicon oxide; due to the multi-interface characteristics of this position Its surface condition is relatively complicated. If the process is not handled properly, it is easy to cause a series of abnormalities in mass production, such as large-area electrode dropouts, and cause irreparable losses.

Invention content:

The object of the present invention is to provide a gallium nitride-based light-emitting diode and a preparation method thereof, so as to improve and increase the luminous efficiency of the gallium nitride-based light-emitting diode.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A gallium nitride-based light-emitting diode, comprising an X-type gallium nitride layer and an X-type electrode disposed on the X-type gallium nitride layer; a current blocking region is formed on the X-type gallium nitride layer under the X-type electrode The area of the current blocking region is smaller than the area of the X-type electrode; the X-type GaN layer is an N-type GaN layer or a P-type GaN layer, and the X-type electrode corresponds to an X-type GaN layer of N Type electrode or P type electrode.

The further improvement of the present invention is that: the current blocking region is formed by performing dry etching with plasma on the X-type GaN layer to reduce the conductivity of the P-type GaN material in this region.

The further improvement of the present invention lies in that: the lower part of the X-shaped electrode is provided with a mirror layer.

The further improvement of the present invention is that: when the gallium nitride-based light-emitting diode is working, the current blocking region has a current blocking effect to guide the current splitting, and the current flows from other low-resistance regions other than the current blocking region of the X-type gallium nitride layer. Flowing through reduces the luminescence loss caused by the blocking effect of the X-shaped electrode, and indirectly improves the luminescence of other areas except the current blocking area.

The further improvement of the present invention is that: when using plasma for dry etching to prepare the current blocking region, _O2 plasma, F-based plasma or a mixture of the two plasmas is used.

The further improvement of the present invention is that: the gallium nitride-based light-emitting diode has a horizontal structure, the X-type gallium nitride layer is a P-type gallium nitride layer, and the X-type electrode is a P-type electrode; the P-type gallium nitride layer is a P-type gallium nitride layer; A multi-quantum well layer, an N-type gallium nitride layer, and a substrate are provided in sequence below the layer; a TCL transparent conductive layer is provided on the P-type gallium nitride layer, and part of the TCL transparent conductive layer is etched away to expose the P-type gallium nitride layer. The current blocking area; the P-type electrode is arranged on the upper part of the etched part of the TCL transparent conductive layer; an N-electrode area is formed on the N-type gallium nitride layer (11), and an N-type electrode is arranged on the N-electrode area.

The further improvement of the present invention is that: the gallium nitride-based light emitting diode has a vertical structure, the X-type gallium nitride layer is an N-type gallium nitride layer, and the X-type electrode is an N-type electrode; the N-type gallium nitride layer is an N-type gallium nitride layer; A multi-quantum well layer, a p-type gallium nitride layer, a metal bonding layer, a conductive substrate and a welding layer are sequentially arranged under the layer.

The further improvement of the present invention lies in: the specific contact resistivity of the current blocking region is >10 ^-5 Ω·cm ² .

A method for preparing a gallium nitride-based light-emitting diode, using O-based plasma, F-based plasma, or a mixture of the two ions on the X-type gallium nitride layer to treat the upper part of the X-type gallium nitride layer Perform plasma dry etching to reduce the conductivity of the X-type gallium nitride material in this region to obtain a current blocking region; then prepare an X-type electrode above the current blocking region.

The invention utilizes photolithography and plasma dry etching technology to carry out surface treatment on the area under the P-type electrode of the LED chip to make it a high-resistance area to obtain a current blocking effect, so that the current flows from other low-resistance areas of the P-type gallium nitride layer. Flowing through reduces the luminous loss of the electrode area due to the shading effect, indirectly improves the luminous light of other areas, and uses aluminum mirrors or silver mirrors as part of the metal structure of the P electrode, so as to achieve the purpose of high-efficiency luminescence.

In the present invention, the epitaxial growth process includes but not limited to metal organic chemical vapor phase epitaxy, molecular beam epitaxy, atomic layer epitaxy, pulsed laser sputtering; the selection of epitaxial growth substrate includes but not limited to sapphire, aluminum nitride, gallium nitride, Silicon, silicon carbide, and zinc oxide, whose crystal orientations include but not limited to polarized, semipolarized, and nonpolarized directions such as 0001; the selected substrate contains patterned surface structures of various feature sizes.

In the present invention, LED chips (gallium nitride-based light emitting diodes) include but are not limited to horizontal structure LED chips, flip-chip structure LED chips, vertical structure LED chips, or LED chips with other unique structures.

In the present invention, the plasma dry etching process includes but not limited to O ₂ plasma, F-based plasma, or a mixture of the two plasmas.

