Semiconductor laser with window structure and method for manufacturing the same

Abstract

The application relates to a semiconductor laser with a window structure and a preparation method thereof. The laser comprises, from bottom to top, a substrate, a buffer layer, an N-limiting layer, an N-waveguide layer, a quantum well active region, a P-waveguide layer, a P-limiting layer, a contact layer, an insulating layer and a P-face electrode; a ridge-shaped structure is arranged on the P-limiting layer, the ridge-shaped structure comprises a ridge-shaped light-emitting structure formed by the P-limiting layer and the contact layer, and a window structure formed by a blank area between the insulating layer and the ridge-shaped light-emitting structure, the window structure is located at one end of the ridge-shaped light-emitting structure and is distributed on both sides of the ridge-shaped light-emitting structure in an axial symmetry. The semiconductor laser with the window structure has the advantages of two common structures of ridge lasers, can effectively improve a light spot and can improve a photoelectric parameter qualified rate.

Description

Technical Field

[0001] This invention relates to the field of semiconductor lasers, specifically to a semiconductor laser with a window structure and its fabrication method. Background Technology

[0002] With the continuous development of science and technology, the research and development and manufacturing of semiconductor lasers have also made rapid progress. Semiconductor lasers can cover wavelengths from infrared to blue-green light. In addition, they are relatively simple to manufacture, have low cost and small size, and are now widely used in various industries, such as laser communication, laser medicine, laser processing and optical metrology. At the same time, as the application scope becomes wider and wider, higher and higher requirements are being placed on the performance and lifespan of lasers.

[0003] Laser performance is primarily characterized by photoelectric parameters such as spot pass rate, threshold current, slope efficiency, peak power, operating voltage, and wavelength. These parameters are influenced by numerous factors, including ridge width, laser cavity length, chip epitaxial structure, and process design. Common defective spots mainly involve side-mode and multimode phenomena, primarily caused by stray light and higher-order modes generated during emission. Therefore, reducing stray light and suppressing higher-order mode lasing are effective means to improve the spot pass rate.

[0004] There are two common types of ridge lasers: one with a ridge emitting area and no insulating layers on either side of the ridge; and the other with insulating layers on all sides except for the ridge emitting area. In actual production, both types of lasers have their advantages and disadvantages. Lasers with a ridge emitting area and no insulating layers on either side of the ridge have advantages because the absence of a dielectric film on the sides allows some stray light emitted during ridge operation to be directly absorbed by the metal. This suppresses higher-order mode lasing to some extent, reduces side-mode phenomena, and results in a relatively high spot quality rate. Furthermore, the good thermal conductivity of the metal allows for faster heat dissipation, thus improving die life. However, the direct absorption of some light by the metal leads to significant light loss and lower photoelectric conversion efficiency. Lasers with insulating layers on all sides of the ridge, with a dense dielectric film on both sides, have relatively small contact between the ridge and the metal, reducing light absorption and light loss, thus improving photoelectric conversion efficiency. However, this type of laser also has disadvantages, namely the existence of a "lateral waveguide" effect. The thermal conductivity of the dielectric film is far inferior to that of the metal, resulting in poor heat dissipation and reduced die life.

[0005] Therefore, it is of great significance to seek a laser that can achieve a high spot qualification rate and good electrical parameter performance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a semiconductor laser with a window structure and its fabrication method.

[0007] A semiconductor laser with a window structure includes, from bottom to top, a substrate, a buffer layer, an N-confining layer, an N-waveguide layer, a quantum well active region, a P-waveguide layer, a P-confining layer, a contact layer, an insulating layer, and a P-surface electrode; a ridge structure is disposed on the P-confining layer, the ridge structure including a ridge-shaped light-emitting structure formed by the P-confining layer and the contact layer, and a window structure formed by the blank area between the insulating layer and the ridge-shaped light-emitting structure, the window structure being located at one end of the ridge-shaped light-emitting structure and axially symmetrically distributed on both sides of the ridge-shaped light-emitting structure.

[0008] According to a preferred embodiment of the present invention, the thickness of the insulating layer is 50–200 nm.

[0009] According to a preferred embodiment of the present invention, the ridge-shaped light-emitting structure extends through the entire cavity length of the laser, with the width of the upper base being 3–10 μm and the width of the lower base being 5–15 μm.

[0010] According to a preferred embodiment of the present invention, the width of the window structure is 15–25 μm and the length is 80–120 μm.

