A high performance DFB laser structure and its growth method

Abstract

A high-performance DFB laser structure comprises an InP substrate, on which an N‑InP buffer layer, an N‑AlInAs epitaxial layer, an N‑AlGaInAs waveguide layer, an AlGaInAs MQW, a P‑AlGaInAs waveguide layer, a P‑AlInAs limiting layer, a P‑InP limiting layer, a grating layer, an InGaAsP barrier transition layer, and an InGaAs ohmic contact layer are deposited in sequence from bottom to top by MOCVD; a layer of N‑InAlAsP is inserted between the N‑InP buffer layer and the N‑AlInAs epitaxial layer; a high-performance DFB laser structure designed in this scheme, wherein a layer of N‑InAlAsP is inserted between the N‑InP buffer layer and the N‑InAlAs epitaxial layer, can obtain a high-volume MQW, improve the reliability of the laser, and can also smooth the conduction band energy level difference between the N‑InP buffer layer and the N‑InAlAs epitaxial layer, reduce the resistance of the DFB laser, and improve the performance of the DFB laser.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor optoelectronics, and in particular relates to a high-performance DFB laser structure and a growth method thereof. Background Art

[0002] As 5G commercialization approaches, dynamic single-mode distributed feedback lasers (DFB-LDs) with narrow linewidth, high side mode suppression ratio and high modulation rate have become the preferred light sources. DFB uses grating modulation with periodic changes in refractive index, has good single longitudinal mode characteristics, side mode suppression ratio of more than 50dB, and modulation rate of more than 50Gb / s, which can meet the high-speed / low-latency application requirements of 5G mobile networks. DFB lasers used in high-speed optical communications generally use InP as the growth substrate and AlGaInAs quantum wells as the active layer. Traditional high-speed AlGaInAs-based DFB lasers grow InAlAs materials directly on InP substrates, and there will be atomic nonlinear mixing at the As-P switching interface; for example, the residual P atoms will inevitably be incorporated into the bulk InAlAs material, causing lattice mismatch of the InAlAs material.

[0003] At the same time, the DFB laser used in 5G mobile communication systems has an operating wavelength of 1200~1600nm, an operating temperature of -40~90℃, and a modulation rate of 10Gb / s~56Gb / s. It is difficult to use MOCVD equipment on InP substrates for the following reasons:

[0004] (1) The oxide layer that may exist on the surface of the InP substrate leads to poor quality of MQW materials; (2) Impurities doped in the non-intrinsic InP substrate will be released during growth, affecting the growth quality of the material; (3) Atomic nonlinear mixing will exist at the As-P switching interface; (4) When the N-InP and N-InAlAs epitaxial layers are close to each other, heterogeneous band steps will be formed, affecting the transmission of carriers, resulting in an increase in the parasitic resistance of the DFB laser and affecting the device performance.

[0005] Therefore, this scheme proposes a DFB laser structure, in which an N-InAlAsP epitaxial layer is inserted between the N-InP layer and the N-InAlAs layer. On the one hand, a high-yield MQW can be obtained to improve the reliability of the laser; on the other hand, the conduction band energy level difference between the N-InP and N-InAlAs epitaxial layers can be smoothed, the resistance of the DFB laser can be reduced, and the performance of the DFB laser can be improved; thereby effectively solving the above technical problems. Summary of the invention

[0006] In order to overcome the above-mentioned deficiencies in the prior art, the present invention aims to provide a high-performance DFB laser structure.

[0007] To achieve the above-mentioned purpose and other related purposes, the technical solution provided by the present invention is: a high-performance DFB laser structure, comprising an InP substrate, on which are deposited, from bottom to top, an N-InP buffer layer, an N-AlInAs epitaxial layer, an N-AlGaInAs waveguide layer, an AlGaInAs MQW, a P-AlGaInAs waveguide layer, a P-AlInAs confinement layer, a P-InP confinement layer, a corrosion barrier layer, an InP connection layer, a grating layer, an InGaAsP barrier transition layer, and an InGaAs ohmic contact layer by MOCVD; characterized in that: a layer of N-InAlAsP is inserted between the N-InP buffer layer and the N-AlInAs epitaxial layer.

