Novel electric pump AlGaN-based deep ultraviolet laser diode and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor devices, in particular to a novel electric pump AlGaN-based deep ultraviolet laser diode and a preparation method thereof. The structure comprises a stacking structure, a passivation layer, an n-type metal electrode layer and a p-type metal electrode layer, a substrate, a template layer, a bottom DBR layer, a step-shaped n-type AlGaN layer, a micro-cavity LED active region layer, a p-type AlGaN layer, a step-shaped p-type AlGaN contact layer, a top DBR layer, a lower waveguide layer, an LD multi-quantum well layer and an upper waveguide layer are stacked on the stacking structure in sequence. The ridge surface width of the p-type AlGaN contact layer is greater than or equal to 100 microns; the passivation layer covers the surface and the side wall of the stacked structure, and electrode layer growth channels are formed in the step surfaces of the n-type AlGaN layer and the p-type AlGaN contact layer respectively; and the n-type metal electrode layer and the p-type metal electrode layer respectively penetrate through the corresponding electrode layer growth channels. The advantages are that the wide ridge design improves the light output power, the performance is excellent, and the etching damage is reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a novel electrically pumped AlGaN-based deep ultraviolet laser diode and its fabrication method. Background Technology

[0002] AlGaN-based deep ultraviolet (DUV) lasers emit wavelengths that extensively cover the deep ultraviolet (200-365nm) band. Their significant advantages in cost, reliability, and portability make them a potential replacement for many traditional gas and solid-state UV lasers, with wide applications in non-line-of-sight communication, sensing, sterilization, and biomedicine. Compared to AlGaN-based LEDs, LDs offer higher power density and better directionality, expanding their application value for large-surface, long-distance sterilization in air. Furthermore, they do not suffer from the limitations of light extraction and efficiency degradation common in LEDs, potentially allowing for smaller size, weight, power consumption, and cost. LDs can operate optically, electrically (electro-injected), or with an electron beam pump. All three methods have been used to demonstrate group III nitride DUV-LDs. Compared to optically pumped or electron beam pumped LDs, electrically injected LDs offer higher optical output power while being robust, reliable, portable, and exhibiting better durability and compactness.

[0003] Due to various limitations, the cavity type of UVC-LD is still limited to simple Fabry-Perot cavity side-emitting lasers. The factors hindering the fabrication and development of UVC-LD can be summarized as follows: (1) Material quality and defect density: There is a large lattice mismatch and thermal mismatch between the high Al content AlGaN film and the sapphire substrate, resulting in a high dislocation defect density (~10) in the epitaxial layer. 9 cm -2(2) Technical challenges in device fabrication: For p-type AlGaN, it is difficult to form good ohmic contacts, resulting in high contact resistance and exacerbating thermal problems. n-type contacts also face challenges under high Al composition. Fabricating high-quality vertical optical cavity mirrors (usually formed by dry etching) is difficult and easily introduces damage and roughness, resulting in high mirror loss. (3) Achieving efficient p-type doping: Mg is a commonly used p-type dopant, but in AlGaN, especially under high Al composition, the Mg acceptor level is very deep, resulting in extremely low ionization rate at room temperature (usually <1%). This causes difficulties in hole injection, high device operating voltage, large series resistance, and severe Joule heating effect. (4) Physical limitations of device structure: In AlGaN materials, the refractive index changes little with the Al composition, which reduces the optical field confinement in the active region and causes severe leakage of the optical field into the highly absorbent p-type surrounding layer, increasing the laser threshold. In addition, carrier injection and confinement also face challenges. Holes are difficult to inject into the active region, and the asymmetry of electron and hole concentrations and mobilities leads to electron leakage into the p-type layer.

[0004] Currently, reports on UVC-LDs all employ a narrow ridge waveguide structure with a width of several micrometers. This is a structural compromise limited by the availability of high-Al content AlGaN materials. Compared to the hundreds of micrometers of ridge width in traditional edge-emitting lasers, the narrow ridge offers the following advantages: (1) it tightly confines the optical field within the active region below the ridge, reducing leakage losses to both sides and improving the lateral light confinement factor; (2) it increases the injection current density; and (3) it reduces the absolute operating current to decrease Joule heating. However, the reduced area of ​​the active region severely limits the device's output power.

[0005] In view of the above technical difficulties and the defects of the existing UVC-LD structure, there is an urgent need to develop a new type of electric pump UVC-LD device. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a novel electrically pumped AlGaN-based deep ultraviolet laser diode and its fabrication method.

[0007] The primary objective of this invention is to provide a novel electrically pumped AlGaN-based deep ultraviolet laser diode, comprising a stacked structure, a passivation layer, an n-type metal electrode layer, and a p-type metal electrode layer; The stacked structure consists of, from bottom to top, a substrate, a template layer, a bottom DBR layer, an n-type AlGaN layer, a microcavity LED active region layer, a p-type AlGaN layer, a p-type AlGaN contact layer, a top DBR layer, a lower waveguide layer, an LD multiple quantum well layer, and an upper waveguide layer. Among them, the n-type AlGaN layer has a stepped structure on the side of the surface away from the substrate; the stepped structure includes a ridge and two independent stepped surfaces, and the ridge supports the active region layer of the microcavity LED; The p-type AlGaN contact layer has a stepped structure on the side of the surface away from the substrate. The stepped structure includes a ridge and two independent stepped surfaces. The ridge supports the top DBR layer and the width of the ridge is not less than 100 μm. The passivation layer covers the surface and sidewalls of the stacked structure, and electrode layer growth channels are respectively opened at the step surface of the n-type AlGaN layer and the step surface of the p-type AlGaN contact layer. The n-type and p-type metal electrode layers penetrate the corresponding electrode layer growth channels and make contact with the step surfaces of the n-type AlGaN layer and the p-type AlGaN contact layer, respectively.

