An ultrathin tunnel junction deep ultraviolet LED chip and its manufacturing method

Abstract

This invention discloses an ultrathin tunnel junction deep ultraviolet LED chip and its manufacturing method. The manufacturing method includes preparing an epitaxial growth layer on a substrate. 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 multiple quantum well layer, a Mg-doped p-AlGaN electron blocking layer, a Mg-doped p-AlGaN hole injection layer, and a Mg-doped p-AlGaN heavily doped p-AlGaN layer with a thickness of 5-15 nm. + -AlGaN layer and Si heavily doped n + A tunnel junction composed of AlGaN layers is used to obtain epitaxial materials; from Si heavily doped with n + Partial etching of the -AlGaN layer until the Si-doped n-AlGaN layer is exposed; in the exposed Si-doped n-AlGaN layer and Si-doped n-AlGaN layer... + An ultrathin tunnel junction deep ultraviolet LED chip is obtained by fabricating n-electrodes and p-electrodes on an AlGaN layer, respectively. This invention utilizes an ultrathin n-electrode layer. + -AlGaN / p + -AlGaN tunnel junction, removing lightly doped n ‑ The AlGaN capping layer not only facilitates the dehydrogenation activation of Mg acceptors but also reduces the operating voltage of deep ultraviolet LED chips, thereby improving their photoelectric performance.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to an ultrathin tunnel junction deep ultraviolet LED chip and its manufacturing method. Background Technology

[0002] As a new generation of deep ultraviolet (200-280nm) solid-state light source, AlGaN-based deep ultraviolet LED chips have many advantages such as energy saving, environmental protection, small size and long life, and 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 the Mg acceptor in p-AlGaN increases with increasing Al content. Higher activation energy leads to decreased hole concentration and mobility, thus increasing the resistivity of p-AlGaN. Therefore, efficient p-type doping of AlGaN is crucial for achieving high-performance deep ultraviolet (DUV) LED devices. Furthermore, increasing Al content also increases the work function, making it difficult to form an ohmic contact with the p-electrode metal. Both of these factors degrade the device performance of AlGaN-based DUV LED chips. To fabricate p-type ohmic contact electrodes, a p-GaN layer is often inserted between the p-AlGaN and the metal electrode as an ohmic contact layer. However, the p-GaN contact layer exhibits strong absorption of ultraviolet light, causing light loss. Therefore, using a tunnel junction instead of the p-GaN contact layer is a suitable approach. However, in AlGaN-based tunneled DUV LED chips, the top of the tunnel junction is typically lightly doped with n-type doping. - -AlGaN capping layer. Lightly doped n - While the AlGaN capping layer can enhance current spread and facilitate the fabrication of n-type ohmic contacts, it hinders the deactivation of Mg acceptors in the p-AlGaN buried layer, further leading to an increase in chip voltage. Summary of the Invention

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

[0005] To achieve the above objectives, the present invention provides a method for manufacturing an ultrathin tunnel junction deep ultraviolet LED chip, comprising,

[0006] An epitaxial growth layer is fabricated on a substrate. 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 multiple quantum well layer, a Mg-doped p-AlGaN electron blocking layer, a Mg-doped p-AlGaN hole injection layer, and a Mg-doped p-AlGaN heavily doped p-AlGaN layer, each with a thickness of 5–15 nm. +-AlGaN layer and Si heavily doped n + -Tunnel junctions composed of AlGaN layers are used to obtain epitaxial materials;

[0007] From Si heavily doped with n + - Partial etching of the AlGaN layer until the Si-doped n-AlGaN layer is exposed;

[0008] In the exposed Si-doped n-AlGaN layer and Si heavily doped n + - An ultrathin tunnel junction deep ultraviolet LED chip was obtained by fabricating n-electrodes and p-electrodes on an AlGaN layer.

[0009] Furthermore, the Mg heavily doped p + The Mg doping concentration of the AlGaN layer is 1×10⁻⁶. 19 ~2×10 20 cm -3 ;

[0010] The Si heavily doped n + The Si doping concentration of the AlGaN layer is 1×10⁻⁶. 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 10–50 nm;

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

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

[0015] The thicknesses of the low-aluminum AlGaN / high-aluminum AlGaN multiple 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 10–30 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 × 10⁻⁶. 18 cm -3 .

[0019] Furthermore, the Mg doping concentration of the Mg-doped p-AlGaN electron blocking layer is 1×10⁻⁶. 18 ~5×10 18 cm -3 .

[0020] Furthermore, the Mg doping concentration of the Mg-doped p-AlGaN hole injection layer is 5 × 10⁻⁶. 18 ~1×10 19 cm -3 .

