Vertical cavity surface emitting laser and preparation method thereof

Abstract

The invention provides a vertical cavity surface emitting laser and a preparation method thereof, and relates to the technical field of semiconductor optoelectronic devices. A vertical cavity surface emitting laser comprises: a surface blazed grating for separating a diffraction main maximum zero order from an interference main maximum zero order to achieve single beam emission; and the surface embossment structure is arranged on the surface, far away from the single-beam emergent surface, of the surface blazed grating and is used for inhibiting high-order mode loss so as to realize single-mode emergent.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor optoelectronic device technology, and more specifically, to a vertical-cavity surface-emitting laser and its fabrication method. Background Technology

[0002] Vertical-cavity surface-emitting lasers (VCSELs) have many advantages over edge-emitting lasers, such as lower cost, better beam quality, easier integration, and lower threshold current. However, the output power of a single device is usually lower, which limits its application in medium- and long-distance optical communication and optical sensing.

[0003] Existing methods for achieving high-power beam output in VCSELs typically involve increasing the oxide aperture of the device to enhance the thermal reversal current, enabling the device to operate at higher currents and thus output greater power. However, increasing the oxide aperture can lead to current pooling, resulting in low electron injection efficiency, which in turn reduces the device's slope efficiency and electro-optic conversion efficiency. Furthermore, a large oxide aperture can cause difficulties in transverse mode control, leading to multiple transverse modes and a decrease in beam quality. Summary of the Invention

[0004] In view of this, the present disclosure provides a vertical cavity surface-emitting laser and a method for fabricating the same.

[0005] This disclosure provides a vertical cavity surface-emitting laser, comprising: a surface blazed grating for separating the diffraction principal maxima zero order from the interference principal maxima zero order to achieve single-beam emission; and a surface relief structure disposed on the surface of the surface blazed grating away from single-beam emission to suppress higher-order mode loss to achieve single-mode emission.

[0006] According to embodiments of this disclosure, a vertical-cavity surface-emitting laser further includes a p-type Bragg reflector layer, a composite layer, an n-type Bragg reflector layer, a buffer layer, and a substrate sequentially stacked on the surface of a surface relief structure away from the surface blazed grating; wherein the surface blazed grating, the surface relief structure, the p-type Bragg reflector layer, and the composite layer form a mesa structure; the composite layer includes N multi-quantum-well active layers, N oxide layers, and N-1 tunnel junction layers; the k-th multi-quantum-well active layer, the k-th oxide layer, and the k-th tunnel junction layer are sequentially stacked and separated by a spacer layer, where 1≤k≤N.

[0007] According to embodiments of this disclosure, N multi-quantum-well active layers are located at the antinodes of the standing wave field of the vertical-cavity surface-emitting laser; N oxide layers and N-1 tunnel junction layers are all located at the nodes of the standing wave field of the vertical-cavity surface-emitting laser.

[0008] According to embodiments of this disclosure, each of the N oxide layers has an oxide pore, the width of which is greater than 4 μm.

[0009] According to embodiments of this disclosure, the materials of the N oxide layers include Al. x Ga 1-x As; both the n-type Bragg reflector and the p-type Bragg reflector are alternately arranged Al x Ga 1-x As layer and Al y Ga 1-y As layer; where x is less than 0.4, y is greater than 0.6, Al x Ga 1-x As layer and Al y Ga 1-y The thickness of the As layer is λ / 4n, where λ is the wavelength of the single-mode emission and n is the refractive index.

[0010] According to embodiments of this disclosure, the blazed grating is a stepped blazed grating with a step number of steps greater than or equal to 2, and the period of the stepped blazed grating satisfies the Bragg equation.

[0011] According to embodiments of this disclosure, the width of the surface relief structure is ≤4μm, and the height is an odd multiple of λ / 4n, where λ is the wavelength of the single-mode emission and n is the refractive index.

