A multi-wavelength light emitting device and a method of fabricating the same

Abstract

The application discloses a kind of multi-wavelength light emitting devices, comprising: M light emitting stacks;Each light emitting stack includes sequentially stacked from bottom to top N type layer, multi-quantum well layer, P type layer and tunnel junction layer;M exposure structures are arranged on the surface of multi-wavelength light emitting device, each exposure structure extends to the corresponding N type layer along the thickness direction and exposes N type layer;(M+1) N electrodes are respectively arranged on the exposed N type layer and the tunnel junction layer on the top surface;Wherein, M is not less than 2 positive integer;(M+1) N electrodes are mutually electrically insulated, and are configured to control multi-quantum well layer in M light emitting stacks by connecting different polarity power supply, to realize single layer or multi-layer combination light emitting. Through structural design, N electrode can realize the equivalent function of P electrode, so it is not necessary to prepare P type ohmic contact electrode on P type layer, and the problem that P type ohmic contact cannot be formed due to damage to P type layer caused by dry etching can be avoided.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a multi-wavelength light-emitting device and its fabrication method. Background Technology

[0002] Gallium nitride (GaN)-based LEDs have broad prospects in the field of white light lighting due to their advantages such as low energy consumption, long lifespan, fast response time, and small size. Currently, there are three main methods for achieving white light, but each has its own significant shortcomings.

[0003] First, monochromatic LED chips of red, green, blue, or complementary colors are combined and mixed. This method requires complex circuitry to drive each chip individually, resulting in high costs. Furthermore, because these monochromatic LED chips are arranged horizontally, there is a problem of spatially uneven light mixing.

[0004] Secondly, the most mainstream method currently is to excite phosphors with blue or ultraviolet LEDs to produce white light. The main drawback is that the phosphors age over time and with environmental changes, causing color temperature drift and decreased color rendering in the emitted white light, affecting the long-term color stability and reliability of the product.

[0005] To overcome the aforementioned problems, the industry has proposed a third solution: epitaxially growing multiple PN junction structures with different wavelengths on the same substrate and vertically stacking them to achieve white light mixing. This solution simplifies the control circuit and achieves uniform light mixing due to the vertical arrangement. However, it faces the following challenges during fabrication: to ensure independent controllability of each light-emitting unit in the vertically stacked structure, multiple patterning photolithography and dry etching processes are required to expose the P-type and N-type layers of the underlying PN junction structure, and separate P-electrodes and N-electrodes must be fabricated for each PN junction structure. This process involves numerous steps, leading to complexity. More importantly, during the process of exposing the lower P-type layer using dry etching, damage to the surface of the P-type layer is inevitable. A good p-type ohmic contact cannot be formed on the damaged P-type layer, resulting in a significant reduction in the electro-optical conversion efficiency of the LED. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a multi-wavelength light-emitting device and its fabrication method, aiming to solve the problem of the inability to form P-type ohmic contacts due to damage to the P-type layer caused by dry etching.

[0007] In a first aspect, the present invention provides a multi-wavelength light-emitting device, comprising: Substrate; M light-emitting layers are stacked sequentially on the substrate; each light-emitting layer includes an N-type layer, a multiple quantum well layer, a P-type layer and a tunnel junction layer stacked sequentially from bottom to top; M exposed structures are disposed on the surface of the multi-wavelength light-emitting device and correspond one-to-one with M light-emitting stacks; each exposed structure extends along the thickness direction to the N-type layer in the corresponding light-emitting stack, and the bottom of the exposed structure exposes the N-type layer; (M+1) N electrodes are respectively disposed on the N-type layer exposed at the bottom of the exposed structure and form an ohmic contact with the N-type layer, and disposed on the tunnel junction layer on the top surface of the multi-wavelength light-emitting device and form an ohmic contact with the tunnel junction layer; Where M is a positive integer not less than 2; the (M+1) N electrodes are electrically insulated from each other and are configured to control the multiple quantum well layers in the M light-emitting stacks by connecting power supplies of different polarities, so as to achieve single-layer or multi-layer combined light emission.

[0008] The multi-wavelength light-emitting device provided by this invention involves setting a tunnel junction layer within each light-emitting stack, and simultaneously fabricating an N-electrode in ohmic contact directly on the top tunnel junction layer. Other N-electrodes are in ohmic contact with the N-type layer in each light-emitting stack, such that each multi-quantum-well layer is sandwiched between two adjacent N-electrodes in the thickness direction. Furthermore, by utilizing the electrical properties of the tunnel junction layer, the light emission of each multi-quantum-well layer can be selectively controlled by connecting the N-electrodes to power supplies of different polarities, thereby achieving independent single-wavelength light emission or even multi-wavelength mixing. Through structural design, this invention allows the N-electrodes to achieve functions equivalent to P-electrodes, thus eliminating the need to fabricate P-type ohmic contact electrodes on the P-type layer and avoiding the problem of P-type ohmic contact failure caused by dry etching damage to the P-type layer.

