Lateral structure deep ultraviolet laser promoting carrier injection and preparation method thereof

Abstract

The present application relates to the technical fields of deep ultraviolet semiconductor laser device manufacturing, and particularly relates to a kind of promoting carrier injection's lateral structure deep ultraviolet laser and preparation method thereof.Deep ultraviolet laser includes substrate, template layer, n-type AlGaN contact layer, n-AlN thin layer, n-type AlGaN surrounding layer, lower waveguide layer, multiple quantum well layer, upper waveguide layer, p-type AlGaN surrounding layer, p-type contact layer and p-type metal electrode layer, which are stacked from bottom to top.The side surface of n-type AlGaN contact layer away from template layer is in stepped structure.The stepped structure includes ridge surface and independent step surface, the ridge surface bears n-AlN thin layer, and the step surface separately sets n-type metal electrode layer.The advantages are that two-dimensional electron gas is generated by introducing heterojunction with different Al components in n-type region and p-type region of the device, better electron injection and hole injection are achieved, electron transmission path is reduced, device joule heat is reduced, lasing threshold is greatly reduced, and light emitting power is improved.

Description

Technical Field

[0001] This invention relates to the field of deep ultraviolet semiconductor laser device manufacturing technology, and in particular to a transverse structure deep ultraviolet laser that promotes carrier injection and its fabrication method. Background Technology

[0002] AlGaN-based deep ultraviolet laser diodes (DUV-LDs) have shown great promise in fields such as sterilization, optical communication, medical diagnosis, and industrial processing due to their unique wavelength range (200–350 nm). AlGaN laser diodes with a wavelength of 222 nm have been proven to be highly effective at killing bacteria and viruses. In non-line-of-sight communication, their small size and high efficiency make them ideal communication light sources. However, research on AlGaN-based deep ultraviolet lasers faces many technical challenges. These challenges stem from the high Al content of AlGaN materials, the physical limitations of the device's epitaxial structure, and the requirements for low-damage processes and low on-resistance in lasing conditions. Among these, low hole injection efficiency and low electron injection efficiency severely limit the efficiency of DUV-LDs. When the Al content in AlGaN increases, the activation energy of p-type doped Mg acceptors increases significantly, leading to a decrease in hole concentration and low hole mobility. These two factors combined result in very high lateral resistance of the p-type layer, confining holes to a very narrow region directly below the electrode for longitudinal flow. This uneven current distribution is also known as the "current crowding" effect. Similarly, as the Al content in AlGaN increases, the donor activation energy of n-type doped Si increases. When the content exceeds 80%, the self-compensating acceptor DX states generated in the highly doped n-type layer limit further increases in carrier concentration, leading to increased resistivity of the n-type layer. For deep ultraviolet laser diodes with a lateral structure, i.e., a non-conductive substrate with both n and p electrodes on the upper side of the substrate, the increased resistivity of the n-type layer leads to poorer electron transport and generates a large amount of Joule heating, deteriorating laser characteristics.

[0003] Two-dimensional electron gas (2DEG) and two-dimensional hole gas (2DHG) are systems that can only move freely within a two-dimensional plane, and whose motion in the direction perpendicular to it is quantized. The number of charge carriers per unit area can reach 102. 13 cm -2 The carrier mobility is significantly higher because the carriers are confined to the interface far from the dopant ions, resulting in greatly reduced ionized impurity scattering. In the AlGaN system, heterostructures formed by changing the Al composition generate polarization charges due to spontaneous polarization and piezoelectric polarization, attracting free carriers with opposite charges to form 2DEGs or 2DHGs. This invention introduces heterostructures with different Al compositions on the n-side and p-side, forming 2DEGs and 2DHGs, respectively, promoting carrier transport and lateral expansion, and reducing Joule heating on the n-side by decreasing the electron transport path, thus significantly improving laser performance. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a transverse structure deep ultraviolet laser that promotes carrier injection and its fabrication method.

[0005] The first objective of this invention is to provide a lateral structure deep ultraviolet laser that promotes carrier injection, comprising, from bottom to top, a substrate, a template layer, an n-type AlGaN contact layer, an n-AlN thin layer, an n-type AlGaN surrounding layer, a lower waveguide layer, a multiple quantum well layer, an upper waveguide layer, a p-type AlGaN surrounding layer, a p-type contact layer, and a p-type metal electrode layer.

[0006] Among them, the surface of the n-type AlGaN contact layer away from the template layer has a stepped structure; the stepped structure includes a ridge surface and two independent stepped surfaces, the ridge surface carries the n-AlN thin layer, and the stepped surfaces are separately provided with n-type metal electrode layers.