[0008] Preferably, the bottom DBR layer is an AlN layer and an Al layer that have been grown alternately for 20 to 40 cycles. x1 Ga 1-x1 N layers; wherein the thickness of the AlN layer is 28~32nm, Al x1 Ga 1-x1 The thickness of the N layer is 30~34nm, and 1>x1≥0.6; the reflectivity of the bottom DBR layer to the emission wavelength of the active region layer of the microcavity LED is not less than 95%.

[0009] Preferably, the n-type AlGaN layer is an n-type Al x2 Ga 1-x2 N layers, 1>x2≥0.6, thickness 100~1000nm, doping concentration ≥5×10 17 cm -3 ; The active region of the microcavity LED is an AlGaN multi-quantum-well layer, comprising 3-5 periods of Al x Ga 1-x N-well layer and Al y Ga 1-y N-layer barrier; where Al x Ga 1-x The thickness of the N-well layer is 2~4 nm, Al y Ga 1-y The thickness of the N-barrier layer is 4~7nm, and y>x.

[0010] Preferably, the p-type AlGaN layer is a p-type Al x3 Ga 1-x3N-layer, with a thickness of 10~400 nm and a doping concentration ≥1×10⁻⁶. 17 cm -3 ; The p-type AlGaN contact layer is a p-type Al x4 Ga 1-x4 N-contact layer, thickness 10~30nm, doping concentration ≥1×10⁻⁶ 17 cm -3 Among them, x4 <x3。

[0011] Preferably, the top DBR layer comprises Al₂O₃ grown in 20-40 alternating cycles. x6 Ga 1-x6 N layer and Al x5 Ga 1-x5 N layers; where Al x5 Ga 1-x5 The thickness of the N layer is 28~34nm, Al x6 Ga 1-x6 The thickness of the N layer is 28~34nm, and 1≥x6>x5>0.4.

[0012] Preferably, the lower waveguide layer is Al. x7 Ga 1-x7 The N-layer has a thickness of 100~400nm; The LD multiple quantum well layer is an AlGaN multiple quantum well layer, comprising 3 to 50 periods of Al y1 Ga 1-y1 N-well layer and Al y2 Ga 1-y2 N-layer barrier; where Al y1 Ga 1-y1 The thickness of the N-well layer is 2~4 nm, Al y2 Ga 1-y2 The thickness of the N-barrier layer is 4~7nm, where y2>y1>x7; The upper waveguide layer is Al. x8 Ga 1-x8 The N-layer has a thickness of 100~400nm; The lower waveguide layer and the upper waveguide layer confine the charge carriers of the LD multi-quantum well layer.

[0013] Preferably, the passivation layer material is selected from SiO2, Al2O3, and SiN. x At least one of AlN and HfO2, with a thickness of 200~2000 nm; The template layer is made of AlN and has a thickness of 10~100nm.

[0014] Preferably, the substrate is made of a heterogeneous substrate material or a homogeneous substrate material, with a thickness of 1~10μm; the heterogeneous substrate material includes any one of sapphire, silicon carbide, and silicon; the homogeneous substrate material is GaN or AlN. The material of the n-type metal electrode layer is selected from at least one of Pt, Ti, Al, Ni, Au, and V, and the thickness is 200~2000 nm; The material of the p-type metal electrode layer is selected from at least one of Ni, Al, Au, ITO, Ti, Pt, Pd, Mg, and Rh, and the thickness is 200~2000 nm.

[0015] The second objective of this invention is to provide a novel method for fabricating an electrically pumped AlGaN-based deep ultraviolet laser diode, specifically comprising the following steps: S1. On the substrate, the template layer, bottom DBR layer, n-type AlGaN layer, microcavity LED active region layer, p-type AlGaN layer, p-type AlGaN contact layer, top DBR layer, lower waveguide layer, LD multi-quantum well layer and upper waveguide layer are epitaxially grown sequentially. After completion, the substrate is annealed at 900~1000℃. S2. Etch downwards from one side of the upper waveguide layer to the top surface of the n-type AlGaN layer, forming a first stepped structure on the side of the n-type AlGaN layer away from the substrate; S3. Etch downwards from one side of the upper waveguide layer to the top surface of the p-type AlGaN contact layer, forming a second stepped structure on the side of the p-type AlGaN contact layer away from the substrate; S4. After two steps of etching, a passivation layer is completely deposited on the stacked structure mesa and sidewalls. Then, the passivation layer is selectively etched through photolithography and etching processes. The step surface area of ​​the n-type AlGaN layer is etched to expose the surface of the n-type AlGaN layer, forming the growth channel of the first electrode layer. S5. Deposit n-type metal electrode material in the growth channel of the first electrode layer, so that the n-type metal electrode material fills the growth channel of the first electrode layer and forms an ohmic contact with the step surface of the n-type AlGaN layer to obtain the n-type metal electrode layer. S6. Selectively etch the passivation layer using photolithography and etching processes, and etch the step surface region of the p-type AlGaN contact layer to expose the surface of the p-type AlGaN contact layer to form a second electrode layer growth channel. S7. Deposit p-type metal electrode material in the growth channel of the second electrode layer, so that the p-type metal electrode material fills the growth channel of the second electrode layer and forms an ohmic contact with the step surface of the p-type AlGaN contact layer, thereby obtaining the p-type metal electrode layer. S8. The device is cut using a cleaving process to form a cavity surface, and a cavity surface DBR layer is deposited on both cavity surfaces to complete the fabrication.

[0016] Preferably, step S5 further includes annealing the n-type metal electrode layer at a temperature of 750~850℃. Step S7 also includes annealing the p-type metal electrode layer at a temperature of 550~650℃.

