TWI811802B - Ridge/Buried Hybrid DFB Semiconductor Laser Epitaxial Manufacturing Method and DFB Semiconductor Laser Structure Made Using It - Google Patents

Abstract

The invention is a ridge/buried hybrid DFB semiconductor laser epitaxial manufacturing method. It sequentially epitaxially generates an N-type material area, an active area and a P-type material area on a substrate to form a pair of heterogeneous materials. structure, and the P-type material region has an etching stop layer and a P-type upper isolation layer in order from bottom to top. A (grating) tunnel junction (TJ) layer is disposed adjacent to the P-type upper isolation layer, and the TJ layer and the P-type upper isolation layer are etched and end at the etching stop layer to form a spine, so that the active After the area is not etched and the light-emitting range is not reduced, an N-type cladding layer and an N-type contact layer are grown sequentially at once, and the N-type cladding layer buries and covers the spine, thereby forming a ridge-like structure. The DFB semiconductor laser structure with shape/buried process characteristics improves process yield and reliability.

Description

Epitaxial manufacturing method of ridged/buried hybrid DFB semiconductor laser and DFB semiconductor laser structure made by using it

The present invention is related to DFB (Distributed Feedback Laser Diode, Distributed Feedback) semiconductor laser, especially a ridge/buried hybrid DFB semiconductor laser epitaxial manufacturing method and the DFB semiconductor laser structure made by the same. .

Optical communication is an electronic communication technology that uses light sources, such as light emitting diodes (LED) or semiconductor lasers (Laser Diode, LD), as signal media. The commonly used LDs are FP (Fabry Perot), There are three types: DFB and vertical cavity surface emitting type (VCSEL). However, edge-emitting laser FP LD and DFB LD mostly use two process methods: RWG (Ridge Waveguide, ridge waveguide) and BH (Buried Heterojunction, buried heterojunction), and generate corresponding structures respectively. Take FP LD as an example , its epitaxial structure roughly includes from bottom to top: a substrate (Substrate), an N-type cladding layer (n-Cladding), an active layer (Active), a P-type cladding layer (p-Cladding) and a P-type contact layer (Contact), and the structural difference between DFB LD and FP LD mainly lies in: DFB LD is equipped with a Bragg grating (Bragg Grating) on the basis of FP LD for filtering light to form a single longitudinal mode for light emission. , therefore, in response to different requirements for optical frequencies or optical modes in various optical fiber communications, the Bragg grating is selected to be disposed within the range of the N-type cladding layer or the P-type cladding layer according to the requirements.

Among them, in the RWG structure, an etching stop layer (Etching Stop) is embedded in the P-type cladding layer and divided into upper and lower parts, and a part of the P-type contact layer and the upper part are etched The P-type cladding layer is removed and ends at the etching stop layer to form a ridge structure; in the BH structure, part of the P-type cladding layer and the active layer are removed and then grown again p/n InP and secondary growth of p InP to complete the P-type cladding layer and form the P-type contact layer. It can be seen that the obvious characteristics of the RWG LD structure are to maintain the integrity of the active layer, and it has the advantages of relatively simple and stable early epitaxy process, although the later etching Ridge process is slightly complicated and the spot is oval, which is not conducive to Problems such as fiber coupling; the BH LD structure is to remove part of the active layer by etching, and use the P-type cladding layer to overlap and cover the active layer to limit the light-emitting area, so as to achieve lower critical current (I _th ) and lower series connection It has the advantages of high resistance, high luminous efficiency, and a nearly circular light spot, but it also involves the need for selective area epitaxy growth because the P-type cladding layer and the active layer are removed except for the spine part, making the process complicated. , and suffers from problems such as poor stability due to the pnpn type current limiting effect.

In view of this, the inventor of this case considered how to use the above two structures based on factors such as the range of the active layer affecting quantum efficiency and modulation speed performance, and the fact that the P-type cladding layer has a higher resistance than the N-type cladding layer. The subject of the present invention is to provide a hybrid structure that combines the advantages of the two structures by truncating the advantages of the two structures to improve the process yield and reduce the process cost by improving the traditional DFB structure.

In view of the above problems, the purpose of the present invention is to provide an epitaxial manufacturing method of a ridge/buried hybrid DFB semiconductor laser and a DFB semiconductor laser structure made by the same, so as to utilize tunneling with n-p junctions. The Tunnel Junction (TJ) structure forms a RWG-like structural spine without etching the active area to optimize the traditional RWG structure to form a BH-like structure, which combines the characteristics of RWG and BH structures and effectively improves semiconductor heat dissipation efficiency and uniform active area utilization. benefits.