[0007] Preferably, the multiple quantum well layer is an AlGaN multiple quantum well layer, which includes 1 to 5 cycles of Al x Ga 1-x N quantum well layer and Al y Ga 1-y N quantum barrier layer; where Al x Ga 1-x The thickness of the N quantum well layer is 1~10 nm, Al y Ga 1- y The thickness of the N quantum barrier layer is 1~10nm, where y>x;

[0008] The Al composition of the lower waveguide layer is greater than or equal to Al. y Ga 1-y The Al composition of the N quantum barrier layer; the bandgap width of the lower waveguide layer is higher than that of the multi-quantum-well layer;

[0009] The upper waveguide layer is Al. x4 Ga 1-x4 N layers, where x4≥y; the thickness of the upper waveguide layer is 50~150nm.

[0010] Preferably, the total thickness of the first quantum barrier layer on the side of the multi-quantum well layer closest to the lower waveguide layer and the lower waveguide layer is 50~150nm.

[0011] Preferably, the n-type AlGaN contact layer is an n-type Al x1 Ga 1-x1 N-layer, 1>x1≥0.6; the thickness of the n-type AlGaN contact layer is 500~1500nm;

[0012] The thickness of the n-AlN thin layer is 1~5nm;

[0013] The n-type AlGaN surrounding layer is an n-type Al x2 Ga 1-x2 N-layer, x2≥x1; the thickness of the n-type AlGaN surrounding layer is 30~500nm;

[0014] The lower waveguide layer is Al. x3 Ga 1-x3 N layers, where x2>x3≥0.3; the thickness of the lower waveguide layer is 50~150nm.

[0015] Preferably, the p-type AlGaN surrounding layer is a p-type Al x6~x7 Ga 1-x6~1-x7 N layers, wherein x6>x7; the thickness of the p-type AlGaN surrounding layer is 100~500nm;

[0016] The p-type contact layer is a p-type Al. x8 Ga 1-x8 N layers, where x7 > x8; the thickness of the p-type contact layer is 10~50nm;

[0017] The material of the n-type metal electrode layer includes at least one of Pt, Ti, Al, Ni, Au, and V; the thickness of the n-type metal electrode layer is 100~300 nm.

[0018] The material of the p-type metal electrode layer includes at least one of Ni, Al, Au, ITO, Ti, Pt, Pd, Mg, and Rh; the thickness of the p-type metal electrode layer is 100~300 nm.

[0019] Preferably, it further includes an electron blocking layer, wherein the surface of the electron blocking layer away from the substrate has a stepped structure, the stepped structure including a ridge surface and two independent stepped surfaces;

[0020] The electron blocking layer is located in one of the following two positions:

[0021] (1) It is disposed between the upper waveguide layer and the p-type AlGaN surrounding layer, wherein the electron blocking layer supports the p-type AlGaN surrounding layer on the ridge surface away from the substrate;

[0022] (2) It is disposed between the multi-quantum well layer and the upper waveguide layer, wherein the electron blocking layer supports the upper waveguide layer on the ridge surface away from the substrate.

[0023] Preferably, the electron blocking layer is p-type Al. x5 Ga 1-x5N layers, wherein 1 ≥ x5; the electron blocking layer has a thickness of 10~30 nm and a doping concentration ≥ 1 × 10⁻⁵. 17 cm -3 .

[0024] The second objective of this invention is to provide a method for fabricating a transverse structure deep ultraviolet laser that promotes carrier injection, specifically comprising the following steps:

[0025] S1. Select a suitable substrate and use metal-organic chemical vapor deposition or molecular beam epitaxy to epitaxially grow a template layer on the substrate surface;

[0026] S2. An n-type AlGaN contact layer, an n-AlN thin layer, an n-type AlGaN surrounding layer, a lower waveguide layer, a multi-quantum well layer, an upper waveguide layer, a p-type AlGaN surrounding layer, and a p-type contact layer are sequentially grown on the template layer.

[0027] S3. After growth is complete, the device is placed in an annealing furnace and annealed at a temperature of 900~1000℃ to activate impurities in the p-type contact layer.

[0028] S4. Using photolithography and etching processes, the surface to be etched is etched to form corresponding ridges and step surfaces;

[0029] S5. On the step surface of the p-type contact layer, p-type electrode metal material is deposited by electron beam evaporation or thermal evaporation technology and then annealed to obtain a p-type metal electrode layer.

[0030] S6. Deposit n-type electrode metal material on the step surface of the n-type AlGaN contact layer and anneal it to obtain an n-type metal electrode layer;

[0031] S7. The device is cut using a cleaving process to form the resonant cavity surface of the laser; a distributed Bragg reflector layer is deposited on the resonant cavity surfaces at both ends.

