Buried heterojunction structure and preparation method thereof, laser and preparation method thereof

Abstract

The invention relates to a preparation method of a buried heterojunction structure, and the method comprises the following steps: S1, growing an epitaxial structure on a substrate, and growing a mask layer on the epitaxial structure; s2, etching the epitaxial structure to the substrate; s3, treating the mask layer by using a hydrofluoric acid solution or a buffer hydrofluoric acid solution to thin the mask layer, and generating an eave structure of the mask layer at the joint of the InP spacer layer and the mask layer; s4, in the treatment process, the depth and height of the eave structure are controlled; and S5, after the processing is completed, continuing to grow a P-InP layer, an N-InP layer, an InP cover layer and a contact layer, and completing the manufacturing of the buried heterojunction structure. The invention also provides a buried heterojunction structure, a preparation method of the laser and the laser. The depth and height of the eave structure are controlled by adjusting the concentration of the hydrofluoric acid solution or the buffer hydrofluoric acid solution or adjusting the corrosion time of the hydrofluoric acid solution or the buffer hydrofluoric acid solution, so that the carrier injection density is adjusted.

Description

Technical Field

[0001] The present invention relates to the field of optical communication technology, and in particular to a buried heterojunction structure and a preparation method thereof, a laser and a preparation method thereof. Background Art

[0002] With the development of high-speed optical communications, higher requirements are placed on the laser source of communications. Compared with FP (Fabry-perot) lasers, DFB (Distributed Feedback) lasers have good mode selection capabilities and can achieve narrower line widths.

[0003] At present, there are two main structures of DFB lasers, RWG (Ridge Waveguide) ridge waveguide structure and BH (Buried Heterojunction) buried heterojunction structure. Compared with the traditional RWG structure, the BH structure can, on the one hand, limit the light in the active layer by burying the low-refractive index material, and on the other hand, limit the carriers in the active layer by burying the grown PN reverse current blocking layer, thus having certain advantages in the far-field divergence angle. With the development and optimization of chips and epitaxial processes, people are more inclined to BH structure lasers with better electric field and light confinement effects. At present, there are two urgent problems to be solved in BH structure lasers: one is how to improve the efficiency of the laser and increase the carrier injection density in the active area. The traditional method can be achieved by reducing the width of the active layer, but reducing the width of the active layer will change the light field distribution, resulting in disadvantages such as mode instability and beam asymmetry; the second is how to reduce leakage, see Figure 7 In the conventional current limiting layer, the current will pass through the P-InP and active layer on both sides, resulting in leakage. Therefore, the technical problem to be solved by the present invention is to increase the carrier injection density in the active area and reduce leakage without changing the width of the active layer. Summary of the invention

[0004] The object of the present invention is to provide a buried heterojunction structure and a preparation method thereof, a laser and a preparation method thereof, which can at least solve some of the defects in the prior art.

[0005] To achieve the above object, the embodiment of the present invention provides the following technical solution: a method for preparing a buried heterojunction structure, comprising the following steps:

[0006] S1, growing an epitaxial structure on a substrate, and growing a mask layer on the epitaxial structure;

[0007] S2, etching the epitaxial structure to the substrate;

[0008] S3, treating the mask layer with a hydrofluoric acid solution or a buffered hydrofluoric acid solution to make the mask layer thinner and generate an eaves structure of the mask layer at the connection between the InP spacer layer and the mask layer;

[0009] S4, during the treatment process, adjusting the concentration of the hydrofluoric acid solution or the buffered hydrofluoric acid solution, or adjusting the corrosion time of the hydrofluoric acid solution or the buffered hydrofluoric acid solution to control the depth and height of the eaves structure;

[0010] S5, after the processing is completed, continue to grow the P-InP layer, the N-InP layer, the InP cap layer and the contact layer to complete the production of the buried heterojunction structure.

