A semiconductor laser emitter

Abstract

The present invention provides a semiconductor laser emitter, characterized in that it includes: a first DBR layer, a second DBR layer, and a quantum well active region disposed between the first DBR layer and the second DBR layer; a first electrode at least partially included within the first DBR layer. The design of including at least part of the first electrode within the first DBR layer reduces the P-type DBR heterojunction interface through which the current flows, thereby reducing the DBR series resistance. At the same time, it can ensure the current density at the center of the active region.

Description

Technical Field

[0001] The present invention relates to the technical field of lasers, and more particularly, to a semiconductor laser emitter. Background Art

[0002] Semiconductor lasers, due to their excellent controllability and the ease of implementing array-type integrated designs, are increasingly used in various detection processes. By controlling characteristics such as voltage, it is also relatively convenient to adjust laser parameters, which is very beneficial for the entire system. A semiconductor laser refers to a laser with a semiconductor material as the working substance, also known as a semiconductor laser diode (LD), which is a type of laser developed in the 1960s. There are dozens of working substances for semiconductor lasers, such as gallium arsenide (GaAs), cadmium sulfide (CdS), etc. The excitation methods mainly include three types: electrical injection, optical pumping, and high-energy electron beam excitation. The advantages of semiconductor lasers mainly include the following aspects: 1) Small size and light weight. 2) Injectable excitation: It can be driven by injecting a current of milliamperes with a voltage of only a few volts. No other excitation equipment and components are required except for the power supply device. Electrical power is directly converted into optical power, with high energy efficiency. 3) Wide wavelength range: By appropriately selecting materials and alloy ratios, lasers with arbitrary wavelengths can be achieved within a very wide wavelength range from infrared to visible light. 4) Direct modulation: By overlapping the signal on the drive current, within the range from direct current to G hertz, the oscillation intensity, frequency, and phase can be modulated. 5) High coherence: High-spatial-coherence output light can be obtained using a single transverse mode laser. Stable single-longitudinal-mode lasing can be achieved in distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers, obtaining high temporal coherence, and other advantages.

[0003] One type of semiconductor laser that is currently widely used is the surface-emitting semiconductor laser, which also has many advantages compared to traditional edge-emitting lasers. Among surface-emitting semiconductor lasers, the vertical-cavity surface-emitting laser (VCSEL) has become a research hotspot in the optoelectronics field due to its low threshold, circular beam, easy coupling, and easy two-dimensional integration, and it also has advantages such as a high side-mode suppression ratio, low threshold, small size, easy integration, and high output power. In fiber optic communication systems, a long-wavelength vertical-cavity surface-emitting laser light source operating in dynamic single-mode is an indispensable key component. It is mainly used for medium-distance and long-distance high-speed data communication, optical interconnection, optical parallel processing, and optical recognition systems, and has important applications in metropolitan area networks and wide area networks.

[0004] The basic structure of the vertical-cavity surface-emitting laser (VCSEL) is as Figure 1As shown in the figure, it includes upper and lower Distributed Bragg Reflectors (DBRs), oxidation confinement holes, multiple quantum well active regions, and ohmic contact electrodes. The quantum well active region is located between the n-type doped and p-type doped DBRs. The DBR mirrors have a reflectivity greater than 99%, and are formed by alternately epitaxially growing high and low refractive index media or semiconductor materials. The optical thickness of each layer of material is 1 / 4 of the laser wavelength. The optical thickness of the active region is an integer multiple of 1 / 2 (or (2k + 1)*1 / 2) of the laser wavelength to satisfy the resonance condition.

