TW200427165A - Laser diode element - Google Patents

Abstract

The invention provides a ridge waveguide type III nitride based compound semiconductor laser diode element formed with a ridge structure that comprises a first domain, including a central portion and continuing in the longitudinal direction, and a second domain, clipping to the first domain from both sides thereof and having average layer thickness smaller than that of the first domain.

Description

200427165 V. Description of the invention (l) I. [Technical field to which the invention belongs] Today = = Profit Application No. 2003-1145137 'L =: The contents of this section are incorporated into this application for reference. The body element is about a group II nitrogen compound-based compound semiconductor laser diode combination: half; the word system is about a ridge waveguide type 111 group nitrogen compound. Improvement of semiconductor laser diode element. 2. [Prior technology] The laser diode light of the device (GaN ^ i semiconductor as the material) has been turned into apricots, wafers, and semiconductors. It is regarded as a promising candidate for oscillating short-wavelength body elements. Refined research and development. GaN-based laser diode semiconducting @ = 仏 is made of η-type and P-type semiconductor laminated layers sandwiching active layers on a sapphire substrate. There are various types of optical waveguides leading to it. The optical waveguide structure is provided with a ridge waveguide structure (hereinafter also referred to as “research”, for example, chemical structure i) that can be provided to close the horizontal “ridge shape = 4 ridges of light.” This ridge structure has been equivalent. Many improved research layers have come to form a GaN-based buried M that absorbs oscillating light on both sides of the ridge shape .: It is not too narrow to avoid the occurrence of higher-order modes, and it has been obtained to: (Japanese Patent Laid-Open No. 2 ° 〇0-3 1 599) Or use the wave path i, st ΐ ϊ of the emissivity type to complete the refraction type waveguide path and the actual effect (^ f12〇n? I way to raise 70 pieces) Structure of reliability and beam characteristics (Japanese Patent Laid-Open No. 2002: 374035), etc. The ridge waveguide structure is under construction. The relatively simple easy to manufacture, can Page 6 200 427 165

It is due to the basic mode in the horizontal and horizontal mode (0 times _ A times shift mode Korean style): the light seal f㈣ is close (that is, the mode: Zeng Yi difference :; person ί 杈 branch type transfer, easy to produce tangles. Although shortened by Ridge width) 4 The stability of the easy-going mode, but this structure causes the operating voltage to rise with the two or seven flat branches. The local resistance of the horizontal 丄 electrode will cause the light confinement coefficient in the direction of the critical current to decrease. III. [Abstract] The present invention is to provide a horizontal and horizontal mode that does not follow the increase of the critical current density and operating voltage. The purpose of the stable ridge waveguide is a π group nitrogen compound 糸 compound semiconductor laser diode element. The ridge waveguide type 11 group I nitrogen compound compound half-body laser diode element of the present invention is provided with: a first region, including a central portion and two longitudinal directions, and a second region. A ridge-shaped laser diode element sandwiched on both sides of the first region and having an average layer thickness smaller than the average layer thickness of the first region. ^ u In this configuration, the first region having a relatively large average layer thickness has a ridge structure lost by the second JI domain. Therefore, in the ridge structure, the effective refractive index of the central portion directly participating in the basic plate-type vibration becomes smaller than the effective refractive index 周边 of the peripheral portion, and effective light sealing of the central portion is performed. That is, the light confinement of the basic plate type is increased, and the light confinement ratio of the high-order mode is decreased. Therefore, the stability of the 'horizontal horizontal mode' is increased, and entanglement can be suppressed. ^ On the other hand, because the total ridge width can be fully ensured, there is no increase in critical current implantation, degree, and operating voltage. Also, closed by the light of the basic mode

200427165 V. Description of the invention (3) Increasing the rate can reduce the critical current density and operating power. And the 'average layer of the first and second regions-the thick region and the D ^ j contact session of the second region "&" children "in the region constituting the second region of the first region: the region of the first layer Average film thickness. The region is composed of a smaller average film population (consisting of a p-type contact layer) than the P-type contact layer constituting the first region. 4. [Embodiment] [Best Mode for Carrying Out the Invention] The following describes each element of the present invention.

