Ultrathin tunnel junction deep ultraviolet LED chip and manufacturing method thereof

Abstract

The invention discloses an ultrathin tunnel junction deep ultraviolet LED chip and a manufacturing method thereof, and the manufacturing method comprises the steps: preparing an epitaxial growth layer on a substrate, and the epitaxial growth layer comprises an AlN nucleating layer, an AlN buffer layer, a Si-doped n-AlGaN layer, a low-aluminum AlGaN / high-aluminum AlGaN multi-quantum well layer, a Mg-doped p-AlGaN electron blocking layer, and a Mg-doped p-AlGaN hole injection layer; the thickness of the Mg heavily-doped p < + >-AlGaN layer is 5-15 nm, and the thickness of the Si heavily-doped n < + >-AlGaN layer is 5-15 nm; partial etching is carried out on the Si heavily doped n < + >-AlGaN layer until the Si doped n-AlGaN layer is exposed; and respectively preparing an n electrode and a p electrode on the exposed Si doped n-AlGaN layer and the Si heavily doped n +-AlGaN layer to obtain the ultra-thin tunnel junction deep ultraviolet LED chip. According to the deep ultraviolet LED chip, the ultrathin n +-AlGaN / p +-AlGaN tunnel junction is adopted, the lightly doped n-AlGaN covering layer is removed, dehydrogenation activation of an Mg acceptor is facilitated, the working voltage of the deep ultraviolet LED chip is reduced, and the photoelectric property of the deep ultraviolet LED chip is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to an ultra-thin tunnel junction deep ultraviolet LED chip and a manufacturing method thereof. Background Art

[0002] As a new generation of deep ultraviolet (200-280nm) solid light source, AlGaN-based deep ultraviolet LED chips have many advantages such as energy saving, environmental protection, small size and long life. They are widely used in surface sterilization and disinfection, water purification, air purification, ultraviolet lithography, non-line-of-sight communication, gas sensing, biomedicine and other fields.

[0003] The activation energy of Mg acceptors in p-AlGaN increases with the increase of Al content. Higher activation energy will lead to lower hole concentration and mobility, and increase the resistivity of p-AlGaN. Therefore, efficient p-type doping of AlGaN is the key to achieving high-performance deep ultraviolet LED devices. In addition, the increase of Al content will also increase the work function, making it difficult to form ohmic contact with the p-electrode metal. Both will reduce the device performance of AlGaN-based deep ultraviolet LED chips. In order to prepare a p-type ohmic contact electrode, it is often necessary to insert a layer of p-GaN as an ohmic contact layer between p-AlGaN and the metal electrode. However, the p-GaN contact layer has a strong absorption effect on ultraviolet light, which will cause light loss. For this reason, using a tunnel junction instead of a p-GaN contact layer is a more suitable method. However, in AlGaN-based tunnel deep ultraviolet LED chips, the top of the tunnel junction usually has a lightly doped n - -AlGaN cap layer. Lightly doped n - Although the -AlGaN capping layer can enhance current spreading and facilitate the preparation of n-type ohmic contacts, it will hinder the dehydrogenation activation of Mg acceptors in the p-AlGaN buried layer, further leading to an increase in chip voltage. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention designs the thickness of the AlGaN-based tunnel junction and the epitaxial growth process to achieve full activation of the Mg acceptor and reduce the operating voltage of the deep ultraviolet LED chip.

[0005] In order to achieve the above object, the present invention provides a method for manufacturing an ultra-thin tunnel junction deep ultraviolet LED chip, comprising:

[0006] An epitaxial growth layer is prepared on the substrate, wherein the epitaxial growth layer includes an AlN nucleation layer, an AlN buffer layer, a Si-doped n-AlGaN layer, a low-aluminum AlGaN / high-aluminum AlGaN multi-quantum well layer, a Mg-doped p-AlGaN electron blocking layer, and a Mg-doped p-AlGaN hole injection layer, all of which are 5 to 15 nm thick. +-AlGaN layer and Si heavily doped n + -A tunnel junction formed by an AlGaN layer to obtain an epitaxial material;

[0007] From Si heavily doped with n + The -AlGaN layer is partially etched until the Si-doped n-AlGaN layer is exposed;

[0008] In the exposed Si-doped n-AlGaN layer and Si heavily doped n + An n-electrode and a p-electrode are prepared on the -AlGaN layer to obtain an ultra-thin tunnel junction deep ultraviolet LED chip.