In order to achieve the above object, the present invention discloses a ridge/buried hybrid DFB semiconductor laser structure, which is epitaxially generated sequentially on a substrate with an N-type material region, an active region and a P-type material region. Its characteristics The N-type material region includes a buffer layer, a grating layer, an N-type isolation layer, a first carrier gradient transition layer and a lower confinement layer in order from bottom to top, and the buffer layer is adjacent to the substrate, and the The lower limiting layer is adjacent to the active area; the active area includes a lower gradient layer, a lower energy barrier layer, an active layer, an upper energy barrier layer and an upper gradient layer from bottom to top, and the lower gradient layer is adjacent to the lower Localization layer, the upper gradient layer is adjacent to the P-type material area; the P-type material area includes an upper localization layer, a P-type lower isolation layer, an etching stop layer and a P-type upper isolation layer from bottom to top, The P-type upper isolation layer is adjacent to a tunnel junction layer including a heavily doped P-type layer and a heavily doped N-type layer. The P-type upper isolation layer and the tunnel junction layer are covered with a tunnel junction layer. N-type cladding layer, an N-type contact layer is provided on the N-type cladding layer, an N-type metal electrode layer is provided on the N-type contact layer, and the upper limiting layer is adjacent to the upper gradient layer, and the heavily doped P The P-type layer is adjacent to the P-type upper isolation layer, the heavily doped N-type layer is adjacent to the heavily doped P-type layer, and a first layer is disposed between the N-type cladding layer and the N-type contact layer from bottom to top. A two-carrier gradient transition layer and a third carrier gradient transition layer; wherein, when the DFB semiconductor laser structure is epitaxially generated, the grating layer is disposed in the N-type material region so that the grating layer and the active Form the N-type isolation layer in intervals, and dispose the etching stop layer in the P-type material area so that the adjacent P-type lower isolation layer and the P-type upper isolation layer are respectively formed below and above the etching stop layer; forming After the tunnel junction layer is adjacent to the P-type upper isolation layer, a strip of photoresist is coated on the tunnel junction layer, and the through hole that is not covered by the strip of photoresist is anisotropically etched downwards. The tunnel junction layer and the P-type upper isolation layer end at the etching stop layer to form a spine, and after the tunnel junction layer of the spine is consistent with the range of the P-type upper isolation layer, the strip-shaped photoresist is removed , after the N-type cladding layer and the N-type contact layer are sequentially formed by one-time growth, the N-type metal electrode layer is disposed on the N-type contact layer; wherein, the active layer is epitaxially formed upward from the substrate. The area is not etched to reduce the light-emitting range, so that the active area range is larger than the spine range, and the spine is the P-type upper isolation layer, the heavily doped P-type layer and the heavily doped N layer from bottom to top. type layer; wherein, the substrate is made of InP material; the buffer layer and the N-type isolation layer are made of n-InP material, the grating layer is made of n-In _0.71 Ga _0.29 As _0.62 P _0.38 material, and the first carrier gradient The transition layer is made of n-(Al _0.85 Ga _0.15 ) _0.47 In _0.53 As material and the lower limiting layer is made of n-In _0.53 Al _0.47 As material; the lower gradient layer and the upper gradient layer are made of (Al _0.85 Ga _0.15 ) _0.47 In _0.53 As<->(Al _0.44 Ga _0.56 ) _0.47 In _0.53 As material, the lower energy barrier layer and the upper energy barrier layer adopt (Al _0.23 Ga _0.77 ) _0.52 In _0.48 As material and the active layer adopt (Al _0.22 Ga _0.78 ) _0.37 In _0.63 As material; the upper confinement layer is made of p-In _0.53 Al _0.47 As material, the P-type lower isolation layer and the P-type upper isolation layer are made of p-InP material, and the etching stop layer is made of p-In _0.84 Ga _0.16 As _0.34 P _0.66 material; the tunnel junction layer is made of InGaAsP, AlGaInAs, InGaAs, AlInAs or InP material; the N-type cladding layer is made of n-InP material; the second carrier gradient transition layer is made of n-In _0.71 Ga _0.29 As _0.62 P _0.38 material; the third carrier gradient transition layer system uses n-In _0.61 Ga _0.39 As _0.84 P _0.16 material; and the N-type contact layer system uses n-In _0.53 Ga _0.47 As material .

In addition, a second purpose of the present invention is to disclose a method for manufacturing epitaxial ridge/buried hybrid DFB semiconductor lasers, which sequentially epitaxially generates an N-type material region, an active region and a P-type on a substrate. material area to form a double heterostructure, which is characterized in that when the double heterostructure is generated by epitaxy, an etching stop layer is set in the P-type material area so that adjacent P-type materials are formed below and above the etching stop layer. Type lower isolation layer and a P-type upper isolation layer; after forming a grating tunnel junction layer with a grating structure adjacent to the P-type upper isolation layer, a strip of photoresist is coated on the grating tunnel junction layer on; wherein the grating tunnel junction layer includes a heavily doped grating P-type layer and a heavily doped grating N-type layer, and the heavily doped grating P-type layer is adjacent to the P-type upper isolation layer, and the heavily doped grating The N-type layer is adjacent to the P-type layer of the heavily doped grating; it is formed by etching downward the grating tunnel junction layer and the P-type upper isolation layer that are not covered by the strip-shaped photoresist and ending at the etching stop layer. After one spine, the strip-shaped photoresist is removed; the active area is not etched and the luminous range is not reduced. and after sequentially forming an N-type cladding layer and an N-type contact layer at one time, an N-type metal electrode layer is disposed on the N-type contact layer; wherein the N-type cladding layer buries and covers the spine, the N-type contact layer is provided on the N-type covering layer.