[0017] Compared with the prior art, the present invention can achieve the following beneficial effects: (1) The deep ultraviolet LD device of the present invention has a significant improvement in maximum optical output power and optical field coupling efficiency. Traditional deep ultraviolet LD devices use a narrow ridge structure to avoid Joule heating and improve the optical field confinement capability to reduce the threshold current. Figure 3 The active region width of traditional LEDs is only a few micrometers, resulting in a very limited area and thus restricting further increases in single-tube power. However, the active region width of the new deep ultraviolet (DUV) LED is not limited by this; it can reach hundreds of micrometers, achieving a larger active region area. This means that at the same current density, the total injected current can be higher, directly increasing the total output power.

[0018] (2) Traditional methods use wafer bonding and introduce metal electrodes between them to achieve electrical injection. There are two drawbacks: First, the unevenness of the bonding interface and the intermediate metal electrodes will cause light field loss. Second, the light field between the microcavity LED and LD in the bonding scheme needs to pass through a heterogeneous structure of tens of micrometers, resulting in very low optical coupling efficiency. However, the novel deep ultraviolet LD device of this invention is monolithically integrated and grown on the same wafer, which eliminates the light field scattering and absorption loss caused by bonding. Moreover, the distance between the microcavity LED and LD is within hundreds of nanometers, and the coupling efficiency is extremely high.

[0019] (3) Dry etching introduces etching damage of about 2 μm in width at the etching edge, generating a large number of surface states and defects. These defects, acting as non-radiative recombination centers, severely reduce the internal quantum efficiency. Traditional deep ultraviolet LD devices require etching to form narrow ridges several micrometers wide, which further reduces the area of ​​the active region capable of emitting light. However, the fabrication method of the deep ultraviolet LD device of this invention greatly simplifies the process flow and avoids introducing fabrication damage; moreover, the novel LD device of this invention does not require the use of a narrow ridge waveguide structure, reducing etching damage and improving the internal quantum efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic cross-sectional view of a novel electric pump AlGaN-based deep ultraviolet laser diode structure provided according to an embodiment of the present invention.

[0021] Figure 2 This is a UVC light output path diagram of a novel electrically pumped AlGaN-based deep ultraviolet laser diode according to an embodiment of the present invention.

[0022] Figure 3This is a schematic diagram of the device structure of an electrically pumped laser in a traditional deep ultraviolet LD device.

[0023] Figure 4 The diagram shows the influence of device structure parameters on performance of a novel electrically pumped AlGaN-based deep ultraviolet laser diode according to an embodiment of the present invention; (a) shows the influence of the etching mesa width on the effective active area ratio (actual active area / device active area) when considering etching edge damage (2µm); (b) shows the influence of the active area width on the optical output power.

[0024] Figure 5 This is a flowchart of a novel electric pump AlGaN-based deep ultraviolet laser diode fabrication method according to an embodiment of the present invention.

[0025] Figure label: 1. Substrate; 2. Template layer; 3. Bottom DBR layer; 4. n-type AlGaN layer; 5. Microcavity LED active region layer; 6. p-type AlGaN layer; 7. p-type AlGaN contact layer; 8. Top DBR layer; 9. Lower waveguide layer; 10. LD multi-quantum-well layer; 11. Upper waveguide layer; 12. Passivation layer; 13. n-type metal electrode layer; 14. p-type metal electrode layer. Detailed Implementation

[0026] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0028] See Figure 1 The present invention provides a novel electrically pumped AlGaN-based deep ultraviolet laser diode, the structure of which includes a stacked structure, a passivation layer 12, an n-type metal electrode layer 13 and a p-type metal electrode layer 14; The stacked structure includes, from bottom to top, a substrate 1, a template layer 2, a bottom DBR layer 3, a stepped n-type AlGaN layer 4, a microcavity LED active region layer 5, a p-type AlGaN layer 6, a stepped p-type AlGaN contact layer 7, a top DBR layer 8, a lower waveguide layer 9, an LD multiple quantum well layer 10, and an upper waveguide layer 11. Among them, the n-type AlGaN layer 4 has a stepped structure on the side of the substrate 1 away from the substrate 1; the stepped structure includes a ridge surface and two independent stepped surfaces, and the ridge surface carries the microcavity LED active region layer 5 (that is, it is directly stacked with the microcavity LED active region layer 5). The p-type AlGaN contact layer 7 has a stepped structure on the side of the substrate 1 away from the substrate 1. The stepped structure includes a ridge and two independent stepped surfaces. The ridge supports the top DBR layer 8 (i.e., it is directly stacked with the top DBR layer 8). The passivation layer 12 covers the surface of the stacked structure (including the step surface of the n-type AlGaN layer 4, the step surface of the p-type AlGaN contact layer 7, the surface of the upper waveguide layer 11 and the device sidewall), and the passivation layer 12 has electrode layer growth channels for the electrode layer to pass through at the step surface of the n-type AlGaN layer 4 and the step surface of the p-type AlGaN contact layer 7, respectively. The n-type metal electrode layer 13 penetrates the step surface etching channel of the n-type AlGaN layer, contacts the step surface of the n-type AlGaN layer 4 at the bottom, and exceeds the height of the passivation layer 12. The p-type metal electrode layer 14 penetrates the etched channel of the p-type AlGaN contact layer step surface, contacts the step surface of the p-type AlGaN contact layer 7 at the bottom, exceeds the passivation layer 12 in height, and is on the same plane as the n-type metal electrode layer 13 (for easy packaging or docking with other devices, etc.).

[0029] Specifically, the substrate 1 is made of a heterogeneous substrate material or a homogeneous substrate material. The heterogeneous substrate material includes any one of sapphire, silicon carbide, and silicon; the homogeneous substrate material is GaN or AlN; and the thickness of the substrate 1 is 1~10μm. In some embodiments, the substrate is a sapphire substrate with a thickness of 10 μm.

[0030] Specifically, template layer 2 is an AlN template layer with a thickness of 10~100nm; In some embodiments, the thickness of template layer 2 is 50 nm.