[0009] As an optional embodiment of the multi-wavelength light-emitting device of the present invention, any two N electrodes from the (M+1) N electrodes are connected to the positive and negative terminals of the power supply, respectively. The upper N electrode is connected to the positive terminal of the power supply, and the lower N electrode is connected to the negative terminal. All quantum well layers between the N electrode connected to the positive terminal and the N electrode connected to the negative terminal emit light. It should be noted that when the adjacent upper N electrode of the quantum well layer to be emitted is connected to the positive terminal of the power supply, and the adjacent lower N electrode is connected to the negative terminal of the power supply, the N electrode connected to the positive terminal can act as a P electrode, enabling the quantum well layer to emit light.

[0010] As an alternative embodiment of the multi-wavelength light-emitting device of the present invention, (M+1) N electrodes are formed from the same conductive material through the same process steps. It should be noted that using the same material and forming all N electrodes through the same process steps can minimize the number of electrode fabrication steps, thereby reducing the total cost of device manufacturing.

[0011] As an alternative embodiment of the multi-wavelength light-emitting device of the present invention, the N-electrode is made of any one of Ti, Al, Cr, Pt, and Au, or a composite structure of multiple materials. It should be noted that using the above-mentioned electrode materials or a composite structure of multiple electrode materials can achieve good ohmic contact with the N-type layer and the tunnel junction layer.

[0012] As an alternative embodiment of the multi-wavelength light-emitting device of the present invention, the tunnel junction layer consists of a heavily doped P-type layer, a barrier layer, and a heavily doped N-type layer stacked sequentially from bottom to top. It should be noted that the barrier layer in the tunnel junction layer effectively suppresses the memory effect of the P-type dopant Mg used during the growth of the heavily doped P-type layer, preventing Mg from entering the subsequently grown quantum well layer.

[0013] As a preferred option among the above-mentioned alternatives, the heavily doped p-type layer is Mg-doped GaN or In. x Ga 1-x The doping concentrations of N and Mg range from 1 × 10⁻⁶. 20 cm -3 -5×10 20 cm -3 The heavily doped N-type layer is Si-doped GaN or In. x Ga 1-x The doping concentration of N and Si ranges from 1×10⁻⁶. 20 cm -3 -5×10 20 cm -3 The barrier layer is made of GaN or In. x Ga 1-x N; where 0 < x < 0.4. It should be noted that at this doping concentration, a low-resistance tunnel junction can be formed, and GaN or In can be used. x Ga 1-x Nitrogen (N) acts as a barrier layer, effectively suppressing the memory effect of magnesium (Mg).

[0014] As an alternative to the multi-wavelength light-emitting device of the present invention, all M exposed structures are through holes or grooves formed by etching.

[0015] As an alternative embodiment of the multi-wavelength light-emitting device of the present invention, between any two adjacent light-emitting layers, the emission wavelength of the quantum well layer in the lower light-emitting layer is shorter than that in the upper light-emitting layer. It should be noted that the shorter emission wavelength of the lower quantum well layer and the longer emission wavelength of the upper quantum well layer prevents the light emitted by the lower quantum well layer from being partially absorbed by the upper quantum well layer.

[0016] Secondly, the present invention also provides a method for fabricating a multi-wavelength light-emitting device, comprising the following steps: S1. M light-emitting stacks are sequentially deposited on the substrate. Each light-emitting stack includes an N-type layer, a multiple quantum well layer, a P-type layer, and a tunnel junction layer stacked sequentially from bottom to top. S2. Along the thickness direction, the tunnel junction layer on the top surface is etched down to the N-type layer of each light-emitting stack to form M exposed structures, and the bottom of each exposed structure exposes the corresponding N-type layer; S3. Simultaneously prepare (M+1) N electrodes on the surface of each exposed N-type layer and the tunnel junction layer on the top surface.

[0017] The method for fabricating a multi-wavelength light-emitting device provided by this invention includes a tunnel junction layer in each light-emitting stack, with an N-electrode fabricated on the surface of the top tunnel junction layer. Simultaneously, an N-electrode is also fabricated on the N-type layer of each light-emitting stack. The N-electrode achieves the same function as a P-electrode by utilizing the electrical properties of the tunnel junction layer, thus avoiding the need to fabricate a P-electrode. This avoids the problem of failing to form a P-type ohmic contact due to damage to the P-type layer caused by dry etching. Furthermore, all N-electrodes can be fabricated simultaneously, reducing the number of steps required for electrode fabrication and lowering manufacturing costs.