[0032] Preferably, step S2 further includes epitaxial growth of an electron blocking layer, i.e., epitaxial growth of an electron blocking layer on the upper waveguide layer followed by growth of a p-type AlGaN surrounding layer; or epitaxial growth of an electron blocking layer on the multi-quantum well layer followed by growth of the upper waveguide layer.

[0033] Preferably, the annealing temperatures in steps S5 and S6 are 500~600℃ and 750~900℃, respectively.

[0034] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0035] (1) Existing technologies employ lateral structures and coplanar electrodes, resulting in insufficient lateral electron expansion on the n-side and Joule heating due to current passing through the n-type layer. This invention introduces n-Al on the n-side. x1 Ga 1-x1 N / n-AlN / n-Al x2 Ga 1-x2 N structure, and in n-Al x1 Ga 1-x1 A high concentration of 2DEG is introduced at the N / n-AlN heterostructure interface. 2DEG has high electron concentration and high mobility, and excellent lateral transport properties. It can significantly improve the problem that electrons on the n-side of the lateral structure of deep ultraviolet lasers cannot be effectively injected into the active region and reduce Joule heating. In addition, the n-AlN thin layer can increase the 2DEG concentration, hinder defect diffusion, and prevent electron overflow.

[0036] (2) Existing technologies use p-type layers with continuously varying or discontinuously varying compositions, and directly deposit p-type electrodes on the p-type contact layer. This results in poor lateral hole expansion, current crowding, and low injection efficiency. This invention introduces p-Al on the p-side. x6~x7 Ga 1-x6~1-x7 N / p-Al x8 Ga 1-x8 The N-structure employs a component gradient method to increase hole concentration while introducing 2DHG at the heterogeneous interface. The better lateral expansion of 2DHG and the high conductivity of 3DHG enable effective hole injection. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a transverse deep ultraviolet laser structure that promotes carrier injection according to an embodiment of the present invention.

[0038] Figure 2 This is a flowchart of a method for fabricating a transverse deep ultraviolet laser that promotes carrier injection according to an embodiment of the present invention.

[0039] Figure 3 The diagram shows the epitaxial structure, electron distribution, and hole distribution of a lateral structure deep ultraviolet laser that promotes carrier injection according to an embodiment of the present invention; (a) shows the epitaxial structure; (b) shows the electron distribution diagram calculated by LASTIP, with the dashed box indicating 2DEG; (c) shows the hole distribution diagram calculated by LASTIP, with the dashed box indicating that 2DHG promotes the lateral expansion of holes.

[0040] Figure 4The results show a comparison of the characteristics of the transverse structure deep ultraviolet laser with carrier injection promotion provided according to the embodiments of the present invention with those of existing conventional structure devices; (a) IV characteristics; (b) IL characteristics; (c) transverse electron distribution in the active region; (d) light field distribution.

[0041] Figure label:

[0042] 1. Substrate;

[0043] 2. Template layer;

[0044] 3. n-type AlGaN contact layer;

[0045] 4. n-AlN thin layer;

[0046] 5. n-type AlGaN surrounding layer;

[0047] 6. Lower waveguide layer;

[0048] 7. Multiple quantum well layers;

[0049] 8. Upper waveguide layer;

[0050] 9. Electron blocking layer;

[0051] 10. p-type AlGaN surrounding layer;

[0052] 11. p-type contact layer;

[0053] 12. p-type metal electrode layer;

[0054] 13. n-type metal electrode layer. Detailed Implementation

[0055] 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.

[0056] 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.

[0057] See Figure 1 The present invention provides a lateral structure deep ultraviolet laser that promotes carrier injection, comprising: a substrate 1, a template layer 2, an n-type AlGaN contact layer 3, an n-AlN thin layer 4, an n-type AlGaN surrounding layer 5, a lower waveguide layer 6, a multiple quantum well layer 7, an upper waveguide layer 8, an electron blocking layer 9, a p-type AlGaN surrounding layer 10, a p-type contact layer 11, and a p-type metal electrode layer 12, stacked from bottom to top;

[0058] Among them, the n-type AlGaN contact layer 3 has a stepped structure on the side of the template layer 2 away from it; the stepped structure includes a ridge surface and two independent step surfaces, the ridge surface carries the n-AlN thin layer 4 (i.e. directly stacked with the n-AlN thin layer 4), and the step surfaces are provided with an n-type metal electrode layer 13 separately.