Moreover, the etching is anisotropic etching to make the grating tunnel junction layer of the spine consistent with the range of the P-type upper isolation layer. In this way, the DFB semiconductor laser structure made by the above-mentioned epitaxial manufacturing method is a semiconductor structure in which a grating is disposed on the P-type material region. The characteristic is that in the DFB semiconductor laser structure, the substrate is The active area formed by upward epitaxy has not been etched to reduce the luminous range, so that the active area range is larger than the spine range, and the spine is the P-type upper isolation layer and the heavily doped grating P from bottom to top. type layer and the heavily doped grating N-type layer.

Wherein, the N-type material region includes a buffer layer, a first carrier gradient transition layer and a lower confinement layer in order from bottom to top, and the buffer layer is adjacent to the substrate, and the lower confinement layer is adjacent to the active region; the active region The area includes a lower gradient layer, a lower energy barrier layer, an active layer, an upper energy barrier layer and an upper gradient layer in order from bottom to top, and the lower gradient layer is adjacent to the lower limiting layer, and the upper gradient layer is adjacent to the P The P-type material region; the P-type material region includes an upper limiting layer, the P-type lower isolation layer, the etching stop layer and the P-type upper isolation layer in order from bottom to top, and the upper limiting layer is adjacent to the upper gradient layer ; And a second carrier gradient transition layer and a third carrier gradient transition layer are provided from bottom to top between the N-type cladding layer and the N-type contact layer. The substrate is made of InP material; the buffer layer is made of n-InP material, the first carrier gradient transition layer is made of n-(Al _0.85 Ga _0.15 ) _0.47 In _0.53 As material and the lower limiting layer is made of n-In _0.53 Al _0.47 As material; the lower gradient layer and the upper gradient layer adopt (Al _0.85 Ga _0.15 ) _0.47 In _0.53 As<->(Al _0.44 Ga _0.56 ) _0.47 In _0.53 As material, the lower energy barrier layer and the upper energy barrier The layer uses (Al _0.23 Ga _0.77 ) _0.52 In _0.48 As material and the active layer uses (Al _0.22 Ga _0.78 ) _0.37 In _0.63 As material; the upper confinement layer uses p-In _0.53 Al _0.47 As material, and the P-type lower isolation layer uses (Al 0.23 Ga 0.77 ) 0.52 In 0.48 As material. The layer and the P-type upper isolation layer are made of p-InP material, the etching stop layer is made of p-In _0.84 Ga _0.16 As _0.34 P _0.66 material; the grating tunnel junction layer is made of InGaAsP, AlGaInAs, InGaAs, AlInAs or InP Material; the N-type cladding layer uses n-InP material; the second carrier gradient transition layer uses n-In _0.71 Ga _0.29 As _0.62 P _0.38 material; the third carrier gradient transition layer uses n-In _0.61 Ga _0.39 As _0.84 P _0.16 material; and the N-type contact layer adopts n-In _0.53 Ga _0.47 As material. The P-type layer of the heavily doped grating is made of p-In _0.71 Ga _0.29 As _0.62 P _0.38 material, and the N-type layer of the heavily doped grating is made of n-In _0.71 Ga _0.29 As _0.62 P _0.38 material.

To sum up, the present invention provides two different grating forming processes in response to different light type requirements, allowing the device to choose to set the grating in the P-type or N-type semiconductor material range according to different needs. When the second-class epitaxial manufacturing method etches the (grating) tunnel junction layer with np junction and the P-type upper isolation layer to form the spine, it does not reduce the scope of the active area and significantly reduces the area of the P-type material area. The scope is reduced to improve the internal quantum efficiency of the active layer and improve overall yield and reliability. Moreover, through the arrangement of the heavily doped (grating) NP-type layer of the (grating) tunnel junction layer, the secondary re-growth process of the traditional BH structure is further simplified and only one re-growth is required, effectively simplifying the It reduces the complexity of the crystal process and improves the overall process efficiency. During the first re-growth, p InP/InGaAs used in the traditional BH structure is replaced by n InP/InGaAs, which transposes the P-type cladding layer and P-type contact layer in the traditional BH structure into an N-type cladding layer and N-type contact. layer, through the low resistance and high heat dissipation efficiency characteristics of N-type materials, DFB LD can achieve high carrier transmission efficiency, low I _th , low series resistance, high luminous efficiency, approximately circular light spot and high heat dissipation efficiency. And further achieve the effect of improving the process yield and reliability of DFB semiconductor laser.