[0005] The DBR mirrors can not only provide high reflectivity, but also become the current path after doping and have conductivity. Moreover, the greater the refractive index difference between the two semiconductor materials of the DBR, the fewer the number of pairs required to obtain high reflectivity. However, since there is an approximately linear relationship between the energy band of semiconductor materials and the refractive index of the materials, the greater the refractive index difference between the two materials, the greater the band gap difference. Therefore, the energy band discontinuity at the interface of the homojunction formed by the two semiconductor materials is also greater, and the potential barrier at the interface of the heterojunction is higher. These potential barriers will form a large resistance. Since holes have a larger effective mass, the situation is more serious in the P-type DBR. The large resistance causes the device to generate more Joule heat, which hinders the high-power output of the device. In order to reduce the resistance, it is necessary to eliminate the potential barrier at the interface of the heterojunction, improve the energy band discontinuity, and achieve the continuity of the conduction band or valence band. Commonly used methods can use high doping near the interface or adopt a superlattice structure to increase the tunneling effect to reduce the heterojunction potential barrier; or use a graded composition at the interface to make the energy band near the interface flat, thereby reducing the potential barrier. However, these methods all have problems such as complex processes, high costs, and poor reliability. Therefore, it is an urgent problem to develop a solution that can eliminate the potential barrier at the interface of the heterojunction and has high reliability and low cost. Summary of the Invention

[0006] The object of the present invention is to provide a semiconductor laser emitter for the deficiencies in the above-mentioned prior art, so as to solve a series of problems caused by the high potential barrier at the interface of the heterojunction in the related art, such as the large resistance formed by these potential barriers resulting in a large amount of heat generation in the device, and even seriously causing the entire laser emitter to be unusable.

[0007] To achieve the above object, the technical solutions adopted in the embodiments of the present invention are as follows:

[0008] The embodiments of the present invention provide a semiconductor laser emitter, characterized in that it includes:

[0009] A first DBR layer, a second DBR layer, a quantum well active region disposed between the first DBR layer and the second DBR layer; a first electrode at least partially included within the first DBR layer.

[0010] Optionally, it further includes a buffer layer, and the buffer layer is connected to the second DBR layer.

[0011] Optionally, the first DBR layer and / or the second DBR layer is a semiconductor multi-layer mirror structure, and the optical thickness of each DBR layer is (2k + 1) times of 1 / 4 wavelength, where k is a natural number.

[0012] Optionally, the first DBR layer is P-type doped and the second DBR layer is N-type doped.

[0013] Optionally, the width of the electrode included in at least one cross-section of the first DBR layer is less than or equal to the width of the electrode not included in the first DBR layer.

[0014] Optionally, the buffer layer or the active region is further connected to a second electrode at the interface with the substrate.

[0015] Optionally, on at least one cross-section of the laser emitter, the width of the first DBR layer is less than the width of the second DBR layer.

[0016] Optionally, it further includes a second electrode that is at least partially connected to the second DBR layer wider than the first DBR layer.

[0017] Optionally, the depth of the first electrode included in the first DBR layer is 1 / 4 to 3 / 4 of the thickness of the first DBR layer.

[0018] Optionally, an oxidation confinement layer is further included between the first electrode included in the first DBR layer and the first DBR layer at least partially.

[0019] The beneficial effects of the present invention are as follows: An embodiment of the present invention provides a semiconductor laser emitter, which is characterized by including: a first DBR layer, a second DBR layer, and a quantum well active region disposed between the first DBR layer and the second DBR layer; a first electrode at least partially included within the first DBR layer. Since there is an approximately linear relationship between the energy band of a semiconductor material and the refractive index of the material, the larger the refractive index difference between two materials, the larger the bandgap difference between them. Therefore, the energy band discontinuity at the interface of a homotype heterojunction formed by two semiconductor materials is also larger, and the potential barrier at the interface of the heterojunction is higher. These potential barriers will form a relatively large resistance. Since holes have a larger effective mass, the situation is more serious in a P-type DBR. The relatively large resistance causes the device to generate more Joule heat, which hinders the high-power output of the device. In order to reduce the resistance, it is necessary to eliminate the potential barrier at the heterojunction interface, improve the energy band discontinuity, and achieve the continuity of the conduction band or valence band. By including at least a part of the first electrode within the first DBR layer, the potential barrier at the heterojunction interface can be eliminated, thereby reducing the resistance. During the use of the device, serious heating phenomena can also be avoided, which further ensures the reliability of the entire device during use, and ensures the accuracy and lifespan of the device, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0021] Figure 1 FIG. 9 is a schematic structural diagram of a laser emitter provided in the prior art;

[0022] Figure 2 FIG. 13 is a schematic structural diagram of another laser emitter provided in the prior art;

