A vertical cavity surface emitting laser with both reduced divergence angle and heat dissipation

Abstract

A vertical cavity surface emitting laser that has both reduced divergence angle and heat dissipation belongs to the field of semiconductor optoelectronics. The laser includes: an n-type electrode, a GaAs substrate, an n-type Bragg reflector, an n-spacer layer, a quantum well structure, a p-spacer layer, a p-type Bragg reflector, an oxidation restriction layer located at the bottom of the p-type Bragg reflector, an isolation layer, a p-type electrode, and a heat dissipation mechanism. The present invention provides a heat dissipation mechanism, and the heat dissipation mechanism is prepared in the light-emitting area, or prepared outside the light-emitting area, or prepared in the light-emitting area and outside the light-emitting area at the same time. Through reasonable design, different temperature difference distributions inside the device can be obtained, and the temperature difference causes the refractive index difference of the material to change, so as to obtain different waveguide effects, and a device with a smaller divergence angle can be obtained, and the thermal performance of the device is significantly improved. The present invention solves the problem that the etching of the upper DBR layer affects the reliability of the device during the preparation of the VCSEL, and also solves the heat dissipation problem of high-power VCSEL.

Description

Technical Field

[0001] The invention relates to a vertical cavity surface emitting laser with the functions of reducing divergence angle and dissipating heat, belonging to the technical field of semiconductor optoelectronics. Background Art

[0002] Vertical cavity surface emitting laser (VCSEL) has the advantages of low power consumption and low threshold current. It is an ideal light source and is widely used in the fields of communication, consumption and military, promoting the rapid development of the information society. Some of these fields require small divergence angle and high power output. Therefore, achieving small divergence angle and high power output of VCSEL has always been a hot topic of research.

[0003] Several devices have been designed for VCSELs with small divergence angles, such as photonic crystal structure devices and surface relief structure devices. Both of these devices are based on etching the upper DBR layer of ordinary oxidation-restricted VCSELs, and achieve the purpose of reducing the divergence angle output through different mechanisms. However, defects will be formed after the device is etched, causing damage to the lattice and affecting the reliability of the device.

[0004] Although the above-mentioned photonic crystal structure VCSEL and surface relief structure VCSEL have the characteristics of small divergence angle output, their output power is not high. Summary of the invention

[0005] In view of the above problems, the present invention proposes a vertical cavity surface emitting laser that has both reduced divergence angle and heat dissipation. On the basis of the traditional VCSEL laser, a special heat dissipation mechanism is prepared: by reasonably selecting heat dissipation materials, such as diamond, transparent electrodes, metal materials and other materials with high thermal conductivity, and designing a heat dissipation module based on the characteristics of the heat dissipation material, a special heat dissipation mechanism is formed, so that the heat distribution inside the VCSEL device changes, and then changes the temperature field. The change in temperature causes the change in the refractive index of the material, and finally changes the waveguide condition of the device, which can change the divergence angle of the device.

[0006] When VCSEL is prepared using this preparation method, the upper DBR layer of the epitaxial wafer is not etched during the preparation process, but the heat dissipation material outside the epitaxial wafer is reasonably processed, which will not cause lattice damage and thus will not affect the reliability of the device. In addition, due to the heat dissipation mechanism, the device can be cooled, thereby improving the thermal performance of the device. Therefore, the use of the above method to prepare high-power VCSEL can solve the heat dissipation problem of the device.

[0007] For the heat dissipation mechanism, different heat dissipation materials have different thermal conductivity coefficients and different heat dissipation effects; different graphic shapes, thicknesses, sizes and arrangements result in different heat dissipation areas and thicknesses, and different heat dissipation effects. Different heat dissipation effects can result in different temperature field distributions inside the device, resulting in different refractive index differences of the materials, and thus different waveguide effects, ultimately resulting in a device with a smaller divergence angle. Therefore, by reasonably designing the heat dissipation material, graphic shape, thickness, size and arrangement, the divergence angle of the device can be reduced.

[0008] 1. A vertical cavity surface emitting laser structure with both reduced divergence angle and heat dissipation, characterized in that, viewed along the vertical section of the device, it includes: an n-type electrode 100, a substrate 101, an n-type Bragg reflector 102, an n-spacer layer 103, a quantum well structure 104, a p-spacer layer 105, an oxidation restriction layer 106, a p-type Bragg reflector 107; an isolation layer 108, a p-type electrode 109, and a heat dissipation mechanism 110.