1:DFB semiconductor laser structure

10:Substrate

11:N type material area

110: Buffer layer

111:Grating layer

112:N type isolation layer

113: First carrier gradient transition layer

114:Lower limit layer

12:Active zone

120: Lower gradient layer

121: Lower energy barrier layer

122:Active layer

123: Upper energy barrier layer

124: Upper gradient layer

13:P type material area

130: Upper limit layer

131:P type lower isolation layer

132: Etch stop layer

133:P type upper isolation layer

140: Tunnel junction layer

1400:Heavily doped P-type layer

1401:Heavily doped N-type layer

141:Grating tunnel junction layer

1410:Heavily doped grating P-type layer

1411:Heavily doped grating N-type layer

15:N type coating layer

16: Second carrier gradient transition layer

17: The third carrier gradient transition layer

18:N-type contact layer

19:N-type metal electrode layer

2: Strip photoresist

S10~S15, S20~S25: steps

Figure 1 is a flow chart of a preferred embodiment of the present invention.

Figures 2A, 2B, and 2C are schematic flow diagrams of the epitaxial state of the second preferred embodiment of the present invention.

Figure 3 is a schematic structural diagram of the second preferred embodiment of the present invention.

Figure 4 is a flow chart of the third preferred embodiment of the present invention.

Figures 5A and 5B are schematic flow diagrams of the epitaxial state of the fourth preferred embodiment of the present invention.

Figure 6 is a schematic structural diagram of the fourth preferred embodiment of the present invention.

In order to enable those with ordinary knowledge in the art to clearly understand the contents of the present invention, the following description is accompanied by the drawings, for which please refer.

Please refer to Figures 1 to 3, which are respectively a flow chart of a preferred embodiment of the present invention and a schematic flow chart and structural schematic diagram of the epitaxial state of the second preferred embodiment. As shown in the figure, the epitaxial manufacturing method of the ridge/buried hybrid DFB semiconductor laser includes the following steps: Step S10, sequentially epitaxially generate an N-type material region 11 and an active region 12 on a substrate 10 and a P-type material region 13 to form a double heterostructure, and in step S11, when the double heterostructure is epitaxially generated, a grating layer 111 is disposed in the N-type material region 11 so that the grating layer 111 and the active An N-type isolation layer 112 is formed between the regions 12 . Step S12 , an etching stop layer 132 is disposed in the P-type material region 13 to form an adjacent P-type lower isolation layer 131 and an adjacent P-type upper isolation layer 133 below and above the etching stop layer 132 . Step S13, after forming a tunnel junction layer 140 adjacent to the P-type upper isolation layer 133, apply a strip of photoresist 2 on the tunnel junction layer 140; wherein the tunnel junction layer 140 includes A heavily doped P-type layer 1400 and a heavily doped N-type layer 1401, and the heavily doped P-type layer 1400 is adjacent to the P-type upper isolation layer 133, and the heavily doped N-type layer 1401 is adjacent to the heavily doped P-type On level 1400. Step S14: Etch down the tunnel junction layer 140 and the P-type upper isolation layer 133 that are not covered by the strip photoresist 2 and stop at the etching stop layer 132 to form a spine, and then remove the strip photoresist 2. Resistance 2; among them The active area 12 is not etched and does not reduce the light emitting range. Step S15, after one-time re-growth sequentially forms an N-type cladding layer 15 and an N-type contact layer 18, an N-type metal electrode layer 19 is disposed on the N-type contact layer 18; wherein the N-type cladding layer 15 buries and covers the spine, and the N-type contact layer 18 is provided on the N-type cladding layer 15 .

In this way, the DFB semiconductor laser structure 1 made by the above-mentioned epitaxial manufacturing method is a semiconductor structure in which a grating is disposed in the N-type material region 11, and the active region 12 is epitaxially formed upward from the substrate 10. The light-emitting range is reduced without etching, so that the range of the active region 12 is larger than the range of the spine, which can effectively increase the carrier transmission efficiency and improve the heat dissipation effect. In other words, since the active area 12 is not etched in this process, it can logically improve the overall process yield and reliability. Moreover, the spine is the P-type upper isolation layer 133, the heavily doped P-type layer 1400 and the heavily doped N-type layer 1401 in sequence from bottom to top, and the etching is anisotropic etching to make the spine The tunnel junction layer 140 is in the same range as the P-type upper isolation layer 133 . Here, according to the characteristics that the heavily doped P-type layer 1400 is adjacent to the P-type upper isolation layer 133, and the heavily doped N-type layer 1401 is adjacent to the heavily doped P-type layer 1400, the cladding can be further transposed The N-type cladding layer 15 and the N-type contact layer 18 are used to simplify the conventional BH structure that requires two re-growth processes into one-time growth.

