Semiconductor deep ultraviolet laser and preparation method thereof

Abstract

The invention discloses a semiconductor deep ultraviolet laser and a preparation method thereof. The preparation method comprises the steps that a substrate is provided, and a first limiting layer, a first waveguide layer, a quantum well active layer, a second waveguide layer and an electron blocking layer are sequentially prepared on one side of the substrate; adopting mixed gas of nitrogen and hydrogen as carrier gas, controlling the concentration of the nitrogen and the hydrogen to gradually change and controlling the growth temperature to gradually change, and preparing a second limiting layer with a composite function on one side, far away from the substrate, of the electron blocking layer; and along the growth direction of the second limiting layer, the doping concentration of aluminum atoms in the second limiting layer is gradually changed, and the refractive index of the second limiting layer is gradually changed. According to the invention, the crystal quality of the limiting layer is improved, mg doping optimization is realized, the working voltage is reduced, the carrier absorption is reduced, the carrier injection efficiency is improved, the p-type light absorption loss is reduced, the slope efficiency of the laser is improved, and the reliability of the device is improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of semiconductor lasers, and in particular to a semiconductor deep ultraviolet laser and a method for preparing the same. Background Art

[0002] Semiconductor UV lasers are widely used in UV curing, UV laser metal processing, biotechnology and other laser processing. In recent years, with the continuous development of UV laser technology, its output power has increased from a few hundred milliwatts to several watts. The main challenge of current research is still to increase the optical output power of semiconductor UV lasers.

[0003] In the field of semiconductor deep ultraviolet laser devices based on the AlGaN material system, optical loss seriously affects the power of the laser. Factors affecting optical loss include epitaxial growth defects, light field position, carrier absorption, etc. Among them, the light absorption in the p-type region is more significant, which significantly increases the light loss and seriously reduces the laser efficiency. Summary of the invention

[0004] The present invention provides a semiconductor deep ultraviolet laser and a preparation method thereof. When an upper confinement layer is grown, a gradual change of growth atmosphere combined with a gradual change of growth temperature is adopted to achieve a gradual change of the refractive index of a second confinement layer, thereby improving the crystal quality of the confinement layer and improving the laser efficiency and reliability of the laser.

[0005] In a first aspect, the present invention provides a method for preparing a semiconductor deep ultraviolet laser, the preparation method comprising:

[0006] providing a substrate;

[0007] Sequentially preparing a first confinement layer, a first waveguide layer, a quantum well active layer, a second waveguide layer and an electron blocking layer on one side of the substrate;

[0008] A mixed gas of nitrogen and hydrogen is used as a carrier gas, and the concentration gradient of nitrogen and hydrogen and the growth temperature are controlled to gradually change, so as to prepare a second confinement layer with a composite function on the side of the electron blocking layer away from the substrate; wherein, along the growth direction of the second confinement layer, the doping concentration of aluminum atoms in the second confinement layer gradually changes, and the refractive index of the second confinement layer gradually changes.

[0009] Optionally, control the concentration gradient of nitrogen and hydrogen, including:

[0010] The gas concentration of nitrogen in the mixed gas is controlled to gradually increase, and the gas concentration of hydrogen in the mixed gas is controlled to gradually decrease.

[0011] Optionally, the gas concentration ratio of nitrogen in the mixed gas gradually increases from 0 to 1 / 3; the gas concentration ratio of hydrogen in the mixed gas gradually decreases from 1 to 2 / 3.

[0012] Optionally, control the growth temperature gradient, including:

[0013] The reaction growth temperature is controlled to gradually increase until the second confinement layer is grown and formed.

[0014] Optionally, the reaction growth temperature ranges from 950°C to 1050°C.

[0015] Optionally, a second confinement layer having a composite function is prepared on a side of the electron blocking layer away from the substrate, comprising:

[0016] During the growth of the second confinement layer, aluminum atoms and magnesium atoms are doped, and the doping concentration of the aluminum atoms is controlled to gradually decrease, while the doping concentration of the magnesium atoms is controlled to remain unchanged.

[0017] Optionally, the doping concentration of aluminum atoms in the second confinement layer is in the range of 60% to 20%.

[0018] Optionally, the thickness of the second limiting layer is controlled to be in the range of 30 nm to 100 nm; and the relative value of the slope of the refractive index between the starting film layer and the ending film layer of the second limiting layer is controlled to be in the range of 1.25 to 2.5.