[0009] The heat dissipation mechanism is prepared inside the light-emitting area, outside the light-emitting area, or both inside and outside the light-emitting area. The heat dissipation mechanism structure is as follows:

[0010] The graphics inside the luminous area are selected from: circle, triangle, square, hexagon or asymmetric polygon, and the number of graphics inside the luminous area is multiple and evenly distributed in the luminous area; the graphics outside the luminous area are selected from: circular ring, equilateral triangle ring, regular quadrilateral ring, regular hexagonal ring or symmetrical polygonal ring; the thickness of the graphics inside the luminous area and the graphics outside the luminous area are the same and are at the micron level; the diameter of the circle where the vertices of the graphics inside the luminous area are located is all at the micron level; the innermost shadow part graphic outside the luminous area is the light exit hole, and the number of shadow part graphics outside the luminous area is multiple, and the shadow part graphics are arranged at equal intervals, and their spacing is the same as the width of the shadow part graphics, both at the micron level.

[0011] 2. Further, the p-type electrode is on the top surface and the n-type electrode is on the bottom surface, or both are on the top surface.

[0012] 3. Furthermore, the heat dissipation material of the heat dissipation mechanism is selected from: diamond, transparent electrode, or metal material.

[0013] 4. Furthermore, the heat dissipation material of the heat dissipation mechanism is conductive or non-conductive.

[0014] The specific structure of the heat dissipation mechanism is as follows:

[0015] The graphics inside the luminous area are multiple triangles, and the graphics outside the luminous area are circular rings; the thickness of the triangle and the circular ring is 1-5 microns; the inner circle diameter where the vertices of the isosceles triangle are located and the outer circle diameter where the two vertices of the base of the isosceles triangle are located are in the micron level, the isosceles triangles are evenly distributed in the luminous area and the number is 8-10, and the base angle of the isosceles triangle is 60°-80°; the inner circle radius of the innermost shadow part ring outside the luminous area is the radius of the light exit hole, the number of the shadow part rings is 6-10, the shadow part rings are arranged at equal intervals, and the spacing between them and the width of the shadow part rings are the same, both in the micron level.

[0016] A new VCSEL with a heat dissipation mechanism, using quantum wells as In x1 Ga 1-x1 As / Al x2 Ga 1-x2 As GaAs-based semiconductor laser as an example, In x1 Ga 1-x1 As and Al x2 Ga 1-x2 The relationship between the real part of the refractive index of As and the temperature conforms to the following formula (1) and formula (2) respectively.

[0017] n1=3.65+0.242×x1+0.03×(T-300)÷100 Formula (1)

[0018] n2=3.65-0.730×x2+0.03×(T-300)÷100 Formula (2)

[0019] Where x1 is the composition of In, x2 is the composition of Al, and T is the temperature at a certain position of the VCSEL. It can be seen from formula (1) and formula (2) that the refractive index is positively correlated with the temperature. The higher the temperature, the greater the refractive index.

[0020] When the traditional VCSEL device and the new VCSEL device with heat dissipation mechanism work at the same current:

[0021] (1) The temperature difference between the quantum well and the spacer layer in the novel VCSEL device with a heat dissipation mechanism is higher than that in the conventional VCSEL device. The refractive index difference of the novel VCSEL device with a heat dissipation mechanism is higher than that of the conventional VCSEL device, which makes the waveguide effect more obvious, thereby reducing the divergence angle of the VCSEL.

[0022] (2) The temperature of the new VCSEL device with a heat dissipation mechanism at the same position is lower than that of the traditional VCSEL device. When the operating current is increased, all VCSELs will reach thermal saturation. In comparison, the current value at which the traditional VCSEL reaches thermal saturation is smaller than the current value of the new VCSEL. The new VCSEL can improve the thermal performance of the device because it has a heat dissipation mechanism.

[0023] From the above, it can be seen that due to the existence of the heat dissipation mechanism, through reasonable design, the temperature difference inside the device becomes larger, the temperature difference causes the refractive index difference of the material to become larger, the waveguide effect is more obvious, and finally a device with a smaller divergence angle is obtained, and the thermal performance of the device is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A top view of a VCSEL that reduces divergence angle and dissipates heat.

[0025] Figure 2 Schematic diagram of the structure of a VCSEL that combines reduced divergence angle with heat dissipation. DETAILED DESCRIPTION

[0026] Figure 1 A top view of a VCSEL that combines reduced divergence angle with heat dissipation. The shaded portion of the figure represents the prepared heat dissipation mechanism. Figure 2 The schematic diagram of the structure of VCSEL with both reduced divergence angle and heat dissipation is as follows Figure 1 The VCSEL includes a substrate 101, an n-type Bragg reflector 102, an n-spacer layer 103, a quantum well structure 104, a p-spacer layer 105, an oxidation restriction layer 106, a p-type Bragg reflector 107, a prepared isolation layer 108, a prepared p-type electrode 109, an n-type electrode 100, and a heat dissipation mechanism 110.

[0027] In step 1, the substrate 101 is made of n-type GaAs material, and an n-type Bragg reflector 102, an n-spacer layer 103, a quantum well structure 104, a p-spacer layer 105, an oxidation restriction layer 106, and a p-type Bragg reflector 107 are sequentially grown on the substrate 101 by a metal organic chemical vapor deposition (MOCVD) method.