[0012] According to embodiments of this disclosure, a vertical-cavity surface-emitting laser further includes: a phase-matching layer disposed on a p-type Bragg reflector layer, wherein the phase-matching layer and the surface relief structure are on the same surface; a primary p-electrode disposed on the surface of the phase-matching layer; a passivation layer disposed on an n-type Bragg reflector layer in a region away from the buffer layer surface that does not contain a composite layer, and covering both sides of the composite layer, the p-type Bragg reflector layer, and the phase-matching layer, and covering a region on the phase-matching layer surface that does not contain a primary p-electrode and partially covering the surface of the primary p-electrode away from the phase-matching layer; a secondary p-electrode disposed on the passivation layer; and an N-electrode disposed on a surface of the substrate away from the buffer layer.

[0013] Another aspect of this disclosure provides a method for fabricating a vertical-cavity surface-emitting laser, comprising: fabricating a surface blazed grating and a surface relief structure, wherein the surface blazed grating is used to separate the diffraction principal maxima zero order from the interference principal maxima zero order to achieve single-beam emission; the surface relief structure is disposed on the surface of the surface blazed grating away from the single-beam emission surface to suppress higher-order mode loss to achieve single-mode emission.

[0014] According to embodiments of this disclosure, a method for fabricating a vertical-cavity surface-emitting laser includes: epitaxially growing a buffer layer, an n-type Bragg reflector layer, a composite layer, a p-type Bragg reflector layer, and a phase-matching layer sequentially on a substrate; wherein the composite layer includes N multi-quantum-well active layers, N oxide layers, and N-1 tunnel junction layers; the k-th multi-quantum-well active layer, the k-th oxide layer, and the k-th tunnel junction layer are sequentially stacked and separated by a spacer layer, 1≤k≤N; etching a surface structure on the phase-matching layer; etching the surface structure to obtain a surface blazed grating and a surface relief structure; growing a primary p-electrode on the phase-matching layer; growing a passivation material and etching a mesa structure on the area of ​​the phase-matching layer without a primary p-electrode and on the primary p-electrode; forming oxide apertures on the N oxide layers; growing a passivation layer on the mesa structure and etching a secondary p-electrode window to expose the underlying primary p-electrode; growing a secondary p-electrode on the passivation layer; and fabricating an N-electrode on the surface of the substrate away from the buffer layer and annealing it to form an ohmic contact.

[0015] According to embodiments of this disclosure, by setting a surface blazed grating, the diffraction principal maxima zero order and the interference principal maxima zero order are separated, so that the light beam of the diffraction order that simultaneously satisfies Snell's law and the diffraction law can achieve concentrated optical power, while the light of other diffraction orders is in a missing order position and the light intensity is greatly suppressed. Therefore, the energy of the diffracted light can be concentrated on a certain diffraction order to achieve single beam emission.

[0016] According to embodiments of this disclosure, by setting a surface relief structure, the loss of higher-order modes is increased, the side-mode suppression ratio is improved, and high-power quasi-single-mode output is achieved. Attached Figure Description

[0017] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0018] Figure 1 The output beam of a Bragg grating according to one embodiment is schematically shown;

[0019] Figure 2 The schematic diagram illustrates the beam propagation path of a vertical cavity surface-emitting laser according to an embodiment of the present disclosure;

[0020] Figure 3 A schematic diagram of the grating groove surface and plane of a blazed grating according to an embodiment of the present disclosure is shown.

[0021] Figure 4 The blazed grating diffraction pattern according to an embodiment of the present disclosure is illustrated schematically;

[0022] Figure 5 The light beam propagation path of a blazed grating according to an embodiment of the present disclosure is schematically shown;

[0023] Figure 6 A schematic diagram of the structure of a vertical cavity surface-emitting laser according to an embodiment of the present disclosure is shown.

[0024] Figure 7 A perspective view of a vertical-cavity surface-emitting laser according to an embodiment of the present disclosure is shown schematically.

[0025] Figure 8 A schematic diagram illustrating the correspondence between a standing wave field and a vertical cavity surface-emitting laser structure according to an embodiment of the present disclosure is shown.

