TW439335B - A semiconductor laser and the fabrication method thereof - Google Patents

Abstract

The present invention is a semiconductor laser and the fabrication method thereof, mainly by epitaxially growing each semiconductor layer of a quantum well active layer for forming the window layer. Etch the desired window layer pattern by microlithography technology, then form AlGaInP by metal-organic chemical vapor deposition (MOCVD), preferably a window layer of (AlxGa1-x)0.5In0.5P material, so that the bandgap of the area near the facet of the semiconductor laser where laser light passes through is larger than that of the quantum well to avoid the catastrophic optical damage (COD) in the high power operation.

Description

4 3 93 3 5 V. Description of the invention (1) [Scope of the invention] The present invention relates to a semiconductor laser and a method for manufacturing the same, and particularly relates to a ridge waveguided and a selectively ridged waveguide. A buried laser ridge semiconductor semiconductor device proposes a required window layer structure and a manufacturing method thereof. [Background of the Invention] There are many methods for forming semiconductor lasers. For a semiconductor laser element with a ridge waveguide or a selective buried ridge, it is often difficult to tolerate the high surfacet of the laser light during operation. Catastrophic optical damage (COD for short) occurs due to the heat generated under power operation. This damage is caused by the band gap of the laser near the quantum well when the laser light escapes the mirror. ) Will reduce [A. Valster et al. IEEE Journal of Selected Topics in Quantum Electronics, Vo 1.3,

No. 2, April 1 997, p.p. 180 ~ 187], part of the laser light is absorbed near the mirror to generate heat, which makes the catastrophic light damage more serious. To solve the above problems, the phenomenon of reducing the energy band difference near the mirror quantum well needs to be eliminated first, that is, the energy band difference of the laser light passing region near the mirror is increased to be greater than the energy band difference of the quantum well. In the past few years, in order to achieve the above objectives, there have been many related previous cases in epitaxy, process and component design methods, including: (1) Japan's Mitsubishi Denki Kabushiki Kaisha proposed that the quantum well energy band difference should be increased before Above, a layer of impurities (such as ZnO) is first mined and then diffused at high temperature to make the laser light escape near the mirror surface.

^ ° 3 3 5 ^ V. Description of the invention (2) The well is enlarged due to the phase transition caused by the diffusion of impurities, which reduces the catastrophic light damage and greatly increases the high-power operation life. Such patents are as US patent 5 '577'063 , 5'469, 457, 5, 089, 437 and 5, 161, 166, etc. (2) Japan ’s Mitsubishi Denki Kabushiki Kaisha also proposed that the GaAs substrate with an offset angle (100) be engraved with a dry name (rie) or an electron beam to produce a crystal surface with an offset angle (100) of 8.3. A 1 GaInP visible light laser epitaxial structure is grown on this composite substrate, because the laser structure grown at different offset crystal planes has different energy band differences, so when forming the laser mirror surface, only the high energy band difference is needed. Areas are formed, naturally forming window layers, as described in US Patent 5,490,159. (3) Japan ’s Mitsubishi Denki Kabushiki Kaisha also proposed to grow the laser epitaxial structure before the (2 11) G a As substrate, and then etched the (1 1 1) plane of the vertical (2 11) plane by wet etching. The test strip is then placed in a MOCVD growth p--AlGaInP or p + -A IGaAs window layer with a band difference greater than that of the quantum well to achieve a reduction in catastrophic light damage, as described in US Patent 5, 677, 922. (4) Kabushiki Kaisha Toshiba of Japan proposed that when n-GaAs is used to cover the P-type cladding layer, the diffusion of impurities (Zn) inside the P-type cladding layer can be controlled so that the laser light can escape from the quantum well near the mirror surface. The band difference is enlarged due to the phase transition caused by impurity diffusion [K, Itaya et al., IEEE Journal of Quantum Electronics, Vo 1. 27, No 6, 1991, pp, 1496-1500], such as US Patent 5, 181, 218 And 4, 987, 0 96 and so on. (5) Japan's Sharp Kabushiki Kaisha proposed

Page 5 V. Description of the invention (3) After the crystal (Molecular Beam Epitaxy, or MBE for short) completes the selective ridge structure and laser bar, the laser bar is fixed with a special jig and placed in it. Metal Organic Chemical Vapor Deposition (Trial VII & 1-Organic Chemical Vapor Deposition, or MOCVD for short) The window layer with a larger energy band difference than the quantum well is grown on the mirror surface [M. Watanabe et al .. IEEE Journal of Selected Topics in Quantum Electronics, Vol. 1, No 2, 1995, pp 728 ～ 732], such as 11 $? 8 七 61 ^ 5,228,0 47 and 5,4 1 3,9 56 etc.