[0059] The electron blocking layer 9 has a stepped structure on the side away from the upper waveguide layer 8. The stepped structure includes a ridge and two independent stepped surfaces. The ridge supports the p-type AlGaN surrounding layer 10 (i.e., it is directly stacked with the p-type AlGaN surrounding layer 10).

[0060] The stacking of each layer is completed in a direction perpendicular to the surface of substrate 1 (i.e., the thickness direction of the device), and the adjacent layers are in direct contact with each other.

[0061] It should be noted that the lateral structure deep ultraviolet laser of the present invention promotes carrier injection by forming heterostructures through changes in Al composition on the n-type side and p-type side, respectively, generating 2DEG and 2DHG. By utilizing the lateral expansion characteristics of these two structures, the injection efficiency of carriers into the active region can be improved, thus addressing the problems of low hole injection efficiency, low electron injection efficiency, and high Joule heating in deep ultraviolet LD devices.

[0062] Specifically, the substrate material is either a heterogeneous substrate material or a homogeneous substrate material. The heterogeneous substrate material includes any one of sapphire, silicon carbide, and silicon. The substrate thickness is 1~10μm. In some embodiments, the homogeneous substrate material is GaN or AlN.

[0063] Specifically, the template layer is an AlN template layer with a thickness of 10~1000nm.

[0064] Specifically, the n-type AlGaN contact layer is an n-type Al x1 Ga 1-x1 N-layer, 1>x1≥0.6; thickness of n-type AlGaN contact layer is 500~1500nm; doping concentration of n-type AlGaN contact layer ≥1×10 17 cm -3 The n-type AlGaN contact layer provides radiative recombination carriers, i.e., electrons, and provides an n-type ohmic contact. In some embodiments, the n-type AlGaN contact layer is a Si-doped n-type AlGaN contact layer. The doping concentration of the n-type region mainly depends on the doping concentration of Si. A higher Si doping concentration results in a higher electron concentration, thereby improving electron mobility.

[0065] Specifically, the thickness of the n-AlN thin layer is 1~5 nm, and the doping concentration (electron concentration) is ≥1×10⁻⁶. 17 cm -3In some embodiments, the n-AlN thin layer is a Si-doped n-AlN thin layer. The doping concentration mainly depends on the Si doping concentration. A higher Si doping concentration results in a higher electron concentration, thereby improving electron mobility.

[0066] Specifically, the n-type AlGaN surrounding layer is an n-type Al x2 Ga 1-x2 N-layer, x2≥x1; n-type AlGaN surrounding layer thickness is 30~500nm, doping concentration (electron concentration)≥1×10 17 cm -3 The n-type AlGaN surrounding layer provides radiative recombination carriers, i.e., electrons, and also serves to confine the optical field. In some embodiments, the n-type AlGaN surrounding layer is a Si-doped n-type AlGaN surrounding layer. The doping concentration of the n-type region mainly depends on the doping concentration of Si. A higher Si doping concentration results in a higher electron concentration, thereby improving electron mobility.

[0067] Specifically, the lower waveguide layer is Al. x3 Ga 1-x3 In the N-layer, x2>x3≥0.3, meaning the Al composition of the lower waveguide layer is higher than 0.3 and lower than the Al composition of the n-type AlGaN surrounding layer; the thickness of the lower waveguide layer is 50~150nm; the refractive index of the lower waveguide layer is lower than that of the n-type surrounding layer, and the band gap of the lower waveguide layer is higher than that of the multi-quantum-well layer. In the AlGaN material system, the refractive index and band gap are controlled by adjusting the Al composition. The higher the Al composition, the higher the band gap and the lower the refractive index.

[0068] Specifically, the multiple quantum well layer is an AlGaN multiple quantum well layer, which includes 1 to 5 periods of Al x Ga 1-x N quantum well layer and Al y Ga 1-y N quantum barrier layer; where Al x Ga 1-x The thickness of the N quantum well layer is 1~10 nm, Al y Ga 1- y The thickness of the N quantum barrier layer is 1~10 nm, y>x; the AlGaN multi-quantum-well layer is the active region, located in the lower waveguide layer (Al x3 Ga 1- x3 N) and upper waveguide layer (Al) x4 Ga 1-x4 Between N), the AlGaN multi-quantum-well layer consists of a series of alternating narrow-bandgap layers and high-bandgap layers, referred to as quantum well layers and quantum barrier layers, respectively. Typically, 1-5 pairs of unintentionally doped Al are used. x Ga 1-x N / Aly Ga 1-y N, y>x, y≥x3, that is, the Al component of the quantum barrier is greater than the Al component of the quantum well, and the Al component of the lower waveguide layer is greater than or equal to the Al component of the quantum barrier layer.