[0026] Figure 9 A schematic diagram of a stepped blazed grating according to an embodiment of the present disclosure is shown;

[0027] Figure 10 A schematic diagram illustrating the relationship between voltage, power, and electro-optical conversion efficiency and current according to embodiments of the present disclosure is shown.

[0028] Figure 11 A far-field view of an etched blazed grating according to an embodiment of the present disclosure is schematically shown;

[0029] Figure 12 The far-field plot of an etched Bragg grating of one embodiment is illustrated schematically.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1. N-electrode; 2. Substrate; 3. Buffer layer; 4. n-type Bragg reflector layer; 5. Passivation layer; 6. Secondary p-electrode; 7. Multiple quantum well active layer; 8. Oxide layer; 9. Tunnel junction layer; 10. Spacer layer; 11. p-type Bragg reflector layer; 12. Phase matching layer; 13. Primary p-electrode; 14. Surface relief structure; 15. Surface blazed grating. Detailed Implementation

[0032] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known systems and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0034] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0035] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0036] Vertical cavity surface-emitting lasers (VCSELs) come in circular and rectangular forms. Compared to conventional circular VCSELs, rectangular VCSELs have advantages such as large aperture, low thermal resistance, and good polarization selectivity. Furthermore, since their oxide aperture is rectangular, increasing the device length does not lead to uneven current injection while maintaining a narrow oxide aperture width. Also, the optical power of a rectangular VCSEL is proportional to the rectangular area, and high-power light emission can be easily achieved by increasing the rectangular length.

[0037] However, increasing the device length leads to an increase in the number of modes, which reduces beam quality.

[0038] Currently, single-mode high-power laser emission is achieved by etching Bragg gratings on the surface of rectangular VCSELs. Although surface Bragg gratings can restrict the transverse modes of VCSELs along the long side of the device, in existing technologies, the short side of the rectangle is still restricted to achieve single-mode emission by limiting the width of the oxide aperture to less than 4 micrometers. The small oxide aperture width leads to an increase in the differential resistance of the device, making it difficult to achieve high slope efficiency and high electro-optic conversion efficiency. At the same time, the small oxide aperture is prone to causing large thermal resistance, which makes the device reach thermal reversal conditions at a small injection current, which is not conducive to achieving high-power light emission.

[0039] In addition, although surface-etched Bragg gratings can reduce the number of transverse modes, the forward and backward propagation directions are opposite. After the light is diffracted by the Bragg grating, it forms two or more beams of light that are symmetrical about the normal. This will lead to the dispersion of light power and reduce the brightness of the far-field beam, which is not conducive to its application in optical sensing and detection fields such as lidar.

[0040] Figure 1 The diagram schematically illustrates the output beam of a Bragg grating according to one embodiment.

[0041] Depend on Figure 1It is known that for a conventional Bragg grating, its structure is symmetrical. When forward and backward waves strike the laser surface, the diffracted light is also symmetrical about the normal, meaning that the refraction angles calculated according to Snell's law are equal. For grating diffraction, the diffraction order that simultaneously satisfies both Snell's law and the grating equations can achieve maximum light enhancement.

[0042] For a transmission grating, the grating equation is:

[0043]

[0044] Snell's Law states:

[0045]

[0046] Where d is the grating constant, m is the diffraction order, and λ is the beam wavelength.

[0047] For a conventional Bragg grating, the incident angles of the forward and backward waves are equal. Therefore, if the forward wave satisfies the interference enhancement condition, the backward wave must also satisfy it. As a result, the outgoing beam consists of two beams whose outgoing directions are symmetrical about the normal, which leads to optical power dispersion and reduces the brightness of the far-field spot.

[0048] Figure 2 The diagram schematically illustrates the beam propagation path of a vertical cavity surface-emitting laser according to an embodiment of the present disclosure.