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

[0022] This invention also provides an ultrathin tunnel junction deep ultraviolet LED chip, obtained using the method described above.

[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) Using ultra-thin n + -AlGaN / p + -AlGaN tunnel junction, removing lightly doped n - The AlGaN capping layer not only facilitates the dehydrogenation activation of Mg acceptors but also reduces the operating voltage of deep ultraviolet LED chips, thereby improving their photoelectric performance. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

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

[0029] Figure 3 The embodiments of the present invention and Comparative Example 1 show p-electrodes made of different materials and Si heavily doped n-electrodes.+ - Current-voltage characteristic curve of AlGaN layer contact;

[0030] Figure 4 The current-voltage characteristic curves of the LED chip materials prepared in the embodiments of the present invention, Comparative Example 2 and Comparative Example 3 are shown.

[0031] Figure 5 The diagram shows a comparison of the luminous intensity of the LED chip materials prepared in the embodiments of the present invention, Comparative Example 2 and Comparative Example 3, under the same current density.

[0032] Explanation of reference numerals in the attached figures:

[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 / Al 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 Implementation

[0034] The endpoints and any values ​​of the ranges disclosed in this 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example

[0037] A method for manufacturing an ultrathin tunnel junction deep ultraviolet LED chip, comprising the following steps:

[0038] (1) Place the cleaned patterned sapphire substrate 1 into the magnetron sputtering reaction chamber and deposit an AlN nucleation layer 2 with a thickness of 20 nm.

[0039] (2) Then it was placed in the MOCVD reaction chamber and an undoped AlN buffer layer with a thickness of 2.8 μm was grown at 650 °C.

[0040] (3) Si-doped n-Al with a thickness of 2.5 μm was grown at 1100℃. 0.5 Ga 0.5 N-layer 4, Si doping concentration is 6×10⁴ 18 cm -3 .

[0041] (4) Al was grown at 750℃. 0.42 Ga 0.58 N / Al 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 thicknesses of N are 3 nm and 12 nm, respectively;

[0042] (5) Mg-doped p-Al with a thickness of 20 nm was grown at 1050℃. 0.65 Ga 0.35 N electron blocking layer 6, Mg doping concentration is 5×10⁶ 18 cm -3 ;

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

[0044] (7) At 1050℃, a heavily doped p-type substrate with a thickness of 5 nm was grown. + -Al 0.4 Ga 0.6 N-layer 8, Mg doping concentration is 5×10⁸ 19 cm -3 ;

[0045] (8) Growing a heavily doped n-type substrate with a thickness of 5 nm at 1050℃. + -Al 0.4 Ga 0.6N-layer 9, Si doping concentration is 1×10⁹ 21 cm -3 This forms a Si-Mg co-doped ultrathin tunnel junction, resulting in an epitaxial material;

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

[0047] (10) Using ICP to heavily dope Si and n in epitaxial materials + Partial etching of the AlGaN layer forms a layer extending to n-Al. 0.5 Ga 0.5 N-layer stepped structure;

[0048] (11) In the etched n-Al 0.5 Ga 0.5 Ti / Al / Ti / Au (50nm / 100nm / 50nm / 100nm) was deposited on the N layer as the n electrode, and annealed at 900℃ for 1 minute in N2 atmosphere to form an n-type ohmic contact;

[0049] (12) In Si heavily doped with n + Ni / Au (25nm / 50nm) electrodes were deposited on AlGaN layer 8 as p-electrodes, and annealed at 600℃ for 3 minutes in air to form p-type ohmic contacts, resulting in an ultrathin tunnel junction deep ultraviolet LED chip with the following structure: Figure 2 As shown.

[0050] Comparative Example 1

[0051] A method for manufacturing an ultrathin tunnel junction deep ultraviolet LED chip is basically the same as the example, except that: in step (12), Ti / Al / Ti / Au (50nm / 100nm / 50nm / 100nm) is deposited as the p electrode.

[0052] Comparative Example 2

[0053] A method for manufacturing a deep ultraviolet LED chip is basically the same as the example, 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 1×10⁻⁶. 19 cm -3 Meanwhile, step (8) is omitted. The Si-Mg co-doped ultrathin 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, except that step (8) is omitted. That is, the Si-Mg co-doped ultrathin tunnel junction of the embodiment is replaced with a 10nm heavily doped p-type junction. + -Al 0.4 Ga 0.6 N-layer, Mg doping concentration is 5×10⁻⁶ 19 cm -3 .