[0019] Optionally, after preparing a second confinement layer having a composite function on a side of the electron blocking layer away from the substrate, the method further comprises:

[0020] The substrate is removed, and a first electrode is prepared on a side of the first confinement layer away from the first waveguide layer, and a second electrode is prepared on a side of the second confinement layer away from the electron blocking layer.

[0021] Based on the same inventive concept, in a second aspect, an embodiment of the present invention further provides a semiconductor deep ultraviolet laser, which is prepared by the method for preparing the semiconductor deep ultraviolet laser provided in the first aspect, and includes a first confinement layer, a first waveguide layer, a quantum well active layer, a second waveguide layer, an electron blocking layer, and a second confinement layer with a composite function, which are sequentially arranged;

[0022] a first electrode, located on a side of the first confinement layer away from the first waveguide layer;

[0023] a second electrode, located on a side of the second confinement layer away from the electron blocking layer;

[0024] The second confinement layer with a composite function uses a mixed gas of nitrogen and hydrogen as a carrier gas, controls the concentration gradient of nitrogen and hydrogen and controls the growth temperature gradient, and prepares the second confinement layer with a composite function on the side of the electron blocking layer away from the substrate; along the growth direction of the second confinement layer, the doping concentration of aluminum atoms in the second confinement layer gradually changes, and the refractive index of the second confinement layer gradually changes.

[0025] In summary, the preparation method of the semiconductor deep ultraviolet laser provided by the present invention optimizes the growth mode of the second confinement layer to solve the problem of light absorption loss of the deep ultraviolet laser, adopts the gradual change of the growth atmosphere combined with the gradual change of the growth temperature to achieve the gradual change of the refractive index of the second confinement layer, and improves the crystal quality of the confinement layer, thereby realizing mg doping optimization, reducing the operating voltage, reducing carrier absorption, and improving the carrier injection efficiency, while reducing the p-type light absorption loss, achieving the improvement of the slope efficiency of the laser, and improving the reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of a method for preparing a semiconductor deep ultraviolet laser provided by an embodiment of the present invention;

[0027] Figure 2 is a schematic diagram of a method for preparing a semiconductor deep ultraviolet laser provided in an embodiment of the present invention;

[0028] Figure 3 is a schematic diagram of a gradual change in the refractive index of a second confinement layer provided by an embodiment of the present invention;

[0029] Figure 4 It is a schematic structural diagram of a semiconductor deep ultraviolet laser provided in an embodiment of the present invention.

[0030] The accompanying drawings are as follows:

[0031] 1. Substrate; 2. First confinement layer; 3. First waveguide layer; 4. Quantum well active layer; 5. Second waveguide layer; 6. Electron blocking layer; 7. Second confinement layer; 8. First electrode; 9. Second electrode. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings and examples. It will be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings. It is obvious to those skilled in the art that various modifications and changes can be made in the present invention without departing from the spirit or scope of the present invention. Therefore, the present invention is intended to cover modifications and changes of the present invention that fall within the scope of the corresponding claims (technical solutions for protection) and their equivalents. It should be noted that the implementation methods provided in the embodiments of the present invention can be combined with each other without contradiction.

[0033] In view of one or more of the above problems existing in the prior art, the present invention proposes a method for preparing a semiconductor deep ultraviolet laser. Figure 1 is a flow chart of a method for preparing a semiconductor deep ultraviolet laser provided by an embodiment of the present invention, Figure 2 Schematic diagram of a method for preparing a semiconductor deep ultraviolet laser provided by an embodiment of the present invention. Figure 1 and Figure 2 The method for preparing a semiconductor deep ultraviolet laser provided in an embodiment of the present invention comprises:

[0034] S101. Provide a substrate.

[0035] Exemplarily, the material of substrate 1 includes, but is not limited to, AlN substrate, sapphire substrate, Si substrate, SiC substrate, Al2O3 / AlN composite substrate, SiC / AlN composite substrate, etc., and is not limited in comparison with the embodiments of the present invention.

[0036] S102, sequentially preparing a first confinement layer, a first waveguide layer, a quantum well active layer, a second waveguide layer and an electron blocking layer on one side of the substrate.