[0018] As an optional embodiment of the preparation method of the present invention, the substrate material is sapphire or gallium nitride; after step S3, a reflective layer is further prepared on the surface of the substrate opposite to the light-emitting stack. It should be noted that when a transparent substrate is used, a reflective layer can be prepared on the surface of the substrate opposite to the N-type layer, further improving the light extraction efficiency of the multi-wavelength light-emitting device.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, some of which will become clear as the description proceeds, and others will be learned by practicing the invention. Attached Figure Description

[0020] Figure 1 This is a schematic cross-sectional view of the deposited luminescent stack in Embodiment 1 of this application.

[0021] Figure 2 This is a cross-sectional schematic diagram of the second N-type layer exposed by etching in Embodiment 1 of this application.

[0022] Figure 3 This is a cross-sectional schematic diagram of the etching that exposes the first N-type layer in Embodiment 1 of this application.

[0023] Figure 4 This is a schematic cross-sectional view of the substrate exposed by etching in Embodiment 1 of this application.

[0024] Figure 5 This is a schematic cross-sectional view of the wet etching process in Embodiment 1 of this application.

[0025] Figure 6 This is a cross-sectional schematic diagram of the passivation layer after it was prepared in Example 1 of this application.

[0026] Figure 7 This is a cross-sectional schematic diagram of the dual-wavelength light-emitting device after it has been fabricated in Embodiment 1 of this application.

[0027] Figure 8 This is a schematic cross-sectional view of the deposited luminescent stack in Embodiment 2 of this application.

[0028] Figure 9 This is a cross-sectional schematic diagram of the third N-type layer exposed by etching in Embodiment 2 of this application.

[0029] Figure 10 This is a cross-sectional schematic diagram of the second N-type layer exposed by etching in Embodiment 2 of this application.

[0030] Figure 11 This is a cross-sectional schematic diagram of the etching process exposing the first N-type layer in Embodiment 2 of this application.

[0031] Figure 12 This is a cross-sectional view of the substrate exposed by etching in Embodiment 2 of this application.

[0032] Figure 13 This is a schematic cross-sectional view of the wet etching process in Embodiment 2 of this application.

[0033] Figure 14 This is a cross-sectional schematic diagram of the passivation layer after it was prepared in Example 2 of this application.

[0034] Figure 15 This is a cross-sectional schematic diagram of the three-wavelength light-emitting device after it has been fabricated in Embodiment 2 of this application.

[0035] Figure 16 This is a schematic cross-sectional view of the reflective layer after it has been prepared in Embodiment 2 of this application.

[0036] Reference numerals: 1 - substrate, 2 - first light-emitting stack, 3 - second light-emitting stack, 4 - third light-emitting stack; 5 - passivation layer; 6 - reflective layer; 7 - first N-electrode, 8 - second N-electrode, 9 - third N-electrode, 10 - fourth N-electrode; 21-First N-type layer, 22-First multi-quantum well layer, 23-First P-type layer, 24-First tunnel junction layer; 31-Second N-type layer, 32-Second multiple quantum well layer, 33-Second P-type layer, 34-Second tunnel junction layer; 41-Third N-type layer, 42-Third multi-quantum well layer, 43-Third P-type layer, 44-Third tunnel junction layer. Detailed Implementation

[0037] To facilitate understanding of the present invention, a more comprehensive description will be given in conjunction with the accompanying drawings. It should be noted that the embodiments described herein are only a part of the present invention, and not all of it. Based on the disclosure of this invention, all other embodiments or modifications obtained by those skilled in the art without inventive effort should fall within the protection scope of this invention.

[0038] Before describing the embodiments of this application, the relevant technologies will be described first.

[0039] A tunnel junction is a pn junction composed of heavily doped n-type and heavily doped p-type sub-semiconductor layers. Due to the quantum tunneling effect, the current flowing through the tunnel junction increases rapidly when a reverse bias is applied. Utilizing this property, assuming the p-type layer of the initial pn junction faces upwards, a tunnel junction can be grown on top of the p-type layer, transforming the top layer of the initial pn junction from p-type to n-type. This avoids the p-type ohmic contact and has no impact on the conduction of the initial pn junction.

[0040] The following are some embodiments of this application, and the embodiments of the present invention will further describe the technical solution of the present invention in detail. Example 1

[0041] This embodiment provides a method for fabricating a multi-wavelength light-emitting device, specifically for fabricating a dual-wavelength light-emitting device, including the following steps: Step S1: M light-emitting stacks are sequentially deposited on the substrate. Each light-emitting stack includes an N-type layer, a multiple quantum well layer, a P-type layer, and a tunnel junction layer stacked sequentially from bottom to top.