The human diode 1 laser diode has a basic structure in which a plurality of semiconductor layers composed of an I I I nitride and a compound semiconductor are laminated on a substrate. The substrate has a ridge structure. A laser diode with such a ridge structure (a ridge waveguide type laser diode element) can realize a narrow current flow and light confinement in the horizontal direction by the ridge structure. Each of the semiconducting f layers laminated on the substrate includes an n-type contact layer, an η-type coating layer, an η-type guide layer, an active layer (single quantum well structure, multiple quantum well structure, etc.), a p-type guide layer, and a p-type Other cladding layers and p-type contact layers.

^ The substrate is not particularly limited as long as it can grow a Group III nitrogen compound-based compound on it, and GaN, sapphire, spinel, anoxite, zinc oxide, gallium phosphide, and aluminized gallium can be used. , Ytterbium oxide, Ion oxide, YSZ (zirconia stabilized with yttrium oxide), ZrB2 (zirconium diboride) and other substrates. A sapphire substrate is preferred when a semiconductor substrate is not used, and particularly it is preferably used for its c-plane. This is a group 111 nitrogen compound-based compound semiconductor layer for making the growth crystal excellent.

Page 8 200427165 V. Description of the invention (4) A buffer layer may be provided between the substrate and the crystalline layer composed of the 11 I nitrogen compound-based compound semiconductor. The buffer layer is provided for the purpose of improving the crystallinity of the group I nitrogen compound-based compound semiconductor grown thereon. The buffer layer can be formed of a group III nitride compound semiconductor such as AIN, InN, GaN, AlGaN, InGaN, AlInGaN, and the like. Here, the group 111 nitrogen compound-based compound semiconductor is represented by the general formula A 1χ GaYIni-x-YN (OSX ^ I, 〇 $ γ $ ι'o ^ x + y ^ j), and includes AIN, GaN, and InN. The so-called two-element system, the so-called three-element system of AlxGai_xN, AlxIrvxN, Ga x I rVx N (above 0 < x < 1). At least part of the ij 丨 group element can also be replaced by boron (B), thorium (T1), etc., and at least part of the nitrogen (N) can be phosphorus (p), arsenic (As), antimony (Sb) , Bismuth) and so on. The II group I nitrogen compound-based compound semiconductor may include any dopant. Silicon (Si), germanium (Ge), selenium (Se), tellurium (butyl eY carbon (C), etc.) can be used as n-type impurities. Magnesium (Mg), zinc on Be), (Ca), ( Sr), Gu (Ba), etc. are p-type impurities: after the second-type impurities can be irradiated with a group III nitrogen compound 糸 compound semiconductor, plasma irradiation, or using a furnace, etc., subject to conditions. However, it is not necessary that the semiconductor layer be formed by a well-known film-forming method. For example, in addition to the i-type organic chemical vapor deposition method (MOCVD method), the σ eight-bundle chestnut method (MBE method), the halide vapor-phase incubation method (用:, knife: method, iontoelectric method. Method), quenching The ridge structure of the stripe-shaped convex part is typically composed of a p-type contact layer and a p-type slope.

200427165 V. Description of the invention (5) Part of the coating. In this way, the p-type semiconductor / structure can be grown on the substrate after the semiconductor layer is formed. The width w of the overall ridge structure is formed by removing π or the like. The laser diode of the present invention is: quot: m ~ 10 _. In the longitudinal direction, there is a continuous 70th region. The first region includes a ridge structure having a central portion with an average layer thickness greater than the current second region, and is located between the first region and the point i. Structured as follows: 7 The ratio of the effective refractive index ratio of Part 2A (Part 2) on both sides will be mentioned,? J wants a high emissivity ’, so the light of the basic mode is closed. ^ FIG. 1 shows two examples of the ridge structure k used in the laser diode element of the present invention. FIG. 1 is a longitudinal vertical sectional view of a ridge structure 40. Satisfying this condition = In the example shown in FIG. 1, both sides (the second region) 42 may be lower than the central portion (the first region) 41 by a ridge structure 4 on the substrate side. 〇 In this ridge structure 40 The width 41a of the first area 41: The ratio of the width 42a of the second area (one side) 42 can be set to 丨: 10 ~ 10: ι. On the other hand, the height 41b of the i-th area 41: the second area 4 The ratio of 2 to 42b can be set to 2: ι ~ η:

In the example of FIG. 1, the second region 42 is formed symmetrically on both sides of the first region 41. Such symmetry can enhance the characteristics of horizontal and horizontal modes. In the example of Fig. 1, each of the first region 41 and the second region 42 has a uniform layer thickness (height) as a whole, but the layer thickness (height) in each region can be continuously or stepwise changed. Fig. 2 (a) shows an example in which the layer thickness (height) continuously changes in the first region. In this example, the first area 41 is pushed on both sides with its center as the boundary.