[0028] Step 2: Photolithography of the mesa structure followed by oxidation.

[0029] Step three: preparing an isolation layer 108 .

[0030] Step 4: preparing the p-type electrode 109 .

[0031] Step 5: reasonably prepare the heat dissipation mechanism 110. For example, the heat dissipation material is copper; the pattern inside the light-emitting area is a triangle, and the pattern outside the light-emitting area is a ring; the thickness of the triangle and the ring is 1 micron; the inner circle diameter of the isosceles triangle vertex is 10 microns, the outer circle diameter of the two vertices of the base of the isosceles triangle is 21 microns, the isosceles triangles are evenly distributed in the light-emitting area and the number is 8, and the base angle of the isosceles triangle is 75°; the inner circle radius of the innermost shadow part ring outside the light-emitting area is 27 microns, the number of shadow part rings is 8, the shadow part rings are arranged at equal intervals and the interval is 10 microns, and the width of the shadow part ring is 10 microns. The design of the heat dissipation mechanism mainly takes into account two points: First, for the annular heat dissipation mechanism outside the light-emitting area, a reflection mechanism is provided: the temperature at the position with the heat dissipation mechanism is lower than the temperature at the position without the heat dissipation mechanism. At this time, the existence of the temperature difference causes the material to form a high and low refractive index difference in the lateral direction, providing high reflectivity for the target wavelength, thereby better limiting the light field in the lateral direction, and ultimately reducing the divergence angle of the device; Second, the heat dissipation mechanism with a triangular shape in the light-emitting area provides a heat dissipation mechanism with a larger temperature difference: the farther away from the center of the light-emitting area, the larger the heat dissipation area of ​​the triangle, the lower the temperature here, and the temperature near the center of the light-emitting area is higher. At this time, the temperature difference between the position far away from the center of the light-emitting area and the center of the light-emitting area is greater, and the light field is concentrated in the center of the light-emitting area and its vicinity with a higher temperature, which can ultimately reduce the divergence angle of the device.

[0032] Step 6: Prepare the n-type electrode 100. Anneal the alloy to achieve good ohmic contact;

[0033] Step seven, split the finished laser chip into single tubes to complete the production.

[0034] This embodiment provides a vertical cavity surface emitting laser that reduces the divergence angle and dissipates heat. A special heat dissipation mechanism is prepared on the light-emitting side of the VCSEL. Compared with the prior art, the present invention has the following beneficial effects. (1) A laser with a smaller divergence angle can be obtained. (2) The heat dissipation mechanism has a heat dissipation effect, which can improve the thermal performance of the device. (3) A laser with a high-power output can be obtained. (4) The reliability of the device will not be affected.

[0035] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only an implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A vertical cavity surface emitting laser structure with both reduced divergence angle and heat dissipation, characterized in that From the vertical cross-section of the device, it includes: n-type electrode, substrate, n-type Bragg reflector, n-spacer layer, quantum well structure, p-spacer layer, oxide confinement layer, p-type Bragg reflector, isolation layer, p-type electrode and heat dissipation mechanism; The heat dissipation mechanism is prepared inside the light-emitting area, outside the light-emitting area, or both inside and outside the light-emitting area. The structure of the heat dissipation mechanism is as follows: The pattern of the heat dissipation mechanism in the light-emitting area is selected from: a circle, a triangle, a square, a hexagon or an asymmetric polygon, and the number of patterns of the heat dissipation mechanism in the light-emitting area is multiple and evenly distributed in the light-emitting area; the pattern of the heat dissipation mechanism outside the light-emitting area is selected from: a circular ring, an equilateral triangle ring, an equilateral quadrilateral ring, an equilateral hexagonal ring or a symmetrical polygonal ring; the thickness of the pattern of the heat dissipation mechanism in the light-emitting area and the pattern of the heat dissipation mechanism outside the light-emitting area are the same and are in the micron level; the diameter of the circle where the vertex of the pattern in the light-emitting area is located is in the micron level; The light-emitting area is a light-emitting hole, and a plurality of annular heat-dissipating mechanisms are arranged at equal intervals outside the light-emitting area, and the intervals and the width of each annular heat-dissipating mechanism are both at the micron level.

2. A vertical cavity surface emitting laser structure with both reduced divergence angle and heat dissipation as claimed in claim 1, wherein the p-type electrode is on the top surface and the n-type electrode is on the bottom surface, or both are on the top surface.

3. A vertical cavity surface emitting laser structure with both reduced divergence angle and heat dissipation as claimed in claim 1, wherein the heat dissipation material of the heat dissipation mechanism is selected from: diamond, transparent electrode or metal material.

4. A vertical cavity surface emitting laser structure with both reduced divergence angle and heat dissipation as claimed in claim 1, wherein the heat dissipation material of the heat dissipation mechanism is conductive or non-conductive.

Images