Furthermore, based on the above-mentioned process means, various functional layers can be expanded in the semiconductor structure to achieve a DFB LD element with better overall efficiency. In this embodiment, in order to reduce the adverse effects caused by the difference in lattice constant and thermal expansion coefficient between the substrate 10 and the semiconductor material, and to effectively improve the carrier transmission efficiency, this structure is further provided with a buffer layer (Buffer) and Carrier gradient transition layer, etc., thereby improving its epitaxial electrical and optical properties. Therefore, the N-type material region 11 may include a buffer layer 110, the grating layer 111, the N-type isolation layer 112, a first carrier gradient transition layer 113 and a lower localization layer 114 in order from bottom to top, and The buffer layer 110 is adjacent to the substrate 10 , and the lower limiting layer 114 is adjacent to the active region 12 . In addition, in order to improve the light localization effect after the active area 12 emits light, this specific structure is additionally equipped with an energy The barrier layer (Barrier) and the gradient layer (GRIN), therefore, the active area 12 sequentially includes a lower gradient layer 120, a lower energy barrier layer 121, an active layer 122, an upper energy barrier layer 123 and an upper energy barrier layer 123 from bottom to top. The upper gradient layer 124 is adjacent to the lower limiting layer 114 , and the upper gradient layer 124 is adjacent to the P-type material region 13 . The P-type material region 13 includes an upper confinement layer 130, the P-type lower isolation layer 131, the etching stop layer 132 and the P-type upper isolation layer 133 in sequence from bottom to top, and the upper confinement layer 130 is adjacent to the upper Gradient layer 124. In addition, a second carrier gradient transition layer 16 and a third carrier gradient transition layer 17 are provided from bottom to top between the N-type cladding layer 15 and the N-type contact layer 18 .

Among them, the substrate 10 can be made of InP material; the buffer layer 110 and the N-type isolation layer 112 can be made of n-InP material, the grating 111 layer can be made of n-In _0.71 Ga _0.29 As _0.62 P _0.38 material, and the first carrier gradient The transition layer 113 is made of n-(Al _0.85 Ga _0.15 ) _0.47 In _0.53 As material and the lower confinement layer 114 is made of n-In _0.53 Al _0.47 As material. The lower gradient layer 120 and the upper gradient layer 124 are made of (Al _0.85 Ga _0.15 ) _0.47 In _0.53 As <-> (Al _0.44 Ga _0.56 ) _0.47 In _0.53 As material, the lower energy barrier layer 121 and the upper energy barrier layer. 123 is made of (Al _0.23 Ga _0.77 ) _0.52 In _0.48 As material and the active layer 122 is made of (Al _0.22 Ga _0.78 ) _0.37 In _0.63 As material. The upper confining layer 130 is made of p-In _0.53 Al _0.47 As material, the P-type lower isolation layer 131 and the P-type upper isolation layer 133 are made of p-InP material, and the etching stop layer 132 is made of p-In _0.84 Ga _0.16 As _0.34 P _0.66 material. The tunnel junction layer 140 is made of InGaAsP, AlGaInAs, InGaAs, AlInAs or InP material, the N-type cladding layer 15 is made of InP material, and the second carrier gradient transition layer 16 is made of n-In _0.71 Ga _0.29 As _0.62 P _0.38 Materials: the third carrier gradient transition layer 17 is made of n-In _0.61 Ga _0.39 As _0.84 P _0.16 material, and the N-type contact layer 18 is made of n-In _0.53 Ga _0.47 As material.

Please refer to Figures 4 to 6, which are respectively a flow chart of the third preferred embodiment of the present invention and a schematic flow chart and structural schematic diagram of the epitaxial state of the fourth preferred embodiment. As shown in the figure, the DFB semiconductor laser structure 1 made by using the epitaxial manufacturing method of the ridge/buried hybrid DFB semiconductor laser is to convert light A structure with a gate disposed on a P-type semiconductor material, which sequentially includes a substrate 10, an N-type material region 11, an active region 12, a P-type material region 13, and a grating tunnel junction layer 141 from bottom to top. , an N-type cladding layer 15, an N-type contact layer 18 and an N-type metal electrode layer 19, to use the grating TJ structure with n-p junction to simplify the secondary re-growth process of the traditional BH structure, and transpose the P-type The cladding layer and the P-type contact layer are N-type, which can optimize the process and improve the carrier transmission efficiency and heat dissipation. The epitaxy manufacturing method of the ridge/buried hybrid DFB semiconductor laser can include the following steps.

Step S20: sequentially epitaxially generate an N-type material region 11, an active region 12 and a P-type material region 13 on the substrate 10 to form a double heterostructure. When the double heterostructure is epitaxially generated, step S21 , an etching stop layer 132 is disposed in the P-type material region 13 so that an adjacent P-type lower isolation layer 131 and an adjacent P-type upper isolation layer 133 are respectively formed below and above the etching stop layer 132 . Step S22: After forming a grating tunnel junction layer 141 with a grating structure adjacent to the P-type upper isolation layer 133, a strip of photoresist 2 is coated on the grating tunnel junction layer 141, and the grating The tunnel junction layer 141 includes a heavily doped grating P-type layer 1410 and a heavily doped grating N-type layer 1411, and the heavily doped grating P-type layer 1410 is adjacent to the P-type upper isolation layer 133. The heavily doped grating P-type layer 1410 is adjacent to the P-type upper isolation layer 133. The N-type layer 1411 is adjacent to the heavily doped grating P-type layer 1410.