Page 10 200427165 V. Description of Invention (6). That is, the layer thickness of j in the first work area 4 i continuously decreases from the center to the periphery with a certain rate of change. The variation rate of the layer thickness is not necessarily required. Fig. 2 (b) shows an example in which the layer thickness (height) does not change stepwise in the first region. In this example, the layer thickness of the first region 41 changes stepwise. For example, since the top surface is formed in a stepped shape, the first region 41 (i.e., the first region 41 including two or more layers having mutually different thicknesses) can be formed in the step thickness. Further, the layer thickness of the first region 41 may be formed and used continuously and in a stepwise manner. 4 Figure 3 (α) shows the layer thickness (height) in a stepwise manner in the second area. In this example, as the second region 42 is gradually separated from the i-th region 41, the thickness of the second layer is continuously reduced to a push shape. That is, the thickness of the second region 42 decreases continuously in the direction from the first working area 41 = direction with a constant rate of change. The variation rate of the layer thickness is not necessarily required. Figure 3 U) shows 'layer thickness (height) in the second region in a stepwise manner :: In this example,' the layer thickness of the second region 42 will change stepwise ^^ ^ The top surface is made into a stepped shape, which can form the layer thickness into stages. The second region 42 (that is, the ground changes S. The layer thickness of the second region 42 can also be formed and used continuously and in stages. The structure is generally made of P type. One part of the coating layer and the p-type contact layer are structured in the second aspect of the invention to form the ridge structure and any of the second area S to include the p-type contact layer. Regionally and 2nd

Page 11 200427165 V. Description of the invention (7) A p-electrode is formed on the region. That is, an electrode surface with a sufficiently wide area can be secured. This can constitute a laser diode element with a low critical current density and a low operating voltage. The manufacturing method of the ridge structure including the first region 41 and the second region 42 is, for example, the following method. First, after each semiconductor layer (n-type contact layer to p-type contact layer) is grown on a substrate, if a region having a ridge structure on the surface of the p-type contact layer is covered, a striped protective film is formed by lithography. The protective film is composed of, for example, ^% oxalate compounds. Second, the area where the protective film cannot be formed is carved in the middle of the p-type coating layer. As the etching method, a reactive ion etching method (RIE) can be preferably used. Then, a protective film is retained only in the first region 4 丨 (central portion), and the protective film covering the other portion (second region) is removed. Then, the recording process was performed in the same manner as described above, and the etching did not cover the p-type junction with the protective film, and the layer = a portion. With the above process, a ridge structure in which the peripheral portion (the second area) is lowered to the substrate side by one layer than the central portion (the first area) is formed. [Embodiment] A diode element is also shown in Fig. 4 as one of the embodiments of the present invention, which is hereinafter also referred to as "LD element". 〇) The components of each layer are as follows: Composition G a N · M g AlGaN: Mg G a N · M g layer 3 p-type layer 1 9 2 p-type layer 18 1 p-type layer 17

Page 12 200427165

MQW layer 16: InGaN / GaN

3rd n-type layer 15: GaN: Si 2nd n-type layer 14: AIGaN: Si 1st n-type layer 1 3: GaN: Si buffer layer 1 2: AIN substrate 11 • Sapphire 1st η The type layer 13 serves as a 1! -Type contact layer, the second type layer 14 serves as an n-type cladding layer, the third n-type layer 15 serves as an n-type guide layer, the ^! ^^ layer 16 serves as a light-emitting layer, and the first p-type The layer 17 functions as a p-type guide layer, the second ip-type layer 18 functions as a ^ -type coating layer, and the third p-type layer 19 functions as a p-type contact layer. The buffer layer 12 is made of GaN, InN, AlGaN, InGaN, AlInGaN, or the like. Here, the n-type layers 13, 14, and 15 are made of GaN, AIGaN, InGaN, AlInGaN, or the like. Also, the η-type layer 1 3, 1, 4, and 15 are doped with Si as η-type impurities, and Ge, Se, D e, and C may also be doped as η-type impurities. In addition to the multiple quantum well structure of InGaN / GaN, the MQW layer 16 may also have a multiple quantum well structure such as AlGaN / AlGalnN. The number of quantum well layers is preferably set to 1 to 30. The P-type layers 17, 18, 19 may be composed of GaN, AIGaN, InGaN, or InAlGaN. Also, Mg of the 'ρ-type impurity may be substituted by Zn, Be, Ca, Sr, and Ba. After the p-type impurity is introduced into the p-type layer, the resistance can be reduced by a well-known method such as electron beam irradiation, plasma irradiation, or heating using a furnace or the like.