However, most of the manufacturing methods of the above methods must use GaAs substrates with special lattice directions. Among them, (1), (2), and (4) require the use of (100) GaAs substrates in the previous cases, and When using this substrate, the wavelength of the laser light obtained is very difficult to reduce and the concentration of the P-type cladding layer cannot be increased; (3) In the previous case, a very rare (2 11) GaAs substrate must be used, making epitaxial technology difficult The degree of improvement has been greatly improved; in the previous case of (5), a special jig must be used to fix the laser rod, and then placed in the M0CVD reaction chamber to plate a window layer, which increased the complexity of the process and increased the yield and The speed of production will also decrease. [Objective and Summary of the Invention] In view of this, the object of the present invention is to provide a semiconductor laser process that can form a window layer with an energy band difference greater than the quantum well energy band difference on the laser light escape mirror surface. The catastrophic light damage produced can be reduced, and this process does not require the use of a substrate with a special lattice direction 'and can be applied to any window layer structure required for substrate formation.

5. Description of the invention on page 6 (4) " According to the object of the present invention, the semiconductor laser process step I includes: (1) providing a worm wafer with a layered structure, and the layered structure of the epitaxial wafer includes A n-type semiconducting first coating layer (a first-type coating layer), a quantum well active layer, and a second-type coating layer of a p-type semiconductor are sequentially grown on a substrate. (2) A dielectric layer is formed on the substrate. Lei wafer; (3) Etching part of the intermediary and the Lei wafer below it, until the first batch of parts are covered ^^ ψ.., E ^ A ^ ^, the increase is also removed. The first layer of the overlying layer (on top to fill the part of the etched epitaxial wafer), # 宽 ό a ^ ^ Η Η 氺 'Dongshan City as Seventh & 111 household layer formed on the remote wafer's predecessor Out of the mirror, and has an energy band difference greater than the active and (5) removing the dielectric layer, and performing subsequent formation, 'this band difference, the step of burying the semiconductor laser structure with a ridge.' 'Waveguide or choice on the other hand, this The invention also provides a semiconductor laser device according to the above. The method produces the object according to the above invention. The provided ridge semiconductor laser element can escape the grid wave V from one of the light or selectively bury the mirror surface. The Emperor ’s light is emitted from the upper and lower layers of a sandwich of a quantum well. The doped aluminum gallium indium semiconductor material is layer-excited, and the layer with a higher energy band difference than the active layer is formed on the mirror surface. In order to make the above and other purposes of the present invention special, the band difference ° Obviously, a preferred embodiment is given below, and g L and its advantages can be explained in more detail as follows. 〇The attached drawings are detailed [Illustration of symbols and symbols] Schematic description: Section 1 A ~ 1 F The figure shows the ridges made according to the method of the present invention

V. Description of the invention (5) Flow chart of the window layer of the waveguide semiconductor laser; and 2A ~ 2I show the flow chart of the window layer of the selective buried ridge semiconductor laser manufactured according to the method of the present invention. Symbols: 1 substrate 2 buffer layer 3 first coating layer 4 active layer 5 second coating layer 6 weakening layer 7 > 15 contact layer 8, 13 dielectric layer 9 '11 photoresist layer 10 window layer 12 mirror surface 14 Current blocking layer [Explanation of the invention] The content of the present invention will be described as an example as follows: The epitaxial wafer with a layered structure used in the present invention is shown in FIG. 1A and FIG. 2A. It is tied to a substrate 1 (there is no restriction on the direction of the substrate). For example, a buffer layer 2 is grown in sequence on the η-GaAs substrate. The material is, for example, n-GaAs, a first cladding layer 3, The material is, for example, an n-type infill | g indium or a plated gallium indium semiconductor layer, and the composition is 5In. 5p or 11- (person 10 7GaQ 3) Q 5In [). 5P, an active layer of a quantum well (active iayer ·) 4, the material is, for example, Gal nP or A 1 Gal nP, and its crystal structure can be ordered ( ordered) or disordered (the second batch of coatings 5), for example, p-type aluminum indium phosphide or aluminum gallium phosphide = semiconductor layer, the composition is? _ / ^. 5111 (). 5? Or 13_ (4; 1 () 7 (^ 3) () 5111 (). 515, a reduction layer (r educ i ng 1 ay er) 6, for example, p-type The composition of the indium gallium indium material is P_GaQ5 In. 5p, and a contact layer