[0042] In this embodiment, a substrate 1 is provided, and a first light-emitting stack 2 and a second light-emitting stack 3 are sequentially deposited on the substrate 1. The first light-emitting stack 2 includes a first N-type layer 21, a first multiple quantum well layer 22, a first P-type layer 23, and a first tunnel junction layer 24, stacked sequentially from bottom to top; the second light-emitting stack 3 includes a second N-type layer 31, a second multiple quantum well layer 32, a second P-type layer 33, and a second tunnel junction layer 34, stacked sequentially from bottom to top, as shown below. Figure 1 As shown.

[0043] Substrate 1 is a silicon substrate. In the first light-emitting stack 2, the first N-type layer 21 is N-type GaN; the first multiple quantum well layer 22 is a stack structure composed of alternating InGaN well layers and GaN barrier layers, and the emission wavelength of the first multiple quantum well layer 22 is 490 nm; the first P-type layer 23 is P-type GaN; the first tunnel junction layer 24 is composed of a heavily Mg-doped GaN layer, an InGaN barrier layer, and a heavily Si-doped GaN layer stacked sequentially from bottom to top, with thicknesses of 20 nm, 25 nm, and 20 nm, respectively, and a Mg doping concentration of 2 × 10⁻⁶. 20 cm -3The Si doping concentration is 2×10⁻⁶. 20 cm -3 In the second light-emitting stack 3, the second N-type layer 31 is N-type GaN; the second multiple quantum well layer 32 is a stack structure composed of alternating InGaN well layers and GaN barrier layers, and the emission wavelength of the second multiple quantum well layer 32 is 590 nm; the second P-type layer 33 is P-type GaN; the second tunnel junction layer 34 is composed of a heavily Mg-doped GaN layer, an InGaN barrier layer, and a heavily Si-doped GaN layer stacked sequentially from bottom to top, with thicknesses of 20 nm, 25 nm, and 20 nm, respectively, and a Mg doping concentration of 2 × 10⁻⁶. 20 cm -3 The Si doping concentration is 2×10⁻⁶. 20 cm -3 The heavily Mg-doped GaN layer is located below and is in contact with the second P-type layer 33.

[0044] Step S2: Etch along the thickness direction from the tunnel junction layer on the top surface to the N-type layer of each light-emitting stack to form M exposed structures, with the corresponding N-type layer exposed at the bottom of each exposed structure.

[0045] In this embodiment, the first exposed structure is formed by etching from the second tunnel layer to the first N-type layer 21 along the thickness direction, and the second exposed structure is formed by etching to the second N-type layer 31. The first exposed structure exposes the first N-type layer 21 at the bottom, and the second exposed structure exposes the second N-type layer 31 at the bottom.

[0046] Specifically, firstly, inductively coupled plasma etching (ICP) or reactive ion etching (RIE) is used to etch the second tunnel junction layer 34, the second P-type layer 33, and the second multiple quantum well 32 in the surrounding area, exposing the second N-type layer 31. The second tunnel junction layer 34, the second P-type layer 33, and the second multiple quantum well 32 in the central area are retained, forming a first mesa structure. Grooves are formed around the first mesa structure; these grooves constitute the second exposed structure. Figure 2 As shown.

[0047] Next, using inductively coupled plasma etching (ICP) or reactive ion etching (RIE), the outermost second N-type layer 31, first tunnel junction layer 24, first P-type layer 23, and first multiple quantum well layer 22 in the surrounding area are further etched to expose the first N-type layer 21. The second N-type layer 31, first tunnel junction layer 24, first P-type layer 23, and first multiple quantum well layer 22 near the center in the surrounding area are retained, forming the second mesa structure. Grooves are formed around the outer perimeter of the second mesa structure; these grooves constitute the first exposed structure. Figure 3 As shown.

[0048] As a specific example, this embodiment also includes using inductively coupled plasma etching (ICP) or reactive ion etching (RIE) methods to etch the edge region of the exposed first N-type layer 21, exposing the substrate 1, such as... Figure 4 As shown.

[0049] As a specific example, this embodiment also includes P-type activation of the first P-type layer 23, the second P-type layer 33, the first tunnel junction layer 24, and the second tunnel junction layer 34. The conditions for P-type activation are: maintaining at 900°C for 30 minutes in an N2 atmosphere.

[0050] As a specific example, this embodiment also includes wet etching of the upper surfaces of the second tunneling layer 34, the second N-type layer 31, and the first N-type layer 21 to create a roughened morphology on the upper surfaces of the second tunneling layer 34, the second N-type layer 31, and the first N-type layer 21, such as... Figure 5 As shown, the light extraction efficiency of the final dual-wavelength light-emitting device is improved. The selected wet etching solution is a KOH solution at 60℃.