[0011] The fabrication method of the above-mentioned semiconductor laser with a window structure includes the following steps:

[0012] (1) A buffer layer, an N-confinement layer, an N-waveguide layer, a quantum well active region, a P-waveguide layer, a P-confinement layer and a contact layer are grown sequentially on the substrate, and then the contact layer is etched to obtain a strip-shaped region.

[0013] (2) In the center of the strip area, a ridge-shaped light-emitting structure is obtained by spraying photoresist, exposure, development and etching of the P-confinement layer, wherein the upper surface of the ridge-shaped light-emitting structure retains photoresist.

[0014] (3) An insulating layer is grown on the surface of the ridge light-emitting structure and its two sides. Then the insulating layer on the upper surface of the ridge light-emitting structure is peeled off. Then, on one side of the ridge light-emitting structure, with the ridge light-emitting structure as the center of symmetry, a laser sample containing a window structure is obtained by spraying photoresist, exposing, developing and etching the insulating layer on both sides of the ridge light-emitting structure.

[0015] (4) The prepared laser sample is processed by electrode deposition, thinning, alloying and packaging to obtain a semiconductor laser with a window structure.

[0016] According to a preferred embodiment of the present invention, in step (1), the strip region extends through the entire cavity length of the laser and has a width of 35–40 μm.

[0017] According to a preferred embodiment of the present invention, in step (3), the insulating layer is a SiO2 dielectric layer, which is grown by plasma-enhanced chemical vapor deposition (PECVD).

[0018] In this invention, the window structure is the area formed after etching the insulating layers on both sides of the ridge-shaped light-emitting structure in step (3). The window structure area formed after etching during the electrode deposition process in step (4) is filled with the metal for growing the P-side electrode.

[0019] In this invention, the processes of spraying photoresist, exposure, development, etching, stripping, electrode deposition, thinning, alloying, and encapsulation are all performed in accordance with existing technologies.

[0020] The beneficial effects of this invention are:

[0021] 1. The semiconductor laser with a window structure provided by this invention combines the advantages of two common ridge laser structures. It effectively improves the beam pattern and enhances heat dissipation, thereby extending the laser's lifespan. The window region is centered on the ridge-shaped light-emitting structure, with the SiO2 layers on both sides of the ridge structure removed. In subsequent processes, the P-side electrode directly contacts both sides of the ridge-shaped light-emitting structure. During operation, the ridge structure emits light, and some of the light is directly absorbed by the P-side electrode. This allows the product to achieve high photoelectric conversion efficiency while suppressing lasing of higher-order modes, resulting in a higher beam pattern yield. Furthermore, the good thermal conductivity of the metal facilitates faster heat dissipation, further improving laser lifespan, increasing product yield, and reducing production costs.

[0022] 2. The semiconductor laser with a window structure provided by this invention removes the SiO2 layer, allowing direct contact with the metal during subsequent evaporation processes. Since the metal has good thermal conductivity, the laser exhibits better heat dissipation performance during operation, resulting in a relatively longer lifespan under the same conditions. In the non-window structure region, after a stripping process, the ridge-shaped light-emitting structure is covered with a dense SiO2 dielectric layer on both sides. The sides of the ridge-shaped light-emitting structure do not directly contact the metal, reducing light absorption by the metal and thus minimizing light loss, resulting in high photoelectric conversion efficiency.

[0023] 3. The preparation method provided by this invention can change the window area size according to actual production requirements. As the window area size changes, the amount of SiO2 dielectric layer removed also changes. When the area of ​​the removed dielectric layer increases, the light absorbed by the metal increases, the loss increases, the photoelectric conversion efficiency decreases, and its electrical parameters change accordingly, with power decreasing and threshold current relatively increasing. Conversely, when the area of ​​the removed dielectric layer decreases, the opposite occurs. Therefore, the window size most suitable for the process parameters can be selected according to actual production requirements, making it applicable to the manufacture of lasers with various photoelectric parameter requirements and improving the photoelectric parameter qualification rate. Attached Figure Description

[0024] Figure 1 This is a schematic cross-sectional view of the semiconductor laser window structure with a window structure described in Example 1;

[0025] Figure 2 This is a schematic cross-sectional view of the non-window structure portion of the semiconductor laser with a window structure described in Example 1;

[0026] Figure 3 This is a planar schematic diagram of the semiconductor laser with a window structure described in Embodiment 1;

[0027] Figure 4 This is a comparison diagram of the laser spot of the laser described in Example 1 and the laser described in Comparative Example 2.