[0037] In an embodiment of the present invention, a first confinement layer 2 of nAlGaN material can be grown on a substrate 1 by a chemical vapor deposition process. Among them, the confinement layer is an important structure in a semiconductor laser, and plays a key role in limiting the injection of electrons and holes and limiting the propagation of light in the laser. The confinement layer can limit carrier injection so that the current is mainly injected into the laser medium region, thereby increasing the laser output power, reducing the I value current and ensuring single-mode output; the confinement layer can also limit the propagation of laser light waves, so that the laser waves propagate along the direction of the confinement layer, thereby reducing the line width of the laser and increasing the modulation speed. In an embodiment of the present invention, the first confinement layer 2 is a lower confinement layer. The first confinement layer 2 can be an n-type doped layer, for example, a Si-doped AlGaN confinement layer, referred to as an nAlGaN lower confinement layer.

[0038] A first waveguide layer 3 is grown on the surface of the first confinement layer 2 away from the substrate 1. The refractive index of the waveguide layer is generally higher than that of the confinement layer, thereby inhibiting the light field from entering the confinement layer and the substrate 1, which is beneficial to achieving the purpose of reducing the loss in the device. In the embodiment of the present invention, the first waveguide layer 3 is a lower waveguide layer. The first waveguide layer 3 can be an n-type doped waveguide layer, for example, a Si-doped InGaN waveguide layer, referred to as an nAlGaN lower waveguide layer, but is not limited thereto.

[0039] A quantum well active layer 4 is grown on the surface of the first waveguide layer 3 away from the first confinement layer 2, wherein the quantum well active layer 4 may be a multi-quantum well active layer, for example, formed by alternating quantum barrier layers and quantum well layers. One to five periods of quantum barrier layers and quantum well layers may be grown, the thickness of a single quantum well layer may be 1 nm to 5 nm, the thickness of a single quantum barrier layer may be 3 nm to 15 nm, and the materials of both the quantum well layer and the quantum barrier layer may be InGaN, but are not limited thereto.

[0040] A second waveguide layer 5 is grown on the surface of the quantum well active layer 4 away from the first waveguide layer 3. In the embodiment of the present invention, the second waveguide layer 5 is an upper waveguide layer. The second waveguide layer 5 can be a p-type waveguide layer, such as a non-doped InGaN waveguide layer, referred to as an AlGaN upper waveguide layer, but is not limited thereto.

[0041] An electron blocking layer 6 is grown on the surface of the second waveguide layer 5 away from the quantum well active layer 4. In the embodiment of the present invention, the presence of the electron blocking layer 6 can reduce carrier leakage, hinder reverse leakage, and improve the output efficiency of the laser. The electron blocking layer 6 can be a p-type doped layer, for example, an AlGaN electron blocking layer doped with magnesium atoms Mg. It is referred to as a pAlGaN electron blocking layer, but is not limited thereto.

[0042] S103, using a mixture of nitrogen and hydrogen as a carrier gas, controlling the concentration gradient of nitrogen and hydrogen and the growth temperature gradient, and preparing a second confinement layer with a composite function on the side of the electron blocking layer away from the substrate.

[0043] Wherein, along the growth direction of the second confinement layer, the doping concentration of aluminum atoms in the second confinement layer changes gradually, and the refractive index of the second confinement layer changes gradually.

[0044] A second confinement layer 7 is grown on the surface of the electron blocking layer 6 away from the second waveguide layer 5. In the embodiment of the present invention, the second confinement layer 7 is an upper confinement layer, which is a p-type doped layer, for example, a Mg-doped AlGaN confinement layer, referred to as a pAlGaN upper confinement layer, but not limited thereto.

[0045] In the growth stage of the second confinement layer 7, a mixture of nitrogen N2 and hydrogen H2 is used as a carrier gas, and the required reaction source is introduced into the reaction chamber, and the concentration gradient of the mixture of nitrogen N2 and hydrogen H2 is controlled, and the growth temperature is controlled to be gradually changed, and the second confinement layer 7 is grown on the surface of the electron blocking layer 6 away from the second waveguide layer 5 by using a chemical vapor deposition process. By changing the growth conditions of the second confinement layer 7, the doping concentration of aluminum atoms Al in the second confinement layer 7 can be gradually changed along the growth direction of the second confinement layer 7, and the refractive index of the second confinement layer 7 can be gradually changed, which is beneficial to improving the crystal quality of the second confinement layer 7, reducing the operating voltage, improving the photoelectric conversion efficiency of the device, reducing carrier absorption, improving the carrier injection efficiency, and reducing the p-type light absorption loss, thereby improving the reliability of the semiconductor deep ultraviolet laser.