[0051] As a specific example, this embodiment also includes the fabrication of a passivation layer 5. Specifically, the passivation layer 5 is fabricated over the entire surface using plasma-enhanced chemical vapor deposition (PECVD). The material of the passivation layer 5 is silicon dioxide (SiO2), and windows are created on the surfaces of the first N-type layer 21, the second N-type layer 31, and the second tunnel junction layer 34 using standard photolithography. Buffered oxide etchant (BOE) is then used to etch the passivation layer 5 beneath the windows, exposing the upper surfaces of the first N-type layer 21, the second N-type layer 31, and the second tunnel junction layer 34. Figure 6 As shown.

[0052] Step S3: Simultaneously prepare (M+1) N electrodes on the surface of each exposed N-type layer and the tunnel junction layer on the top surface.

[0053] In this embodiment, electron beam evaporation is used to simultaneously fabricate a first N-electrode 7, a second N-electrode 8, and a third N-electrode 9 on the exposed surfaces of the first N-type layer 21, the second N-type layer 31, and the second tunnel junction layer 34. The N-electrode material is Cr / Pt / Au. This completes the fabrication of the dual-wavelength light-emitting device, whose structure is as follows: Figure 7 As shown.

[0054] The structure of the dual-wavelength light-emitting device prepared in this embodiment is as follows: Figure 7As shown, it includes: a substrate 1, a first light-emitting stack 2, a second light-emitting stack 3, a passivation layer 5, a first N-electrode 7, a second N-electrode 8, and a third N-electrode 9. The first light-emitting stack 2 comprises, from bottom to top, a first N-type layer 21, a first multiple quantum well layer 22, a first P-type layer 23, and a first tunnel junction layer 24. The second light-emitting stack 3 comprises, from bottom to top, a second N-type layer 31, a second multiple quantum well layer 32, a second P-type layer 33, and a second tunnel junction layer 34.

[0055] The dual-wavelength light-emitting device has a first exposure structure and a second exposure structure corresponding to the first light-emitting stack and the second light-emitting stack. The first exposure structure extends from the second tunnel junction layer 34 along the thickness direction to the first N-type layer 21, and the first N-type layer 21 is exposed at the bottom of the first exposure structure. The second exposure structure extends from the second tunnel junction layer 34 along the thickness direction to the second N-type layer 31, and the second N-type layer 31 is exposed at the bottom of the second exposure structure.

[0056] The first N electrode 7 is disposed on the surface of the exposed first N-type layer 21 and forms an ohmic contact with the first N-type layer 21; the second N electrode 8 is disposed on the surface of the exposed second N-type layer 31 and forms an ohmic contact with the second N-type layer 31; the third N electrode 9 is disposed on the surface of the second tunnel junction layer 34 and forms an ohmic contact with the second tunnel junction layer 34.

[0057] When the dual-wavelength light-emitting device is operating, if the first N-electrode 7 is connected to the negative terminal of the power supply and the second N-electrode 8 is connected to the positive terminal, the first quantum well layer 22 emits blue light, which is emitted along the surface where the material grows. If the second N-electrode 8 is connected to the negative terminal and the third N-electrode 9 is connected to the positive terminal, the second quantum well layer 32 emits orange light, which is emitted along the surface where the material grows. If the first N-electrode 7 is connected to the negative terminal and the third N-electrode 9 is connected to the positive terminal, the first quantum well layer 22 and the second quantum well layer 32 emit light simultaneously, and the mixture of the two lights emits white light, which is emitted along the surface where the material grows. Example 2

[0058] This embodiment provides a method for fabricating a multi-wavelength light-emitting device, specifically for fabricating a three-wavelength light-emitting device, including the following steps: Step S1: M light-emitting stacks are sequentially deposited on the substrate. Each light-emitting stack includes an N-type layer, a multiple quantum well layer, a P-type layer, and a tunnel junction layer stacked sequentially from bottom to top.

[0059] In this embodiment, a substrate 1 is provided, and a first light-emitting stack 2, a second light-emitting stack 3, and a third light-emitting stack 4 are sequentially deposited on the substrate 1. The first light-emitting stack 2 includes a first N-type layer 21, a first multiple quantum well layer 22, a first P-type layer 23, and a first tunnel junction layer 24, stacked sequentially from bottom to top; the second light-emitting stack 3 includes a second N-type layer 31, a second multiple quantum well layer 32, a second P-type layer 33, and a second tunnel junction layer 34, stacked sequentially from bottom to top; the third light-emitting stack 4 includes a third N-type layer 41, a third multiple quantum well layer 42, a third P-type layer 43, and a third tunnel junction layer 44, stacked sequentially from bottom to top, as shown below. Figure 8 As shown.