[0049] like Figure 2 As shown, this is a rectangular VCSEL structure with a surface-etched grating, consisting of... Figure 3 It can be seen that there is both lateral and longitudinal propagation of light. The superposition of these two mutually perpendicular directions of propagation is equivalent to light propagating along a zigzag path in the device, where θ i Let θ be the angle of incidence. r For the angle of refraction, Let be the propagation constant of light. for The horizontal component, n air n is the refractive index of air. wg The waveguide refractive index is the weighted average of the refractive indices of each layer of the device with respect to the thickness of each layer. During the transverse propagation of light, there are both forward and backward waves, and the angles of incidence of the forward and backward waves when they strike the grating surface are symmetrical about the normal.

[0050] Figure 3 A schematic diagram of the grating groove surface and plane of a blazed grating according to an embodiment of the present disclosure is shown.

[0051] Figure 4 The diagram schematically illustrates a blazed grating diffraction pattern according to an embodiment of the present disclosure.

[0052] Figure 5The diagram schematically illustrates the beam propagation path of a blazed grating according to an embodiment of the present disclosure.

[0053] Figure 6 A schematic diagram of a vertical cavity surface-emitting laser according to an embodiment of the present disclosure is shown.

[0054] Figure 7 A perspective view of a vertical cavity surface-emitting laser according to an embodiment of the present disclosure is shown schematically.

[0055] like Figure 6 and Figure 7 As shown, this disclosure provides a vertical cavity surface-emitting laser, including: a surface blazed grating 15 for separating the diffraction principal maxima zero order from the interference principal maxima zero order to achieve single beam emission; and a surface relief structure 14 disposed on the surface of the surface blazed grating away from the single beam emission surface to suppress higher-order mode loss to achieve single-mode emission.

[0056] In embodiments of this disclosure, by Figure 3 It is known that the groove surface of a blazed grating is not parallel to the plane, but has a certain tilt angle, which facilitates the concentration of light energy of a specific wavelength onto a certain diffraction order. Figure 4 As can be seen, the first curve represents the zero-order distribution of single-slit diffraction, the second curve represents the distribution of inter-slit interference, and the third curve shows that as inter-slit interference intensifies, the zero-order positions of single-slit diffraction and inter-slit interference gradually approach each other, but do not completely coincide. This is because the tilt of the groove surface of the blazed grating causes a change in the direction of light propagation, resulting in a certain deviation between the zero-order distribution of inter-slit interference and the zero-order distribution of single-slit diffraction.

[0057] Therefore, although the incident angles of the forward and backward waves in a VCSEL are symmetrical about the normal to the grating plane, the incident angles of the two waves are not equal when they are refracted by the grating groove surface.

[0058] like Figure 5 As shown, for a blazed grating, the grating equation and Snell's law can be expressed as follows:

[0059] ,

[0060] ,

[0061] Where a is the groove width, d is the grating groove pitch, φ is the blaze angle, and n R Let θ be the refractive index. i Let θ be the angle of incidence. d It is the angle of refraction.

[0062] For a blazed grating with a defined blaze angle and grating period, the forward and backward waves cannot simultaneously satisfy both equations. Therefore, light that does not meet the conditions cannot be enhanced by interference, and the mode light is weakened. This achieves single-beam emission, improves the beam emission quality, and can be applied to lidar to enhance its detection range and accuracy.

[0063] Simultaneously, by creating a surface relief structure along the short side of the VCSEL and etching it, the loss of higher-order modes is increased, the edge mode suppression ratio is improved, and quasi-single-mode output is achieved. This solves the problem in existing technologies where the oxide aperture width needs to be limited to less than 4 micrometers to achieve single-mode operation. However, small oxide apertures severely affect heat dissipation, which is even more pronounced for multi-junction VCSELs, which are more prone to heat accumulation. Furthermore, the large differential resistance caused by small oxide apertures increases the difficulty of device driving and significantly reduces device efficiency. Moreover, for multi-junction VCSELs, to achieve lower differential resistance and thermal resistance, and higher slope efficiency and electro-optic conversion efficiency, the oxide aperture typically needs to be greater than 6 micrometers, making it difficult to achieve single-mode operation along the short side of the device.