[0011] Further, the epitaxial structure includes sequentially growing an InP buffer layer, a grating layer, a grating buried layer, an active layer, and an InP spacer layer, or the epitaxial structure also includes sequentially growing an InP buffer layer, an active layer, a grating layer, a grating buried layer, and an InP spacer layer; in the S2 step, firstly dry etching is used to etch the unmasked area to the InP buffer layer, and then wet etching is used to etch the unmasked area to the substrate.

[0012] Furthermore, the thickness of the mask layer is 20-1000 nm.

[0013] Furthermore, the mask layer is a SiO2 mask layer or a SiN x Mask layer.

[0014] Furthermore, in the step S5, the height of the grown N-InP layer is above the InP spacer layer.

[0015] Furthermore, in the step S5, after the P-InP layer and the N-InP layer are grown in sequence, the mask layer is removed using a hydrofluoric acid solution or a buffered hydrofluoric acid solution, and then the InP cap layer and the contact layer are grown in sequence.

[0016] Furthermore, the eaves structure has a depth w of 10-500 nm and a height h of 10-1000 nm.

[0017] The embodiment of the present invention provides another technical solution: a buried heterojunction structure, which is manufactured by the above method.

[0018] An embodiment of the present invention provides another technical solution: a method for preparing a laser, using the above method to prepare a buried heterojunction structure, then growing a mask layer, opening a current injection window, making an electrode, then thinning the sputtered alloy, and finally striping to complete the production of the laser.

[0019] The embodiment of the present invention provides another technical solution: a laser manufactured by the above method.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. By adjusting the concentration of the hydrofluoric acid solution or the buffered hydrofluoric acid solution, or adjusting the etching time of the hydrofluoric acid solution or the buffered hydrofluoric acid solution, the depth and height of the eaves structure are controlled, thereby adjusting the carrier injection density.

[0022] 2. By making the height of the N-InP layer higher than the InP spacer layer, or in other words, the height of the N-InP layer is not lower than the InP spacer layer, the morphology of the current limiting layer can be optimized to form a tall and effective current limiting layer, reduce leakage, improve the current injection efficiency of the laser, and simplify the manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of an epitaxial structure of a method for preparing a buried heterojunction structure provided by an embodiment of the present invention;

[0024] Figure 2 A schematic diagram of a dry etching structure of a method for preparing a buried heterojunction structure provided by an embodiment of the present invention;

[0025] Figure 3 A schematic diagram of a wet etching structure of a method for preparing a buried heterojunction structure provided by an embodiment of the present invention;

[0026] Figure 4 A schematic diagram of a mask layer structure treated with a hydrofluoric acid solution or a buffered hydrofluoric acid solution in a method for preparing a buried heterojunction structure provided by an embodiment of the present invention;

[0027] Figure 5 A schematic diagram of the structure of a P-InP layer and an N-InP layer after buried growth in a method for preparing a buried heterojunction structure provided by an embodiment of the present invention;

[0028] Figure 6 A schematic diagram of a method for preparing a buried heterojunction structure provided in an embodiment of the present invention, in which an InP cap layer and a contact layer are grown after removing the buried layer;

[0029] Figure 7 This is a schematic diagram of the current channel after the growth of the P-InP layer and the N-InP layer of the traditional BH structure;

[0030] Figure 8 A schematic diagram of a current channel after the growth of a P-InP layer and an N-InP layer in a method for preparing a buried heterojunction structure provided by an embodiment of the present invention;