[0060] Substrate 1 is a sapphire substrate. In the first light-emitting stack 2, the first N-type layer 21 is N-type GaN; the first multiple quantum well layer 22 is a stack structure composed of alternating InGaN well layers and GaN barrier layers, and the emission wavelength of the first multiple quantum well layer 22 is 460 nm; the first P-type layer 23 is P-type GaN; the first tunnel junction layer 24 is composed of a heavily Mg-doped GaN layer, an InGaN barrier layer, and a heavily Si-doped GaN layer stacked sequentially from bottom to top, with thicknesses of 20 nm, 25 nm, and 20 nm, respectively, and the Mg doping concentration is 3 × 10⁻⁶. 20 cm -3 The Si doping concentration is 3×10⁻⁶. 20 cm -3 In the second light-emitting stack 3, the second N-type layer 31 is N-type GaN; the second multiple quantum well layer 32 is a stack structure composed of alternating InGaN well layers and GaN barrier layers, and the emission wavelength of the second multiple quantum well layer 32 is 520 nm; the second P-type layer 33 is P-type GaN; the second tunnel junction layer 24 is composed of a heavily Mg-doped GaN layer, an InGaN barrier layer, and a heavily Si-doped GaN layer stacked sequentially from bottom to top, with thicknesses of 20 nm, 25 nm, and 20 nm, respectively, and a Mg doping concentration of 3 × 10⁻⁶. 20 cm -3 The Si doping concentration is 3×10⁻⁶. 20 cm -3 In the third light-emitting stack 4, the third N-type layer 41 is N-type GaN; the third multiple quantum well layer 42 is a stack structure composed of alternating InGaN well layers and GaN barrier layers, and the emission wavelength of the third multiple quantum well layer 42 is 620 nm; the third P-type layer 43 is P-type GaN; the third tunnel junction layer 44 is composed of a heavily Mg-doped GaN layer, an InGaN barrier layer, and a heavily Si-doped GaN layer stacked sequentially from bottom to top, with thicknesses of 20 nm, 25 nm, and 20 nm, respectively, and a Mg doping concentration of 3 × 10⁻⁶. 20 cm -3 The Si doping concentration is 3×10⁻⁶. 20 cm -3The heavily Mg-doped GaN layer is located below and is in contact with the third P-type layer 43.

[0061] Step S2: Etch along the thickness direction from the tunnel junction layer on the top surface to the N-type layer of each light-emitting stack to form M exposed structures, with the corresponding N-type layer exposed at the bottom of each exposed structure.

[0062] In this embodiment, along the thickness direction, the second tunnel layer is etched to the first N-type layer 21 to form a first exposed structure, to the second N-type layer 31 to form a second exposed structure, and to the third N-type layer 41 to form a third exposed structure; the bottom of the first exposed structure exposes the first N-type layer 21, the bottom of the second exposed structure exposes the second N-type layer 31, and the bottom of the third exposed structure exposes the third N-type layer 41.

[0063] Specifically, firstly, inductively coupled plasma etching (ICP) or reactive ion etching (RIE) is used to etch the third tunnel junction layer 44, the third P-type layer 43, and the third multiple quantum well layer 42 in the surrounding area, exposing the third N-type layer 41. The third tunnel junction layer 44, the third P-type layer 43, and the third multiple quantum well layer 42 in the central region are retained, forming the first mesa structure. Grooves are formed around the outer perimeter of the first mesa structure; these grooves constitute the third exposed structure. Figure 9 As shown.

[0064] Next, using inductively coupled plasma etching (ICP) or reactive ion etching (RIE), the third N-type layer 41, the second tunnel junction layer 34, the second P-type layer 33, and the second multiple quantum well layer 32 in the outermost part of the surrounding region are etched to expose the second N-type layer 31. The third N-type layer 41, the second tunnel junction layer 34, the second P-type layer 33, and the second multiple quantum well layer 32 near the center of the surrounding region are retained, forming a second mesa structure. Grooves are formed around the outer perimeter of the second mesa structure; these grooves constitute the second exposed structure. Figure 10 As shown.

[0065] Finally, inductively coupled plasma etching (ICP) or reactive ion etching (RIE) is used to continue etching the outermost second N-type layer 31, first tunnel junction layer 24, first P-type layer 23, and first multiple quantum well layer 22 in the surrounding area, exposing the first N-type layer 21. The second N-type layer 31, first tunnel junction layer 24, first P-type layer 23, and first multiple quantum well layer 22 near the center area in the surrounding region are retained, forming a third mesa structure. Grooves are formed around the outer perimeter of the third mesa structure; these grooves constitute the first exposed structure. Figure 11 As shown.

[0066] As a specific example, this embodiment also includes using inductively coupled plasma etching (ICP) or reactive ion etching (RIE) methods to etch the edge region of the exposed first N-type layer 21, exposing the substrate 1, such as... Figure 12 As shown.

