Semiconductor laser and method of fabrication

Abstract

The application provides a semiconductor laser and a manufacturing method, comprising the following steps: providing an InP substrate; forming a plurality of spaced-apart openings in the InP substrate, the openings extending from the upper surface of the InP substrate to the interior of the InP substrate; forming a buffer layer on the InP substrate, the buffer layer covering the openings to form air gaps, the material of the buffer layer comprising InGaAs and / or InGaAsP; and forming a laser functional stack on the buffer layer. In the semiconductor laser and the manufacturing method, stress is released by introducing air gaps, a buffer layer with a larger lattice constant is obtained on the InP substrate, and a 2.1-2.3 mu m laser functional stack is grown based on the buffer layer, so that a laser epitaxial structure with the characteristics of large strain and high-quality material is obtained on the InP substrate.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology and relates to a semiconductor laser and its manufacturing method. Background Technology

[0002] Semiconductor lasers with lasing wavelengths in the range of 2.1μm-2.3μm have wide applications in gas detection, biosensing, and emission detection. InP-based InGaAlAs and InGaAsP material systems cover emission wavelengths from 900nm to 2000nm. When extending to wavelengths above 2.1μm, the lattice size of the luminescent material required has a greater mismatch with the InP substrate. At this point, the strain of the coherently grown luminescent material on the InP substrate is typically >2%. Large strain can easily introduce growth defects such as penetrating dislocations into the material, which can have disastrous consequences for the reliability of the device. Large lattice mismatch has become the main factor limiting the extension of InP-based materials to longer wavelengths.

[0003] GaSb has a larger lattice constant than InP, making it easier to grow high-quality materials with emission wavelengths above 2.1 μm on GaSb substrates compared to InP substrates. However, obtaining GaSb substrates is more difficult than obtaining InP substrates. In addition, InP substrates have more mature process technology. Therefore, how to prepare 2.1 μm-2.3 μm semiconductor lasers on InP substrates is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a semiconductor laser and a method for fabricating it, so as to solve the problem that it is difficult to prepare a 2.1μm-2.3μm semiconductor laser epitaxial structure on an InP substrate in the prior art.

[0005] To achieve the above and other related objectives, the present invention provides a method for manufacturing a semiconductor laser, comprising the following steps:

[0006] Provide InP substrates;

[0007] A plurality of spaced openings are formed in the InP substrate, the openings extending from the upper surface of the InP substrate into the interior of the InP substrate;

[0008] A buffer layer is formed on an InP substrate, the buffer layer covering the opening to form an air gap, and the material of the buffer layer includes InGaAs and / or InGaAsP;

[0009] A laser functional stack is formed on the buffer layer.

[0010] Optionally, the characteristic size of the opening is 50nm to 100nm, and the spacing between adjacent openings is 100nm to 200nm.

[0011] Optionally, the depth of the opening is 500nm to 2000nm, and the thickness of the buffer layer is not less than 300nm.

[0012] Optionally, the laser functional stack includes, from bottom to top, an N-type waveguide layer, an N-type confinement layer, a quantum well layer, a P-type confinement layer, and a P-type waveguide layer, wherein the N-type waveguide layer is made of InGaAsP, the N-type confinement layer is made of InGaAsP, the quantum well layer is made of InGaAs, the P-type confinement layer is made of InGaAsP, and the P-type waveguide layer is made of InGaAsP.

[0013] Optionally, the emission wavelength of the semiconductor laser is 2.1 μm to 2.3 μm.

[0014] The present invention also provides a semiconductor laser, comprising:

[0015] An InP substrate having a plurality of spaced openings that extend from the upper surface of the InP substrate into the interior of the InP substrate;

[0016] A buffer layer is located above the InP substrate, the buffer layer covers the opening to form an air gap, and the material of the buffer layer includes InGaAs and / or InGaAsP;

[0017] The laser functional stack is located above the buffer layer.