[0069] In some embodiments, the first quantum barrier layer on the side of the multi-quantum well layer (active region) close to the lower waveguide layer is merged with the lower waveguide layer into one layer, that is, an unintentionally doped AlGaN layer with a thickness of 50~150nm is used. This layer simultaneously serves as the first quantum barrier layer of the lower waveguide layer and the multi-quantum well layer (as both the lower waveguide layer and the quantum barrier layer).

[0070] Specifically, the upper waveguide layer is Al x4 Ga 1-x4 N layers, where x4≥y, meaning the Al composition of the upper waveguide layer is higher than or equal to the Al composition of the quantum barrier layer; the thickness of the upper waveguide layer is 50~150nm.

[0071] Specifically, the electron blocking layer is p-type Al x5 Ga 1-x5 N layers, where 1 ≥ x5 > y, meaning the Al composition of the electron blocking layer is less than or equal to 1 and greater than the Al composition of the quantum barrier layer; the thickness of the electron blocking layer is 10~30 nm, and the doping concentration (hole concentration) is ≥ 1 × 10⁻⁶. 17 cm -3 The electron blocking layer (EBL) uses p-type Al. x5 Ga 1-x5 The N-layer increases conduction band offset and reduces valence band offset, thereby better blocking electrons and injecting holes;

[0072] In some embodiments, the electron blocking layer and the upper waveguide layer can be interchanged, i.e., the electron blocking layer is located on the side of the multi-quantum well layer away from the substrate, and the upper waveguide layer is located on the side of the electron blocking layer away from the substrate; in other embodiments, no electron blocking layer is included.

[0073] Specifically, the p-type AlGaN surrounding layer is a p-type Al x6~x7 Ga 1-x6~1-x7 N layers, where x5 ≥ x6 > x7, and x6 to x7 decrease linearly in the direction away from the substrate, i.e., p-type Al x6~x7 Ga 1-x6~1-x7 The Al composition of the N-layer near the substrate is lower than or equal to that of the electron blocking layer, and decreases linearly or otherwise away from the substrate; the thickness of the p-type AlGaN surrounding layer is 100~500 nm, and the doping concentration is ≥1×10⁻⁶. 17 cm -3 ;

[0074] In some embodiments, p-type Al x6~x7 Ga1-x6~1-x7 The N-layer is a Mg-doped p-type Al x6~x7 Ga 1-x6~1-x7 N-layer, p-type Al x6~x7 Ga 1-x6~1-x7 N-layer hole concentration ≥ 1 × 10 17 cm -3 The hole doping concentration is increased by using a component gradient method to improve hole injection.

[0075] In other embodiments, the p-type AlGaN surrounding layer does not employ a composition gradient to increase the hole doping concentration; that is, the p-type AlGaN surrounding layer is Mg-doped p-type Al. x6 Ga 1-x6 N-layer, x5≥x6, thickness 100~500nm; or p-type AlGaN surrounding layer using a compositional gradient to increase hole carrier concentration, but without Mg doping, i.e. p-type AlGaN surrounding layer is p-type Al x6~x7 Ga 1-x6~1-x7 In the N-layer, x5≥x6>x7, and x6 to x7 decreases linearly away from the substrate. Hole carriers in the p-type AlGaN surrounding layer are provided by other layers.

[0076] Specifically, the p-type contact layer is p-type Al. x8 Ga 1-x8 N layers, where x7 > x8, meaning the Al composition of the p-type contact layer is lower than that of the p-type AlGaN surrounding layer; the thickness of the p-type contact layer is 10~50 nm, and the doping concentration of the p-type contact layer is ≥1×10⁻⁶. 17 cm -3 In some embodiments, p-type Al x8 Ga 1-x8 The N-layer is a Mg-doped p-type Al x8 Ga 1-x8 N-layer, p-type Al x8 Ga 1-x8 N-layer hole concentration ≥ 1 × 10 17 cm -3 .

[0077] Specifically, the material of the n-type metal electrode layer includes at least one of Pt, Ti, Al, Ni, Au, and V; the thickness of the n-type metal electrode layer is 100~300nm; in some embodiments, the material of the n-type metal electrode layer is Ti / Al / Ti / Au (i.e., Ti layer, Al layer, Ti layer, Au layer stacked sequentially from bottom to top), and the thicknesses of the Ti layer, Al layer, Ti layer, and Au layer are 20nm, 80nm, 50nm, and 50nm, respectively.