[0023] Figure 3 FIG. 17 is a schematic structural diagram of yet another laser emitter provided in the prior art;

[0024] Figure 4 FIG. 21 is a schematic structural diagram of a laser emitter provided by an embodiment of the present invention;

[0025] Figure 5 FIG. 25 is a schematic structural diagram of another laser emitter provided by an embodiment of the present invention;

[0026] Figure 6 FIG. 29 is a schematic structural diagram of yet another laser emitter provided by an embodiment of the present invention;

[0027] Figure 7Schematic diagram of another structure of the laser emitter provided by an embodiment of the present invention;

[0028] Figure 8 Schematic diagram of another structure of the laser emitter provided by an embodiment of the present invention;

[0029] Figure 9 Schematic diagram of a structure of a first electrode provided by an embodiment of the present invention. Detailed implementation manners

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0031] Figure 1This is an example diagram of a laser emitter disclosed in the prior art, including a first electrode 101. The first electrode can be made of materials such as gold (Au), germanium (Ge), silver (Ag), palladium (Pd), platinum (Pt), nickel (Ni), titanium (Ti), vanadium (V), tungsten (W), chromium (Cr), aluminum (Al), copper (Cu), zinc (Zn), tin (Sn), and indium (In). Of course, it is not limited to metal materials and can also be a transparent electrode formed from metal oxides. The first electrode is connected to a first DBR layer 102, wherein the first DBR layer 102 has a stacked structure in which low-refractive index layers and high-refractive index layers are alternately stacked. The low-refractive index layer is, for example, p-type AlX1Ga(1-X1)As (0<X1<1) with an optical film thickness of λ / 4 (or (2k+1)*λ / 4). The high refractive index layer is, for example, p-type AlX2Ga(1-X2)As (0≤X2<X7) with an optical film thickness of λ / 4 (or (2k+1)*λ / 4). This is only an exemplary explanation, and there is no specific limitation on the implementation material. It only needs to meet the Bragg-type structure setting of alternating stacking of medium and low refractive indices and high refractive indices. 107 is an oxidized confinement layer, which plays a role in limiting the generated photons, so that the generated laser is emitted more centrally. At the same time, it can reduce the refractive index of the resonator to increase the light loss of the high-order transverse mode in this position and thereby suppress oscillation, wherein the strongest intensity can be obtained in the high-order transverse mode, thereby achieving a better focusing effect. The specific material is not limited here. 103a, 103b and 103c constitute the active region of the emitter. The active region 103 has a quantum well structure. In the quantum well structure, quantum well layers of undoped Al0.11As0.89GaAs quantum well layers with a thickness of 8nm and barrier layers of undoped Al0.3Ga0.7As layers with a thickness of 5nm are alternately stacked. For example, the active region 103 is designed to emit light with a wavelength of 780nm. The optical thickness of the active region 103 is an integer multiple of 1 / 2 laser wavelength to meet the resonance condition. The isolation layer formed by the undoped Al0.6Ga0.4As layer as a layer used to form the active region 3 includes a quantum well structure at its center. Of course, this is only an example description and does not limit the specific material and thickness, as well as the wavelength of the emitted light and other characteristics. The film thickness of the entire isolation layer is the same as λ / n r is as large as an integer multiple of λ, where λ is the oscillation wavelength and n ris the refractive index of the medium. The other end of the active region 103 is connected to the second DBR layer 104, which has a laminated structure in which low refractive index layers and high refractive index layers are alternately stacked. The low refractive index layer is, for example, n-type AlX3Ga(1-X3)As (0 < X3 < 1) with an optical film thickness of λ / 4 (or (2k + 1)*λ / 4). λ represents the oscillation wavelength of the semiconductor laser 1. The high refractive index layer is, for example, n-type AlX4Ga(1-X4)As (0 ≤ X4 < X3) with an optical film thickness of λ / 4 (or (2k + 1)*λ / 4). Similar to the structure of the first DBR layer 102, the specific materials are not limited here, and a Bragg-type structure with alternately stacked low and high refractive indices can also be formed by other materials. The DBR reflection region set in this way can have a reflectivity greater than 99%. The second DBR layer 104 can further be connected to a substrate layer 105, which is, for example, composed of a gallium arsenide (GaAs) substrate layer 105. The substrate layer 105 is made of a material that is highly transparent to the stacked structure (more specifically, to the light generated by the active layer 103). The substrate layer 105 can be made of indium phosphide (InP), gallium nitride (GaN), indium gallium nitride (InGaN), sapphire, silicon (Si), silicon carbide (SiC), etc. The materials listed here are not the only ones that can be used. Further, the substrate layer 105 is also connected to the second electrode 106, which can be made of a material similar to the first electrode 101. By applying pressure to the electrodes, Figure 1 The emitter can emit laser light. The DBR mirror (including the first DBR layer 101 and the second DBR layer 104) can not only provide a high reflectivity, but also become a current path after doping to make it conductive. Moreover, the greater the refractive index difference between the two semiconductor materials of the DBR, the fewer the number of pairs required to obtain a high reflectivity. However, since there is an approximately linear relationship between the energy band of the semiconductor material and the refractive index of the material, the greater the refractive index difference between the two materials, the greater the band gap difference. Therefore, the energy band discontinuity at the homojunction interface formed by the two semiconductor materials is also greater, and the potential barrier at the interface of the heterojunction is also higher. These potential barriers will form a large resistance. Since holes have a larger effective mass, the situation is more serious in the P-type DBR. The large resistance causes the device to generate more Joule heat, which hinders the high-power output of the device. To reduce the resistance, it is necessary to eliminate the potential barrier at the heterojunction interface, improve the energy band discontinuity, and achieve the continuity of the conduction band or valence band. Commonly used methods can be to use high doping near the interface or adopt a superlattice structure to increase the tunneling effect to reduce the heterojunction potential barrier; or to adopt a graded composition at the interface to make the energy band near the interface flat, thereby reducing the potential barrier; or to insert a single intermediate composition layer between the high and low Al composition layers to form a gradient composition, which can reduce the potential barrier. To reduce the DBR series resistance, the electrode is usually directly in contact with the active region, such as Figure 2 , Figure 3As shown, however, this structure will reduce the current density at the center of the active region and increase the threshold current. From the above analysis, it can be seen that in the prior art, for the scheme of reducing or eliminating the barrier to obtain a lower resistance and a smaller heat generation, there is a defect of reducing the current density at the center of the active region and increasing the threshold current, resulting in problems such as quality, reliability, and lifespan in the application of the device.