[0067] As a specific example, this embodiment also includes P-type activation of the first P-type layer 23, the second P-type layer 33, the third P-type layer 43, the first tunnel junction layer 24, the second tunnel junction layer 34, and the third tunnel junction layer 44. The conditions for P-type activation are: maintaining at 900°C for 30 minutes in an N2 atmosphere.

[0068] As a specific example, this embodiment also includes wet etching of the upper surfaces of the third tunneling layer 44, the third N-type layer 41, the second N-type layer 31, and the first N-type layer 21, to create a roughened morphology on the upper surfaces of these layers. Figure 13 As shown, the light extraction efficiency of the final dual-wavelength light-emitting device is improved. The selected wet etching solution is a KOH solution at 60℃.

[0069] As a specific example, this embodiment also includes the fabrication of a passivation layer 5. Specifically, the passivation layer 5 is fabricated over the entire surface using plasma-enhanced chemical vapor deposition (PECVD). The material of the passivation layer 5 is silicon dioxide (SiO2), and windows are created on the surfaces of the first N-type layer 21, the second N-type layer 31, the third N-type layer 41, and the third tunnel junction layer 44 using standard photolithography. Buffered oxide etchant (BOE) is then used to etch the passivation layer 5 beneath the windows, exposing the upper surfaces of the first N-type layer 21, the second N-type layer 31, the third N-type layer 41, and the third tunnel junction layer 44. Figure 14 As shown.

[0070] Step S3: Simultaneously prepare (M+1) N electrodes on the surface of each exposed N-type layer and the tunnel junction layer on the top surface.

[0071] In this embodiment, electron beam evaporation is used to simultaneously fabricate a first N-electrode 7, a second N-electrode 8, a third N-electrode 9, and a fourth N-electrode 10 on the surfaces of the exposed first N-type layer 21, second N-type layer 31, third N-type layer 41, and second tunnel junction layer 34. The N-electrode material is Cr / Pt / Au. This completes the fabrication of the three-wavelength light-emitting device, whose structure is as follows: Figure 15 As shown.

[0072] As a specific example, this embodiment also includes thinning and polishing the substrate 1, followed by depositing a reflective layer 6 on the surface of the substrate 1 opposite to the first N-type layer 21. The reflective layer 6 has a DBR structure, as shown in the figure. Figure 16As shown. The reflective layer 6 is used to reflect the light emitted by the first quantum well layer 22, the second quantum well layer 32 and the third quantum well layer 42, further improving the external quantum efficiency of the three-wavelength light-emitting device.

[0073] The structure of the three-wavelength light-emitting device prepared in this embodiment is as follows: Figure 16 As shown, it includes: a substrate 1, a first light-emitting stack 2, a second light-emitting stack 3, a passivation layer 5, a reflective layer 6, a first N-electrode 7, a second N-electrode 8, a third N-electrode 9, and a fourth electrode 10. The first light-emitting stack 2 includes, from bottom to top, a first N-type layer 21, a first multiple quantum well layer 22, a first P-type layer 23, and a first tunnel junction layer 24, stacked sequentially. The second light-emitting stack 3 includes, from bottom to top, a second N-type layer 31, a second multiple quantum well layer 32, a second P-type layer 33, and a second tunnel junction layer 34, stacked sequentially. The third light-emitting stack 4 includes, from bottom to top, a third N-type layer 41, a third multiple quantum well layer 42, a third P-type layer 43, and a third tunnel junction layer 44, stacked sequentially.

[0074] The three-wavelength light-emitting device has a first exposed structure, a second exposed structure, and a third exposed structure corresponding to the first light-emitting stack, the second light-emitting stack, and the third light-emitting stack. The first exposed structure extends from the third tunnel junction layer 44 along the thickness direction to the first N-type layer 21, and the first N-type layer 21 is exposed at the bottom of the first exposed structure. The second exposed structure extends from the third tunnel junction layer 44 along the thickness direction to the second N-type layer 31, and the second exposed structure exposes the second N-type layer 31 at the bottom of the second exposed structure. The third exposed structure extends from the third tunnel junction layer 44 along the thickness direction to the third N-type layer 41, and the third exposed structure exposes the third N-type layer 41 at the bottom of the third exposed structure.

[0075] The first N-electrode 7 is disposed on the surface of the exposed first N-type layer 21 and forms an ohmic contact with the first N-type layer 21; the second N-electrode 8 is disposed on the surface of the exposed second N-type layer 31 and forms an ohmic contact with the second N-type layer 31; the third N-electrode 9 is disposed on the surface of the exposed third N-type layer 41 and forms an ohmic contact with the third N-type layer 41; and the fourth N-electrode 10 is disposed on the surface of the third tunnel junction layer 44 and forms an ohmic contact with the third tunnel junction layer 44.