[0078] Specifically, the material of the p-type metal electrode layer includes at least one of Ni, Al, Au, ITO, Ti, Pt, Pd, Mg, and Rh (one material or an alloy of two or more materials); the thickness of the p-type metal electrode layer is 100~300nm; in some embodiments, the material of the p-type metal electrode layer is Ni / Au (i.e., Ni layer and Au layer stacked sequentially from bottom to top), and the thicknesses of the Ni layer and Au layer are 20nm and 80nm respectively.

[0079] This invention also provides a method for fabricating the above-mentioned deep ultraviolet laser, the flowchart of which can be found here. Figure 2 Specifically, it includes the following steps:

[0080] S1. Select a suitable substrate and use metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) to epitaxially grow a template layer on the substrate surface;

[0081] S2. Using MOCVD or MBE methods, sequentially epitaxially grow an n-type AlGaN contact layer, an n-AlN thin layer, an n-type AlGaN surrounding layer, a lower waveguide layer, a multi-quantum well layer, an upper waveguide layer, a p-type AlGaN surrounding layer, and a p-type contact layer on the template layer.

[0082] This step also includes the epitaxial growth of an electron blocking layer, that is, the epitaxial growth of an electron blocking layer on the upper waveguide layer followed by the growth of a p-type AlGaN surrounding layer; or the epitaxial growth of an electron blocking layer on the multi-quantum well layer followed by the growth of the upper waveguide layer.

[0083] S3. After growth is complete, the device is placed in an annealing furnace and annealed at a temperature of 900~1000℃ to activate impurities in the p-type contact layer.

[0084] In a specific embodiment, the annealing temperature is 950°C;

[0085] S4. Using micro-nano processing techniques such as photolithography and etching, the surface to be etched is etched to form corresponding ridges and step surfaces;

[0086] S5. On the step surface of the p-type contact layer, p-type electrode metal material is deposited by electron beam evaporation or thermal evaporation technology and then annealed to obtain a p-type metal electrode layer.

[0087] Specifically, annealing is performed at an annealing temperature of 500~600℃;

[0088] S6. Deposit n-type electrode metal material on the step surface of the n-type AlGaN contact layer and anneal it to obtain an n-type metal electrode layer;

[0089] Specifically, annealing is performed at an annealing temperature of 750~900℃;

[0090] S7. The device is cut using a cleaving process to form the resonant cavity surface of the laser; a distributed Bragg reflector (DBR) layer is deposited on the resonant cavity surface at both ends to improve the reflectivity of the cavity surface and enhance the optical feedback capability of the laser.

[0091] Example 1

[0092] This embodiment provides a method for fabricating a transverse deep-ultraviolet laser that promotes carrier injection. The structure of the fabricated laser is described in [reference needed]. Figure 1 Specifically, it includes the following steps:

[0093] S1. Select a substrate 1 suitable for epitaxy of AlGaN-based materials, and the subsequent epitaxial growth direction of each layer is the c-axis direction; use metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) to epitaxially grow a template layer 2 on the surface of substrate 1 to improve the crystal quality of subsequent epitaxial layers; the template layer 2 is made of AlN.

[0094] S2. Using MOCVD or MBE, sequentially epitaxially grow an n-type AlGaN contact layer 3, an n-AlN thin layer 4, an n-type AlGaN surrounding layer 5, a lower waveguide layer 6, a multi-quantum well layer 7, an upper waveguide layer 8, an electron blocking layer 9, a p-type AlGaN surrounding layer 10, and a p-type contact layer 11 on template layer 2.

[0095] n-type AlGaN contact layer 3 is an n-type AlGaN contact layer. x1 Ga 1-x1 For N layers, 1 > x1 ≥ 0.6;

[0096] n-AlN thin layer 4 is a Si-doped n-AlN thin layer;

[0097] The n-type AlGaN surrounding layer 5 is an n-type Al x2 Ga 1-x2 For N layers, x2 ≥ x1;

[0098] Lower waveguide layer 6 is Al x3 Ga 1-x3 N, with a thickness of 50~150nm;

[0099] The multiple quantum well layer 7 consists of Al with 1 to 5 cycles. x Ga 1-x N quantum well layer and Al y Ga 1-y The structure consists of alternating N-quantum barrier layers; in which Al x Ga 1-x The thickness of the N quantum well layer is 1~10 nm, and Al y Ga 1-yThe thickness of the N quantum barrier layer is 1~10nm, and the Al composition satisfies y>x and y≥x3; the multi-quantum well layer 7 is the active region, which is prepared by unintentional doping process;

[0100] Upper waveguide layer 8 is Al x4 Ga 1-x4 N layers, where x4≥y; the thickness of the upper waveguide layer 8 is 50~150nm;

[0101] Electron blocking layer 9 is p-type Al x5 Ga 1-x5 N layers, where 1 ≥ x5 > y;

[0102] The p-type AlGaN surrounding layer 10 is a p-type Al x6~x7 Ga 1-x6~1-x7 N layers, where x5≥x6>x7, and x6 to x7 decrease linearly in the direction away from substrate 1;

[0103] p-type contact layer 11 is p-type Al x8 Ga 1-x8 There are N layers, where x7 > x8.