In the present invention, the chip preparation process flow includes but not limited to photolithography, wet and dry etching, electron beam or sputtering, chemical vapor deposition, and annealing methods.

In the present invention, the reflector layer under the P-type electrode is arranged on the P-type GaN layer, which is a single or multi-layer metal or compound structure, including but not limited to silver, aluminum, gold, DBR or ODR layers.

In the present invention, the P-type gallium nitride layer is provided with a P-type electrode metal layer, and the N-type gallium nitride layer is provided with an N-type electrode metal layer, respectively forming good ohmic contact with the P/N-type layer semiconductor material, which is a single Or multilayer metal structures, including but not limited to nickel, titanium, aluminum, gold, platinum and their alloys.

The invention utilizes photolithography and plasma dry etching technology to form a high-resistance area on the treated surface, finally realizes the purpose of current splitting and guiding, and greatly reduces the invalid light emission of the LED electrode area. Compared with the prior art, it has the following beneficial effects:

(1) The process is simple and reduces the original process steps, eliminating the need for dielectric film deposition and chemical wet etching processes, while reducing the process steps, it also reduces the cost of industrial production; (2) The line width fineness reaches several The ten-nanometer-level dry etching process replaces the micron-level wet etching process, which greatly improves the process control capability; (3) The present invention does not introduce other materials and The interface reduces the complexity of the interface, which can avoid subsequent electrode drop conditions caused by complex interface conditions and improper chemical wet etching treatment, and improve the process yield; (4) The present invention is not only applicable to horizontal structure LED chips, but also applicable to Make LED chips of various other structures.

Description of drawings

Fig. 1 is a structural schematic diagram of a horizontal structure LED chip;

Fig. 2 is a schematic structural diagram of a vertical structure LED chip.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

The preparation method of a gallium nitride-based light-emitting diode of the present invention uses photolithography and plasma dry etching technology to carry out surface treatment on the area under the P-type electrode of the LED chip, making it a high-resistance area to obtain a current blocking effect, so that The current flows through other low-resistance regions of the P-type gallium nitride layer, which reduces the loss of luminescence caused by the shading effect in this electrode region, indirectly improves the luminescence of other regions, and uses aluminum mirrors or silver mirrors as part of the metal structure of the P electrode , so as to achieve the purpose of high-efficiency light emission, the preparation method at least includes the following steps:

1) Using MOCVD (Metal-organic Chemical Vapor Deposition, Metal Organic Compound Chemical Vapor Deposition) method to grow and obtain LED epitaxial structure, LED epitaxial structure includes substrate 10 and sequentially deposited on and P-type gallium nitride layer 13; through photolithography Form the N electrode area on the surface of the wafer, and then use the dry etching process to etch the epitaxial layer in this area to expose N-type gallium nitride, form the same-side PN junction, and complete the chip pattern and size definition;

2) On the P-type gallium nitride layer 13 of the LED epitaxial wafer, the TCL transparent conductive layer 15 is prepared by using PVD physical deposition technology such as electron beam evaporation or sputtering. The material of the TCL transparent conductive layer 15 is nickel gold or ITO oxidation Indium tin conductive material; then according to the LED chip design, use photolithography and wet etching to complete the preparation of the required TCL transparent conductive layer;

3) Prepare the current blocking layer 17 under the P electrode region. This method is different from the conventional method of using a dielectric material (such as silicon oxide or silicon nitride) to form a non-conductive insulating layer under the electrode. Part of the TCL transparent conductive layer 15 below the P-type electrode 162 is etched away, so that a part of the P-type GaN layer 13 is exposed, and other regions are protected by photoresist. Then adopt plasma dry etching technology, use O, F base plasma to carry out dry etching on this area, make the conductivity of the P-type gallium nitride material in this area drop sharply, and obtain the current blocking layer 17 in the high resistance area , the specific contact resistivity of the current blocking layer>10 ^-5 Ω·cm ² ;

4) By making P-type electrodes (high reflection mirrors, ohmic electrodes) 162, N-type electrodes 161, and passivation protection layer 14, the front-end manufacturing process of the LED chip is finally completed. The P-type electrode 162 is disposed on the top of the etched part of the TCL transparent conductive layer 15 .

In the present invention, the epitaxial growth process includes but not limited to metal organic chemical vapor phase epitaxy, molecular beam epitaxy, atomic layer epitaxy, pulsed laser sputtering; the selection of the epitaxial growth substrate includes but not limited to sapphire, aluminum nitride, nitride Gallium, silicon, silicon carbide, and zinc oxide, whose crystal orientations include but not limited to polarized, semipolarized, and nonpolarized directions such as 0001; the selected substrate contains patterned surface structures of various feature sizes.