[0018] Optionally, the characteristic size of the opening is 50nm to 100nm, and the spacing between adjacent openings is 100nm to 200nm.

[0019] Optionally, the depth of the opening is 500nm to 2000nm, and the thickness of the buffer layer is not less than 300nm.

[0020] Optionally, the laser functional stack includes, from bottom to top, an N-type waveguide layer, an N-type confinement layer, a quantum well layer, a P-type confinement layer, and a P-type waveguide layer, wherein the N-type waveguide layer is made of InGaAsP, the N-type confinement layer is made of InGaAsP, the quantum well layer is made of InGaAs, the P-type confinement layer is made of InGaAsP, and the P-type waveguide layer is made of InGaAsP.

[0021] Optionally, the emission wavelength of the semiconductor laser is 2.1 μm to 2.3 μm.

[0022] As described above, in the semiconductor laser and fabrication method of the present invention, by introducing an air gap to release stress, a buffer layer with a larger lattice constant is obtained on the InP substrate, and a laser functional stack of 2.1 μm to 2.3 μm is grown on the buffer layer as a substrate, thereby realizing a laser epitaxial structure with both large strain and high-quality material properties on the InP substrate. Attached Figure Description

[0023] Figure 1 The diagram shown is a process flow chart of the semiconductor laser fabrication method in an embodiment of the present invention.

[0024] Figure 2 The diagram shown is a schematic representation of an InP substrate provided in an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of a mask layer formed on an InP substrate in an embodiment of the present invention.

[0026] Figure 4 The diagram shown is a schematic representation of the patterned mask layer in an embodiment of the present invention.

[0027] Figure 5 The diagram shown illustrates the formation of an opening in an embodiment of the present invention.

[0028] Figure 6 The diagram shown is a schematic diagram of removing the mask layer in an embodiment of the present invention.

[0029] Figure 7 The diagram shown is a schematic diagram of the formation of a buffer layer in an embodiment of the present invention.

[0030] Figure 8 The diagram shown is a schematic diagram of the formation of a laser functional stack in an embodiment of the present invention.

[0031] Component designation explanation

[0032] 1 InP substrate

[0033] 2. Mask layer

[0034] 3 Openings

[0035] 4. Buffer layer

[0036] 5 N-type waveguide layer

[0037] 6 N-type confinement layer

[0038] 7. Quantum well layer

[0039] 8 P-type confinement layers

[0040] 9 P-type waveguide layers

[0041] 10 P-type ohmic contact layer

[0042] Steps S1 to S4 Detailed Implementation

[0043] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0044] Please see Figures 1 to 8 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0045] This embodiment provides a method for fabricating a semiconductor laser. Please refer to [link / reference]. Figure 1 This includes the following steps:

[0046] S1: Provides an InP substrate;

[0047] S2: A plurality of spaced openings are formed in the InP substrate, the openings extending from the upper surface of the InP substrate into the interior of the InP substrate;

[0048] S3: A buffer layer is formed on an InP substrate, the buffer layer covering the opening to form an air gap, the material of the buffer layer including InGaAs and / or InGaAsP;

[0049] S4: A laser functional stack is formed on the buffer layer.

[0050] The fabrication method of the semiconductor laser in this embodiment will be described in detail below with reference to the specific accompanying drawings.

[0051] First, please refer to Figure 2 Step S1: Provide InP substrate 1.

[0052] As an example, the InP substrate 1 adopts a (100) crystal plane substrate. The (100) crystal plane is beneficial for obtaining a flat epitaxial layer, which is conducive to the subsequent formation of a flatter buffer layer 4 (see Figure 7 This improves the performance of the laser.

[0053] Next, please refer to Figures 3 to 5Step S2: A plurality of spaced openings 3 are formed in the InP substrate 1, the openings 3 extending from the upper surface of the InP substrate 1 into the interior of the InP substrate 1.