[0104] S3. After growth is complete, the device is placed in an annealing furnace and annealed at 950°C to activate impurities in the p-type contact layer.

[0105] S4. Using micro-nano processing techniques such as photolithography and etching, the surface to be etched is etched to form corresponding ridges and step surfaces;

[0106] Positive photoresist, negative photoresist, or positive photoresist with reversal properties are selected as photolithography materials. The mesa pattern is completed through photolithography. Then, dry etching or wet etching is used to etch the ridge and step surface structure required for the device.

[0107] S5. On the stepped surface of the p-type contact layer, p-type electrode metal material is deposited by electron beam evaporation or thermal evaporation technology; after the deposition is completed, annealing treatment is performed at an annealing temperature of 500~600℃ to improve the ohmic contact performance between the electrode and the p-type contact layer, thus obtaining a p-type metal electrode layer.

[0108] S6. An n-type electrode metal material is deposited on the step surface of the n-type AlGaN contact layer and annealed at an annealing temperature of 750~900℃ to improve the ohmic contact performance between the electrode and the n-type contact layer, thus preparing an n-type metal electrode layer.

[0109] S7. The device is cut using a cleaving process to form the resonant cavity surface of the laser, ensuring the flatness and perpendicularity of the cavity surface; a distributed Bragg reflector (DBR) layer is deposited on the resonant cavity surface at both ends to improve the reflectivity of the cavity surface and enhance the optical feedback capability of the laser.

[0110] The device performance was measured, and the results are shown in [the table below]. Figures 3-4 .like Figure 3 As shown, this invention utilizes LASTIP simulation software to calculate the electron and hole distributions of the present invention. It can be seen that the present invention, by introducing a heterostructure with varying Al composition on the n-side and introducing 2DEG at the interface, can promote the lateral expansion of electrons; similarly, the present invention, by introducing a heterostructure with varying Al composition on the p-side and introducing 2DHG below the contact layer, can promote the lateral expansion of holes. Figure 4 As shown, it is the IV characteristics of the present invention and conventional devices calculated using LASTIP simulation software. Figure 4 a) IL characteristics ( Figure 4 (b) and active region ( Figure 4 The transverse distribution of electrons and the light field distribution within (c) Figure 4 (d). It can be seen that the present invention effectively promotes carrier injection and significantly improves optical output power.

[0111] 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.

[0112] 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 transverse structure deep ultraviolet laser that promotes carrier injection, characterized in that: It includes, from bottom to top, a substrate, a template layer, an n-type AlGaN contact layer, an n-AlN thin layer, an n-type AlGaN surrounding layer, a lower waveguide layer, a multiple quantum well layer, an upper waveguide layer, a p-type AlGaN surrounding layer, a p-type contact layer, and a p-type metal electrode layer. Among them, the surface of the n-type AlGaN contact layer away from the template layer has a stepped structure; the stepped structure includes a ridge surface and two independent stepped surfaces, the ridge surface carries the n-AlN thin layer, and the stepped surfaces are separately provided with n-type metal electrode layers. The n-type AlGaN contact layer is an n-type Al x1 Ga 1-x1 N-layer, 1>x1≥0.6; the thickness of the n-type AlGaN contact layer is 500~1500nm; The n-AlN thin layer is a Si-doped n-AlN thin layer with a thickness of 1~5nm; The multi-quantum-well layer is an AlGaN multi-quantum-well layer, which includes 1 to 5 periods of Al... x Ga 1-x N quantum well layer and Al y Ga 1-y N quantum barrier layer; Al composition of the lower waveguide layer is greater than or equal to Al y Ga 1-y The Al composition of the N quantum barrier layer; the bandgap width of the lower waveguide layer is higher than that of the multi-quantum-well layer; The upper waveguide layer is Al. x4 Ga 1-x4 N layers, where x4≥y; the thickness of the upper waveguide layer is 50~150nm.

2. A transverse structure deep ultraviolet laser for promoting carrier injection according to claim 1, characterized in that: Al x Ga 1-x The thickness of the N quantum well layer is 1~10 nm, Al y Ga 1-y The thickness of the N quantum barrier layer is 1~10nm, and y>x.