[0046] It should be noted that when the second confinement layer 7 is grown in a mixed atmosphere of nitrogen N2 and hydrogen H2, and the concentrations of nitrogen N2 and hydrogen H2 gradually change, the luminous flux maintenance rate of the device can be maintained at a relatively optimal value as the light decay time increases; when the light decay time is 1000h, the luminous flux maintenance rate can still be maintained at more than 90%, which can greatly improve the device reliability.

[0047] Among them, the nitrogen N2 and hydrogen H2 used in the embodiment of the present invention are high-purity carrier gases, and the reaction source can use trimethylaluminum (TMAl), trimethylgallium (TMGa), trimethylindium (TMIn), bismuth magnesium (CP2Mg), and ammonia (NH3) as Al, Ga, In, Mg and N sources respectively. The above reaction source materials are introduced into the reaction chamber by the carrier gas to grow each film layer structure.

[0048] The preparation of each film layer in the embodiment of the present invention can utilize a chemical vapor deposition process, such as a metal organic chemical vapor deposition process. Metal organic chemical vapor deposition is a chemical vapor deposition technology that utilizes an organic metal thermal decomposition reaction to perform vapor phase epitaxial growth of thin films, and is widely used in the field of semiconductor growth.

[0049] In the embodiment of the present invention, during the growth stage of the second confinement layer 7, the concentrations of nitrogen N2 and hydrogen H2 are controlled to change gradually, and the steps include:

[0050] The gas concentration of nitrogen N2 in the mixed gas is controlled to gradually increase, and the gas concentration of hydrogen H2 in the mixed gas is controlled to gradually decrease.

[0051] Specifically, as the second confinement layer 7 grows, the gas concentration of nitrogen N2 in the mixed gas is controlled to gradually increase, and the gas concentration of hydrogen H2 in the mixed gas is controlled to gradually decrease. The concentrations of the two mixed gases change gradually, which is beneficial to the gradual change of the Al atomic component in the second confinement layer 7.

[0052] In the embodiment of the present invention, at the initial stage of growth of the second confinement layer 7, the gas concentration of nitrogen N2 in the mixed gas is greater than the gas concentration of hydrogen H2 in the mixed gas, and during the growth of the second confinement layer 7, the gas concentration ratio of nitrogen N2 in the mixed gas gradually increases from 0 to 1 / 3, and the gas concentration ratio of hydrogen H2 in the mixed gas gradually decreases from 1 to 2 / 3, that is, after the growth of the second confinement layer 7 is completed, the gas concentration of nitrogen N2 in the mixed gas is less than the gas concentration of hydrogen H2 in the mixed gas.

[0053] In the embodiment of the present invention, during the growth stage of the second confinement layer 7, controlling the growth temperature to change gradually includes:

[0054] The reaction growth temperature is controlled to gradually increase until the second confinement layer is grown and formed.

[0055] Specifically, as the second confinement layer 7 grows, the reaction growth temperature is controlled to be in the range of 950° C. to 1050° C. Exemplarily, the reaction growth temperature at the initial growth stage of the second confinement layer 7 is 950° C., and increases by 1° C. per second until the second confinement layer 7 grows and forms, which can effectively control the carbon content in the second confinement layer 7 and mitigate the polarization effect.

[0056] In an embodiment of the present invention, during the growth stage of the second confinement layer, a second confinement layer having a composite function is prepared on a side of the electron blocking layer away from the substrate, including:

[0057] During the growth of the second confinement layer, aluminum atoms and magnesium atoms are doped, and the doping concentration of the aluminum atoms is controlled to gradually decrease, while the doping concentration of the magnesium atoms is controlled to remain unchanged.