Page 13 200427165 V. Description of the invention (9) In the LD element 1 having the above structure, a group III nitrogen compound-based compound semiconductor layer on the top surface of the first n-type layer 13 may use a molecular beam pump in addition to the MOCVD method It is formed by crystallization method (MBE method), halide vapor phase incubation method (HVPE method), sputtering method, iontoelectric ore method and the like. After the semiconductor layers are stacked, a ridge structure 20 is formed. The ridge structure 20 is formed by lithography and the rest. First, a protective film (S i 02) is formed on the third p-type layer 19 in its entirety. Next, use lithography to remove a protective film.

A stripe-shaped protective film with a desired width (the width of the ridge structure 20) is made. Next, the remaining protective film is used as a mask, and the exposed portion without the protective film is sequentially removed by the third p-type layer 19 by reactive ion etching. This etching process is continued until a part of the second p-type layer 18 is removed. Next, the first region 20a and the second region 20b are formed by processing the convex portion (ridge structure 20) formed in this process. First, lithography is used to form only a portion 20a of the first area (that is, the central portion of the ridge structure 20).

Protective film, and remove the protective film covering other parts. Thus, a stripe-shaped protective film covering the central portion of the ridge structure 20 can be formed. Then, the ion etching is performed again. The third p-type layer 9 which is not covered with a protective film is etched. Finally, the protective film was removed. According to the above process, as shown in FIG. 丨, a ridge structure 20 is formed in the peripheral portion (second, domain 20b) that is one layer lower than the central portion (first area 20a) to the substrate 11 side. However, in this embodiment, any one of the i-th region 20a and the second region 20b includes the third p-type layer 19. After forming the ridge structure 20 in the above order, the n-electrode a and the mouth electrode 23 are formed. The 1 ^ electrode 22 is made of a material including ^ or 丨. After forming the ridge structure 20, the third electrode is removed by etching. P-type layer ~ 2 in type layer, and the first ^

Page 14 200427165 V. Description of the invention (ίο) The inner layer 13 does not show that the Shen layer 23 is made of Baozhou milk, Au and other materials on the first layer. It is used to make deposition electrodes. After the conventional method is formed into a wafer, the light reflection side end surface (rear end surface) is formed into an absorptive light reflection film (not shown; Γ; FIG. 5 shows a half-body laser device using an LD element manufactured through each of the above processes). For example, in order to find some elements such as today ’s g ^ θ pole, let alone the month 'is omitted in Fig. 5. The electrode or η electric LD element 1 is passed on a support 71 vertically arranged on the support 70. A discrete piece (conductive substrate) 72 is provided. The LD element "places the electrode side underneath to carry the heat dissipation member 72. A layer of insulating material is formed on the surface of the heat dissipation member 72, and this layer of insulating material is used to prevent the electrode and the Short circuit between the ρ electrodes. The cover 75 is provided with a condenser lens 77, and the LD element i is radiated to the outside through the condenser lens 77. Fig. 6A and Fig. 6B show a simulation of manufacturing a laser diode by the above method. The conditions of the $ output characteristics of the physical components. Figure 6A shows the simulation of the ridge shape. The structure is not intended. In the previous ridge structure, the width of the ridge is shown in Figure 6). The ① part is 1 · 8 // m. In the ridge structure of this embodiment, the ridge width is set. As shown in 6A (b), the part ① (the} region) is 0.6, and the part (the second region) is 0.6 # m (one side), and the total is 〇 β χ 3 = work · 8 “m . Fig. 6B shows the equivalent emissivity nef f calculated in each part ① to ③ of the ridge structure. The equivalent refractive index nef f is calculated by the following formula 3 ... "...". However, the ratio of η and the ratio ′ Γ is the ratio of light existing in each layer, which can be obtained by simulation.