5. Description of the invention (6)) The 7 'material is, for example, p-GaAs. If the above active layer 4 uses GaAs or

The material of AlGaAs' is that the first and second batches of layers can be made of A 丨 GaAs. The first embodiment of the present invention is to form a laser semiconductor die with a ridged waveguide structure for the above-mentioned epitaxial wafer, and complete The components are shown in the "Figure 1F", and the process steps are as follows: (1) As shown in the "Figure", a dielectric layer 8 is deposited on the contact layer 7 of p-GaAs; and The required photoresist layer 9 pattern was fabricated on Lei Jingyue using the lithography C photo 1 i thography technology, which is used as a mask for subsequent name carving. The purpose of this step is to define the laser mirror split Split direction, so the direction is perpendicular to the laser waveguide direction. (2) As shown in "Figure 1c", contact the dielectric layer 8 formed in step (1) with p-GaAs by reactive ion silvering (RIE) method or wet coining method. The layer 7 is exposed; and the contact layers 7 and p-Ga of p-GaAs are successively etched away with the same RIE or wet money. 5In. 5P attenuating layer 6, p-AlQ 5InQ 5P or Mouth- (person 10 / a. 3) fl 5 1110.5? Second batch of cladding layer 5, active layer 4 at 11-Aug 1 (). 5111 [) 5? Or n-UUao 3) 〇5InQ.5P stopped in the first coating layer 3, so that the first coating layer 3 was exposed. (3) As shown in "Figure 1D", the test piece is placed in a reaction chamber of a metal organic chemical vapor deposition (MOCVD) machine, and a window layer 10 is grown on the exposed first coating layer 3 0 In order to fill in the trenches touched in step (2), the window layer 10 is selected, for example, as an undoped aluminum gallium indium semiconductor layer

Page 9 i 'Explanation of the invention' is composed as follows: (A lxGa! _X) 51 n0i 5P x = 0 ~! The area outside the trench is protected by the dielectric layer 8 formed in step (1), and the semiconductor material of the window layer 10 will not grow. (4) As shown in "Figure 1E", the dielectric layer 8 of step (1) is removed by active ion etching or wet etching; and another photoresist is fabricated on the wafer by lithography. The layer 11 pattern is also used as a mask for etching, and the direction = perpendicular to the photoresist layer 9 in step (1). This step aims to define the direction of the laser waveguide. :) (5) Then the semiconductor is etched by active ion money engraving or wet silver engraving to about 0 to 0.5 from the quantum well active layer 4 and then stopped, and then according to a conventional process until the grain is completed So far, you can get the semiconductor laser structure as shown in "Figure i F". It can be known from the results of "Fig. 1F" that the present invention uses the above-mentioned etching to pattern the window layer, and then fills in the selected undoped aluminum gallium indium semiconductor layer material as the window layer 10. According to the composition of the active layer 4, the appropriate selection can be made. The resulting value of the tunnel layer 10 has an energy band difference AEgi greater than the energy band difference ΔΕβ2 of the active layer 4 of the quantum well. Therefore, the energy band difference of the laser light passing region near the mirror 12 is greater than that of the quantum well. The energy band is poor, which reduces catastrophic light damage. The second embodiment of the present invention is directed to the above-mentioned epitaxial wafer to form a laser semiconductor die with a selective buried ridge structure. The completed device is shown in "Fig. 2G". The process steps are as follows: Π ) As shown in "Figure 2B", a dielectric layer 8 is deposited on the contact layer γ of p_GaAs; and the required light is produced on the wafer by lithography technology.