[0076] When the three-wavelength light-emitting device prepared in this embodiment is in operation, if the first N-electrode 7 is connected to the negative terminal of the power supply and the second N-electrode 8 is connected to the positive terminal of the power supply, the first quantum well layer 22 emits blue light, which is emitted along the surface where the material grows. If the second N-electrode 8 is connected to the negative terminal of the power supply and the third N-electrode 9 is connected to the positive terminal of the power supply, the second quantum well layer 32 emits green light, which is emitted along the surface where the material grows. If the third N-electrode 9 is connected to the negative terminal of the power supply and the fourth N-electrode 10 is connected to the positive terminal of the power supply, the third quantum well layer 42 emits red light, which is emitted along the surface where the material grows. If the first N-electrode 7 is connected to the negative terminal of the power supply and the fourth N-electrode 10 is connected to the positive terminal of the power supply, the first quantum well layer 22, the second quantum well layer 32, and the third quantum well layer 42 emit light simultaneously, and white light is emitted after the three types of light are mixed, which is emitted along the surface where the material grows.

[0077] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-wavelength light-emitting device, characterized in that, include: Substrate; M light-emitting layers are sequentially stacked on the substrate; each light-emitting layer includes an N-type layer, a multiple quantum well layer, a P-type layer and a tunnel junction layer stacked sequentially from bottom to top; M exposed structures are disposed on the surface of the multi-wavelength light-emitting device and correspond one-to-one with the M light-emitting stacks; each exposed structure extends along the thickness direction to the N-type layer in the corresponding light-emitting stack, and the bottom of the exposed structure exposes the N-type layer; (M+1) N electrodes are respectively disposed on the N-type layer exposed at the bottom of the exposed structure and form an ohmic contact with the N-type layer, and disposed on the tunnel junction layer on the top surface of the multi-wavelength light-emitting device and form an ohmic contact with the tunnel junction layer; Where M is a positive integer not less than 2; the (M+1) N electrodes are electrically insulated from each other and are configured to control the multiple quantum well layers in the M light-emitting stacks by connecting power supplies of different polarities, so as to achieve single-layer or multi-layer combined light emission.

2. The multi-wavelength light-emitting device according to claim 1, characterized in that: Any two of the (M+1) N electrodes are connected to the positive and negative terminals of the power supply, respectively. The upper N electrode is connected to the positive terminal of the power supply, and the lower N electrode is connected to the negative terminal of the power supply. All multi-quantum well layers located between the N electrode connected to the positive terminal of the power supply and the N electrode connected to the negative terminal of the power supply emit light.

3. The multi-wavelength light-emitting device according to claim 1, characterized in that: The (M+1) N electrodes are formed from the same conductive material through the same process steps.

4. The multi-wavelength light-emitting device according to claim 1, characterized in that: The N electrode is made of any one of Ti, Al, Cr, Pt, and Au, or a composite structure of multiple combinations thereof.

5. The multi-wavelength light-emitting device according to claim 1, characterized in that: The tunnel junction consists of a heavily doped P-type layer, a barrier layer, and a heavily doped N-type layer stacked sequentially from bottom to top.

6. The multi-wavelength light-emitting device according to claim 5, characterized in that: The heavily doped P-type layer is Mg-doped GaN or In. x Ga 1-x The doping concentrations of N and Mg range from 1 × 10⁻⁶. 20 cm -3 -5×10 20 cm -3 The heavily doped N-type layer is Si-doped GaN or In. x Ga 1-x The doping concentration of N and Si ranges from 1×10⁻⁶. 20 cm -3 -5×10 20 cm -3 The material of the barrier layer is GaN or In. x Ga 1-x N; where 0 < x < 0.

4.

7. The multi-wavelength light-emitting device according to claim 1, characterized in that: The M exposed structures are all through holes or grooves formed by etching.

8. The multi-wavelength light-emitting device according to claim 1, characterized in that: Between any two adjacent light-emitting layers, the emission wavelength of the multi-quantum well layer in the lower light-emitting layer is shorter than that in the upper light-emitting layer.

9. A method for fabricating a multi-wavelength light-emitting device, characterized in that, Includes the following steps: S1. M light-emitting stacks are sequentially deposited on the substrate. Each light-emitting stack includes an N-type layer, a multiple quantum well layer, a P-type layer, and a tunnel junction layer stacked sequentially from bottom to top. S2. Along the thickness direction, the tunnel junction layer on the top surface is etched down to the N-type layer of each light-emitting stack to form M exposed structures, and the bottom of each exposed structure exposes the corresponding N-type layer; S3. Simultaneously prepare (M+1) N electrodes on the surface of each exposed N-type layer and the tunnel junction layer on the top surface.

10. The preparation method according to claim 9, characterized in that: The substrate material is sapphire or gallium nitride; after step S3, a reflective layer is also prepared on the surface of the substrate away from the light-emitting stack.

Images