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V. Description of the invention (π) Fig. 7A and Fig. 7B show the characteristic curves of the simulated junction light output, and Fig. 7B is a line graph. As illustrated by such graphs, the peaks of the peak mode of the basic mode in the structure of the embodiment are low. That is, the horizontal horizontal mode (kink level) of the embodiment of the embodiment in which the light confinement rate is south and is in the sub-mode. In addition, the closing rate of this implementation is increased, and the critical current density is reduced. Although the present invention is completely and clearly disclosed, it is attached to the application. Please explain the patent scope as including those that can be thought of by those skilled in the art and covered in this specification. All fruit. Fig. 7A shows the light output characteristic curve of the high-order mode showing the basic mode. Compared with the previous structure, the real value is high, while the light-blocking rate of the high-order mode in the basic mode is low. Therefore, it can be said that this book is more stable, and the structure of improving the level of entanglement is in the basic mode. The purpose of light sealing is not limited to specific records. It should not be limited to this record, but should be familiar with the basic teachings recorded. Change the form and replace the composition. [Industrial Applicability] According to the present invention, it is possible to provide a 111-group nitrogen compound-based compound semiconductor laser diode device of a ridge waveguide path capable of stabilizing the horizontal and lateral modes without increasing the critical current density and the operating voltage. .

Page 16 200427165 Brief description of the drawings 5. [Simplified description of the drawings] FIG. 1 is a cross-sectional view showing an example of a ridge structure used in the laser diode element of the present invention. Fig. 2 is a sectional view showing another example of the ridge structure used in the laser diode element of the present invention. Fig. 3 is a sectional view showing another example of the ridge structure used in the laser diode element of the present invention. Fig. 4 is a cross-sectional view showing the structure of a laser diode body according to an embodiment of the present invention. Fig. 5 is a diagram showing a semiconductor laser device using the laser diode element 1 of the embodiment. FIG. 6A is a schematic diagram showing a ridge structure used in an analog device. Fig. 6B is a table showing film thickness and refractive index of each layer used in the analog device. FIG. 7A is a graph showing light output characteristics in the basic mode. FIG. 7B is a graph showing light output characteristics in a high-order mode. Description of device symbols: 1 to 〃LD device 11 to substrate 12 to buffer layer 13 to first n-type layer 14 to second n-type layer 15 to third n-type layer

Page 17 200427165 Schematic illustration of 16, 4QW layer 17, 〃P-type layer 18 ~ 2 P-type layer 19 ~ 〃P-type 3 layer 2 0 ~ ridge structure 20a ~ 1 area 20b ~ 2nd area 22 ~ electrode 23, / ρ electrode 40 ~ ridge structure 41 ~ 〃 1st area 41a ~ 1st area width 41b ~ 1st area height 42 ~ / 2nd area 42a ~ 2nd area width 42b ~ 2nd area height 5 0 ~ P-type layer 70 ~ / support 71 ~ / support 72 ~ / heat dissipation member 75 ~, cover 7 7 ~ condenser lens

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Claims (1)

200427165 VI. Application Patent Scope 1. A laser diode element, which is a ridge waveguide type I group 11 nitrogen compound compound semiconductor laser diode element, having a ridge structure, the ridge structure includes: a) the first region including the central portion and continuous in the longitudinal direction; and b) the second region sandwiching the first region from both sides and having an average layer thickness smaller than the average layer thickness of the first region. 2. For the laser diode device according to item 1 of the patent application scope, wherein the second region has a bilaterally symmetrical shape in a cross section perpendicular to the longitudinal direction. 3. For the laser diode device in the first or second scope of the patent application, the layer thickness of the first area is uniform throughout. 4. If the laser diode element in the first or second scope of the patent application, wherein the top surface of the first area is formed in a stepped or push-out shape, it is continuously or stepwise reduced from the center to the periphery. Layer thickness. 5. For the laser diode device in the first or second scope of the patent application, the layer thickness of the second area is uniform throughout. 6. For the laser diode device of the first or second scope of the patent application, wherein the second region includes two or more regions with different average layer thicknesses. 7. If the laser diode element of item 1 or item 2 of the scope of patent application, Page 19 200427165 6. Scope of patent application The top surface of the second area is formed in a stepped or pushed shape, and its layer thickness is continuously or stepwise reduced as it moves away from the first area. 8. The laser diode device according to item 1 or item 2 of the patent application scope, wherein the first region and the second region each include a p-type contact layer, and a p-electrode is formed on the two regions. Page 20