[0031] Specifically, the bottom DBR layer 3 is AlN / Al x1 Ga 1-x1 A multilayered structure with alternating Al and N growth, containing 20-40 cycles of AlN and Al. x1 Ga 1-x1 The AlN layer has a low Al composition; the thickness of the AlN layer is 28~32nm, and the Al content is...x1 Ga 1-x1 The thickness of the N layer is 30~34nm, and 1>x1≥0.6; The bottom DBR layer 3 is located between the template layer 2 and the n-type AlGaN layer 4 (n-type Al x2 Ga 1-x2 Between the N layers, a series of alternating narrow bandgap layers and high bandgap layers are used as a high reflectivity (>95%) thin film for the emission wavelength of microcavity LEDs. Typically, 20-40 pairs of unintentionally doped AlN / Al layers are employed. x1 Ga 1-x1 N.

[0032] Specifically, the n-type AlGaN layer 4 is an n-type Al x2 Ga 1-x2 For the N-layer, 1>x2≥0.6, the thickness of the n-type AlGaN layer 4 is 100~1000nm, and the doping concentration is ≥5×10⁻⁶. 17 cm -3 ; In some embodiments, the n-type AlGaN layer 4 is a Si-doped n-type AlGaN layer. The doping concentration of the n-type region mainly depends on the Si doping concentration. A higher Si doping concentration results in a higher electron concentration, thereby improving electron mobility. The electron concentration of the n-type AlGaN layer 4 is ≥5×10⁻⁶. 17 cm -3 The n-type AlGaN layer 4 provides radiative recombination carriers, i.e., electrons, and provides an n-type ohmic contact; n-type Al x2 Ga 1-x2 For N layers, 1 > x² ≥ 0.6, i.e., n-type Al x2 Ga 1-x2 The Al content in the N layer is higher than 0.6.

[0033] Specifically, the active region layer 5 of the microcavity LED is an AlGaN multi-quantum-well layer, which includes 3 to 5 cycles of Al x Ga 1-x N-well layer and Al y Ga 1-y N-layer barrier, where Al x Ga 1-x The thickness of the N-well layer is 2~4 nm, Al y Ga 1-y The thickness of the N-barrier layer is 4~7nm, and y>x; The AlGaN multiple quantum well layer is located between n-type AlGaN layer 4 and p-type AlGaN layer 6 (p-type AlGaN layer 6). x3 Ga 1-x3Between the N layers, that is, between the n-type and p-type carrier injection layers, the AlGaN multiple quantum well layer consists of a series of alternating narrow-bandgap layers and high-bandgap layers, which are respectively called quantum wells and quantum barriers. Generally, 3-5 pairs of unintentionally doped Al y Ga 1-y N / Al x Ga 1-x N, where y > x.

[0034] Specifically, the p-type AlGaN layer 6 is a p-type Al x3 Ga 1-x3 N layer. The thickness of the p-type Al x3 Ga 1-x3 N layer is 10 - 400 nm, and the doping concentration of the p-type Al x3 Ga 1-x3 N layer ≥ 1 × 10 17 cm -3 ; In some embodiments, the p-type AlGaN layer 6 is a Mg-doped p-type Al x3 Ga 1-x3 N layer. The hole concentration of the p-type Al x3 Ga 1-x3 N layer ≥ 1 × 10 17 cm -3 ; The method of gradually changing the composition gradient can be used to increase the hole doping concentration and improve the hole injection; the p-type Al x3 Ga 1-x3 N provides holes for the microcavity LED active region layer 5.

[0035] Specifically, the p-type AlGaN contact layer 7 is a p-type Al x4 Ga 1-x4 N contact layer, where x4 < x3. The thickness of the p-type Al x4 Ga 1-x4 N contact layer is 10 - 30 nm, and the doping concentration of the p-type Al x4 Ga 1-x4 N contact layer ≥ 1 × 10 17 cm -3 ; In some embodiments, the p-type AlGaN contact layer 7 is a Mg-doped p-type Al x4 Ga 1-x4 N contact layer. The hole concentration of the p-type Al x4 Ga 1-x4 N contact layer ≥ 1 × 10 17 cm -3 ; In other embodiments, the p-type AlGaN layer 6 and the p-type AlGaN contact layer 7 can also be combined into one layer, namely a p-type AlGaN layer tens to hundreds of nm thick, which also serves as a hole-providing layer and an ohmic contact layer.

[0036] Specifically, the top DBR layer 8 is Al x5 Ga 1-x5 N / Al x6 Ga 1-x6 Al alternating N-layer structures containing 20-40 Al cycles x6 Ga 1-x6 N high Al composition layer and Al x5 Ga 1-x5 N low Al composition layer, in which Al x5 Ga 1-x5 The thickness of the N layer is 28~34nm, Al x6 Ga 1-x6 The thickness of the N layer is 28~34nm, and 1≥x6>x5>0.4; In some embodiments, the top DBR layer 8 is located between the p-type AlGaN contact layer 7 and the lower waveguide layer 9 (AlGaN). x7 Ga 1-x7 Between N), a series of alternating narrow bandgap and high bandgap layers are used as a high-reflectivity thin film for the emission wavelength of the microcavity LED. However, the reflectivity of the top DBR layer 8 is lower than that of the bottom DBR layer 3 to achieve the output of the microcavity LED light. Generally, 20-40 pairs of unintentionally doped Al are used. x5 Ga 1-x5 N / Al x6 Ga 1-x6 N.

[0037] Specifically, the lower waveguide layer 9 is Al x7 Ga 1-x7 The N-layer has a thickness of 100~400nm; the lower waveguide layer 9 is unintentionally doped Al. x7 Ga 1-x7 The N-layer, which confines the charge carriers of the LD multi-quantum well layer, can also act as an optical waveguide.

