KR100776099B1 - Dual type laser diode and fabricating method therefor - Google Patents

Abstract

Dual type laser diode according to the present invention, the distribution feedback oscillator for generating a single mode laser light; Fabry-Perot oscillator for generating a multi-mode laser light; And an electrode for injecting current into the distributed feedback oscillator and the Fabry-Perot oscillator, wherein the distributed feedback oscillator, the Fabry-Perot oscillator, and the electrode are provided on one chip.

In addition, the dual type laser diode manufacturing method according to the present invention, forming a protective film on the base substrate; Selectively removing a portion of the protective film; Etching a substrate in the protective film removing region to form a diffraction grating; Removing the remaining portion of the protective film to expose the surface of the substrate; Growing a double heterostructure layer on a surface of the substrate other than the diffraction grating and the diffraction grating; Growing a cladding layer over the double heterostructure layer; And forming an electrode on an upper side of the clad layer and a lower side of the substrate.

Distributed Feedback Laser Diode, Fabry-Perot Laser Diode, Multiple Quantum Well, Diffraction Grating, DH, Photolithography, Mesa Structure

Description

Dual type laser diode and its manufacturing method {DUAL TYPE LASER DIODE AND FABRICATING METHOD THEREFOR}

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to

1 is a block diagram of a general Fabry-Perot laser diode oscillator.

2 is a spectrum diagram showing oscillation characteristics of a Fabry-Perot laser diode.

3 is a configuration diagram of a general distributed feedback laser diode oscillator.

4 is a spectrum diagram showing oscillation characteristics of a distributed feedback laser diode;

5 is a perspective view showing a dual type laser diode according to a preferred embodiment of the present invention.

6 is a schematic plan view of a dual type laser diode according to a preferred embodiment of the present invention.

7 to 19 are diagrams illustrating a manufacturing process of a dual type laser diode according to a preferred embodiment of the present invention.

<Description of main reference numerals in the drawings>

100: N-type InP substrate 101: distributed feedback oscillator

102: active layer 103: diffraction grating

104: Fabry-Perot oscillator 107: current blocking layer

108: cladding layer 109: 'U' channel

112,112 ': P-type electrode 113: N-type electrode

200: shield

The present invention relates to a laser diode and a method of manufacturing the same, and more particularly, to a dual type laser diode having both a Fabry-Perot oscillation mode and a distributed feed back oscillation mode; It relates to a manufacturing method.

Among the semiconductor laser diodes, the Fabry-Perot laser diode (FP-LD) is a double heterostructure layer having a multi-quantum well structure between the P-type InP substrate 10 and the N-type InP substrate 12 as shown in FIG. 1. A double heterostructure layer (DH layer) 11 is provided, and a resonator is formed by mutually opposite cleaved faces to provide a multi-mode laser oscillation characteristic.

FP-LD has the same optical loss for all wavelengths resonating in the resonator, so that the difference in optical loss and optical gain at any two adjacent wavelengths is minute and much around the gain peak wavelength. It shows the multi-mode spectral characteristics (see FIG. 2) at which the wavelength oscillates.

Meanwhile, the DF-LD and the distributed feedback laser diode (DFB-LD), which are widely used in communication optical modules, further include a diffracting grating 13 under the DH layer 11 as shown in FIG. 3. This provides a single mode laser oscillation characteristic that selectively reflects light in a specific wavelength range.

Unlike FP-LD, DFB-LD differs in the light loss of all wavelengths resonating in the resonator due to the grating structure, and the light loss and the light gain difference between the two wavelengths near the gain peak are large. This oscillation shows the single mode spectral characteristics (see FIG. 4).

As described above, FP-LD and DFB-LD have completely different structures and properties. For this reason, the conventional optical module for communication has been provided in a TO-CAN type in which FP-LD or DFB-LD is selected and packaged together with a stem and a lens.

However, in the case of manufacturing a package for each type of laser diode as described above, the number of parts or manufacturing cost is high, and it is difficult to miniaturize an optical module.

The present invention has been made to solve the above problems, to provide a laser diode having a structure that can provide both the oscillation characteristics of FP-LD and DFB-LD in one device and its manufacturing method There is this.

In order to achieve the above object, the dual type laser diode according to the present invention has a configuration in which a distributed feedback oscillator and a Fabry-Perot oscillator are disposed in one chip.