[0058] Specifically, the reaction source uses trimethylaluminum (TMAl), trimethylgallium (TMGa), trimethylindium (TMIn), bismuth magnesium (CP2Mg), and ammonia (NH3) as Al, Ga, In, Mg and N sources respectively. In the growth of the second confinement layer 7, by controlling the flow of nitrogen N2 and hydrogen H2, and then controlling the flow of the reaction source, the doping concentration of aluminum atoms Al is gradually reduced, and the doping concentration of magnesium atoms mg remains unchanged. In the embodiment of the present invention, the doping concentration of aluminum atoms Al in the second confinement layer 7 can be controlled to gradually change from 60% to 20%, and the thickness of the second confinement layer 7 is in the range of 30nm to 100nm.

[0059] In this way, effective doping of magnesium atoms mg can be achieved, which can reduce the self-compensation effect of magnesium atoms mg to a certain extent and reduce the deep energy level defects of magnesium atoms mg doping, which is beneficial to improving the injection efficiency of hole carriers and reducing the operating voltage of the device.

[0060] Among them, the self-compensation effect refers to the fact that when donor impurities are doped into the material, acceptor defects will be generated in the crystal to compensate; conversely, when acceptor impurities are doped, donor defects will be generated in the crystal to compensate. This phenomenon is called the self-compensation effect.

[0061] Deep energy levels refer to donor energy levels that are far from the bottom of the conduction band and acceptor energy levels that are far from the top of the valence band. These energy levels form multiple energy levels in the bandgap, and deep energy level impurities can produce multiple ionizations, each ionization corresponding to an energy level, thereby introducing several energy levels in the bandgap.

[0062] Injection efficiency refers to the ratio of the minority carrier current in the base region to the total current. In order to improve the injection efficiency, the doping concentration of the emitter region should be much greater than the doping concentration of the base region.

[0063] In the embodiment of the present invention, during the growth stage of the second confinement layer 7, the relative value of the slope of the refractive index between the starting film layer and the ending film layer of the second confinement layer 7 is controlled to be between 1.25 and 2.5.

[0064] For example, taking the material of the second confinement layer 7 as AlGaN, the Al component of aluminum atoms in the initial film layer of the second confinement layer 7 is controlled to be 60%, and the refractive index is 2.3225. The Al component of aluminum atoms in the end film layer of the second confinement layer 7 is 20%, and the refractive index is 2.3975. The difference in refractive index between the starting film layer and the end film layer of the second confinement layer 7 is 0.075, and the thickness range of the second confinement layer 7 is controlled to be 30nm to 60nm. By controlling the thickness change of the second confinement layer 7, the change of the refractive index can be achieved, and then the slope of the refractive index of the second confinement layer 7 can be calculated. Figure 3 is a schematic diagram of the refractive index gradient of the second confinement layer provided in an embodiment of the present invention. Figure 3 ,refer to Figure 3 , segment ab is a schematic diagram of the refractive index of the electron blocking layer 6, and segment bc is a schematic diagram of the refractive index change of the second confinement layer. The laser slope efficiency is an important parameter of laser performance, which is related to the injection efficiency and internal loss. Among them, the slope efficiency is proportional to the injection efficiency and inversely proportional to the internal loss. The slope efficiency satisfies the following formula:

[0065]

[0066] Where SE is the laser slope efficiency, η inj is the injection efficiency, α i is the internal loss, λ is the wavelength, q, h, c, α m is a constant, i, j, m are natural numbers.

[0067] In the embodiment of the present invention, the thickness of the second confinement layer 7 is between 30 nm and 60 nm, and the relative value of the slope of the refractive index between the starting film layer and the ending film layer of the second confinement layer 7 satisfies 1.25 (75 / 60) to 2.5 (75 / 30). This is beneficial to avoid light absorption caused by thick thickness, and at the same time has a higher carrier concentration, thereby improving the injection efficiency of hole carriers.

[0068] In an embodiment of the present invention, after preparing a second confinement layer having a recombination function on a side of the electron blocking layer away from the substrate, the method further includes:

[0069] The substrate is removed, and a first electrode is prepared on a side of the first confinement layer away from the first waveguide layer, and a second electrode is prepared on a side of the second confinement layer away from the electron blocking layer.

[0070] Specifically, the substrate 1 is removed, and the first electrode 8 is made on the first limiting layer 2, and the first electrode 8 is an n-electrode. A transparent conductive film ITO is prepared in advance on the second limiting layer 7, and then a p-electrode is made on the transparent conductive film ITO, that is, the second electrode 9 is composed of the transparent conductive film ITO and the p-electrode. The transparent conductive film ITO is conducive to improving the conductivity, thereby preparing a semiconductor deep ultraviolet laser with good conductivity.