[0038] Specifically, the LD multiple quantum well layer 10 is an AlGaN multiple quantum well layer, and the AlGaN multiple quantum well layer consists of 3 to 50 periods of Al y1 Ga 1-y1 N-well layer and Al y2 Ga 1-y2 N layers, y2>y1>x7, where Al y1 Ga 1-y1 The thickness of the N-well layer is 2~4 nm, Al y2 Ga 1-y2The thickness of the N-barrier layer is 4~7nm, where y2>y1>x7; In some embodiments, the LD multiple quantum well layer 10 is located between the lower waveguide layer 9 and the upper waveguide layer 11 (Al). x8 Ga 1-x8 Between the N layers, there is a series of alternating narrow-bandgap layers and high-bandgap layers, called quantum wells and quantum barriers, respectively, using 3 to 50 pairs of unintentionally doped Al. y2 Ga 1-y2 N / Al y1 Ga 1-y1 N, y2>y1>x7.

[0039] Specifically, the upper waveguide layer 11 is Al x8 Ga 1-x8 N layer, Al x8 Ga 1-x8 The thickness of the N layer is 100~400nm; the upper waveguide layer 11 is unintentionally doped Al. x8 Ga 1-x8 The N-layer, which confines the charge carriers of the LD multi-quantum well layer, can also act as an optical waveguide.

[0040] Specifically, the passivation layer 12 is composed of SiO2, Al2O3, and SiN. x At least one of AlN and HfO2, the passivation layer 12 has a thickness of 200~2000 nm; In some embodiments, the passivation layer 12 is made of SiO2 or Al2O3 and is grown by PECVD or atomic layer deposition, with a thickness of 1800 nm.

[0041] Specifically, the material of the n-type metal electrode layer 13 includes at least one of Pt, Ti, Al, Ni, Au, and V, and the thickness is 200~2000 nm; In some embodiments, the material of the n-type metal electrode layer 13 is V / Al / Ti / Au (i.e., V layer, Al layer, Ti layer, Au layer stacked sequentially from bottom to top), and the thicknesses of the V layer, Al layer, Ti layer, and Au layer are 50nm, 1850nm, 50nm, and 50nm, respectively.

[0042] Specifically, the material of the p-type metal electrode layer 14 includes at least one of Ni, Al, Au, ITO, Ti, Pt, Pd, Mg, and Rh, and the thickness is 200~2000 nm. In some embodiments, the material of the p-type metal electrode layer 14 is Ni / Au (i.e., Ni layers and Au layers are stacked sequentially from bottom to top); specifically, it is Ni / Au / Ni / Au (i.e., Ni layers, Au layers, Ni layers, Au layers are stacked sequentially), the thickness of the first Ni layer is 20nm, the thickness of the first Au layer is 80nm, the thickness of the second Ni layer is 1850nm, and the thickness of the second Au layer is 50nm.

[0043] The present invention also provides a method for fabricating the above-mentioned device, which specifically includes the following steps: S1. On substrate 1, a template layer 2, a bottom DBR layer 3, an n-type AlGaN layer 4, a microcavity LED active region layer 5, a p-type AlGaN layer 6, a p-type AlGaN contact layer 7, a top DBR layer 8, a lower waveguide layer 9, an LD multi-quantum well layer 10, and an upper waveguide layer 11 are epitaxially grown sequentially; and then activated by annealing at 900~1000℃. In some embodiments, the annealing temperature is 950°C; S2. Using photolithography and etching techniques, etching is performed from the upper waveguide layer 11 down to the top surface of the n-type AlGaN layer 4, forming the first step-like structure on the side of the n-type AlGaN layer 4 away from the substrate 1. S3. Using photolithography and etching techniques, etching is performed from the upper waveguide layer 11 downwards to the top surface of the p-type AlGaN contact layer 7, forming a second stepped structure on the side of the p-type AlGaN contact layer 7 away from the substrate 1. S4. After two-step etching, a passivation layer 12 is completely deposited on the stacked structure mesa and sidewall surfaces. Selective etching is performed using photolithography and etching techniques to etch the step surface area of ​​the n-type AlGaN layer 4, and the first electrode layer growth channel is formed at the n-type AlGaN layer 4. S5. Deposit n-type metal electrode material in the growth channel of the first electrode layer, so that the n-type metal electrode material fills the growth channel of the first electrode layer and makes reliable contact with the step surface of the n-type AlGaN layer 4, i.e., forming an ohmic contact, and extend the n-type metal electrode material to the surface of the passivation layer 12 outside the growth channel of the first electrode layer to cover a small area; anneal at 750~850℃ to obtain the n-type metal electrode layer 13. S6. Selective etching is performed using photolithography and etching techniques to etch the step surface area of ​​the p-type AlGaN contact layer 7, and the second electrode layer growth channel is formed at the p-type AlGaN contact layer 7. S7. Deposit p-type metal electrode material in the growth channel of the second electrode layer, so that the p-type metal electrode material fills the growth channel of the second electrode layer and makes reliable contact with the step surface of the p-type AlGaN contact layer 7, that is, to form an ohmic contact, and make the p-type metal electrode material completely cover the area of ​​the passivation layer 12 corresponding to the upper waveguide layer 11; anneal at 550~650℃ to obtain the p-type metal electrode layer 14. S8. The device is cut using a cleaving process to form a cavity surface; a cavity surface DBR layer is deposited on both cavity surfaces.

[0044] In a specific embodiment, the annealing temperatures in steps S5 and S7 are 800°C and 600°C, respectively.

[0045] Example 1 See Figures 1-2 This embodiment provides a novel electrically pumped AlGaN-based deep ultraviolet laser diode, the structure of which includes a stacked structure, a passivation layer 12, an n-type metal electrode layer 13 and a p-type metal electrode layer 14; The stacked structure includes, from bottom to top, a substrate 1, a template layer 2, a bottom DBR layer 3, a stepped n-type AlGaN layer 4, a microcavity LED active region layer 5, a p-type AlGaN layer 6, a stepped p-type AlGaN contact layer 7, a top DBR layer 8, a lower waveguide layer 9, an LD multi-quantum well layer 10, and an upper waveguide layer 11.