That is, the dual type laser diode according to a preferred embodiment of the present invention, the distribution feedback oscillator for generating a single mode laser light; Fabry-Perot oscillator for generating a multi-mode laser light; And an electrode for injecting current into the distributed feedback oscillator and the Fabry-Perot oscillator, wherein the distributed feedback oscillator, the Fabry-Perot oscillator, and the electrode are provided on one chip.

The distribution feedback oscillator and the Fabry-Perot oscillator are preferably provided with an active layer having a multi-quantum well structure for converting the injected current into light.

The dual type laser diode includes an InP substrate serving as a common base of the distribution feedback oscillation unit and the Fabry-Perot oscillation unit, and between the active layer and the InP substrate of the distribution feedback oscillation unit, any one of light generated in the active layer It is preferable that the; diffraction grating for selectively reflecting the wavelength.

Preferably, the double hetero structure layer having the active layer is formed of a mesa structure, formed on the InP substrate, the current blocking layer extending to both sides of the mesa structure; A cladding layer covering an upper portion of the current blocking layer and an active layer; And a 'U' channel spaced apart from the active layer to be parallel to the mesa direction and formed by etching the cladding layer and the current blocking layer to the surface of the substrate.

It is preferable that 1 to 4 'U' channels are formed between the distribution feedback oscillator and the Fabry-Perot oscillator.

It is preferable that the distance between a distribution feedback oscillation part and a Febri-Perot oscillation part is 30-100 micrometers.

According to another aspect of the invention, the first step of forming a protective film on the base substrate; Selectively removing a portion of the protective film in a vertical direction in which a diffraction grating pattern is to be formed; Forming a diffraction grating by etching the substrate of the protective film removing region; Removing a remaining portion of the passivation layer to expose a surface of the substrate; A fifth step of growing a diffraction grating and a double heterostructure layer having an active layer on a surface of the substrate other than the diffraction grating; A sixth step of growing a cladding layer on the double heterostructure layer; And a seventh step of forming an electrode on the clad layer and on the bottom of the substrate.

In the first step, SiO ₂ Or preferably by depositing a Si ₃ N ₄ to form the protective film.

The second step is performed by a photolithography process, and in the third step, the substrate is etched according to the diffraction grating pattern by performing a laser holographic photolithography process and an etching process using an HBr-based etching solution.

In the fifth step, it is preferable to grow the double heterostructure layer collectively on the diffraction grating and the substrate surface other than the diffraction grating, and then selectively etch the double hetero structure layer for each oscillation region.

Preferably, the fifth step may be performed to etch the double hetero structure layer into a mesa structure.

After the sixth step, forming a 'U' channel between the oscillation regions may be further performed.

In the fifth step, the double heterostructure layer is etched so that the distance between the distributed feedback oscillator including the diffraction grating and the Fabry-Perot oscillator without the diffraction grating is 30 to 100 μm. It is preferable.

In the seventh step, the electrode formed on the clad layer is divided to correspond to the distributed feedback oscillation unit and the Fabry-Perot oscillation unit, the electrode formed under the substrate is the Fabry-Perot oscillation unit and the distribution feedback oscillation unit It is preferable to form in common with respect to.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

5 is a cutaway perspective view showing the configuration of a dual type laser diode according to a preferred embodiment of the present invention.

Referring to FIG. 5, a dual type laser diode according to a preferred embodiment of the present invention includes an N-type InP substrate 100 and a distributed feedback oscillator 101 and Fabry- which are provided on the N-type InP substrate 100. A ferot oscillation unit 104 and electrodes 112, 112 ′ and 113 for injecting current into the oscillation units 101 and 104 are included.

The distribution feedback oscillator 101 is an oscillation part for generating a single mode laser light when the current is injected. The active layer 102 and the active layer 102 and the N-type InP of the multi-quantum well structure convert the injected current into light. A diffraction grating 103 is provided between the substrates 100 to selectively reflect any one wavelength of light generated by the active layer 102.

The Fabry-Perot oscillator 104 is formed on the N-type InP substrate 100 so as to be spaced apart from the distributed feedback oscillator 101 by a predetermined distance, and oscillates during current injection to generate a multi-mode laser light. Like the distributed feedback oscillator 101, the Fabry-Perot oscillator 104 is provided with an active layer 102 having a multi-quantum well structure for converting an injected current into light, but does not include a diffraction grating.

The oscillation wavelengths of the distribution feedback oscillator 101 and the Fabry-Perot oscillator 104 are composed of a double heterostructure layer (DH layer) and an diffraction grating 103 (distribution feedback oscillator 101) including the active layer 102. ) Is determined for various optical communication wavelengths. As the preferable light wavelength, 1310 nm, 1490 nm, 1510 nm, 1550 nm, etc. are mentioned.

