Semiconductor laser and manufacturing method

Abstract

The invention provides a semiconductor laser and a manufacturing method thereof. The manufacturing method comprises the following steps: providing an InP substrate; forming a plurality of openings arranged at intervals in the InP substrate, wherein the openings extend into the InP substrate from the upper surface of the InP substrate; a buffer layer is formed on the InP substrate, the buffer layer covers the opening to form an air gap, and the material of the buffer layer comprises InGaAs and / or InGaAsP; a laser function stack is formed on the buffer layer. According to the semiconductor laser and the manufacturing method, stress is released by introducing an air gap, a buffer layer with a larger lattice constant is obtained on the InP substrate, and a 2.1-2.3 [mu] m laser function lamination layer is grown by taking the buffer layer as a substrate, so that a laser epitaxial structure with large strain and high-quality material characteristics is obtained on the InP substrate.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors and relates to a semiconductor laser and a manufacturing method thereof. Background Art

[0002] Semiconductor lasers with lasing wavelengths in the range of 2.1μm-2.3μm are widely used in gas detection, biosensing, emission detection and other fields. The InP-based InGaAlAs and InGaAsP material systems cover 900nm-2000nm emission wavelengths. When further expanded to wavelengths above 2.1μm, the lattice size of the luminescent material required has a greater mismatch with the InP substrate. At this time, the strain of the luminescent material coherently grown on the InP substrate is usually >2%. Large strains can easily introduce growth defects such as threading dislocations in the material, causing catastrophic consequences for the reliability of the device. Large lattice mismatch has become the main factor limiting the expansion of InP-based materials to longer wavelengths.

[0003] GaSb has a larger lattice constant than InP. It is easier to grow high-quality materials with a light emission wavelength above 2.1um on GaSb substrates than on InP substrates. However, it is more difficult to obtain GaSb substrates than on InP substrates. In addition, InP substrates have a more mature process. Therefore, how to prepare 2.1μm-2.3μm semiconductor lasers on InP substrates is a technical problem that needs to be urgently solved by technicians in this field. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a semiconductor laser and a manufacturing method for solving 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 object and other related objects, the present invention provides a method for manufacturing a semiconductor laser, comprising the following steps:

[0006] Providing an InP substrate;

[0007] forming a plurality of openings arranged at intervals in the InP substrate, wherein the openings extend from the upper surface of the InP substrate to the interior of the InP substrate;

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

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

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

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

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

[0013] Optionally, the light 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, wherein a plurality of openings arranged at intervals are provided in the InP substrate, and the openings extend from the upper surface of the InP substrate to the interior of the InP substrate;

[0016] A buffer layer, 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 50 nm to 100 nm, and the spacing between adjacent openings is 100 nm to 200 nm.

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

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

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

[0022] As described above, in the semiconductor laser and manufacturing method of the present invention, an air gap is introduced to release stress, a buffer layer with a larger lattice constant is obtained on the InP substrate, and a 2.1μm to 2.3μm laser functional stack is grown on the buffer layer as a substrate, thereby achieving a laser epitaxial structure with both large strain and high-quality material properties on the InP substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Shown is a process flow chart of a method for manufacturing a semiconductor laser in an embodiment of the present invention.

[0024] Figure 2 Shown is a schematic diagram of providing an InP substrate in an embodiment of the present invention.

[0025] Figure 3 It is a schematic diagram showing a process of forming a mask layer on an InP substrate according to an embodiment of the present invention.

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

[0027] Figure 5 It is a schematic diagram showing the formation of an opening in an embodiment of the present invention.

[0028] Figure 6 It is a schematic diagram showing the removal of the mask layer according to an embodiment of the present invention.

[0029] Figure 7 It is a schematic diagram showing the formation of a buffer layer according to an embodiment of the present invention.

[0030] Figure 8 It is a schematic diagram showing the formation of a laser functional stack according to an embodiment of the present invention.