[0046] Substrate 1 is a sapphire substrate with a thickness of 10 μm; Template layer 2 is an AlN template layer with a thickness of 50nm; The bottom DBR layer 3 is a 30-cycle AlN / Al x1 Ga 1-x1 N, x1=0.7, AlN thickness is 31nm, Al x1 Ga 1-x1 The thickness of N is 28 nm; n-type AlGaN layer 4 is an n-type Al x2 Ga 1-x2 N-layer, x2=0.8, the thickness of n-type AlGaN layer 4 is 300nm (the distance between the ridge surface of n-type AlGaN layer 4 in contact with the multi-quantum-well layer and the side surface of n-type AlGaN layer 4 near the substrate 1 is 300nm, and the distance between the step surface of n-type AlGaN layer 4 in contact with n-type metal electrode layer 13 and the side surface of n-type AlGaN layer 4 near the substrate is 200nm), the doping concentration of n-type AlGaN layer 4 is ≥5×10 17 cm -3 ; The active region layer 5 of the microcavity LED is an AlGaN multi-quantum-well layer, which consists of 5 periods of Al... x Ga1-x N-well layer and Al y Ga 1-y N-layer barrier, where Al x Ga 1-x The thickness of the N-well layer is 3 nm, Al y Ga 1-y The thickness of the N-barrier layer is 5 nm, y = 0.85, x = 0.80; p-type AlGaN layer 6 is p-type Al x3 Ga 1-x3 N layers, x3=0.7, p-type Al x3 Ga 1-x3 The N-layer thickness is 100 nm, p-type Al x3 Ga 1-x3 N-layer doping concentration ≥ 1 × 10 17 cm -3 ; p-type AlGaN contact layer 7 is a p-type Al x4 Ga 1-x4 N-type contact layer, where x4 = 0.3, p-type Al x4 Ga 1-x4 The thickness of the N-type contact layer is 50 nm (the ridge width in contact with the top DBR layer 8 is 50 nm, and the step width is 30 nm), p-type Al x4 Ga 1-x4 N-contact layer doping concentration ≥ 1 × 10⁻⁶ 17 cm -3 ; The ridge width of the p-type AlGaN contact layer 7 on the side away from the substrate 1 is not less than 100 μm; the ridge extends upward, so that the top DBR layer 8, the lower waveguide layer 9, the LD multi-quantum well layer 10 and the upper waveguide layer 11 form a convex ridge waveguide core region of corresponding width; compared with the traditional micron-level (only a few microns) narrow ridge structure, the wide ridge design of the present invention can effectively increase the active area and improve the optical output power; Top DBR layer 8 is 20-cycle Al x5 Ga 1-x5 N / Al x6 Ga 1-x6 N, x5=0.75, x6=1, Al x5 Ga 1-x5 The thickness of N is 31 nm, and Al x6 Ga 1-x6 The thickness of N is 28 nm; Lower waveguide layer 9 is Al x7 Ga 1-x7 N layers, x7=1, Al x7 Ga 1-x7 The thickness of the N layer is 100 nm; LD multi-quantum-well layer 10 is an AlGaN multi-quantum-well layer with 5 periods of Al y1 Ga 1-y1 N-well layer and Al y2 Ga 1-y2 N-layer barrier, y1=0.5, y2=0.65, where Al y1 Ga 1-y1 The thickness of the N-well layer is 2 nm, Al y2 Ga 1-y2 The thickness of the N-barrier layer is 4 nm; Upper waveguide layer 11 is Al x8 Ga 1-x8 N layer, Al x8 Ga 1-x8 The thickness of the N layer is 100 nm; The passivation layer 12 is made of SiO2 and has a thickness of 1800 nm; The material of the n-type metal electrode layer 13 is V / Al / Ti / Au (i.e., V layer, Al layer, Ti layer, Au layer stacked sequentially), and the thicknesses of the V layer, Al layer, Ti layer, and Au layer are 50nm, 1850nm, 50nm, and 50nm, respectively. The material of the p-type metal electrode layer 14 is Ni / Au / Ni / Au (i.e., Ni layer, Au layer, Ni layer, Au layer stacked sequentially). The thickness of the first Ni layer is 20nm, the thickness of the first Au layer is 80nm, the thickness of the second Ni layer is 1850nm, and the thickness of the second Au layer is 50nm.