[0031] In the figure markings: 1-substrate; 2-InP buffer layer; 3-grating layer; 4-grating buried layer; 5-active layer; 6-InP spacer layer; 7-mask layer; 9-eaves structure; 10-P-InP layer; 11-N-InP layer; 12-InP cap layer; 13-contact layer. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] See also Figures 1 to 6 The embodiment of the present invention provides a method for preparing a buried heterojunction structure, comprising the following steps: S1, growing an epitaxial structure on a substrate 1, and growing a mask layer 7 on the epitaxial structure; S2, etching the epitaxial structure to the substrate 1; S3, treating the mask layer 7 with a hydrofluoric acid solution or a buffered hydrofluoric acid solution to make the mask layer 7 thinner, and generating an eaves structure 9 of the mask layer 7 at the connection between the InP spacer layer 6 and the mask layer 7; S4, during the treatment process, adjusting the concentration of the hydrofluoric acid solution or the buffered hydrofluoric acid solution, or adjusting the etching time of the hydrofluoric acid solution or the buffered hydrofluoric acid solution to control the depth and height of the eaves structure 9; S5, after the treatment is completed, continuing to grow a P-InP layer 10, an N-InP layer 11, an InP cap layer 12 and a contact layer 13 to complete the preparation of the buried heterojunction structure. In this embodiment, the depth and height of the eaves structure 9 are controlled by adjusting the concentration of the hydrofluoric acid solution or the buffered hydrofluoric acid solution, or adjusting the etching time of the hydrofluoric acid solution or the buffered hydrofluoric acid solution, so as to adjust the carrier injection density. Specifically, when the mask layer 7 is treated with the hydrofluoric acid solution or the buffered hydrofluoric acid solution, the morphology of the eaves structure 9 obtained by etching can be controlled by adjusting the solution concentration or the etching time. Figure 4 The depth w and height h are shown, so that the carrier injection density can be adjusted.

[0034] See also Figures 1 to 6, the epitaxial structure includes sequentially growing an InP buffer layer 2, a grating layer 3, a grating buried layer 4, an active layer 5, and an InP spacer layer 6. In the step S2, dry etching is first used to etch the unmasked area to the InP buffer layer 2, and then wet etching is used to etch the unmasked area to the substrate 1. In this embodiment, etching is divided into two steps. The first step is to etch the InP buffer layer 2, and the second step is to etch the substrate 1. The first step can be dry etching, and the second step can be wet etching. In other embodiments, the epitaxial structure also includes sequentially growing an InP buffer layer 2, an active layer 5, a grating layer 3, a grating buried layer 4, and an InP spacer layer 6.

[0035] See also Figures 1 to 6 , the height of the grown N-InP layer 11 is above the InP spacer layer 6. In this embodiment, by making the height of the N-InP layer 11 above the InP spacer layer 6, or in other words, the height of the N-InP layer 11 is not less than the InP spacer layer 6, the morphology of the current limiting layer can be optimized, a tall and effective current limiting layer can be formed, leakage can be reduced, the current injection efficiency of the laser can be improved, and the manufacturing process is simple. The schematic diagram of the current channel after the growth of the traditional BH structure P-type InP and N-type InP is shown in FIG. Figure 7 As shown in FIG. 1 , it can be seen that the current will pass through the P-InP and active layer 5 on both sides, resulting in leakage. After adopting the method of this embodiment, as shown in FIG. Figure 8 As shown, current only passes through the active layer 5, reducing leakage.

[0036] The following is a specific implementation method:

[0037] 1. Using MOCVD to sequentially grow an InP buffer layer 2 and a grating layer 3 on a substrate 1;

[0038] 2. Use holographic / electron beam technology to make a grating on the surface of the grating layer 3, use a combination of dry and wet methods to etch the grating morphology, and then use MOCVD to grow a grating buried layer 4 to fill the grooves on the grating surface to make the surface flat; then grow an active layer 5 and an InP spacer layer 6 in sequence. Figure 1 ;

[0039] 3. Growth of SiO2 or SiN x The mask layer 7 has a thickness of 20-1000 nm. The mask layer 7 on the waveguide layer is retained by photolithography and etching processes, and then the mask-free area is dry-etched to the InP buffer layer 2. Figure 2 ;

[0040] 4. Wet etching is used to etch the unmasked area to the substrate 1, see Figure 3 ;