[0031] Component number description

[0032] 1 InP substrate

[0033] 2 Mask layer

[0034] 3 Opening

[0035] 4 Buffer layer

[0036] 5 N-type waveguide layer

[0037] 6 N-type limiting layer

[0038] 7 Quantum Well Layer

[0039] 8 P-type confinement layer

[0040] 9 P-type waveguide layer

[0041] 10 P-type ohmic contact layer

[0042] Steps S1 to S4 DETAILED DESCRIPTION

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

[0044] See also Figures 1 to 8 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0045] This embodiment provides a method for manufacturing a semiconductor laser. Figure 1 , including the following steps:

[0046] S1: providing an InP substrate;

[0047] S2: forming a plurality of openings arranged at intervals in the InP substrate, wherein the openings extend from the upper surface of the InP substrate to the interior of the InP substrate;

[0048] S3: forming a buffer layer on the InP substrate, wherein the buffer layer covers the opening to form an air gap, and the material of the buffer layer includes InGaAs and / or InGaAsP;

[0049] S4: forming a laser functional stack on the buffer layer.

[0050] The method for manufacturing the semiconductor laser of this embodiment is described in detail below with reference to the specific drawings.

[0051] First, see Figure 2 , perform step S1: provide an InP substrate 1.

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

[0053] Next, see Figures 3 to 5, executing step S2: forming a plurality of openings 3 arranged at intervals in the InP substrate 1 , wherein the openings 3 extend from the upper surface of the InP substrate 1 to the interior of the InP substrate 1 .

[0054] As a specific example, a method for forming a plurality of the openings 3 arranged at intervals 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, wherein a plurality of the openings 3 are evenly distributed in the InP substrate 1; any suitable etching process may be used, for example, the InP substrate 1 is etched using an ICP etching process, and 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 the opening 3 is formed, the mask layer 2 is removed; the mask layer 2 can be removed in any suitable manner, for example, a BOE solution can be used to remove the mask layer 2; preferably, after removing the mask layer 2, the surface of the InP substrate can be cleaned with concentrated sulfuric acid and then dried with isopropyl alcohol (IPA).

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

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

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

[0060] Next, see Figure 7 , executing step S3: forming a buffer layer 4 on the InP substrate 1, the buffer layer 4 covers 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 a MOCVD chamber, and the temperature is raised to 560° C. to 590° C. 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. During the formation of the buffer layer 4, the opening 3 is covered to be completely closed 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 air gaps can release stress, so that the buffer layer 4 is subjected to a compressive strain of 0.8-1.2% compared to the InP substrate 1, or is subjected to a gradually increasing gradient strain of 0-1.2%, or has a dislocation-turning superlattice strain structure, that is, the strain of the buffer layer 4 is less than 2% (maximum 1.2%).

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

[0065] Next, see Figure 8 , executing step S4: forming a laser functional stack on the buffer layer 4.

[0066] As an example, the laser functional stack includes 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 stacked from bottom to top, 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 of different components, 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, the strain of other layers in the laser functional stack except the quantum well layer 7 relative to the buffer layer 4 is less than ±0.1%, and the strain of the quantum well layer 7 relative to the buffer layer 4 is 1% to 1.5%. Under the effect of 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 an energy barrier, confine carriers and light fields, and improve 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, a P-type ohmic contact layer 10 is formed. The P-type ohmic contact layer 10 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.

[0071] As an example, the method further includes 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 is electrically connected to the P-type ohmic contact layer 10, and the second electrode is located below the InP substrate 1 and is electrically connected to the InP substrate 1, and the first electrode and the second electrode are used to electrically connect the semiconductor laser to a power source and / or an external device.