[0064] According to embodiments of this disclosure, a vertical-cavity surface-emitting laser further includes a p-type Bragg reflector layer 11, a composite layer, an n-type Bragg reflector layer 4, a buffer layer 3, and a substrate 2, which are sequentially stacked on the surface of a surface relief structure away from the surface blazed grating; wherein the surface blazed grating, the surface relief structure, the p-type Bragg reflector layer, and the composite layer form a mesa structure; the composite layer includes N multi-quantum-well active layers 7, N oxide layers 8, and N-1 tunnel junction layers 9; the k-th multi-quantum-well active layer, the k-th oxide layer, and the k-th tunnel junction layer are sequentially stacked and separated by a spacer layer 10, where 1 ≤ k ≤ N.

[0065] According to embodiments of this disclosure, the p-type Bragg reflector layer 11, the composite layer, and the n-type Bragg reflector layer 4 are separated by a spacer layer.

[0066] In the embodiments of this disclosure, the N value of the composite layer can be designed according to actual needs.

[0067] Figure 8 A schematic diagram showing the correspondence between a standing wave field and a vertical cavity surface-emitting laser structure according to an embodiment of the present disclosure is provided.

[0068] like Figure 8 As shown, according to an embodiment of this disclosure, N multi-quantum-well active layers are located at the antinodes of the standing wave field of the vertical-cavity surface-emitting laser; N oxide layers and N-1 tunnel junction layers are all located at the nodes of the standing wave field of the vertical-cavity surface-emitting laser.

[0069] According to embodiments of this disclosure, all N-1 tunnel junctions are heavily doped tunnel junctions.

[0070] In the embodiments of this disclosure, by adjusting the thickness of the spacer layer disposed between the tunnel junction layer, the oxide layer and the multi-quantum well active layer, the multi-quantum well active layer is located at the antinode of the standing wave field to improve the optical gain of the active region; the tunnel junction layer is located at the node of the standing wave field to reduce the free carrier absorption loss caused by the heavily doped tunnel junction; and the oxide layer is located at the node of the standing wave field to reduce the current crowding effect at the edge of the oxide layer.

[0071] According to embodiments of this disclosure, each of the N oxide layers has an oxide pore, the width of which is greater than 4 μm.

[0072] According to embodiments of this disclosure, the oxide pores are rectangular with a width greater than 4 μm, and are not limited by the width of the oxide pores, enabling single-mode emission and exhibiting a high side-mode suppression ratio.

[0073] According to embodiments of this disclosure, the materials of the N oxide layers include Al. x Ga 1-x As, wherein the Al component is higher than 95%; both the n-type Bragg reflector and the p-type Bragg reflector are alternating Al layers. x Ga 1-x As layer and Al y Ga 1-y As layer; where x is less than 0.4, y is greater than 0.6, Al x Ga 1-x As layer and Al y Ga 1-y The thickness of the As layer is λ / 4n, where λ is the wavelength of the single-mode emission and n is the refractive index.

[0074] Figure 9 A schematic diagram of a stepped blazed grating according to an embodiment of the present disclosure is shown.

[0075] like Figure 9 As shown, according to an embodiment of the present disclosure, the blazed grating is a stepped blazed grating, the number of steps of the stepped blazed grating is greater than or equal to 2, and the period of the stepped blazed grating satisfies the Bragg equation.

[0076] In the embodiments of this disclosure, each step of the stepped blazed grating is planar and can be fabricated using standard photolithography and etching processes. A stepped blazed grating with an asymmetric structure can be fabricated with at least two photolithography and etching processes. Simultaneously, because light propagates in a zigzag path within the Bragg reflector layer, it forms a slow wave along the long side of the rectangular VCSEL, resulting in an effective refractive index of less than 1 in this direction. According to the Bragg condition, a small effective refractive index corresponds to a larger grating period. This allows for a larger width of the grating teeth etched on the Bragg reflector layer, significantly reducing the complexity of the process. Electron beam lithography or even ordinary photolithography can be used to fabricate it, solving the problem of incompatibility between the triangular periodic structure of conventional blazed gratings and the planar fabrication process of VCSELs.