[0028] 1. Substrate; 2. Buffer layer; 3. N-confining layer; 4. N-waveguide layer; 5. Quantum well active region; 6. P-waveguide layer; 7. P-confining layer; 8. Insulating layer; 9. P-surface electrode; 10. Contact layer; 11. Window structure; 12. Ridge structure. Detailed Implementation

[0029] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0030] Example 1:

[0031] like Figures 1-3 As shown, a semiconductor laser with a window structure includes, from bottom to top, a substrate 1, a buffer layer 2, an N-confining layer 3, an N-waveguide layer 4, a quantum well active region 5, a P-waveguide layer 6, a P-confining layer 7, a contact layer, an insulating layer 8, and a P-surface electrode 9. A ridge structure 12 is disposed on the P-confining layer 7. The ridge structure 12 includes a ridge-shaped light-emitting structure formed by the P-confining layer 7 and the contact layer 10, and a window structure 11 formed by the blank area between the insulating layer 8 and the ridge-shaped light-emitting structure. The window structure 11 is located at one end of the ridge-shaped light-emitting structure 10 and is axially symmetrically distributed on both sides of the ridge-shaped light-emitting structure 10. The insulating layer is a SiO2 dielectric layer with a thickness of 100 nm. The ridge-shaped light-emitting structure extends through the entire cavity length of the laser, with a width of 5 μm at the top and 10 μm at the bottom. The window structure has a width of 10 μm and a length of 100 μm.

[0032] The fabrication method of the above-mentioned semiconductor laser with a window structure includes the following steps:

[0033] (1) A buffer layer, an N-confining layer, an N-waveguide layer, a quantum well active region, a P-waveguide layer, a P-confining layer and a contact layer are grown sequentially on the substrate. Then the contact layer is etched, and the strip region located in the center of the P-confining layer covered by the contact layer is retained, while the rest is exposed to the P-confining layer. The strip region runs through the entire cavity length of the laser and has a width of 35 μm.

[0034] (2) In the center of the strip area, a ridge-shaped light-emitting structure is obtained by spraying photoresist, exposure, development and etching of the P-confinement layer, wherein the upper surface of the ridge-shaped light-emitting structure retains photoresist.

[0035] (3) A SiO2 dielectric layer is grown on the surface of the ridge light-emitting structure and the P-confining layer on both sides of the ridge light-emitting structure. Then, the SiO2 dielectric layer on the upper surface of the ridge light-emitting structure is peeled off. Then, on one side of the ridge light-emitting structure, with the ridge light-emitting structure as the center of symmetry, a window structure is prepared by exposure, development and etching of the insulating layer on both sides of the ridge light-emitting structure to obtain a laser sample containing a window structure.

[0036] (4) The prepared laser sample is processed by electrode deposition, thinning, alloying and packaging to obtain a semiconductor laser with a window structure.

[0037] Example 2:

[0038] A semiconductor laser with a window structure, the structure of which is the same as that described in Embodiment 1, except that the thickness of the insulating layer is 50 nm.

[0039] Example 3:

[0040] A semiconductor laser with a window structure, the structure of which is the same as that described in Embodiment 1, except that the thickness of the insulating layer is 200 nm.

[0041] Example 4:

[0042] A semiconductor laser with a window structure is provided, with the same structure as described in Embodiment 1, except that the ridge-shaped light-emitting structure 10 extends through the entire cavity length of the laser and has a width of 3 μm.

[0043] Example 5:

[0044] A semiconductor laser with a window structure is provided, which is the same as described in Embodiment 1, except that the ridge-shaped light-emitting structure 10 extends through the entire cavity length of the laser and has a width of 10 μm.

[0045] Example 6:

[0046] A semiconductor laser with a window structure is provided, which has the same structure as described in Embodiment 1, except that the width of the window structure is 15 μm and the length is 120 μm.

[0047] Example 7:

[0048] A semiconductor laser with a window structure is provided, which has the same structure as described in Embodiment 1, except that the width of the window structure is 25 μm and the length is 80 μm.

[0049] Comparative Example 1:

[0050] A semiconductor laser has the same structure as described in Example 1, except that there are no insulating layers on either side of the ridge-shaped light-emitting structure.

[0051] Comparative Example 2:

[0052] A semiconductor laser has the same structure as described in Example 1, except that there are insulating layers on both sides of the ridge-shaped light-emitting structure.