[0009] Furthermore, the Mg heavily doped p + -The Mg doping concentration of the AlGaN layer is 1×10 19 ~2×10 20 cm -3 ;

[0010] The Si is heavily doped with n + -The Si doping concentration of the AlGaN layer is 1×10 20 ~1×10 21 cm -3 .

[0011] Furthermore, the n-electrode and the p-electrode are Ti / Al / Ti / Au and Ni / Au respectively, wherein the thickness of Ti is 10-50 nm, Al is 50-100 nm, Ni is 25-50 nm, and Au is 50-100 nm.

[0012] Furthermore, the thickness of the AlN nucleation layer is 10 to 50 nm;

[0013] The thickness of the AlN buffer layer is 2.5 to 3 μm;

[0014] The thickness of the Si-doped n-AlGaN layer is 2 to 3 μm;

[0015] The thicknesses of the low-aluminum AlGaN / high-aluminum AlGaN multi-quantum well layers are 1-5 nm and 10-15 nm respectively;

[0016] The thickness of the Mg-doped p-AlGaN electron blocking layer is 10 to 30 nm;

[0017] The thickness of the Mg-doped p-AlGaN hole injection layer is 40-60 nm.

[0018] Furthermore, the Si doping concentration of the Si-doped n-AlGaN layer is 6×10 18 cm -3 .

[0019] Furthermore, the Mg doping concentration of the Mg doped p-AlGaN electron blocking layer is 1×10 18 ~5×10 18 cm -3 .

[0020] Furthermore, the Mg doping concentration of the Mg doped p-AlGaN hole injection layer is 5×10 18 ~1×10 19 cm -3 .

[0021] Furthermore, in the exposed Si-doped n-AlGaN layer and the Si heavily doped n-AlGaN layer, + After the n-electrode and the p-electrode are prepared on the -AlGaN layer, a heat treatment is performed to enhance the ohmic contact.

[0022] The present invention also provides an ultra-thin tunnel junction deep ultraviolet LED chip, which is obtained using the above method.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) Si-Mg co-doping is used in the tunnel junction to promote the activation of Mg acceptors and increase the hole concentration;

[0025] (2)Use ultra-thin + -AlGaN / p + -AlGaN tunnel junction, removing lightly doped n - -AlGaN covering layer is beneficial to the dehydrogenation activation of Mg acceptors, and reduces the operating voltage of deep ultraviolet LED chips, thereby improving the photoelectric performance of deep ultraviolet LED chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 A schematic diagram showing the structure of an epitaxial material in an embodiment of the present invention is shown;

[0028] Figure 2 A schematic diagram of the structure of an ultra-thin tunnel junction deep ultraviolet LED chip in an embodiment of the present invention is shown;

[0029] Figure 3 The p-electrode and Si heavily doped n-electrode of different materials in the embodiment of the present invention and the comparative example 1 are shown.+ - Current-voltage characteristic curve of AlGaN layer contact;

[0030] Figure 4 The current-voltage characteristic curves of the LED chip materials prepared in the embodiment of the present invention, comparative example 2 and comparative example 3 are shown;

[0031] Figure 5 A comparison chart of the luminous intensity of LED chip materials prepared in the embodiment of the present invention, comparative example 2 and comparative example 3 at the same current density is shown;

[0032] Description of reference numerals:

[0033] 1. Sapphire substrate; 2. AlN nucleation layer; 3. AlN buffer layer; 4. Si-doped n-Al 0.5 Ga 0.5 N layer; 5, Al 0.42 Ga 0.58 N / A 0.5 Ga 0.5 N quantum well layer; 6. Mg doped p-Al 0.65 Ga 0.35 N electron blocking layer; 7. Mg doped p-Al 0.5 Ga 0.5 N hole injection layer; 8. Heavily doped p + -Al 0.4 Ga 0.6 N layer; 9. Heavily doped n + -Al 0.4 Ga 0.6 N layers. DETAILED DESCRIPTION

[0034] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0035] The following will be combined with the specific embodiments of the present invention and the drawings of the specification to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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 creative work are within the scope of protection of the present invention.

[0036] Example

[0037] A method for manufacturing an ultra-thin tunnel junction deep ultraviolet LED chip, the steps are as follows:

[0038] (1) placing a cleaned patterned sapphire substrate 1 into a magnetron sputtering reaction chamber to deposit an AlN nucleation layer 2 with a thickness of 20 nm;

[0039] (2) Then, the substrate is placed in a MOCVD reaction chamber and a 2.8 μm thick undoped AlN buffer layer 3 is grown at 650°C;

[0040] (3) At 1100°C, grow Si-doped n-Al with a thickness of 2.5 μm 0.5 Ga 0.5 N layer 4, Si doping concentration is 6×10 18 cm -3 .