3. A transverse structure deep ultraviolet laser for promoting carrier injection according to claim 2, characterized in that: The total thickness of the first quantum barrier layer on the side of the multi-quantum well layer closest to the lower waveguide layer and the lower waveguide layer is 50~150nm.

4. A transverse structure deep ultraviolet laser for promoting carrier injection according to claim 1, characterized in that: The n-type AlGaN surrounding layer is an n-type Al x2 Ga 1-x2 N-layer, x2≥x1; the thickness of the n-type AlGaN surrounding layer is 30~500nm; The lower waveguide layer is Al. x3 Ga 1-x3 N layers, where x2>x3≥0.3; the thickness of the lower waveguide layer is 50~150nm.

5. A transverse structure deep ultraviolet laser for promoting carrier injection according to claim 1, characterized in that: The p-type AlGaN surrounding layer is a p-type Al x6~x7 Ga 1-x6~1-x7 N layers, wherein x6 > x7; the thickness of the p-type AlGaN surrounding layer is 100~500 nm; The p-type contact layer is a p-type Al. x8 Ga 1-x8 N layers, where x7 > x8; the thickness of the p-type contact layer is 10~50nm; The material of the n-type metal electrode layer includes at least one of Pt, Ti, Al, Ni, Au, and V; the thickness of the n-type metal electrode layer is 100~300 nm. The material of the p-type metal electrode layer includes at least one of Ni, Al, Au, ITO, Ti, Pt, Pd, Mg, and Rh; the thickness of the p-type metal electrode layer is 100~300 nm.

6. A transverse structure deep ultraviolet laser for promoting carrier injection according to claim 1, characterized in that: It also includes an electron blocking layer, wherein the side of the electron blocking layer away from the substrate has a stepped structure, the stepped structure including a ridge and two independent stepped surfaces; The electron blocking layer is located in one of the following two positions: (1) It is disposed between the upper waveguide layer and the p-type AlGaN surrounding layer, wherein the electron blocking layer supports the p-type AlGaN surrounding layer on the ridge surface away from the substrate; (2) It is disposed between the multi-quantum well layer and the upper waveguide layer, wherein the electron blocking layer supports the upper waveguide layer on the ridge surface away from the substrate.

7. A transverse structure deep ultraviolet laser for promoting carrier injection according to claim 6, characterized in that: The electron blocking layer is a p-type Al. x5 Ga 1-x5 N layers, wherein 1 ≥ x5; the electron blocking layer has a thickness of 10~30 nm and a doping concentration ≥ 1 × 10⁻⁵. 17 cm -3 .

8. A method for fabricating a transverse structure deep ultraviolet laser with enhanced carrier injection, used to fabricate the transverse structure deep ultraviolet laser with enhanced carrier injection as described in claim 1, characterized in that: Specifically, the steps include the following: S1. Select a suitable substrate and use metal-organic chemical vapor deposition or molecular beam epitaxy to epitaxially grow a template layer on the substrate surface; S2. An n-type AlGaN contact layer, an n-AlN thin layer, an n-type AlGaN surrounding layer, a lower waveguide layer, a multi-quantum well layer, an upper waveguide layer, a p-type AlGaN surrounding layer, and a p-type contact layer are sequentially grown on the template layer. S3. After growth is complete, the device is placed in an annealing furnace and annealed at a temperature of 900~1000℃ to activate impurities in the p-type contact layer. S4. Using photolithography and etching processes, the surface to be etched is etched to form corresponding ridges and step surfaces; S5. On the step surface of the p-type contact layer, p-type electrode metal material is deposited by electron beam evaporation or thermal evaporation technology and then annealed to obtain a p-type metal electrode layer. S6. Deposit n-type electrode metal material on the step surface of the n-type AlGaN contact layer and anneal it to obtain an n-type metal electrode layer; S7. The device is cut using a cleaving process to form the resonant cavity surface of the laser; a distributed Bragg reflector layer is deposited on the resonant cavity surfaces at both ends.

9. The method for fabricating a transverse deep ultraviolet laser with enhanced carrier injection according to claim 8, characterized in that: Step S2 further includes epitaxial growth of an electron blocking layer, i.e., epitaxial growth of an electron blocking layer on the upper waveguide layer followed by growth of a p-type AlGaN surrounding layer; or epitaxial growth of an electron blocking layer on a multi-quantum-well layer followed by growth of the upper waveguide layer.

10. The method for fabricating a transverse deep ultraviolet laser with enhanced carrier injection according to claim 8, characterized in that: The annealing temperatures in steps S5 and S6 are 500~600℃ and 750~900℃, respectively.

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