Step S23: Etch down the grating tunnel junction layer 141 and the P-type upper isolation layer 133 that are not covered by the strip photoresist 2 and stop at the etching stop layer 132 to form a spine, and then remove the strip. Photoresist 2, wherein the active area 12 is not etched and does not reduce the light-emitting range. Step S24, an N-type cladding layer 15 and an N-type contact layer 18 are sequentially formed in one go, so that the N-type cladding layer 15 buries and covers the spine, and the N-type contact layer 18 is disposed on the N-type cladding layer 15. After the N-type cladding layer 15 is formed on the N-type cladding layer 15 , in step S25 , an N-type metal electrode layer 19 is disposed on the N-type contact layer 18 . Since during the process, the etching is anisotropic etching to make the grating tunnel junction layer 141 of the spine consistent with the P-type upper isolation layer 133, it can be seen that in the DFB semiconductor laser structure 1, the substrate 10 The active region 12 formed by upward epitaxy is not etched to reduce the luminous range, so that The range of the active region 12 is larger than the range of the spine, and the spine is the P-type upper isolation layer 133, the heavily doped grating P-type layer 1410 and the heavily doped grating N-type layer 1411 from bottom to top. Progressively successfully transposed the P-type cladding layer in the traditional BH structure into an N-type one.

In this embodiment, the above-mentioned process means can be used as a basis, and various functional layers can be expanded in the semiconductor structure accordingly. For example, the substrate 10 can be made of InP material, and in order to reduce the interaction between the substrate 10 and the semiconductor material Considering the adverse effects caused by differences in lattice constants and thermal expansion coefficients and effectively improving carrier transmission efficiency, a buffer layer (Buffer) and a carrier gradient transition layer can be provided between the structure of the substrate 10 and the N-type material region 11. To improve its epitaxial electrical and optical properties. Therefore, the N-type material region 11 includes, from bottom to top, a buffer layer 110 made of n-InP material, and a first carrier gradient transition layer made of n-(Al _0.85 Ga _0.15 ) _0.47 In _0.53 As material. 113 and a lower confinement layer 114 of n-In _0.53 Al _0.47 As material is used, and the buffer layer 110 is adjacent to the substrate 10 , and the lower confinement layer 114 is adjacent to the active region 12 . In order to improve the light localization effect of the active area 12 after emitting light, an energy barrier layer and a gradient layer are added to this specific structure, so that the active area 12 can include a gradient layer 120, an energy barrier layer 121, and a gradient layer 120 from bottom to top. Active layer 122, an upper energy barrier layer 123 and an upper gradient layer 124, the lower gradient layer 120 is adjacent to the lower confinement layer 114, the upper gradient layer 124 is adjacent to the P-type material region 13, and the lower gradient layer 120 and the The upper gradient layer 124 is made of (Al _0.85 Ga _0.15 ) _0.47 In _0.53 As <-> (Al _0.44 Ga _0.56 ) _0.47 In _0.53 As material, the lower energy barrier layer 121 and the upper energy barrier layer 123 are made of (Al _0.23 Ga _0.77 ) _{The 0.52} In _0.48 As material and the active layer 122 are made of (Al _0.22 Ga _0.78 ) _0.37 In _0.63 As material. The P-type material region 13 includes, in order from bottom to top, an upper confinement layer 130 made of p-In _0.53 Al _0.47 As material, the P-type lower isolation layer 131 , and a layer made of p-In _0.84 Ga _0.16 As _0.34 P _0.66 material. The etch stop layer 132 and the P-type upper isolation layer 133 are made of p-InP material, and the P-type lower isolation layer 131 and the P-type upper isolation layer 133 are made of p-InP material. The upper confinement layer 130 is adjacent to the upper gradient layer 124 . The grating tunnel junction layer 141 is made of InGaAsP, AlGaInAs, InGaAs, AlInAs or InP material, and the heavily doped grating P-type layer 1410 is made of p-In _0.71 Ga _0.29 As _0.62 P _0.38 material, and the heavily doped grating N Type 1411 layer uses n-In _0.71 Ga _0.29 As _0.62 P _0.38 material. In addition, a second carrier gradient transition layer 16 and a first carrier gradient transition layer 16 are provided from bottom to top between the N-type cladding layer 15 made of InP material and the N-type contact layer 18 made of n-In _0.53 Ga _0.47 As material. Three-carrier gradient transition layer 17, and the second carrier gradient transition layer 16 adopts n-In _0.71 Ga _0.29 As _0.62 P _0.38 material, and the third carrier gradient transition layer 17 adopts n-In _0.61 Ga _0.39 As _0.84 P _{The 0.16} material uses gradient energy levels to ensure epitaxial quality, thus achieving a DFB LD element with better overall performance.