[0054] As a specific example, a method for forming multiple spaced-apart openings 3 includes:

[0055] like Figure 3 As shown, a mask layer 2 is first formed on the InP substrate 1; in this embodiment, the material of the mask layer 2 is SiO2, and the mask layer 2 is formed on the substrate 1 by PECVD, and the thickness of the mask layer 2 is not less than 200nm;

[0056] like Figure 4 As shown, the mask layer 2 is then patterned based on processes such as photolithography and etching; wherein, the patterned mask layer 2 defines the position of the opening 3;

[0057] like Figure 5 As shown, the InP substrate 1 is then etched using the patterned mask layer 2 as a mask to form the openings 3. Multiple openings 3 are evenly distributed in the InP substrate 1. Any suitable etching process can be used, such as ICP etching process to etch the InP substrate 1. The etching depth is selected to be 500nm to 2000nm, that is, the depth of the openings 3 is 500nm to 2000nm.

[0058] like Figure 6 As shown, after forming the opening 3, the mask layer 2 is removed. The mask layer 2 can be removed in any suitable manner, for example, the mask layer 2 can be removed with BOE solution. Preferably, after removing the mask layer 2, the surface of the InP substrate can be cleaned with concentrated sulfuric acid and then dried with isopropanol (IPA).

[0059] As an example, the shape of the opening 3 is square or circular, the feature size of the opening 3 is 50nm to 100nm, and the spacing between adjacent openings 3 is 100nm to 200nm. When the shape of the opening 3 is circular, its diameter is 50 to 100nm; when the shape of the opening 3 is square, its side length is 50 to 100nm, and the side length is parallel or perpendicular to the

[110] crystal orientation of the InP substrate 1, so that the perpendicular and parallel

[110] crystal orientation directions have the same duty cycle, thereby improving the uniformity of the micro-region of epitaxial growth.

[0060] Next, please refer to Figure 7 Step S3: A buffer layer 4 is formed on the InP substrate 1, the buffer layer 4 covering the opening 3 to form an air gap, and the material of the buffer layer 4 includes InGaAs and / or InGaAsP.

[0061] As an example, the InP substrate 1 after the opening 3 is formed is transferred to the MOCVD cavity and heated to 560℃~590℃ to grow the N-type buffer layer 4.

[0062] As an example, the thickness of the buffer layer 4 is not less than 300 nm, and the opening 3 is completely closed during the formation of the buffer layer 4 to form the air gap.

[0063] Although the lattice constant of the buffer layer 4 is greater than that of the InP substrate 1, the presence of the air gap can release stress, so that the buffer layer 4 is subjected to 0.8-1.2% compressive strain compared to the InP substrate 1, or to a gradually increasing graded strain of 0-1.2%, or to a superlattice strain structure with dislocation orientation, that is, the strain of the buffer layer 4 is less than 2% (maximum 1.2%).

[0064] In this invention, by introducing an air gap, a buffer layer 4 with lower stress and a larger lattice constant can be formed on the InP substrate 1. Then, a laser functional stack is subsequently grown on the buffer layer 4 as a substrate to achieve an emission wavelength of 2.1μm to 2.3μm.

[0065] Next, please refer to Figure 8 Step S4: Form a laser functional stack on the buffer layer 4.

[0066] As an example, the laser functional stack includes, from bottom to top, an N-type waveguide layer 5, an N-type confinement layer 6, a quantum well region 7, a P-type confinement layer 8, and a P-type waveguide layer 9, wherein the N-type waveguide layer 5 is made of InGaAsP, the N-type confinement layer 6 is made of InGaAsP, the quantum well layer 7 is a periodic structure of two layers of InGaAs materials with different compositions, the P-type confinement layer 8 is made of InGaAsP, and the P-type waveguide layer 9 is made of InGaAsP.

[0067] As an example, in the laser functional stack, the strain of the layers other than the quantum well layer 7 relative to the buffer layer 4 is < ±0.1%, and the strain of the quantum well layer 7 relative to the buffer layer 4 is 1% to 1.5%. Under quantum confinement, the emission wavelength of photoluminescence (PL) is 2.1 μm to 2.3 μm.