[0056] Test case

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

[0058] Figure 4 The current-voltage characteristic curves of Examples 1, 2, and 3 are shown. It can be seen that under the same voltage, the current magnitude is: Comparative Example 2 > Example 2 > Comparative Example 3. This indicates that the resistance of the Si-Mg co-doped ultrathin tunnel junction is slightly increased compared to a p-GaN layer of the same thickness; compared to heavily doped p-GaN layers... + -Al 0.4 Ga 0.6 N layers have lower resistance.

[0059] Figure 5 Examples 1, 2, and 3 are shown at 25 A·cm. -2 The comparison of emission curves under different current densities shows that the emission intensity of Example 1 is higher than that of Comparative Examples 2 and 3. Combined with... Figure 4 and Figure 5 Analysis revealed that while the resistance of the Si-Mg co-doped ultrathin tunnel junction was slightly increased compared to p-GaN, its luminous intensity at the same voltage was significantly higher. Furthermore, compared to heavily doped p-GaN... + -Al 0.4 Ga 0.6 Compared to p-GaN, p-GaN has lower resistance and higher luminous intensity. Therefore, it can be concluded that using an ultrathin tunnel junction is superior to p-GaN and p-GaN. + -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 description 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 foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for manufacturing an ultrathin tunnel junction deep ultraviolet LED chip, characterized in that, Comprising, An epitaxial growth layer is prepared on a substrate, which comprises 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, a Mg-doped p-AlGaN hole injection layer, and a Mg heavily-doped p-AlGaN layer with a thickness of 5-15 nm + -AlGaN layer and a Si heavily-doped n + -AlGaN layer, to obtain an epitaxial material; from Si heavily doped n + - partially etching the -AlGaN layer until the Si doped n-AlGaN layer is exposed; n-AlGaN layer and Si heavily doped n + n-electrode and p-electrode are prepared on the exposed Si doped n-AlGaN layer and Si heavily doped n The Mg heavily dopes p + The Mg doping concentration of the AlGaN layer is 1 x 10 19 2 x 10 20 cm -3 ; The Si heavily dopes n + The Si doping concentration of the AlGaN layer is 1 x 1018 20 1 x 1018 21 cm -3 ; Mg from Mg heavily doped p + -AlGaN layer diffuses to Si heavily doped n + -AlGaN layer forms Si-Mg co-doped state, which is beneficial to dehydrogenation activation of Mg acceptor and reduces the working voltage of deep ultraviolet LED chip.

2. The method of fabricating an ultrathin tunnel junction deep UV LED chip of claim 1, wherein, The n electrode is Ti / Al / Ti / Au, wherein the thickness of Ti is 10-50 nm, the thickness of Al is 50-100 nm, and the thickness of Au is 50-100 nm; the thickness of Ni in the p electrode is 25-50 nm, and the thickness of Au is 50-100 nm.

3. The method of fabricating an ultrathin tunnel junction deep UV LED chip of claim 1, wherein, The thickness of the AlN nucleation layer is 10-50 nm; The thickness of the AlN buffer layer is 2.5-3 μm; The thickness of the Si-doped n-AlGaN layer is 2-3 μm; The thicknesses of the low-aluminum AlGaN / high-aluminum AlGaN multi-quantum well layer are 1-5 nm and 10-15 nm, respectively; The thickness of the Mg-doped p-AlGaN electron blocking layer is 10-30 nm; The thickness of the Mg-doped p-AlGaN hole injection layer is 40-60 nm.

4. The method of fabricating an ultrathin tunnel junction deep UV LED chip of claim 3, wherein, The Si-doped n-AlGaN layer has a Si-doping concentration of 1 x 10 18 6 x 10 18 cm -3 .

5. The method of fabricating an ultrathin tunnel junction deep UV LED chip of claim 3, wherein, The Mg-doped p-AlGaN electron blocking layer has a Mg-doped concentration of 1 x 10 18 5 x 10 18 cm -3 .

6. The method of fabricating an ultrathin tunnel junction deep UV LED chip of claim 3, wherein, The Mg-doped p-AlGaN hole injection layer has a Mg-doped concentration of 5 x 1019cm-3 18 1 x 1019cm-3 19 cm -3 .

7. The method of fabricating an ultrathin tunnel junction deep UV LED chip according to any one of claims 1-6, wherein, After the n-electrode and the p-electrode are respectively prepared on the Si-doped n-AlGaN layer and the Si heavily-doped n + A heat treatment is further performed after the n-electrode and the p-electrode are respectively prepared on the Si-doped n-AlGaN layer and the Si heavily-doped n 8. An ultrathin tunnel junction deep UV LED chip, characterized in that, The method of any one of claims 1-7 is used.

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