In summary, the process of the present invention does not etch the active region 12 and does not reduce the light-emitting range of the active layer 122, so that the overall process yield and reliability can be improved. Moreover, the N-type cladding layer 15 completely buries and covers the spine, and the N-type contact layer 18 is provided on the N-type cladding layer 15. In this way, the light field can be more coupled with the quantum well of the active layer 122. Approaching the middle position of the active layer 122, the lower half of the active layer 122 can be effectively used to compensate for the light field shift in the vertical direction, thereby improving the modal gain and reducing _Ith .

The above is only an illustration of the preferred embodiments within the patentable scope of the present invention, and is not intended to limit the scope of rights of the present invention based on the content of these embodiments; therefore, any changes in the meaning of the present invention may be made without departing from the equal scope of the present invention. or modifications should still be covered by the patentable scope of the present invention.

S20~S25: steps

Claims (7)

A ridge/buried hybrid DFB semiconductor laser structure, which is epitaxially generated sequentially on a substrate with an N-type material region, an active region and a P-type material region, characterized in that: the N-type material region is formed from the bottom The upper layer sequentially includes a buffer layer, a grating layer, an N-type isolation layer, a first carrier gradient transition layer and a lower localization layer, and the buffer layer is adjacent to the substrate, and the lower localization layer is adjacent to the active region; The active area includes a lower gradient layer, a lower energy barrier layer, an active layer, an upper energy barrier layer and an upper gradient layer in order from bottom to top, and the lower gradient layer is adjacent to the lower limiting layer, and the upper gradient layer is adjacent to the P-type material area; the P-type material area includes an upper limiting layer, a P-type lower isolation layer, an etching stop layer and a P-type upper isolation layer from bottom to top. The P-type upper isolation layer is adjacent to There is a tunnel junction layer including a heavily doped P-type layer and a heavily doped N-type layer. The P-type upper isolation layer and the tunnel junction layer are covered with an N-type cladding layer. The N-type An N-type contact layer is provided on the cladding layer. An N-type metal electrode layer is provided on the N-type contact layer. The upper limiting layer is adjacent to the upper gradient layer. The heavily doped P-type layer is adjacent to the P-type upper isolation layer. , the heavily doped N-type layer is adjacent to the heavily doped P-type layer, and a second carrier gradient transition layer and a first carrier gradient transition layer are provided from bottom to top between the N-type cladding layer and the N-type contact layer. A three-carrier gradient transition layer; wherein, when the DFB semiconductor laser structure is epitaxially generated, the grating layer is disposed in the N-type material region so that the grating layer and the active region form the N-type isolation layer, and The etching stop layer is disposed in the P-type material region so that the adjacent P-type lower isolation layer and the P-type upper isolation layer are respectively formed below and on the etching stop layer; the tunnel junction layer is formed adjacent to the P-type upper isolation layer. After the P-type upper isolation layer is applied, a strip of photoresist is coated on the tunnel junction layer, and anisotropic downward etching is performed on the tunnel junction layer and the P-type that are not covered by the strip of photoresist. The isolation layer ends at the etching stop layer to form a spine, and after the tunnel junction layer of the spine is consistent with the range of the P-type upper isolation layer, the strip-shaped photoresist is removed, and then grown again in sequence to form After the N-type cladding layer and the N-type contact layer, the N-type metal electrode layer is disposed on the N-type contact layer; wherein, the active region formed by upward epitaxy of the substrate is not etched to reduce the light-emitting range, The range of the active region is larger than the range of the spine, and the spine is the P-type upper isolation layer, the heavily doped P-type layer and the heavily doped N-type layer in order from bottom to top; wherein, the substrate is made of InP material; the buffer layer and the N-type isolation layer are made of n-InP material, the grating layer is made of n-In _0.71 Ga _0.29 As _0.62 P _0.38 material, and the first carrier gradient transition layer is made of n-(Al _0.85 Ga _0.15 ) _0.47 In _0.53 As material and the lower localization layer adopt n-In _0.53 Al _0.47 As material; the lower gradient layer and the upper gradient layer adopt (Al _0.85 Ga _0.15 ) _0.47 In _0.53 As<->(Al _0.44 Ga _0.56 ) _0.47 In _0.53 As material, the lower energy barrier layer and the upper energy barrier layer adopt (Al _0.23 Ga _0.77 ) _0.52 In _0.48 As material, and the active layer adopts (Al _0.22 Ga _0.78 ) _0.37 In 0.63 As material; the upper energy barrier layer adopts (Al 0.23 Ga 0.77 ) 0.52 In _0.48 As material. The localization layer is made of p-In _0.53 Al _0.47 As material, the P-type lower isolation layer and the P-type upper isolation layer are made of p-InP material, and the etching stop layer is