[0068] As an example, the N-type confinement layer 6 and the P-type confinement layer 8 are used to provide energy barriers to confine carriers and the optical field, thereby improving the efficiency and gain of the laser.

[0069] As an example, the N-type waveguide layer 5 and the P-type waveguide layer 9 are used to guide and confine the light field, thereby improving the optical gain and mode stability of the laser.

[0070] As an example, it also includes forming a P-type ohmic contact layer 10, which is located above the P-type waveguide layer 9 to reduce the contact resistance between the electrode and the device. The material of the P-type ohmic contact layer 10 includes InGaAs.

[0071] As an example, the method also includes the steps of forming a first electrode and a second electrode (not shown in the figure), wherein the first electrode is located above the P-type ohmic contact layer 10 and electrically connected to the P-type ohmic contact layer 10, and the second electrode is located below the InP substrate 1 and electrically connected to the InP substrate 1, wherein the first electrode and the second electrode are used to electrically connect the semiconductor laser to a power supply and / or external devices.

[0072] Thus, a semiconductor laser has been fabricated. Please refer to [link / reference]. Figure 8 The semiconductor laser includes an InP substrate 1, a buffer layer 4, and a laser functional stack. The InP substrate 1 has a plurality of spaced openings 3 extending from the upper surface of the InP substrate 1 into the interior of the InP substrate 1. The buffer layer 4 is located above the InP substrate 1 and covers the openings 3 to form an air gap. The material of the buffer layer 4 includes InGaAs and / or InGaAsP. The laser functional stack is located above the buffer layer 4.

[0073] As an example, the InP substrate 1 is a (100) crystal plane substrate, which is beneficial for obtaining a flat epitaxial layer, thereby improving the performance of the laser.

[0074] As an example, the shape of the opening 3 is square or circular, the characteristic size of the opening 3 is 50nm to 100nm, and the spacing between adjacent openings 3 is 100nm to 200nm. When the shape of the opening 3 is circular, its diameter is 50 to 100nm; when the shape of the opening 3 is square, its side length is 50 to 100nm, and the side length is parallel or perpendicular to the

[110] crystal orientation of the InP substrate 1.

[0075] As an example, the depth of the opening 3 is 500nm to 2000nm.

[0076] As an example, the thickness of the buffer layer 4 is not less than 300 nm.

[0077] Although the lattice constant of the buffer layer 4 is greater than that of the InP substrate 1, the presence of air gaps can release stress, causing the buffer layer 4 to be subjected to 0.8-1.2% compressive strain compared to the InP substrate 1, or to a gradually increasing gradient strain of 0-1.2%, or to a dislocation-oriented superlattice strain structure, i.e., the strain of the buffer layer 4 is less than 2% (maximum 1.2%).

[0078] As an example, the laser functional stack includes, from bottom to top, an N-type waveguide layer 5, an N-type confinement layer 6, a quantum well region 7, a P-type confinement layer 8, and a P-type waveguide layer 9, wherein the N-type waveguide layer 5 is made of InGaAsP, the N-type confinement layer 6 is made of InGaAsP, the quantum well layer 7 is a periodic structure of two layers of InGaAs materials with different compositions, the P-type confinement layer 8 is made of InGaAsP, and the P-type waveguide layer 9 is made of InGaAsP.

[0079] As an example, in the laser functional stack, the strain of the layers other than the quantum well layer 7 relative to the buffer layer 4 is < ±0.1%, and the strain of the quantum well layer 7 relative to the buffer layer 4 is 1% to 1.5%. Under quantum confinement, the emission wavelength of photoluminescence (PL) is 2.1 μm to 2.3 μm.

[0080] As an example, the N-type confinement layer 6 and the P-type confinement layer 8 are used to provide energy barriers to confine carriers and the optical field, thereby improving the efficiency and gain of the laser.

[0081] As an example, the N-type waveguide layer 5 and the P-type waveguide layer 9 are used to guide and confine the light field, thereby improving the optical gain and mode stability of the laser.