[0047] The preparation method includes the following steps: S1. Substrate selection and epitaxial growth of stacked structures: Sapphire substrate was selected as substrate 1. On substrate 1, template layer 2, bottom DBR layer 3, n-type AlGaN layer 4, microcavity LED active region layer 5, p-type AlGaN layer 6, p-type AlGaN contact layer 7, top DBR layer 8, lower waveguide layer 9, LD multi-quantum well layer 10, and upper waveguide layer 11 were grown sequentially; annealing and activation were performed at 950℃. S2. Using micro-nano fabrication processes such as photolithography and etching, etching is performed from the upper waveguide layer 11 down to the top surface of the n-type AlGaN layer 4, forming the first step-like structure on the side of the n-type AlGaN layer 4 away from the substrate 1. S3. Using micro-nano fabrication processes such as photolithography and etching, etching is performed from the upper waveguide layer 11 down to the top surface of the p-type AlGaN contact layer 7, forming a second stepped structure on the side of the p-type AlGaN contact layer 7 away from the substrate 1. S4. Passivation layer deposition and etching of electrode layer growth channel: Passivation layer 12 is completely deposited on the stacked structure mesa and sidewall surfaces after two-step etching; selective etching is performed using micro-nano processing techniques such as photolithography and etching, and the etching is aligned with the step surface area of ​​n-type AlGaN layer 4, and the first electrode layer growth channel is formed at n-type AlGaN layer 4. S5. Deposit n-type metal electrode material in the growth channel of the first electrode layer, so that the n-type metal electrode material fills the growth channel of the first electrode layer, and extend the n-type metal electrode material to the surface of the passivation layer 12 outside the growth channel of the first electrode layer to cover a small part of the area; anneal at 800°C to obtain n-type metal electrode layer 13. Control the extended coverage width to ensure reliable contact between the bottom of the n-type metal electrode layer 13 and the step surface of the n-type AlGaN layer 4, and the height of the main body of the n-type metal electrode layer 13 exceeds the surface of the passivation layer 12; S6. Selective etching is performed using micro-nano fabrication processes such as photolithography and etching technology. The etching is aligned with the step surface area of ​​the p-type AlGaN contact layer 7 and etched to the p-type AlGaN contact layer 7 to form a second electrode layer growth channel. S7. Deposit p-type metal electrode material in the growth channel of the second electrode layer, so that the p-type metal electrode material fills the growth channel of the second electrode layer and completely covers the area of ​​the passivation layer 12 corresponding to the waveguide layer 11; anneal at 600°C to obtain p-type metal electrode layer 14. The deposition thickness is controlled to ensure reliable contact between the bottom of the p-type metal electrode layer 14 and the step surface of the p-type AlGaN contact layer 7, and the height of the p-type metal electrode layer 14 exceeds the surface of the passivation layer 12. S8. The device is cut using a cleaving process to form a cavity surface; a cavity surface DBR layer is deposited on both cavity surfaces; the cavity surface DBR layer is a 4-cycle alternating HfO2 / SiO2 layer with a thickness of 33nm for the HfO2 layer and a thickness of 47nm for the SiO2 layer.

[0048] The key technical points and advantages of this invention are: It combines the structures of a microcavity LED and an optically pumped LD to realize an electrically pumped deep ultraviolet LD device; by growing on the same wafer, the fabrication process is simplified, avoiding damage and optical loss introduced by bonding processes and intermediate metal electrodes. Simultaneously, compared to traditional edge-emitting lasers, its structure is simpler, fabrication damage is lower, and the active region area is significantly increased, thereby improving overall performance. Specifically, such as... Figures 1-2As shown, a multilayer structure of a microcavity LED and an optically pumped LD is epitaxially grown sequentially from bottom to top on the same wafer. The basic device structure is achieved through photolithography and etching processes. Cavity surfaces are formed through cleavage, and a high-reflectivity DBR layer with a specific wavelength is deposited on the cavity surface to achieve a high-quality FP cavity. In the device, electrons and holes are injected into the active region layer of the microcavity LED to achieve radiative recombination. Lower wavelength light achieves high-power directional output in the microcavity between the bottom and top DBR layers, and is output to the LD multi-quantum-well layer of the optically pumped LD, realizing UVC light pumping lasing. This invention completes all epitaxial growth on the same wafer, eliminating the need for bonding steps and intermediate metal electrodes. Therefore, there is no light field loss caused by bonding interface unevenness and metal absorption. Simultaneously, the light field between the microcavity LED and the optically pumped LD is confined to the hundreds of nanometers scale, resulting in a significant improvement in optical coupling efficiency compared to the tens of micrometers in bonding schemes. This invention eliminates the need for the complex ridge structure of traditional deep ultraviolet LD devices (such as...). Figure 3 As shown), this not only significantly simplifies the fabrication process and reduces the stringent requirements for process precision, but also reduces etching and heat treatment steps, helping to avoid material lattice damage, thereby improving carrier injection efficiency and photoelectric conversion performance (e.g. Figure 4 (As shown). More importantly, this invention can achieve a larger active area, thereby achieving greater optical output power. These characteristics make this structure particularly suitable for applications with extremely high requirements for device consistency and optical output power, such as optical integration, communications, sensor chips, and biomedicine.

[0049] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0050] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A novel electrically pumped AlGaN-based deep ultraviolet laser diode, characterized in that: It includes a stacked structure, a passivation layer, an n-type metal electrode layer, and a p-type metal electrode layer; The stacked structure consists of, from bottom to top, a substrate, a template layer, a bottom DBR layer, an n-type AlGaN layer, a microcavity LED active region layer, a p-type AlGaN layer, a p-type AlGaN contact layer, a top DBR layer, a lower waveguide layer, an LD multiple quantum well layer, and an upper waveguide layer. Among them, the n-type AlGaN layer has a stepped structure on the side of the surface away from the substrate; the stepped structure includes a ridge and two independent stepped surfaces, and the ridge supports the active region layer of the microcavity LED; The p-type AlGaN contact layer has a stepped structure on the side of the surface away from the substrate. The stepped structure includes a ridge and two independent stepped surfaces. The ridge supports the top DBR layer and the width of the ridge is not less than 100 μm. The passivation layer covers the surface and sidewalls of the stacked structure, and electrode layer growth channels are respectively opened at the step surface of the n-type AlGaN layer and the step surface of the p-type AlGaN contact layer. The n-type and p-type metal electrode layers penetrate the corresponding electrode layer growth channels and make contact with the step surfaces of the n-type AlGaN layer and the p-type AlGaN contact layer, respectively.

2. The novel electrically pumped AlGaN-based deep ultraviolet laser diode according to claim 1, characterized in that: The bottom DBR layer consists of AlN layers and Al layers grown alternately over 20-40 cycles. x1 Ga 1-x1 N layers; wherein the thickness of the AlN layer is 28~32nm, Al x1 Ga 1-x1 The thickness of the N layer is 30~34nm, and 1>x1≥0.6; the reflectivity of the bottom DBR layer to the emission wavelength of the active region layer of the microcavity LED is not less than 95%.