[0072] At this point, a semiconductor laser has been produced. Figure 8 The semiconductor laser includes an InP substrate 1, a buffer layer 4 and a laser functional stack. The InP substrate 1 is provided with a plurality of openings 3 arranged at intervals, and the openings 3 extend from the upper surface of the InP substrate 1 to the interior of the InP substrate 1; the buffer layer 4 is located above the InP substrate 1, and the buffer layer 4 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 adopts a (100) crystal plane substrate. The (100) crystal plane is conducive to 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-100nm, and the spacing between adjacent openings 3 is 100nm-200nm. When the shape of the opening 3 is circular, its diameter is 50-100nm; when the shape of the opening 3 is square, its side length is 50-100nm, and the side length is parallel or perpendicular to the

[110] crystal direction of the InP substrate 1.

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

[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 the air gap can release stress, so that the buffer layer 4 is subjected to a compressive strain of 0.8-1.2% compared to the InP substrate 1, or is subjected to a gradually increasing gradient strain of 0-1.2%, or has a dislocation-turning superlattice strain structure, that is, the strain of the buffer layer 4 is less than 2% (maximum 1.2%).

[0078] As an example, the laser functional stack includes 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 stacked from bottom to top, 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 of different components, 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, the strain of other layers in the laser functional stack except the quantum well layer 7 relative to the buffer layer 4 is less than ±0.1%, and the strain of the quantum well layer 7 relative to the buffer layer 4 is 1% to 1.5%. Under the effect of 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 an energy barrier, confine carriers and light fields, and improve 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 further included. The P-type ohmic contact layer 10 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 step of forming a first electrode and a second electrode (not shown in the figure) is also included, wherein the first electrode is located above the P-type ohmic contact layer 10 and is electrically connected to the P-type ohmic contact layer 10, and the second electrode is located below the InP substrate 1 and is electrically connected to the InP substrate 1, and the first electrode and the second electrode are used to electrically connect the semiconductor laser to a power supply and / or an external device.

[0084] In summary, in the semiconductor laser and the manufacturing method of the present invention, an air gap is introduced 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, so as to obtain a laser epitaxial structure having both large strain and high-quality material properties on the InP substrate. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0085] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for manufacturing a semiconductor laser, characterized in that: The following steps are involved: Providing an InP substrate; forming a plurality of openings arranged at intervals in the InP substrate, wherein the openings extend from the upper surface of the InP substrate to the interior of the InP substrate; A buffer layer is formed on the InP substrate, wherein the buffer layer covers the opening to form an air gap, and the material of the buffer layer includes InGaAs and / or InGaAsP; A laser function stack is formed on the buffer layer.

2. The method for manufacturing 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 manufacturing 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 manufacturing a semiconductor laser according to claim 1, characterized in that: The laser functional stack includes 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 stacked from bottom to top, wherein the material of the N-type waveguide layer includes InGaAsP, the material of the N-type confinement layer includes InGaAsP, the material of the quantum well layer includes InGaAs, the material of the P-type confinement layer includes InGaAsP, and the material of the P-type waveguide layer includes InGaAsP.

5. The method for manufacturing a semiconductor laser according to claim 1, characterized in that: The light emission wavelength of the semiconductor laser is 2.1 μm to 2.3 μm.

6. A semiconductor laser, characterized in that: include: An InP substrate, wherein a plurality of openings arranged at intervals are provided in the InP substrate, and the openings extend from the upper surface of the InP substrate to the interior of the InP substrate; A buffer layer, 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; The laser functional stack is located above the buffer layer.

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

8. The semiconductor laser according to claim 6, characterized in that: The depth of the opening is 500nm-2000nm, and the thickness of the buffer layer is not less than 300nm.

9. The semiconductor laser according to claim 6, characterized in that: The laser functional stack includes 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 stacked from bottom to top, wherein the material of the N-type waveguide layer includes InGaAsP, the material of the N-type confinement layer includes InGaAsP, the material of the quantum well layer includes InGaAs, the material of the P-type confinement layer includes InGaAsP, and the material of the P-type waveguide layer includes InGaAsP.

10. The semiconductor laser according to claim 6, characterized in that: The light emission wavelength of the semiconductor laser is 2.1 μm to 2.3 μm.

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