made of p-In _0.84 Ga _0.16 As _0.34 P _0.66 material; The tunnel junction layer is made of InGaAsP, AlGaInAs, InGaAs, AlInAs or InP material; the N-type cladding layer is made of InP material; the second carrier gradient transition layer is made of n-In _0.71 Ga _0.29 As _0.62 P _0.38 material ; The third carrier gradient transition layer is made of n-In _0.61 Ga _0.39 As _0.84 P _0.16 material; and the N-type contact layer is made of n-In _0.53 Ga _0.47 As material. A ridge/buried hybrid DFB semiconductor laser epitaxial manufacturing method is to sequentially epitaxially generate an N-type material region, an active region and a P-type material region on a substrate to form a dual heterostructure. The characteristic is that when epitaxy generates the double heterostructure, an etching stop layer is disposed in the P-type material region so that an adjacent P-type lower isolation layer and an adjacent P-type upper isolation layer are formed below and above the etching stop layer. layer; after forming a grating tunnel junction layer with a grating structure adjacent to the P-type upper isolation layer, a strip of photoresist is coated on the grating tunnel junction layer; wherein the grating tunnel junction layer It includes a heavily doped grating P-type layer and a heavily doped grating N-type layer, and the heavily doped grating P-type layer is adjacent to the P-type upper isolation layer, and the heavily doped grating N-type layer is adjacent to the heavily doped grating On the P-type layer; After etching down the grating tunnel junction layer and the P-type upper isolation layer that are not covered by the strip-shaped photoresist and ending at the etching stop layer to form a spine, remove the strip-shaped photoresist; wherein the active area It is not etched and does not reduce the light-emitting range; and after one-time re-growth in order to form an N-type cladding layer and an N-type contact layer, an N-type metal electrode layer is set on the N-type contact layer; wherein the N-type The covering layer buries and covers the spine, and the N-type contact layer is provided on the N-type covering layer. The epitaxial manufacturing method of claim 2, wherein the etching is anisotropic etching to make the grating tunnel junction layer of the spine consistent with the range of the P-type upper isolation layer. A DFB semiconductor laser structure made by the epitaxial manufacturing method as described in any one of claims 2 and 3, characterized in that: in the DFB semiconductor laser structure, the substrate is epitaxially formed upward. The active area is not etched to reduce the light-emitting range, so that the active area range is larger than the spine range, and the spine is the P-type upper isolation layer, the heavily doped grating P-type layer and the heavy-duty grating in sequence from bottom to top. Doped grating N-type layer. The DFB semiconductor laser structure of claim 4, wherein the N-type material region includes a buffer layer, a first carrier gradient transition layer and a lower confinement layer in order from bottom to top, and the buffer layer is adjacent to the The substrate, the lower localization layer is adjacent to the active area; the active area includes a lower gradient layer, a lower energy barrier layer, an active layer, an upper energy barrier layer and an upper gradient layer from bottom to top, and the lower gradient layer Adjacent to the lower limiting layer, the upper gradient layer is adjacent to the P-type material region; the P-type material region includes an upper limiting layer, the P-type lower isolation layer, the etching stop layer and the P-type upper layer in sequence from bottom to top. an isolation layer, and the upper localization layer is adjacent to the upper gradient layer; and a second carrier gradient transition layer and a third carrier gradient are provided from bottom to top between the N-type cladding layer and the N-type contact layer transition layer. The DFB semiconductor laser structure as described in claim 5, wherein the substrate is made of InP material; the buffer layer is made of n-InP material, and the first carrier gradient transition layer is made of n-(Al _0.85 Ga _0.15 ) _0.47 In _0.53 As material and the lower limiting layer adopt n-In _0.53 Al _0.47 As material; the lower gradient layer and the upper gradient layer adopt (Al _0.85 Ga _0.15 ) _0.47 In _0.53 As<->(Al _0.44 Ga _0.56 ) _0.47 In _0.53 As material, the lower energy barrier layer and the upper energy barrier layer adopt (Al _0.23 Ga _0.77 ) _0.52 In _0.48 As material, and the active layer adopts (Al _0.22 Ga _0.78 ) _0.37 In _0.63 As material; the upper confinement layer system p-In _0.53 Al _0.47 As material is used, the P-type lower isolation layer and the P-type upper isolation layer are made of p-InP material, and the etching stop layer is made of p-In _0.84 Ga _0.16 As _0.34 P _0.66 material; the grating through The tunnel junction layer is made of InGaAsP, AlGaInAs, InGaAs, AlInAs or InP material; the N-type cladding layer is made of n-InP material; the second carrier gradient transition layer is made of n-In _0.71 Ga _0.29 As _0.62 P _0.38 material ; The third carrier gradient transition layer is made of n-In _0.61 Ga _0.39 As _0.84 P _0.16 material; and the N-type contact layer is made of n-In _0.53 Ga _0.47 As material. The DFB semiconductor laser structure as described in claim 6, wherein the heavily doped grating P-type layer is made of p-In _0.71 Ga _0.29 As _0.62 P _0.38 material, and the heavily doped grating N-type layer is made of n-In _0.71 Ga _0.29 As _0.62 P _0.38 material.