[0071] Based on the same inventive concept, an embodiment of the present invention further provides a semiconductor deep ultraviolet laser, which is prepared using the method for preparing the semiconductor deep ultraviolet laser provided in the above embodiment. Figure 4 is a schematic diagram of the structure of a semiconductor deep ultraviolet laser provided by the present invention, with reference to Figure 4 In the embodiment of the present invention, the semiconductor deep ultraviolet laser includes a first confinement layer 2, a first waveguide layer 3, a quantum well active layer 4, a second waveguide layer 5, an electron blocking layer 6 and a second confinement layer 7 with a recombination function, which are arranged in sequence. The first electrode 8 is located on a side of the first confinement layer 2 away from the first waveguide layer 3, and the second electrode 9 is located on a side of the second confinement layer 7 away from the electron blocking layer 6.

[0072] Among them, the semiconductor deep ultraviolet laser has a second confinement layer 7 with a composite function, which is prepared by the preparation method provided in the above embodiment. During the growth of the second confinement layer 7, a mixed gas of nitrogen N2 and hydrogen H2 is used as a carrier gas, and the concentration gradient of nitrogen N2 and hydrogen H2 and the growth temperature gradient are controlled to grow the second confinement layer 7 with a composite function on the surface of the electron blocking layer 6 away from the substrate 1. The second confinement layer 7 is prepared, and along its growth direction, the doping concentration of aluminum atoms Al in the second confinement layer 7 gradually decreases, and the refractive index of the second confinement layer 7 changes gradually.

[0073] Exemplarily, the present invention also provides a specific implementation of a method for preparing a semiconductor deep ultraviolet laser, and the following is an overall introduction to the method for preparing a semiconductor deep ultraviolet laser using this specific implementation. The drawings and implementations disclosed in this application are only for illustrative purposes and are not intended to limit the scope of protection of the present disclosure.

[0074] Embodiment 1

[0075] In the first embodiment of the present invention, reference is made to Figure 2 Taking the preparation of a semiconductor deep ultraviolet laser with a wavelength of 280nm as an example, the preparation method is divided into the following steps:

[0076] Step S10, providing a substrate 1. The substrate 1 may be an AlN substrate, a sapphire substrate, a Si substrate, a SiC substrate, an Al2O3 / AlN composite substrate, a SiC / AlN composite substrate, or the like.

[0077] Step S11: grow a first confinement layer 2, i.e., a nAlGaN lower confinement layer, on the substrate 1. The growth temperature is 1000°C to 1200°C, and the Si-doped InGaN material has a Si atom doping concentration of 1×10 18 cm -3 ~2×10 18 cm -3 , Al% is in the range of 50%-70%, and the thickness is 2000nm~3500nm.

[0078] Step S12, growing a first waveguide layer 3, i.e., a uAlGaN lower waveguide layer, on the first confinement layer 2 material, with a growth temperature of 1000° C. to 1200° C., a thickness of 50 nm to 500 nm, and Al%: 40%-60%. For example, Al% is 50%. Al% refers to the doping concentration percentage of aluminum atoms in the first waveguide layer 3.

[0079] Step S13, growing a quantum well active layer 4 on the first waveguide layer 3. The growth temperature is 950°C to 1150°C, the Al% is in the range of 35% to 45%, and the growth is 1 to 2 cycles, wherein the thickness of the quantum well layer in the quantum well active layer 4 is 3nm to 5nm, and the thickness of the quantum barrier layer is 5nm to 15nm.

[0080] Step S14: grow a second waveguide layer 5, namely, a uAlGaN upper waveguide layer, on the quantum well active layer 4. The growth temperature is 900° C. to 1050° C., the Al% is in the range of 35% to 55%, and the thickness is 20 nm to 100 nm.

[0081] Step S15, growing an electron blocking layer 6 on the second waveguide layer 5, namely, a pAlGaN electron blocking layer, with a growth temperature of 900°C to 1050°C, an Al% in the range of 85% to 95%, a thickness of 5nm to 30nm, and a magnesium atom mg doping concentration of 5×10 17 cm -3 ~8×10 18 cm -3 .