[0041] (4) Growth of Al at 750°C 0.42 Ga 0.58 N / A 0.5 Ga 0.5 N quantum well layer 5, Al 0.42 Ga 0.58 N and Al 0.5 Ga 0.5 The thickness of N is 3nm and 12nm respectively;

[0042] (5) At 1050℃, a 20nm thick Mg-doped p-Al 0.65 Ga 0.35 N electron blocking layer 6, Mg doping concentration 5×10 18 cm -3 ;

[0043] (6) At 1050°C, Mg-doped p-Al with a thickness of 50 nm was grown. 0.5 Ga 0.5 N hole injection layer 7, Mg doping concentration is 1×10 19 cm -3 ;

[0044] (7) At 1050℃, a heavily doped p-type nanostructured nanostructure with a thickness of 5 nm was grown. + -Al 0.4 Ga 0.6 N layer 8, Mg doping concentration 5×10 19 cm -3 ;

[0045] (8) At 1050℃, a 5nm thick heavily doped n + -Al 0.4 Ga 0.6N layer 9, Si doping concentration is 1×10 21 cm -3 , forming a Si-Mg co-doped ultra-thin tunnel junction to obtain an epitaxial material;

[0046] (9) The epitaxial material is annealed at 550°C for 20 minutes in a N2 atmosphere. The schematic diagram of the structure of the epitaxial material is shown in FIG. Figure 1 As shown;

[0047] (10) Using ICP to heavily dope the Si of the epitaxial material with n + -AlGaN layer is partially etched to form a direct n-Al 0.5 Ga 0.5 N-layer step structure;

[0048] (11) The n-Al exposed by etching 0.5 Ga 0.5 Ti / Al / Ti / Au (50nm / 100nm / 50nm / 100nm) was deposited on the N layer as an n-electrode and annealed at 900°C for 1 minute in a N2 atmosphere to form an n-type ohmic contact.

[0049] (12) In Si heavily doped with n + Ni / Au (25nm / 50nm) is deposited on the AlGaN layer 8 as a p-electrode and annealed at 600°C for 3 minutes in an air atmosphere to form a p-type ohmic contact, thereby obtaining an ultra-thin tunnel junction deep ultraviolet LED chip. Figure 2 shown.

[0050] Comparative Example 1

[0051] A method for manufacturing an ultra-thin tunnel junction deep ultraviolet LED chip is basically the same as the embodiment, with the only difference being that step (12) deposits Ti / Al / Ti / Au (50nm / 100nm / 50nm / 100nm) as a p-electrode.

[0052] Comparative Example 2

[0053] A method for manufacturing a deep ultraviolet LED chip is basically the same as the embodiment, except that: in step (7), a p-GaN layer with a thickness of 10 nm is grown at 1050° C., and the Mg doping concentration is 1×10 19 cm -3 , and there is no step (8). That is, the Si-Mg co-doped ultra-thin tunnel junction of the embodiment is replaced with a p-GaN layer of the same thickness.

[0054] Comparative Example 3

[0055] A method for manufacturing a deep ultraviolet LED chip is basically the same as the embodiment, the only difference being that there is no step (8). That is, the Si-Mg co-doped ultra-thin tunnel junction of the embodiment is replaced with a 10 nm heavily doped p + -Al 0.4 Ga 0.6 N layer, Mg doping concentration is 5×10 19 cm -3 .

[0056] Test Case

[0057] Figure 3 The current-voltage characteristic curves of the ultra-thin tunnel junction deep ultraviolet LED chips manufactured in Example 1 and Comparative Example 1 are shown. The results show that Si heavily doped with n + The -AlGaN layer is in a Si-Mg co-doped state, and the Ti / Al / Ti / Au metal electrodes usually used to form n-type ohmic contact with the n-AlGaN layer are no longer applicable. Instead, Ni / Au metal electrodes with higher work function are required to form ohmic contact.

[0058] Figure 4 The current-voltage characteristic curves of the embodiment, comparative example 2 and comparative example 3 are shown. It can be seen that at the same voltage, the current magnitude is: comparative example 2> embodiment> comparative example 3, which shows that the resistance of the Si-Mg co-doped ultra-thin tunnel junction is slightly increased compared with the p-GaN layer with the same thickness; + -Al 0.4 Ga 0.6 N layer, has smaller resistance.