Distance between distribution feedback oscillator 101 and Fabry-Perot oscillator 104 (L _{1 in} FIG. 19) Reference) is determined to be 30 ~ 100㎛ according to the optimum conditions of the selective etching process for forming the diffraction grating (103). Further, the horizontal length (see L _{2 in} FIG. 19) from the edge of the distributed feedback oscillator 101 to the edge of the Fabry-Perot oscillator 104, that is, the length perpendicular to the light oscillation direction is 200 to 400 μm. It is preferred to be determined.

The DH layer including the distribution feedback oscillator 101 and the active layer 102 of the Fabry-Perot oscillator 104 is formed in a mesa structure, and the current blocking layer 107 is in contact with both sides of each mesa structure to inject the injected current. Is prevented from leaking to regions other than the active layer 102. Here, the current blocking layer 107 is formed on the N-type InP substrate 100 and extends to the side of the mesa structure, and is formed on the P-type current blocking layer 105 and the mesa structure. It has a laminated structure of the N-type current blocking layer 106 extending to the side of.

The P-type InP cladding layer 108 is provided on the current blocking layer 107 and the active layer 102, and the cladding layer 108 is disposed between the distribution feedback oscillation portion 101 and the Fabry-Perot oscillation portion 104. A 'U'-shaped channel 109 formed by etching the current blocking layer 107 is provided to reduce the parasitic capacitance. Here, the 'U'-shaped channel 109 is the distribution feedback oscillator 101 and the Fabry-Perot oscillator (in consideration of the optimum conditions of the selective etching process for forming the diffraction grating 103, and the reduction efficiency of the parasitic capacitance) It is preferable that 1-4 pieces are formed between 104).

The 'U' channel 109 is spaced apart from the active layer 102 to be parallel to the mesa direction, and is formed by etching the cladding layer 108 and the current blocking layer 107 to the surface of the N-type InP substrate 100. Can be.

After the ohmic contact layer 110 and the surface protection insulating film 111 are formed on the cladding layer 108, the distribution feedback oscillator 101 and the Fabry- are formed by photolithography and metal film deposition. P-type electrodes 112 and 112 'are deposited to correspond to the ferret oscillator 104 (see FIG. 6), and an N-type electrode 113, which is a common electrode, is deposited on the bottom surface of the N-type InP substrate 100.

According to the connection relationship between the U-shaped channel 109, the P-type electrodes 112 and 112 ′, and the N-type electrode 113 as described above, the distributed feedback oscillator 101 or Fabry- is applied to the N-type electrode 113. By selectively shorting the P-type electrodes 112 and 112 'of the ferret oscillator 104, the distribution feedback oscillator 101 and the Febri-Perot oscillator 104 can be driven independently.

As the P-type electrodes 112 and 112 'and the N-type electrode 113, multilayer electrodes of Ti (titanium) / Pt (platinum) / Au (gold) are preferably used, and Cr (chromium) / Au (gold) of Double layer electrodes can be used. Here, in the case of the Ti / Pt / Au multilayer electrode, the thickness of the Ti film is preferably 300 to 500 kPa, the thickness of the Pt film is 400 to 700 kPa, and the thickness of the Au film is 5000 to 8000 kPa. In the case of the Cr / Au double layer electrode, the thickness of the Cr film is preferably 500 to 700 GPa, and the thickness of the Au film is 5000 to 8000 GPa.

After the formation of the P-type electrodes 112 and 112 'and the N-type electrode 113, the dual-type laser diode is cut in units of chip bars, and one side of the cut surface is coated with the antireflective film 114, and the other side. The silver high reflection film 115 is coated.

Next, a method of manufacturing a dual type laser diode according to a preferred embodiment of the present invention will be described with reference to FIGS. 7 to 19.

First, as shown in FIG. 7, SiO ₂ is formed on an N-type InP substrate 100. Alternatively, after forming the protective film 200 by depositing Si ₃ N ₄ , a process of partially removing the protective film 200 is performed as shown in FIG. 8. The deposition of the protective film 200 may be performed using a process such as conventional PECVD (Plasma Chemical Vapor Deposition), LPCVD (Low Pressure Chemical Vapor Deposition), Sputtering, etc., and the deposition thickness is 500 to 2000Å. desirable.

Where SiO ₂ , Si ₃ N ₄ Such a silicon-based material does not form a composite with an InP-based or InGaAsP-based substrate, and does not react with HBr (hydrogen bromide) used in a general grating process, and thus is suitable as a protective film 200 material.