In the present invention, LED chips include but are not limited to horizontal structure LED chips, flip-chip structure LED chips, vertical structure LED chips, or LED chips with other special structures. Fig. 2 is a vertical structure LED chip, N-type GaN layer 11 is provided with N-type electrode 161; N-type GaN layer 11 is provided with multi-quantum well layer 12, P-type GaN layer 13, metal bond Composite layer 20, conductive substrate 21 and soldering layer 22; current blocking layer 17 is provided on the N-type gallium nitride layer 11 below the N-type electrode 161.

In the present invention, the plasma dry etching process includes but not limited to O ₂ plasma, F-based plasma, or a mixture of the two plasmas.

In the present invention, the chip preparation process flow includes but not limited to photolithography, wet and dry etching, electron beam or sputtering, chemical vapor deposition, and annealing methods.

In the present invention, the reflector layer under the P-type electrode is arranged on the P-type GaN layer, which is a single or multi-layer metal or compound structure, including but not limited to silver, aluminum, gold, DBR or ODR layers.

In the present invention, the P-type gallium nitride layer is provided with a P-type electrode metal layer, and the N-type gallium nitride layer is provided with an N-type electrode metal layer, respectively forming good ohmic contact with the P/N-type layer semiconductor material, which is a single Or multilayer metal structures, including but not limited to nickel, titanium, aluminum, gold, platinum and their alloys.

Claims (9)

1. a gallium nitride based light emitting diode, is characterized in that, comprises X-type gallium nitride layer and is arranged at the X-type electrode on X-type gallium nitride layer; On the X-type gallium nitride layer of described X-type electrode bottom, be formed with current blocked region; The area in current blocked region is less than the area of X-type electrode; Described X-type gallium nitride layer is n type gallium nitride layer or P type gallium nitride layer, and it is N-type electrode or P type electrode that described X-type electrode pair is answered X-type gallium nitride layer.

2. a kind of gallium nitride based light emitting diode according to claim 1, is characterized in that, described current blocked region, for using plasma on X-type gallium nitride layer carries out dry etching, makes the conductive capability of this region P type gallium nitride material decline and form.

3. a kind of gallium nitride based light emitting diode according to claim 1, is characterized in that, the bottom of X-type electrode is provided with mirror layer.

4. a kind of gallium nitride based light emitting diode according to claim 1, it is characterized in that, during described gallium nitride based light emitting diode work, current blocked region has current blocking effect electric current is divided to guiding, electric current flows through from other low-resistance regions beyond the current blocked region of X-type gallium nitride layer, reduce X-type electrode because of the luminous loss that occlusion effect causes, indirectly improved the luminous of other regions beyond current blocked region.

5. a kind of gallium nitride based light emitting diode according to claim 2, is characterized in that, using plasma carries out dry etching while preparing current blocked region, adopts O ₂plasma, F base plasma or both mix plasma.

6. a kind of gallium nitride based light emitting diode according to claim 1, is characterized in that, described gallium nitride based light emitting diode is horizontal structure, and described X-type gallium nitride layer is P type gallium nitride layer, and described X-type electrode is P type electrode; P type gallium nitride layer below is provided with multiple quantum well layer (12), n type gallium nitride layer (11) and substrate (10) successively; P type gallium nitride layer is provided with TCL transparency conducting layer (15), and TCL transparency conducting layer (15) part is etched away the current blocked region of exposing on P type gallium nitride layer; P type electrode is arranged at the top that TCL transparency conducting layer (15) is etched away part; N type gallium nitride layer is formed with N electrode zone on (11), and N electrode zone is provided with N-type electrode.

7. a kind of gallium nitride based light emitting diode according to claim 1, is characterized in that, described gallium nitride based light emitting diode is vertical stratification, and described X-type gallium nitride layer is n type gallium nitride layer, and described X-type electrode is N-type electrode; N type gallium nitride layer below is provided with multiple quantum well layer (12), P type gallium nitride layer (13), metal bonding layer (20), conductive substrates (21) and weld layer (22) successively.

8. a kind of gallium nitride based light emitting diode according to claim 1, is characterized in that, the specific contact resistivity rate >10 in current blocked region ^-5Ω cm ².

9. the preparation method of a kind of gallium nitride based light emitting diode described in any one in claim 1 to 8, it is characterized in that, on described X-type gallium nitride layer, utilize the gas ions of O base plasma, F base plasma or the two mixing to carry out dry plasma etch to subregion on this X-type gallium nitride layer, the conductive capability of this region X-type gallium nitride material is declined, obtain current blocked region, wherein specific contact resistivity rate >10 ^-5Ω cm ²; And then above current blocked region, prepare X-type electrode.

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