[0008] Preferably, the N-InAlAsP material is represented by (Al0.48In0.52As)X(InP)(1-X), wherein X represents the proportion of Al0.48In0.52As material in the AlInAsP material, and its value is between 0.5-0.99.

[0009] Preferably, the Al0.48In0.52As material is lattice matched with InP.

[0010] Preferably, the N-InAlAsP material is grown by MOCVD.

[0011] Preferably, the conductivity of the InP substrate is 2-8x10 18 cm -2 .

[0012] The present invention also discloses a method for preparing a high-performance DFB laser, which comprises the following steps:

[0013] Step 1: With a conductivity of 2-8x10 18 cm -2 InP was used as the growth substrate and placed in the MOCVD system for growth. The reaction chamber pressure was 50 mbar, the growth temperature was 670 ° C, hydrogen was used as the carrier gas, trimethyl indium, trimethyl gallium, trimethyl aluminum, diethyl zinc, silane, arsine and phosphine were used as the reaction source gases, and the N-InP buffer layer was first grown. The flow rate of trimethyl indium was 300 sccm, and the flow rate of phosphine was 1800 sccm.

[0014] Step 2: After the growth of the N-InP buffer layer is completed, trimethyl indium and silane are turned off, and arsine is introduced with a flow rate of 600 sccm. At the same time, the flow rate of phosphine is reduced; after 3 minutes, trimethyl indium and silane are introduced to start growing the N-AlInAsP epitaxial layer;

[0015] Step 3: Based on step 2, the source flow rate of trimethyl indium is 100 sccm. After 200 seconds, turn off the phosphine.

[0016] The source flow rates of trimethylaluminum, trimethylindium and silane are continuously increased to start growing the N-AlInAs epitaxial layer; then the N-AlGaInAs waveguide layer, AlGaInAs MQW, P-AlGaInAs waveguide layer, P-AlInAs confinement layer, P-InP confinement layer are sequentially grown, and the grating is made;

[0017] Step 4: Finally, the InP connection layer, InGaAsP barrier transition layer, and InGaAs ohmic contact layer are grown by pulse deposition method.

[0018] Preferably, in step 2, the flow rate of phosphine is reduced, specifically, the flow rate of phosphine is reduced to 300 sccm.

[0019] Preferably, in the step 3, the Source flow rates of trimethylaluminum, trimethylindium and silane are continuously increased, and the flow rates are increased in a linear manner.

[0020] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0021] The present invention proposes a new DFB laser structure based on the traditional DFB laser structure, that is, inserting a layer of N-InAlAsP between the N-InP buffer layer and the N-InAlAs epitaxial layer, on the one hand, a high-yield MQW can be obtained, and the reliability of the laser can be improved; on the other hand, the conduction band energy level difference between the N-InP and N-InAlAs epitaxial layers can be smoothed, the resistance of the DFB laser can be reduced, and the performance of the DFB laser can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the epitaxial structure of the DFB laser of the present invention.

[0023] Figure 2 Schematic diagram of the energy band structure of the DFB laser of the present invention.

[0024] Figure 3 It is a schematic diagram of the growth of the AlInAsP epitaxial layer of the present invention.

[0025] In the above figures, there are InP substrate 001, N-InP buffer layer 002, N-AlInAsP insertion layer 101, N-AlInAs epitaxial layer 003, N-AlGaInAs waveguide layer 004, AlGaInAs MQW 005, P-AlGaInAs waveguide layer 006, P-AlInAs confinement layer 007, P-InP confinement layer 008, corrosion barrier layer 009, InP connection layer 010, grating layer 011, InGaAsP barrier transition layer 012, and InGaAs ohmic contact layer 013. DETAILED DESCRIPTION

[0026] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0027] See also Figure 1~Figure 3 . It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings in this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0028] Example: Figure 1 As shown, a high-performance DFB laser structure includes an InP substrate 001, on which are deposited, from bottom to top, an N-InP buffer layer 002, an N-AlInAs epitaxial layer 003, an N-AlGaInAs waveguide layer 004, an AlGaInAs MQW 005, a P-AlGaInAs waveguide layer 006, a P-AlInAs confinement layer 007, a P-InP confinement layer 008, a corrosion barrier layer 009, an InP connection layer 010, a grating layer 011, an InGaAsP barrier transition layer 012, and an InGaAs ohmic contact layer 013; and an N-InAlAsP insertion layer 101 is inserted between the N-InP buffer layer 002 and the N-AlInAs epitaxial layer 003.