Removal of the protective layer 200 may be performed by a conventional photo lithography process. That is, after coating the PR film on the upper surface of the protective film 200 using a spin coater and a PR (Photo resister) used in the semiconductor process, using an aligner and a photo mask for photolithography Alignment and exposure are performed on the PR according to the pattern of the diffraction grating 103.

Subsequently, the exposed PR film is removed using a developer, and thus the stripe-shaped protective film exposed is removed using chemicals such as BOE (Buffered Oxide Etchant), DML equipment such as RIE, and the like.

After the protective film 200 is removed in the vertical direction in which the diffraction grating 103 pattern is to be formed, the photolithography process and the etching process are performed again on the stripe-shaped protective film 200 to remove the region shown in FIGS. 9 and 10. As described above, the process of forming the diffraction grating 103 proceeds. That is, after PR coating on the surface of the N-type InP substrate 100 having a stripe shape, a pattern for etching the diffraction grating 103 is formed using a laser hologram and a PR developer, and an HBr-based etching solution is used. The diffraction grating 103 is selectively etched.

At this time, the protective film 200 blocked on the remaining portion of the N-type InP substrate 100 does not respond to the HBr-based etching solution as described above, so that the selective etching of the diffraction grating 103 is possible. . FIG. 11 shows an actual photograph of a diffraction grating 103 having a repeated concave-convex structure formed by etching a wafer-shaped InP substrate.

Next, as shown in FIG. 12, a process of exposing the substrate surface 202 of the region by removing the remaining portion of the protective film 200 with BOE or the like is performed, and then as shown in FIG. 13, a diffraction grating. A step of growing the 103 and the DH layer 102 'including the active layer 102 on the surface of the substrate other than the diffraction grating 103 is performed.

The DH layer 102 'is grown in MOCVD (Modified Chemical Vapor Deposition) equipment, and after the growth process is completed, the protective film 200 is deposited on the DH layer 102' and shown in FIG. As described above, a wafer etching process of forming a mesa structure for each of the oscillation regions 101 and 104 is performed. In FIG. 14, the side where the diffraction grating 103 is present becomes the distributed feedback oscillation unit 101, and the side where the diffraction grating 103 is absent becomes the Fabry-Perot oscillating unit 104.

The protective film 200 is SiO ₂ , Si ₃ N ₄ It is preferably deposited through a process such as PECVD, LPCVD, sputtering, etc. using a silicon-based material as a material, and the deposition thickness thereof is preferably 500 to 2000 GPa. In addition, the mesa structure is formed by a photolithography process and an etching process using an HBr-based etching solution similarly to the etching process of the diffraction grating 103 described above.

Thereafter, as shown in FIG. 15, a P-type current blocking layer 105 is formed by growing P-type InP on the N-type InP substrate 100 so as to contact both sides of the mesa, and again, as shown in FIG. 16. A process of forming an N-type current blocking layer 106 by growing an N-type InP on the type current blocking layer 105 is performed.

After forming the current blocking layer 107, as shown in FIG. 17, a cladding layer 108 of P-type InP is grown on the current blocking layer 107 and the DH layer 102 ', and then shown in FIG. As shown in FIG. 18, a process of etching the 'U'-shaped channel 109 is performed between the distribution feedback oscillator 101 and the Fabry-Perot oscillator 104.

The 'U' channel 109 is etched to be parallel to the mesa direction but its cross section is substantially 'U' shaped, and the optimum conditions of the selective etching process for forming the diffraction grating 103 and the reduction efficiency of the parasitic capacitance In consideration of the above, it is preferable that two (see FIG. 18) or three (see FIG. 19) are formed between the distributed feedback oscillator 101 and the Fabry-Perot oscillator 104, and the channel width thereof is It is preferable to form in 10-40 micrometers. Here, the 'U'-shaped channel 109 may be formed to etch the cladding layer 108 and the current blocking layer 107 to the surface of the N-type InP substrate 100.

After the etching of the 'U'-shaped channel 109 is completed, forming an ohmic contact layer 110 and a surface protection insulating film 111 on the clad layer 108, photolithography and metal film deposition process Depositing the P-type electrodes 112 and 112 'to correspond to the distributed feedback oscillator 101 and the Fabry-Perot oscillator 104, and an N-type electrode 113 which is a common electrode on the bottom surface of the N-type InP substrate 100; ) Is carried out.