3. The novel electrically pumped AlGaN-based deep ultraviolet laser diode according to claim 1, characterized in that: The n-type AlGaN layer is an n-type Al x2 Ga 1-x2 N layers, 1>x2≥0.6, thickness 100~1000nm, doping concentration ≥5×10 17 cm -3 ; The active region of the microcavity LED is an AlGaN multi-quantum-well layer, comprising 3-5 periods of Al x Ga 1-x N-well layer and Al y Ga 1-y N-layer; Among them, Al x Ga 1-x The thickness of the N-well layer is 2~4 nm, Al y Ga 1-y The thickness of the N-barrier layer is 4~7nm, and y>x.

4. A novel electrically pumped AlGaN-based deep ultraviolet laser diode according to claim 1, characterized in that: The p-type AlGaN layer is a p-type Al x3 Ga 1-x3 N-layer, with a thickness of 10~400 nm and a doping concentration ≥1×10⁻⁶. 17 cm -3 ; The p-type AlGaN contact layer is a p-type Al x4 Ga 1-x4 N-contact layer, thickness 10~30nm, doping concentration ≥1×10⁻⁶ 17 cm -3 Among them, x4 <x3。 5. A novel electrically pumped AlGaN-based deep ultraviolet laser diode according to claim 1, characterized in that: The top DBR layer comprises Al₂O₃ layers that grow in 20-40 alternating cycles. x6 Ga 1-x6 N layer and Al x5 Ga 1-x5 N layers; Among them, Al x5 Ga 1-x5 The thickness of the N layer is 28~34nm, Al x6 Ga 1-x6 The thickness of the N layer is 28~34nm, and 1≥x6>x5>0.

4.

6. A novel electrically pumped AlGaN-based deep ultraviolet laser diode according to claim 1, characterized in that: The lower waveguide layer is Al. x7 Ga 1-x7 N layers, with a thickness of 100~400nm; The LD multiple quantum well layer is an AlGaN multiple quantum well layer, comprising 3 to 50 periods of Al y1 Ga 1-y1 N-well layer and Al y2 Ga 1- y2 N-layer; Among them, Al y1 Ga 1-y1 The thickness of the N-well layer is 2~4 nm, Al y2 Ga 1-y2 The thickness of the N-barrier layer is 4~7nm, where y2>y1>x7; The upper waveguide layer is Al. x8 Ga 1-x8 N layers, with a thickness of 100~400nm; The lower waveguide layer and the upper waveguide layer confine the charge carriers of the LD multi-quantum well layer.

7. A novel electrically pumped AlGaN-based deep ultraviolet laser diode according to claim 1, characterized in that: The passivation layer material is selected from SiO2, Al2O3, and SiN. x At least one of AlN and HfO2, with a thickness of 200~2000 nm; The template layer is made of AlN and has a thickness of 10~100nm.

8. A novel electrically pumped AlGaN-based deep ultraviolet laser diode according to claim 1, characterized in that: The substrate is made of a heterogeneous substrate material or a homogeneous substrate material, with a thickness of 1~10μm; the heterogeneous substrate material includes any one of sapphire, silicon carbide, and silicon; the homogeneous substrate material is GaN or AlN. The material of the n-type metal electrode layer is selected from at least one of Pt, Ti, Al, Ni, Au, and V, and the thickness is 200~2000 nm; The material of the p-type metal electrode layer is selected from at least one of Ni, Al, Au, ITO, Ti, Pt, Pd, Mg, and Rh, and the thickness is 200~2000 nm.

9. A method for fabricating a novel electrically pumped AlGaN-based deep ultraviolet laser diode, used to fabricate the novel electrically pumped AlGaN-based deep ultraviolet laser diode as described in claim 1; characterized in that: Specifically, the steps include the following: S1. On the substrate, the template layer, bottom DBR layer, n-type AlGaN layer, microcavity LED active region layer, p-type AlGaN layer, p-type AlGaN contact layer, top DBR layer, lower waveguide layer, LD multi-quantum well layer and upper waveguide layer are epitaxially grown sequentially. After completion, the substrate is annealed at 900~1000℃. S2. Etch downwards from one side of the upper waveguide layer to the top surface of the n-type AlGaN layer, forming a first stepped structure on the side of the n-type AlGaN layer away from the substrate; S3. Etch downwards from one side of the upper waveguide layer to the top surface of the p-type AlGaN contact layer, forming a second stepped structure on the side of the p-type AlGaN contact layer away from the substrate; S4. After two steps of etching, a passivation layer is completely deposited on the stacked structure mesa and sidewalls. Then, the passivation layer is selectively etched through photolithography and etching processes. The step surface area of ​​the n-type AlGaN layer is etched to expose the surface of the n-type AlGaN layer, forming the growth channel of the first electrode layer. S5. Deposit n-type metal electrode material in the growth channel of the first electrode layer, so that the n-type metal electrode material fills the growth channel of the first electrode layer and forms an ohmic contact with the step surface of the n-type AlGaN layer to obtain the n-type metal electrode layer. S6. Selectively etch the passivation layer using photolithography and etching processes, and etch the step surface region of the p-type AlGaN contact layer to expose the surface of the p-type AlGaN contact layer to form a second electrode layer growth channel. S7. Deposit p-type metal electrode material in the growth channel of the second electrode layer, so that the p-type metal electrode material fills the growth channel of the second electrode layer and forms an ohmic contact with the step surface of the p-type AlGaN contact layer, thereby obtaining the p-type metal electrode layer. S8. The device is cut using a cleaving process to form a cavity surface, and a cavity surface DBR layer is deposited on both cavity surfaces to complete the fabrication.

10. The method for fabricating a novel electrically pumped AlGaN-based deep ultraviolet laser diode according to claim 9, characterized in that: Step S5 further includes annealing the n-type metal electrode layer at a temperature of 750~850℃. Step S7 further includes annealing the p-type metal electrode layer at a temperature of 550~650℃.

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