[0077] According to embodiments of the present disclosure, a stepped blazed grating is etched across the entire light-emitting surface, and the stepped blazed grating profile has an asymmetry.

[0078] According to embodiments of this disclosure, the stepped blazed grating is fabricated using multiple photolithography or electron beam lithography and etching processes, with a total etching depth between 50 nm and 1 μm.

[0079] According to embodiments of this disclosure, the width of the surface relief structure is ≤4μm, and the height is an odd multiple of λ / 4n, where λ is the wavelength of the single-mode emission and n is the refractive index.

[0080] According to an embodiment of this disclosure, the surface relief structure is rectangular.

[0081] According to embodiments of this disclosure, a vertical-cavity surface-emitting laser further includes: a phase-matching layer disposed on a p-type Bragg reflector layer, wherein the phase-matching layer and the surface relief structure are on the same surface; a primary p-electrode disposed on the surface of the phase-matching layer; a passivation layer disposed on an n-type Bragg reflector layer in a region away from the buffer layer surface that does not contain a composite layer, and covering both sides of the composite layer, the p-type Bragg reflector layer, and the phase-matching layer, and covering a region on the phase-matching layer surface that does not contain a primary p-electrode and partially covering the surface of the primary p-electrode away from the phase-matching layer; a secondary p-electrode disposed on the passivation layer; and an N-electrode disposed on a surface of the substrate away from the buffer layer.

[0082] Another aspect of this disclosure provides a method for fabricating a vertical-cavity surface-emitting laser, comprising: fabricating a surface blazed grating and a surface relief structure, wherein the surface blazed grating is used to separate the diffraction principal maxima zero order from the interference principal maxima zero order to achieve single-beam emission; the surface relief structure is disposed on the surface of the surface blazed grating away from the single-beam emission surface to suppress higher-order mode loss to achieve single-mode emission.

[0083] According to embodiments of this disclosure, a method for fabricating a vertical-cavity surface-emitting laser includes:

[0084] Step 1: Epitaxially grow a buffer layer, an n-type Bragg reflector layer, a composite layer, a p-type Bragg reflector layer, and a phase matching layer sequentially on the substrate; wherein, the composite layer includes N multi-quantum well active layers, N oxide layers, and N-1 tunnel junction layers; the k-th multi-quantum well active layer, the k-th oxide layer, and the k-th tunnel junction layer are stacked sequentially and separated by a spacer layer, 1≤k≤N;

[0085] Step 2: Etch the surface structure on the phase matching layer; perform etching on the surface structure to obtain the surface blazed grating and surface relief structure.

[0086] Step 3: Grow a primary p-electrode on the phase matching layer; grow passivation material and etch mesa structures in the region on the phase matching layer surface that does not contain the primary p-electrode and on the primary p-electrode.

[0087] Step 4: Wet oxidation is performed on N oxide layers to form oxide pores;

[0088] Step 5: Grow a passivation layer on the mesa structure and etch out a secondary p-electrode window to expose the primary p-electrode underneath; grow a secondary p-electrode on the passivation layer.

[0089] Step 6: Prepare an N-electrode on the surface of the substrate away from the buffer layer and anneal it to form an ohmic contact.

[0090] In the embodiments of this disclosure, by etching surface relief and stepped blazed gratings on the surface of a multi-junction rectangular VCSEL, high-power, high-efficiency, and high side-mode suppression ratio beam emission is achieved, successfully reducing the emitted beam to a single beam. Furthermore, by adjusting the injection current to regulate the wavelength, light emission at different angles can be achieved. This technology can be applied to medium- and long-range laser detection fields, improving the detection range and accuracy of lidar.