[0053] Test case

[0054] The lasers described in Example 1 and Comparative Example 1 were subjected to spot testing.

[0055] The specific method for testing light spots is as follows:

[0056] A receiving paper screen was placed 15cm in front of the laser. After a 30mA current was applied to the laser described in Example 1 and Comparative Example 1, a test spot was obtained on the receiving paper, and the results are as follows: Figure 4 As shown.

[0057] Depend on Figure 4 As shown in Figure a, the light spot obtained using the laser of Comparative Example 1 is obviously thick and blurry, the main light spot is divergent, and there are multiple stray lights at the edge; the light spot obtained using the laser of Example 1 is shown in Figure b, and the light spot is a regular ellipse with uniform and symmetrical light pattern and clear edge contour.

[0058] The parameters of the lasers described in Example 1 and Comparative Examples 1 and 2 are shown in Table 1.

[0059] Table 1. Laser parameters described in Example 1 and Comparative Example 1

[0060] Slope efficiency Threshold current (mA) Peak power (mW) Light spot pass rate (%) Example 1 0.86 10.5 25.3 92 Comparative Example 1 0.78 11.2 24.4 91 Comparative Example 2 0.92 10.9 24.9 88

[0061] As shown in Table 1, the laser described in Example 1 achieved a spot pass rate of 92%, which is basically the same as the 91% spot pass rate of the laser described in Comparative Example 1. However, it is significantly improved compared to the 88% spot pass rate of the laser described in Comparative Example 2. Furthermore, the threshold current of the laser described in Example 1 is 10.5 mA and the peak power is 25.3 mW, which is basically the same as the threshold current of 10.5 mA and the peak power of 24.9 mW of the laser described in Comparative Example 2. However, it has a significant advantage over the threshold current of 11.2 mA and the peak power of 24.4 mW of the laser described in Comparative Example 1. This indicates that a semiconductor laser with a window structure combines the advantages of both common ridge laser structures. It can effectively improve the spot size and enhance heat dissipation.

Claims

1. A semiconductor laser with a window structure, characterized in that, The laser comprises, from bottom to top, a substrate, a buffer layer, an N-confining layer, an N-waveguide layer, a quantum well active region, a P-waveguide layer, a P-confining layer, a contact layer, an insulating layer, and a P-surface electrode; characterized in that a ridge structure is provided on the P-confining layer, the ridge structure comprising a ridge-shaped light-emitting structure formed by the P-confining layer and the contact layer, and a window structure formed by the blank area between the insulating layer and the ridge-shaped light-emitting structure, the window structure being located at one end of the ridge-shaped light-emitting structure and axially symmetrically distributed on both sides of the ridge-shaped light-emitting structure; The thickness of the insulating layer is 50~200nm; the ridge-shaped light-emitting structure extends through the entire cavity length of the laser, with the width of the upper base being 3~10μm and the width of the lower base being 5~15μm; the width of the window structure is 15~25μm and the length is 80~120μm.

2. The method for fabricating the semiconductor laser with a window structure according to claim 1, characterized in that, The steps include the following: (1) A buffer layer, an N-confinement layer, an N-waveguide layer, a quantum well active region, a P-waveguide layer, a P-confinement layer and a contact layer are grown sequentially on the substrate, and then the contact layer is etched to obtain a strip-shaped region located in the center; (2) In the center of the strip area, a ridge-shaped light-emitting structure is obtained by spraying photoresist, exposure, development and etching of the P-confinement layer, wherein the upper surface of the ridge-shaped light-emitting structure retains photoresist; (3) An insulating layer is grown on the surface of the ridge-shaped light-emitting structure and its two sides. Then the insulating layer on the upper surface of the ridge-shaped light-emitting structure is peeled off. Then, on one side of the ridge-shaped light-emitting structure, with the ridge-shaped light-emitting structure as the center of symmetry, the insulating layer on both sides of the ridge-shaped light-emitting structure is exposed, developed and etched to obtain a laser sample containing a window structure. (4) The prepared laser sample is processed by electrode deposition, thinning, alloying and packaging to obtain a semiconductor laser with a window structure.

3. The preparation method according to claim 2, characterized in that, In step (1), the strip region extends through the entire cavity length of the laser and has a width of 35~40μm.

4. The preparation method according to claim 2, characterized in that, In step (3), the insulating layer is a SiO2 dielectric layer, which is grown by plasma-enhanced chemical vapor deposition.

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