[0082] Step S16, on the electron blocking layer 6, grow an optimized second confinement layer 7, i.e., a pAlGaN upper confinement layer. In the growth stage, the growth temperature is 900°C to 1150°C, and a nitrogen N2 and hydrogen H2 growth atmosphere is gradually changed in combination with a growth temperature gradient. N2 adopts a gradual atmosphere, and the gas concentration of nitrogen N2 in the mixed gas gradually increases from 0 to 1 / 3, and the gas concentration of hydrogen H2 in the mixed gas gradually decreases from 1 to 2 / 3. The Al component of aluminum atoms in the second confinement layer 7 gradually decreases from 60% to 20%, and the thickness is 30nm to 100nm. The magnesium atom mg doping concentration is 1×10 18 cm -3 ~1×10 19 cm -3 , the relative value of the refractive index slope is between 1.25 and 2.5. By controlling the growth temperature to gradually increase, the impurity defects of the second confinement layer 7 can be effectively controlled, such as reducing the carbon content. Since the refractive index of the second confinement layer 7 changes gradually, it is beneficial to control the minimum light absorption loss and improve the crystal quality of the confinement layer; the effective doping of magnesium atoms mg is achieved, and the self-compensation effect of magnesium atoms mg is reduced to a certain extent, thereby reducing the deep energy level defects doped with magnesium atoms mg, improving the injection efficiency of hole carriers, reducing carrier absorption, reducing p-type light absorption loss, and reducing the device operating voltage.

[0083] It should be noted that the thickness of the second confinement layer 7 cannot be too thick. If it is too thick, light absorption will increase.

[0084] Step S17 , growing a transparent conductive film ITO on the second limiting layer 7 with a thickness of 5 nm to 50 nm, making a p-electrode on the transparent conductive film ITO, and making an n-electrode on the first limiting layer 2 .

[0085] After the epitaxial growth of the device is completed, it is made into a semiconductor deep ultraviolet laser with a wavelength of 280nm through processes such as chip preparation. This laser has the advantages of high output power, low light absorption loss, better light field limitation ability, and high device reliability.

[0086] Example 2, reference Figure 2 Taking the preparation of a semiconductor deep ultraviolet laser with a wavelength of 280nm as an example, the preparation method is divided into the following steps:

[0087] Step S21, providing a substrate 1. The material of the substrate 1 can be an AlN substrate, a sapphire substrate, a Si substrate, a SiC substrate, an Al2O3 / AlN composite substrate, a SiC / AlN composite substrate, etc.

[0088] Step S22: grow a first confinement layer 2, i.e., a nAlGaN lower confinement layer, on the substrate 1. The growth temperature is 1000°C to 1200°C, and the AlGaN material is doped with Si at a doping concentration of 1×10 18 cm -3 ~2×10 18 cm -3 , Al% is in the range of 50%-70%, and the thickness is 2000nm~3500nm.

[0089] Step S23, growing the first waveguide 3, ie, the uAlGaN lower waveguide layer, on the first confinement layer 2 material, with a growth temperature of 1000° C. to 1200° C., a thickness of 50 nm to 500 nm, an Al% in the range of 40% to 60%, preferably an Al% of 50%.

[0090] Step S24, continue to grow the quantum well active layer 4 on the first waveguide layer 3, the growth temperature is 950°C to 1150°C, Al% is in the range of 35%-45%, and grows for 1 to 2 cycles, wherein the thickness of the well is 3nm to 5nm, and the thickness of the barrier is 5nm to 15nm.

[0091] Step S25, growing a second waveguide layer 5, namely a uAlGaN upper waveguide layer, on the quantum well active layer 4. The growth temperature is 900°C to 1050°C, the Al% is in the range of 35% to 55%, and the thickness is 20nm to 100nm.

[0092] Step S26, growing an electron blocking layer 6 on the second waveguide layer 5, namely, a pAlGaN electron blocking layer, with a growth temperature of 900°C to 1050°C, an Al% in the range of 85% to 95%, a thickness of 5nm to 30nm, and an Mg doping concentration of 5×10 17 cm -3 ~8×10 18 cm -3 .