[0032] Figure 4 FIG. is a schematic structural diagram of a laser emitter provided by an embodiment of the present invention. Similar to Figure 1 the functions and materials of each layer therein, details are not described herein. The improvement of the present invention lies in that at least a part of the first electrode 401 is included in the first DBR layer 402. Here, it can be etched in the DBR layer through processes such as etching, and then the first electrode is embedded therein. The vertical electrode is located in the P-type DBR. This structure reduces the P-type DBR heterojunction interface through which the current flows, thereby reducing the DBR series resistance. At the same time, it can ensure the current density at the center of the active region. Considering the current-limiting effect of the oxidation confinement hole 407, through experiments and other means, it can be found that the depth of the first electrode included in the first DBR layer is 1 / 4 to 3 / 4 of the thickness of the first DBR layer. The optimal position of the bottom of the P vertical electrode should be higher than 1 / 4 times the height of the P-type DBR, so as to ensure the maximum reduction of the barrier and the reliability defined by the oxidation confinement hole 407.

[0033] Figure 5 FIG. is a schematic structural diagram of another laser emitter provided by an embodiment of the present invention. Different from Figure 4 it is that on at least one cross-section of the laser emitter, the width of the first DBR layer 502 is smaller than the width of the second DBR layer 504, thus forming a stepped shape. The second electrode 506 can be arranged at the step, which can further reduce the barrier and also reduce the current threshold. The voltage applied to the active region is also easier to accurately control, and the heat generation of the device is smaller.

[0034] Figure 6 FIG. is a schematic structural diagram of yet another laser emitter provided by an embodiment of the present invention. Similar to Figure 5 its structure, it is provided with more steps and gradients, so that the first electrode can partially act directly on the active region, further reducing the barrier on the premise of ensuring higher energy efficiency conversion, and further improving the reliability, lifespan, and quality of the entire device.