[0041] 5. The mask layer 7 is treated with a hydrofluoric acid solution or a buffered hydrofluoric acid solution to make the mask layer 7 thinner. At the same time, an undercut (eaves structure 9) of the mask layer 7 is generated at the connection between the InP spacer layer 6 and the mask layer 7. The depth w of the eaves structure is 10-500nm and the height h is 10-1000nm. Figure 4 ;

[0042] 6. Use MOCVD to sequentially grow a P-InP layer 10 and an N-InP layer 11, wherein the N-InP layer 11 fills the undercut (eaves structure 9) of the mask layer 7, so that the growth height of the N-InP layer 11 is above the spacer layer 6, as shown in FIG. Figure 5 ;

[0043] 7. Remove the mask layer 7 using hydrofluoric acid or buffered hydrofluoric acid, and then use MOCVD to grow the InP cap layer 12 and the contact layer 13 in sequence to complete the production of the heterojunction current blocking layer. Figure 6 .

[0044] The embodiment of the present invention provides a buried heterojunction structure, which is prepared by the above method. At the same time, the embodiment also provides a method for preparing a laser, which uses the above method to prepare a buried heterojunction structure, then grows a mask layer, opens a current injection window, makes an electrode, then thins the sputtered alloy, and finally debonds to complete the production of the laser. The embodiment also provides a laser, which is prepared by the laser preparation method.

[0045] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a buried heterojunction structure, characterized in that: The steps include: S1, growing an epitaxial structure on a substrate, and growing a mask layer on the epitaxial structure; S2, etching the epitaxial structure to the substrate; S3, treating the mask layer with a hydrofluoric acid solution or a buffered hydrofluoric acid solution to make the mask layer thinner and generate an eaves structure of the mask layer at the connection between the InP spacer layer and the mask layer; S4, during the treatment process, adjusting the concentration of the hydrofluoric acid solution or the buffered hydrofluoric acid solution, or adjusting the corrosion time of the hydrofluoric acid solution or the buffered hydrofluoric acid solution to control the depth and height of the eaves structure; S5, after the processing is completed, continue to grow the P-InP layer, the N-InP layer, the InP cap layer and the contact layer to complete the production of the buried heterojunction structure.

2. The method for preparing a buried heterojunction structure according to claim 1, characterized in that: The epitaxial structure includes sequentially growing an InP buffer layer, a grating layer, a grating buried layer, an active layer, and an InP spacer layer, or the epitaxial structure also includes sequentially growing an InP buffer layer, an active layer, a grating layer, a grating buried layer, and an InP spacer layer; in the S2 step, firstly dry etching the unmasked area to the InP buffer layer, and then wet etching the unmasked area to the substrate.

3. The method for preparing a buried heterojunction structure according to claim 1, characterized in that: The thickness of the mask layer is 20-1000 nm.

4. The method for preparing a buried heterojunction structure according to claim 1, characterized in that: The mask layer is a SiO2 mask layer or a SiN x Mask layer.

5. The method for preparing a buried heterojunction structure according to claim 1, characterized in that: In the step S5, the height of the grown N-InP layer is above the InP spacer layer.

6. The method for preparing a buried heterojunction structure according to claim 1, characterized in that: In the step S5, after the P-InP layer and the N-InP layer are grown in sequence, the mask layer is removed using a hydrofluoric acid solution or a buffered hydrofluoric acid solution, and then the InP cap layer and the contact layer are grown in sequence.

7. The method for preparing a buried heterojunction structure according to claim 1, characterized in that: The eaves structure has a depth w of 10-500 nm and a height h of 10-1000 nm.

8. A buried heterojunction structure, characterized in that: The method is prepared by any one of claims 1 to 7.

9. A method for preparing a laser, characterized in that: The buried heterojunction structure is prepared by the method described in any one of claims 1 to 7, followed by growth of a mask layer, opening a current injection window, fabrication of electrodes, subsequent thinning of the sputtered alloy, and finally striping to complete fabrication of the laser.

10. A laser, characterized in that: Prepared by the method as claimed in claim 9.

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