[0091] According to embodiments of this disclosure, the raw materials for the passivation material and the passivation layer include SiO2 or SiN. x .

[0092] According to embodiments of this disclosure, growing passivation material and etching mesa structures on the phase-matching layer surface in regions without primary p-electrodes and on the primary p-electrodes includes: surface growth of SiO2 or SiN. x The passivation layer is retained on the top of the mesa after photolithography and etching. The mesa structure is etched using the passivation layer as a mask, and the etching depth is greater than the total thickness of the p-type Bragg reflector layer and the composite layer.

[0093] According to embodiments of this disclosure, growing a passivation layer on a mesa structure includes removing the passivation layer at the top of the mesa structure and growing SiO2 or SiN over the entire top of the device. x Passivation layer.

[0094] In some possible embodiments disclosed herein, the length × width of the mesa structure is 300 μm × 25 μm, the rectangular VCSEL is an 808 nm 3-junction VCSEL, i.e., the N value is 3, and the specific material structure parameters are shown in Table 1, wherein p-DBR is a p-type Bragg reflector layer and n-DBR is an n-type Bragg reflector layer.

[0095] Table 1

[0096]

[0097] Wherein, the doping concentration of tunnel level-1 / 10 18 cm -3 8 / 4 in n is represented as n + -Al 0.3 Ga 0.7 The As doping concentration is 8 × 10⁻⁶. 18 cm -3 p + -Al 0.3 Ga 0.7 The As doping concentration is 4 × 10⁻⁶. 18 cm -3 ; 15 / 15 is represented as Al 0.3 Ga 0.7 The thickness of As is 15 nm, p + -Al 0.3 Ga 0.7 The thickness of As is 15 nm; the material of the multi-quantum-well active layer-2 is Al. 0.01 Ga 0.99 As(trap) / Al 0.3 Ga 0.7 As (base), 5 / 10 is represented as Al 0.01 Ga 0.99 The thickness of the As (trap) is 5 nm, and the Al 0.3 Ga 0.7 The thickness of As (barrier) is 10nm, and well 3 and bar 4 represent four layers of barriers sandwiched with three layers of wells.

[0098] Figure 10 The diagram illustrates the relationship between voltage, power, and electro-optical conversion efficiency and current according to embodiments of the present disclosure.

[0099] Figure 11 A far-field view of an etched blazed grating according to an embodiment of the present disclosure is schematically shown.

[0100] Figure 12 The diagram schematically illustrates a far-field view of an etched Bragg grating according to one embodiment.

[0101] like Figure 10As shown, the 3-junction VCSEL of this disclosure achieves high power while maintaining a high side-mode suppression ratio in optical output, and has high electro-optical conversion efficiency and slope efficiency.

[0102] Depend on Figure 11 and Figure 12 It can be seen that the stepped blazed grating disclosed in the etching paper effectively suppresses -1st order diffraction, achieving single-beam emission, while Figure 12 The image shows the far-field plot of the Bragg grating, where multiple modes of beams exist.

[0103] Those skilled in the art will understand that the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments and / or claims of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0104] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A vertical-cavity surface-emitting laser, characterized in that, include: A surface blazed grating is used to separate the diffraction principal maxima zero order from the interference principal maxima zero order in order to achieve single beam emission; A surface relief structure is disposed on the surface of the surface blazed grating away from the single beam emission surface, used to suppress higher-order mode loss to achieve single-mode emission.

2. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, It also includes, A p-type Bragg reflector layer, a composite layer, an n-type Bragg reflector layer, a buffer layer, and a substrate are sequentially stacked on the surface of the surface relief structure away from the surface blazed grating. The surface blazed grating, the surface relief structure, the p-type Bragg reflector layer, and the composite layer form a mesa structure. The composite layer comprises N multi-quantum-well active layers, N oxide layers, and N-1 tunnel junction layers; The k-th multi-quantum well active layer, the k-th oxide layer, and the k-th tunnel junction layer are stacked sequentially and separated by a spacer layer, where 1≤k≤N.