[0029] The preferred implementation is:

[0030] like Figure 2As shown in Figure 2, after adding the AlInAsP insertion layer, the band structure is as follows: Figure 2 As shown (the corrosion barrier layer 009009 and above are not drawn). It can be seen that the conduction band of N-AlInAsP is located between N-InP and N-AlInAs, which is conducive to smoothing the energy band and reducing parasitic resistance. The quaternary compound AlInAsP that is lattice-matched with the InP substrate 001 can be represented by (Al0.48In0.52As)X(InP)(1-X), where X represents the proportion of Al0.48In0.52As (lattice-matched with InP) material in the AlInAsP material, and its value is between 0.5-0.99. Therefore, the bandgap width of the AlInAsP material is between AlInAs and InP.

[0031] The Al0.48In0.52As material is lattice matched with InP.

[0032] The N-InAlAsP material is grown by MOCVD.

[0033] The electrical conductivity of the InP substrate 001 is 2-8x1018cm-2.

[0034] The present invention also discloses a method for preparing a high-performance DFB laser, which comprises the following steps: Step 1: Using InP with a conductivity of 2-8x1018cm-2 as a growth substrate, placing it in an MOCVD system for growth, the reaction chamber pressure is 50mbar, the growth temperature is 670°C, hydrogen is used as a carrier gas, trimethylindium, trimethylgallium, trimethylaluminum, diethylzinc, silane, arsine and phosphine are used as reaction source gases, firstly growing an N-InP buffer layer 002, the flow rate of trimethylindium is 300sccm, and the flow rate of phosphine is 1800sccm; Step 2: After the growth of the N-InP buffer layer 002 is completed, turning off trimethylindium and silane, introducing arsine, and the flow rate of arsine is 600 sccm, and at the same time, the flow rate of phosphine is reduced; after 3 minutes, trimethylindium and silane are introduced to start growing the N-AlInAsP epitaxial layer; Step 3: Based on step 2, the Source flow rate of trimethylindium is 100sccm, and after 200 seconds, the phosphine is turned off; and the Source flows of trimethylaluminum, trimethylindium and silane are continuously increased to start growing the N-AlInAs epitaxial layer 003; then the N-AlGaInAs waveguide layer 004, AlGaInAs MQW 005, P-AlGaInAs waveguide layer 006, P-AlInAs confinement layer 007, P-InP confinement layer 008 are grown in sequence, and a grating is made; Step 4: Finally, the InP connection layer 010, the InGaAsP barrier transition layer 012, and the InGaAs ohmic contact layer 013 are grown by pulsed deposition.

[0035] The preferred implementation is as follows:

[0036] In step 2, the flow rate of phosphine is reduced, specifically, the flow rate of phosphine is reduced to 300 sccm.

[0037] Preferably, in the step 3, the Source flow rates of trimethylaluminum, trimethylindium and silane are continuously increased, and the flow rates are increased in a linear manner.

[0038] The epitaxial structure growth method provided by the present invention is as follows: Figure 3 As shown in FIG. 1 , the InP substrate 001 is placed in the MOCVD device. After the InP buffer layer is grown, an AlInAsP epitaxial layer of a certain thickness is grown at a low speed for a long time, and then an AlInAs epitaxial layer is grown at a variable speed. The growth process of the AlInAsP epitaxial layer is shown in FIG. Figure 3 It means: after the growth of N-InP buffer layer 002 is completed, the source flow of phosphine is first reduced, and then arsenic is introduced. After a period of time, trimethylindium, silane and trimethylaluminum are turned on to grow n-AlInAsP material. It is worth noting that the source flow of trimethylindium and silane when growing n-AlInAsP is much smaller than the source flow when growing InP. After growing AlInAsP, turn off the source of phosphine, and gradually increase the flow of trimethylindium, silane and trimethylaluminum to grow N-InAlAs material.