Page 10 V. Description of the invention (8) The pattern of the resist layer 9 is used as a mask for subsequent etching. The purpose of this step is to define the laser mirror splitting direction, so the direction is perpendicular to the laser waveguide direction. As shown in "Figure 2C", the dielectric layers 8 to p-GaAs contact layer 7 formed by the RIE or wet etching step are exposed; and successively etched away by the same RIE or wet etching Contact layer of p_GaAs? , '〇 · 3) 〇.5 P-GaG.5Irv5P attenuating layer 6, p_Ai〇5 Ιη "ρ or ^ ⑴. [First = layer 5, active layer 4 center is" with or n — (A1 " Ga ") 1 As the U layer 3 stops, the first batch of coatings 3 are exposed: as shown in Figure 2D, the test piece is placed in a CVD (CVD) machine and the reaction is exposed on the organic coating 3 A window layer 10 is grown, so that the second trench 'window layer' exiting from the path is selected, for example: etched, the composition is as follows: U, used as an undoped phosphide gallium thin semiconductor layer, (A lxGa1-x). 51 η. 5ρ χ = 〇 ~ 1 and the area outside the trench will be protected by the semiconductor material / electrical layer 8 that will grow the window layer 10 because of the step (). (4) As shown in "Figure 2E", _, ' The dielectric layer 8 of the step (丨) is removed by a conventional etching method. The f-type ion etching method or the wet-dielectric layer 1 3 is used. Then, the lithography technique is used to say :: ⑴, another pattern is evaporated, and it is also used for etching. Mask, ancient: the piece of clothing is made another—the photoresist layer 11 is straightened. The purpose of this step is to define the photoresistance of the laser shot ==) (5) As shown in "Figure 2F", the direction of the re-radiated wave / . (4) The dielectric layer 13 to the p-GaAs contact layer 7 * ^ y step (2) The etching step to the distance from the quantum well active layer is about 0! To 〇 R, and the laser wafer is etched. Υ · 3 "m. 4 3 93 3 5 V. Description of the invention (9) (6) Place the test piece in the MOCVD reaction chamber to grow n-GaAs as the current blocking layer 1 4 and the area etched in step (5) Fill out, the waveguides to be defined outside the area will not grow η-G a A s because of the formation of the dielectric layer 13; then the remaining dielectric layer 13 is removed by active ion rice engraving or wet silver engraving. Finally, the test piece is placed in a MOCVD reaction chamber to grow p-GaAs as the contact layer 15 to obtain a semiconductor laser structure as shown in FIG. 2G. In addition, this selective buried ridge semiconductor laser element can also be formed into a structure as shown in "Fig. 2H" or "Fig. 21". The difference between the "Figure 2h" structure and the "Figure 2G" is the timing of growing the window layer 10, which is after repeating the n-GaAs current blocking layer 14 and repeating the manufacturing steps (1) to (3) and (4) ) Procedure to remove the dielectric layer. For the "Figure 2I" structure, steps (5) and (6) are performed first. After the p-GaAs contact layer 15 is grown, the procedures of removing the dielectric layer in steps (1 and (4)) can be performed. 'From the results of "Fig. 2 G ~ 2 I", it can be seen that the present invention adopts the method of engraving the window layer pattern with I insects', and then fills in the selected undoped aluminum phosphide. The semiconductor layer material is used as the window layer. Can make the formed window layer 10 have an energy band difference Δ Eg 1 greater than the energy band difference A Eg2 of the active layer 4 of the quantum well, therefore, the energy band difference of the laser light passing region near the mirror 12 is greater than the energy band difference of the quantum well. 'Enable catastrophic photodamage (CD0) can be reduced.-Although the present invention has been disclosed in the preferred embodiment as above, it is not intended to limit = the present invention' Anyone skilled in this art will not depart from the spirit of the present invention = "Chao 4 Wai" should be able to make some changes and retouching, so the scope of protection of the present invention shall be determined by the scope of the attached patent application.

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Claims (1)

1 4 3 93 3 5 VI. Scope of Patent Application 1. A semiconductor laser manufacturing process includes at least the following steps: Provide a layered structure of an epitaxial wafer, which includes a first batch of cladding layers sequentially grown on a substrate, An active layer and a second batch of cladding layers; a dielectric layer is formed on the remote wafer, and a part of the dielectric layer and the worm wafer underneath are engraved until a portion of the first batch of coatings are also removed and exposed Grow; a window layer is grown on the exposed first cover layer to fill the portion of the epitaxial wafer carved by the tapeworm, so that the window layer is formed on the epitaxial light of the epitaxial wafer and has a band difference Greater than the energy band difference of the active layer; and removing the dielectric layer and performing the subsequent structure formation steps. 2. The semiconductor laser manufacturing process as described in item 1 of the scope of the patent application, wherein the layered structure of the epitaxial wafer includes the substrate, a buffer layer, the first coating layer, the active layer, and the second coating layer in order. , A weakened layer, and a contact layer. 3. The semiconductor laser process described in item 1 of the scope of the patent application, wherein the first batch of coating layers is an n-type semiconductor layer, and the second batch of coating layers is a p-type semiconductor layer. 4. The semiconductor laser manufacturing process as described in item 3 of the patent application scope, wherein the n-type semiconductor layer is any one selected from an n-type aluminum indium phosphide or an aluminum gallium indium semiconductor layer. 5. The semiconductor laser manufacturing process as described in item 3 of the patent application scope, wherein the P-type semiconductor layer is any one selected from a P-type aluminum indium phosphide or an aluminum gallium indium semiconductor layer. Page 13 6. Scope of Patent Application Any of the conductor layers. 14. The semiconductor laser according to item 12 of the scope of the patent application, wherein the P-type semiconductor layer is any one selected from a P-type aluminum indium phosphide or an aluminum gallium indium semiconductor layer. 15. The semiconductor laser as described in item 11 of the scope of patent application, wherein the composition of the Linhua Shaolu semiconductor is: (AlxGa 1 -X aQ. 6. As described in item 11 of the scope of patent application The semiconductor laser system is a ridge waveguide semiconductor laser element. 7. The semiconductor laser system described in item 11 of the scope of patent application is a selective buried ridge semiconductor laser element. Page 15