3. The vertical-cavity surface-emitting laser according to claim 2, characterized in that, The N multi-quantum-well active layers are located at the antinodes of the standing wave field of the vertical cavity surface-emitting laser; The N oxide layers and the N-1 tunnel junction layers are all located at nodes of the standing wave field of the vertical cavity surface-emitting laser.

4. The vertical-cavity surface-emitting laser according to claim 2, characterized in that, Each of the N oxide layers has an oxide pore, and the width of the oxide pore is greater than 4 μm.

5. The vertical-cavity surface-emitting laser according to claim 4, characterized in that, The materials of the N oxide layers include Al. x Ga 1-x As; The n-type Bragg reflector and the p-type Bragg reflector are both Al layers that are alternately arranged. x Ga 1-x As layer and Al y Ga 1- y As layer; Where x is less than 0.4 and y is greater than 0.6, the Al x Ga 1-x As layer and Al y Ga 1-y The thickness of the As layer is λ / 4n, where λ is the wavelength of the single-mode emission and n is the refractive index.

6. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The blazed grating is a stepped blazed grating, the number of steps of the stepped blazed grating is greater than or equal to 2, and the period of the stepped blazed grating satisfies the Bragg equation.

7. The vertical-cavity surface-emitting laser according to claim 1, characterized in that, The width of the surface relief structure is ≤4μm, and the height is an odd multiple of λ / 4n, where λ is the wavelength of the single-mode emission and n is the refractive index.

8. The vertical-cavity surface-emitting laser according to claim 2, characterized in that, Also includes: A phase-matching layer is disposed on the p-type Bragg reflector layer, and the phase-matching layer and the surface relief structure are on the same surface; A primary p-electrode is disposed on the surface of the phase matching layer; A passivation layer is disposed on the n-type Bragg reflector layer in a region away from the surface of the buffer layer that does not contain the composite layer, and covers both sides of the composite layer, the p-type Bragg reflector layer and the phase matching layer, and covers the region of the phase matching layer surface that does not contain the primary p electrode and partially covers the surface of the primary p electrode away from the phase matching layer; A secondary p-electrode is disposed on the passivation layer; The N electrode is disposed on the surface of the substrate away from the buffer layer.

9. A method for fabricating a vertical-cavity surface-emitting laser, characterized in that, include: A surface blazed grating and a surface relief structure are fabricated, wherein the surface blazed grating is used to separate the diffraction principal maxima zero order from the interference principal maxima zero order in order to achieve single beam emission; The surface relief structure is disposed on the surface of the surface blazed grating away from the single beam emission surface, and is used to suppress higher-order mode loss to achieve single-mode emission.

10. The method for fabricating a vertical-cavity surface-emitting laser according to claim 9, characterized in that, include: A buffer layer, an n-type Bragg reflector layer, a composite layer, a p-type Bragg reflector layer, and a phase matching layer are epitaxially grown sequentially on a substrate. The composite layer includes N multi-quantum well active layers, N oxide layers, and N-1 tunnel junction layers. The k-th multi-quantum well active layer, the k-th oxide layer, and the k-th tunnel junction layer are stacked sequentially and separated by a spacer layer, where 1≤k≤N. Etch the surface structure on the phase-matching layer; Etching is performed on the surface structure to obtain a surface blazed grating and a surface relief structure; A p-electrode is grown on the phase-matching layer; In the region on the surface of the phase matching layer that does not contain the primary p electrode and on the primary p electrode, a passivation material is grown and a mesa structure is etched. Oxidation pores are formed on the N oxide layers; A passivation layer is grown on the mesa structure, and a secondary p-electrode window is etched to expose the primary p-electrode underneath; A secondary p-electrode is grown on the passivation layer; An N-electrode is fabricated on the surface of the substrate away from the buffer layer and annealed to form an ohmic contact.

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