[0039] In summary, this embodiment has the following beneficial effects compared with the traditional solution:

[0040] 1. Inserting a layer of N-InAlAsP between the N-InP and N-InAlAs epitaxial layers can obtain high-yield MQW and improve the reliability of the laser.

[0041] 2. Inserting a layer of N-InAlAsP between the N-InP and N-InAlAs epitaxial layers can smooth the conduction band energy level difference between the N-InP and N-InAlAs epitaxial layers, reduce the resistance of the DFB laser, and improve the performance of the DFB laser.

[0042] 3. The N-InAlAsP material is grown at a low speed by MOCVD, and then N-AlInAs is gradually grown, which can improve the growth quality of the N-InAlAsP material.

[0043] 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 high-performance DFB laser structure, comprising an InP substrate, wherein the conductivity of the InP substrate is 2-8x10 18 cm -2 , on the InP substrate, N-InP buffer layer, N-AlInAs epitaxial layer, N-AlGaInAs waveguide layer, AlGaInAs MQW, P-AlGaInAs waveguide layer, P-AlInAs confinement layer, P-InP confinement layer, corrosion barrier layer, InP connection layer, grating layer, InGaAsP barrier transition layer, InGaAs ohmic contact layer are deposited in sequence from bottom to top by MOCVD; characterized in that: A layer of N-InAlAsP is inserted between the N-InP buffer layer and the N-AlInAs epitaxial layer. The N-InAlAsP material is (Al 0.48 In 0.52 As) X (InP) (1-X) Indicates, where X represents Al in AlInAsP material 0.48 In 0.52 The ratio of As material is between 0.5-0.99, and the Al 0.48 In 0.52 The As material is lattice matched with InP, the N-InAlAsP material is grown by MOCVD, the N-InAlAsP material is grown at a low speed, and the N-AlInAs epitaxial layer is grown gradually.

2. A method for preparing a high-performance DFB laser, characterized in that: It includes the following steps: Step 1: With a conductivity of 2-8x10 18 cm -2 InP was used as the growth substrate and placed in the MOCVD system for growth. The reaction chamber pressure was 50 mbar, the growth temperature was 670 ° C, hydrogen was used as the carrier gas, trimethyl indium, trimethyl gallium, trimethyl aluminum, diethyl zinc, silane, arsine and phosphine were used as the reaction source gases, and the N-InP buffer layer was first grown. The flow rate of trimethyl indium was 300 sccm, and the flow rate of phosphine was 1800 sccm. Step 2: After the growth of the N-InP buffer layer is completed, trimethyl indium and silane are turned off, and arsine is introduced, and the flow rate of arsine is 600 sccm. At the same time, the flow rate of phosphine is reduced; after 3 minutes, trimethyl indium and silane are introduced to start growing the N-AlInAsP epitaxial layer, and the N-InAlAsP material grows at a low speed; Step 3: Based on step 2, the source flow rate of trimethylindium is 100 sccm. After 200 seconds, turn off the phosphine. The flow rates of trimethylaluminum, trimethylindium and silane are continuously increased to start growing an N-AlInAs epitaxial layer, which grows gradually; then, an N-AlGaInAs waveguide layer, an AlGaInAs MQW, a P-AlGaInAs waveguide layer, a P-AlInAs confinement layer, and a P-InP confinement layer are sequentially grown, and a grating is manufactured; Step 4: Finally, the InP connection layer, InGaAsP barrier transition layer, and InGaAs ohmic contact layer are grown by pulse deposition method.

3. A method for preparing a high performance DFB laser according to claim 2, characterized in that: In step 2, the flow rate of phosphine is reduced, specifically, the flow rate of phosphine is reduced to 300 sccm.

4. The method for preparing a high performance DFB laser according to claim 2, characterized in that: In step 3, the source flow rates of trimethylaluminum, trimethylindium and silane are continuously increased, and the flow rates are increased in a linear manner.

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