[0059] Figure 5 The results of Example 1, Comparative Example 2 and Comparative Example 3 at 25 A·cm -2 The comparison of the luminescence curves under current density shows that compared with Comparative Examples 2 and 3, the luminescence intensity of Example 1 is higher. Figure 4 and Figure 5 , the analysis shows that, although the resistance of the ultra-thin tunnel junction co-doped with Si-Mg is slightly increased compared to p-GaN, its luminous intensity at the same voltage is much higher than that of p-GaN. + -Al 0.4 Ga 0.6 Compared with p-GaN, it has lower resistance and higher luminous intensity. Therefore, it can be concluded that the use of ultra-thin tunnel junctions is more effective than p-GaN and p + -Al 0.4 Ga 0.6 As an electrode contact layer, N can achieve higher luminous efficiency.

[0060] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for manufacturing an ultra-thin tunnel junction deep ultraviolet LED chip, characterized in that: include, An epitaxial growth layer is prepared on the substrate, wherein the epitaxial growth layer includes an AlN nucleation layer, an AlN buffer layer, a Si-doped n-AlGaN layer, a low-aluminum AlGaN / high-aluminum AlGaN multi-quantum well layer, a Mg-doped p-AlGaN electron blocking layer, and a Mg-doped p-AlGaN hole injection layer, all of which are 5 to 15 nm thick. + -AlGaN layer and Si heavily doped n + -A tunnel junction formed by an AlGaN layer to obtain an epitaxial material; From Si heavily doped with n + The -AlGaN layer is partially etched until the Si-doped n-AlGaN layer is exposed; In the exposed Si-doped n-AlGaN layer and Si heavily doped n + An n-electrode and a p-electrode are prepared on the -AlGaN layer to obtain an ultra-thin tunnel junction deep ultraviolet LED chip.

2. The method for manufacturing an ultra-thin tunnel junction deep ultraviolet LED chip according to claim 1, characterized in that: The Mg heavily doped p + -The Mg doping concentration of the AlGaN layer is 1×10 19 ~2×10 20 cm -3 ; The Si is heavily doped with n + -The Si doping concentration of the AlGaN layer is 1×10 20 ~1×10 21 cm -3 .

3. The method for manufacturing an ultra-thin tunnel junction deep ultraviolet LED chip according to claim 1, characterized in that: The n-electrode and the p-electrode are Ti / Al / Ti / Au and Ni / Au respectively, wherein the thickness of Ti is 10-50nm, Al is 50-100nm, Ni is 25-50nm, and Au is 50-100nm.

4. The method for manufacturing an ultra-thin tunnel junction deep ultraviolet LED chip according to claim 1, characterized in that: The thickness of the AlN nucleation layer is 10 to 50 nm; The thickness of the AlN buffer layer is 2.5 to 3 μm; The thickness of the Si-doped n-AlGaN layer is 2 to 3 μm; The thicknesses of the low-aluminum AlGaN / high-aluminum AlGaN multi-quantum well layers are 1-5 nm and 10-15 nm respectively; The thickness of the Mg-doped p-AlGaN electron blocking layer is 10 to 30 nm; The thickness of the Mg-doped p-AlGaN hole injection layer is 40-60 nm.

5. The method for manufacturing an ultra-thin tunnel junction deep ultraviolet LED chip according to claim 4, characterized in that: The Si doping concentration of the Si-doped n-AlGaN layer is 1×10 18 ~6×10 18 cm -3 .

6. The method for manufacturing an ultra-thin tunnel junction deep ultraviolet LED chip according to claim 4, characterized in that: The Mg doping concentration of the Mg doped p-AlGaN electron blocking layer is 1×10 18 ~5×10 18 cm -3 .

7. The method for manufacturing an ultra-thin tunnel junction deep ultraviolet LED chip according to claim 4, characterized in that: The Mg doping concentration of the Mg doped p-AlGaN hole injection layer is 5×10 18 ~1×10 19 cm -3 .

8. The method for manufacturing an ultra-thin tunnel junction deep ultraviolet LED chip according to any one of claims 1 to 7, characterized in that: In Si-doped n-AlGaN layer and Si heavily doped n + After the n-electrode and the p-electrode are prepared on the -AlGaN layer, a heat treatment is performed.

9. An ultra-thin tunnel junction deep ultraviolet LED chip, characterized in that: Obtained by the method according to any one of claims 1 to 8.

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