[0093] Step S27: grow a second confinement layer 7, i.e., a pAlGaN upper confinement layer, on the electron blocking layer 6 at a growth temperature of 900°C to 1150°C, a thickness of 30nm to 100nm, and a mg doping concentration of 1×10 18 cm -3 ~1×10 19 cm -3 ; The Al component here is set to grow gradually by controlling the carrier gas flow rate.

[0094] Step S28 , growing a transparent conductive film ITO with a thickness of 5 nm to 50 nm on the second limiting layer 7 , making a p-electrode on the transparent conductive film ITO, and making an n-electrode on the first limiting layer 2 .

[0095] After the epitaxial growth of the device is completed, it is made into a semiconductor deep ultraviolet laser with a wavelength of 280nm through processes such as chip preparation. This laser has the advantages of high output power, low light absorption loss and high device reliability.

[0096] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for preparing a semiconductor deep ultraviolet laser, characterized in that: The preparation method comprises: providing a substrate; Sequentially preparing a first confinement layer, a first waveguide layer, a quantum well active layer, a second waveguide layer and an electron blocking layer on one side of the substrate; A mixed gas of nitrogen and hydrogen is used as a carrier gas, and the concentration gradient of nitrogen and hydrogen and the growth temperature are controlled to gradually change, so as to prepare a second confinement layer with a composite function on the side of the electron blocking layer away from the substrate; wherein, along the growth direction of the second confinement layer, the doping concentration of aluminum atoms in the second confinement layer gradually changes, and the refractive index of the second confinement layer gradually changes.

2. The preparation method according to claim 1, characterized in that: Control the concentration gradient of nitrogen and hydrogen, including: The gas concentration of nitrogen in the mixed gas is controlled to gradually increase, and the gas concentration of hydrogen in the mixed gas is controlled to gradually decrease.

3. The preparation method according to claim 2, characterized in that: The gas concentration ratio of nitrogen in the mixed gas gradually increases from 0 to 1 / 3; the gas concentration ratio of hydrogen in the mixed gas gradually decreases from 1 to 2 / 3.

4. The preparation method according to claim 1, characterized in that: Controlling the growth temperature gradient, including: The reaction growth temperature is controlled to gradually increase until the second confinement layer grows and forms.

5. The preparation method according to claim 4, characterized in that: The reaction growth temperature ranges from 950°C to 1050°C.

6. The preparation method according to claim 1, characterized in that: A second confinement layer having a composite function is prepared on a side of the electron blocking layer away from the substrate, comprising: During the growth of the second confinement layer, aluminum atoms and magnesium atoms are doped, and the doping concentration of the aluminum atoms is controlled to gradually decrease, while the doping concentration of the magnesium atoms is controlled to remain unchanged.

7. The preparation method according to claim 1, characterized in that: The doping concentration of aluminum atoms in the second confinement layer is in the range of 60% to 20%.

8. The preparation method according to claim 1, characterized in that: The thickness of the second limiting layer is controlled to be in the range of 30 nm to 100 nm; and the relative value of the slope of the refractive index between the starting film layer and the ending film layer of the second limiting layer is controlled to be in the range of 1.25 to 2.

5.

9. The preparation method according to claim 1, characterized in that: After preparing a second confinement layer having a recombination function on a side of the electron blocking layer away from the substrate, the method further comprises: The substrate is removed, and a first electrode is prepared on a side of the first confinement layer away from the first waveguide layer, and a second electrode is prepared on a side of the second confinement layer away from the electron blocking layer.

10. A semiconductor deep ultraviolet laser, prepared by the method for preparing a semiconductor deep ultraviolet laser according to any one of claims 1 to 9, characterized in that: It includes a first limiting layer, a first waveguide layer, a quantum well active layer, a second waveguide layer, an electron blocking layer and a second limiting layer with a composite function which are arranged in sequence; A first electrode is located on a side of the first confinement layer away from the first waveguide layer; a second electrode, located on a side of the second confinement layer away from the electron blocking layer; The second confinement layer with a composite function uses a mixed gas of nitrogen and hydrogen as a carrier gas, controls the concentration gradient of nitrogen and hydrogen and controls the growth temperature gradient, and prepares the second confinement layer with a composite function on the side of the electron blocking layer away from the substrate; along the growth direction of the second confinement layer, the doping concentration of aluminum atoms in the second confinement layer gradually changes, and the refractive index of the second confinement layer gradually changes.

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