[0082] As an example, a P-type ohmic contact layer 10 is also included, which is located above the P-type waveguide layer 9 and is used to reduce the contact resistance between the electrode and the device. The material of the P-type ohmic contact layer 10 includes InGaAs.

[0083] As an example, the method also includes the steps of a first electrode and a second electrode (not shown in the figure), wherein the first electrode is located above the P-type ohmic contact layer 10 and electrically connected to the P-type ohmic contact layer 10, and the second electrode is located below the InP substrate 1 and electrically connected to the InP substrate 1, wherein the first electrode and the second electrode are used to electrically connect the semiconductor laser to a power supply and / or external devices.

[0084] In summary, the semiconductor laser and its fabrication method of the present invention, by introducing an air gap to release stress, obtains a buffer layer with a larger lattice constant on an InP substrate. A laser functional stack of 2.1 μm to 2.3 μm is then grown on this buffer layer as a substrate, achieving a laser epitaxial structure on an InP substrate that simultaneously possesses large strain and high-quality material properties. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial applicability.

[0085] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for fabricating a semiconductor laser, characterized in that, Includes the following steps: Provide InP substrates; A plurality of spaced openings are formed in the InP substrate, the openings extending from the upper surface of the InP substrate into the interior of the InP substrate; A buffer layer is formed on an InP substrate, the lattice constant of the buffer layer being greater than that of the InP substrate, the buffer layer covering the opening to form an air gap, the air gap relieving the stress of the buffer layer, and the material of the buffer layer including InGaAs and / or InGaAsP. A laser functional stack is formed on the buffer layer, and the emission wavelength of the semiconductor laser is 2.1μm~2.3μm.

2. The method for fabricating a semiconductor laser according to claim 1, characterized in that: The characteristic size of the opening is 50nm~100nm, and the spacing between adjacent openings is 100nm~200nm.

3. The method for fabricating a semiconductor laser according to claim 1, characterized in that: The depth of the opening is 500nm~2000nm, and the thickness of the buffer layer is not less than 300nm.

4. The method for fabricating a semiconductor laser according to claim 1, characterized in that: The laser functional stack comprises, from bottom to top, an N-type waveguide layer, an N-type confinement layer, a quantum well layer, a P-type confinement layer, and a P-type waveguide layer, wherein the N-type waveguide layer is made of InGaAsP, the N-type confinement layer is made of InGaAsP, the quantum well layer is made of InGaAs, the P-type confinement layer is made of InGaAsP, and the P-type waveguide layer is made of InGaAsP.

5. A semiconductor laser, characterized in that, include: An InP substrate having a plurality of spaced openings that extend from the upper surface of the InP substrate into the interior of the InP substrate; A buffer layer is located above the InP substrate. The lattice constant of the buffer layer is greater than that of the InP substrate. The buffer layer covers the opening to form an air gap. The air gap releases the stress of the buffer layer. The material of the buffer layer includes InGaAs and / or InGaAsP. A laser functional stack is located above the buffer layer, and the emission wavelength of the semiconductor laser is 2.1μm~2.3μm.

6. The semiconductor laser according to claim 5, characterized in that: The characteristic size of the opening is 50nm~100nm, and the spacing between adjacent openings is 100nm~200nm.

7. The semiconductor laser according to claim 5, characterized in that: The depth of the opening is 500nm~2000nm, and the thickness of the buffer layer is not less than 300nm.

8. The semiconductor laser according to claim 5, characterized in that: The laser functional stack comprises, from bottom to top, an N-type waveguide layer, an N-type confinement layer, a quantum well layer, a P-type confinement layer, and a P-type waveguide layer, wherein the N-type waveguide layer is made of InGaAsP, the N-type confinement layer is made of InGaAsP, the quantum well layer is made of InGaAs, the P-type confinement layer is made of InGaAsP, and the P-type waveguide layer is made of InGaAsP.

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