The deposition process of the P-type electrodes 112 and 112 'and the N-type electrode 113 is performed using a multilayer electrode of Ti / Pt / Au or a double layer electrode of Cr / Au, and particularly, the' U'-shaped channel 109 In order to compensate for the decrease in the deposition thickness, the deposition on the sidewall portion is preferably carried out two or more times by tilting the deposition angle, for which a plating process may be used.

After the deposition of the P-type electrodes 112 and 112 ′ and the N-type electrode 113 is completed, the wafer is cut in units of chip bars, and one side of the cut surface coats the antireflective film 114. On the other hand, when the high reflection film 115 is coated, a dual type laser diode as shown in FIG. 5 is manufactured.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

The dual type laser diode according to the present invention is manufactured in a system on a chip (SoC) type to provide an effect of mounting two light sources in a chip having distribution feedback oscillation characteristics and Fabry-Perot oscillation characteristics.

Therefore, when the present invention is applied to an ultra-high speed optical communication system that needs to mount a large number of optical modules, it can contribute to reduction of system construction cost and miniaturization of the device.

Claims (14)

A distributed feedback oscillator for generating a single mode laser light; Fabry-Perot oscillator for generating a multi-mode laser light; And An electrode for injecting current into the distribution feedback oscillator and the Fabry-Perot oscillator; The distributed feedback oscillator, the Fabry-Perot oscillator and the electrode are provided on one chip, The dual type laser diode, characterized in that 1 to 4 'U' channel is formed between the distributed feedback oscillator and the Fabry-Perot oscillator. The method of claim 1, The dual-type laser diode of the distributed feedback oscillator and the Fabry-Perot oscillator are provided with an active layer having a multi-quantum well structure for converting the injected current into light. The method of claim 2, An InP substrate serving as a common base of the distributed feedback oscillator and the Fabry-Perot oscillator; And a diffraction grating selectively reflecting any wavelength of light generated in the active layer between the active layer of the distributed feedback oscillator and the InP substrate. The method of claim 3, The double hetero structure layer having the active layer is formed of a mesa structure, A current blocking layer formed on the InP substrate and extending to both sides of the mesa structure; And And a cladding layer covering an upper portion of the current blocking layer and the active layer. And the 'U' channel is spaced apart from the active layer to be parallel to the mesa direction and formed by etching the cladding layer and the current blocking layer to the surface of the substrate. delete The method of claim 4, wherein Dual type laser diode, characterized in that the distance between the distribution feedback oscillator and the Fabry-Perot oscillator is 30 ~ 100㎛. Forming a passivation layer on the base substrate; Selectively removing a portion of the protective film according to a diffraction grating pattern; Forming a diffraction grating by etching the substrate of the protective film removing region; Removing a remaining portion of the passivation layer to expose a surface of the substrate; A fifth step of growing a diffraction grating and a double heterostructure layer having an active layer on a surface of the substrate other than the diffraction grating; A sixth step of growing a cladding layer on the double heterostructure layer; And A seventh step of forming an electrode on the clad layer and on the lower part of the substrate; After the sixth step, forming 1 to 4 'U'-shaped channels between the diffraction gratings and the oscillation regions corresponding to the portions other than the diffraction gratings; Manufacturing method. The method of claim 7, wherein In the first step, SiO ₂ Or depositing Si ₃ N ₄ to form the protective film. The method of claim 8, The second step is performed by a photolithography process, The method of claim 3, wherein the substrate is etched according to the diffraction grating pattern by performing a laser holographic photolithography process and an etching process using an HBr-based etching solution. The method of claim 7, wherein In the fifth step, the double hetero-structure layer is grown on the diffraction grating and the substrate surface other than the diffraction grating in a batch, and then the double hetero-structure layer is selectively etched for each oscillation region. Method for manufacturing a dual type laser diode. The method of claim 10, In the fifth step, the dual-type laser diode manufacturing method, characterized in that for etching the mesa structure. delete The method of claim 10, wherein in the fifth step, Dual type etching is performed on the double hetero structure layer such that the distance between the distribution feedback oscillator including the diffraction grating and the Fabry-Perot oscillator not including the diffraction grating is 30 to 100 μm. Method of manufacturing a laser diode. The method of claim 13, wherein in the seventh step, The electrode formed on the clad layer is divided to correspond to the distribution feedback oscillation part and the Fabry-Perot oscillation part, The electrode formed under the substrate is formed in common with respect to the Fabry-Perot oscillation portion and the distribution feedback oscillation portion.

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