[0035] Figure 7 FIG. is a schematic structural diagram of yet another laser emitter provided by an embodiment of the present invention. Different from Figure 4The difference lies in that considering that metals have a relatively large absorption rate for photons, more photons will be encountered on the sidewalls of the first electrode 701 embedded in the first DBR region 702 than on the upper surface, thus affecting the light extraction efficiency of the VCSEL. The lower surface of the first electrode 701 is located above the oxidation confinement layer, and the oxidation confinement layer has already restricted photons, so the absorption of photons by the lower surface of the electrode is also very limited. Therefore, the photon absorption on the sidewalls of the first electrode 701 close to the active region should be mainly restricted. After etching out the groove, the sidewalls close to the center of the active region can be slightly oxidized to form an oxidation confinement layer 708, thereby reducing the absorption of photons by the metal. Other structures are similar to Figure 4 the structure and will not be elaborated here.

[0036] Figure 8 As shown in the structural schematic diagram of another laser emitter provided by an embodiment of the present invention, considering the modulation effect of the electrode on light extraction, a part of the vertical electrode may not coincide with the projection area of the surface electrode. For example, Figure 8 as shown, the electrode can be a T-shaped structure, so as to form a higher modulation efficiency. At the same time, it is not necessary to set a large-sized etching structure in the first DBR layer of the device, thereby ensuring the reliability of the device. Combined with the oxidation confinement layer 808 on the sidewalls, it is ensured that while reducing the DBR series resistance of the device, the current density at the center of the active region can be effectively guaranteed, the photoelectric conversion rate is improved, and the threshold current is reduced.

[0037] Figure 9 As shown in the structural schematic diagram of a first electrode provided by an embodiment of the present invention, this structure is Figure 8 a specific implementation of the first electrode in

[0038] The following technical advantages are achieved through the technical solution of the present invention: 1) While reducing the DBR series resistance, the current density at the center of the active region can be effectively guaranteed; 2) The photoelectric conversion rate is improved and the threshold current is reduced.

[0039] It should be noted that in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0040] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application. It should be noted that similar reference numerals and letters indicate similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A semiconductor laser emitter, characterized in that, Comprising: A first DBR layer, a second DBR layer, and a quantum well active region disposed between the first DBR layer and the second DBR layer; A first electrode at least partially contained within the first DBR layer, the first electrode being a P-type vertical electrode; The depth of the first electrode is 1 / 4 - 3 / 4 of the thickness of the first DBR layer; the lowest position of the first electrode is higher than 1 / 4 of the height of the first DBR layer.

2. The semiconductor laser emitter according to claim 1, characterized in that, It further includes a substrate layer, and the substrate layer is connected to the second DBR layer.

3. The semiconductor laser emitter according to claim 1, characterized in that, The first DBR layer and / or the second DBR layer is a semiconductor multi-layer mirror structure, and the optical thickness of each DBR layer is (2k + 1) times 1 / 4 wavelength, where k is a natural number.

4. The semiconductor laser emitter according to claim 1, characterized in that, The first DBR layer is P-type doped, and the second DBR layer is N-type doped.

5. The semiconductor laser emitter according to claim 1, characterized in that, The width of the electrode contained in at least one cross-section of the first DBR layer is less than or equal to the width of the electrode not contained in the first DBR layer.

6. The semiconductor laser emitter according to claim 2, characterized in that, A second electrode is also connected at the interface between the substrate layer or the active region and the substrate.

7. The semiconductor laser emitter according to claim 1, characterized in that, On at least one cross-section of the laser emitter, the width of the first DBR layer is less than the width of the second DBR layer.

8. The semiconductor laser emitter according to claim 7, characterized in that, It further includes a second electrode at least partially connected to the second DBR layer wider than the first DBR layer.

9. The semiconductor laser emitter according to claim 1, wherein The depth of the first electrode contained within the first DBR layer is 1 / 4 - 3 / 4 of the thickness of the first DBR layer.

10. The semiconductor laser emitter according to claim 1, characterized in that, An oxidation confinement layer is further included between at least a part of the first electrode contained within the first DBR layer and the first DBR layer.

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