Epitaxial structure of ultraviolet electronic device and optoelectronic device

Abstract

The utility model discloses an epitaxial structure of an ultraviolet electronic device and an optoelectronic device. The stacked structure comprises an n-type semiconductor structure layer, a functional layer and a p-type semiconductor structure layer which are stacked, and the p-type semiconductor structure layer comprises an electron barrier layer, a hole transport layer and a contact layer which are stacked in a selected direction; the p-type semiconductor structure layer further comprises a black line layer, the black line layer is arranged between the hole transport layer and the contact layer, the electron blocking layer, the hole transport layer and the black line layer are all made of an Al-containing III-nitride semiconductor material, the contact layer is made of an Al-containing or Al-free III-nitride semiconductor material, and the hole transport layer and the contact layer are arranged on the p-type semiconductor structure layer. The band gap of the black line layer is higher than the band gap of any one of the contact layer and the hole transport layer. The laminated structure provided by the utility model can effectively prevent impurities, vacancies and other defects of the low-temperature contact layer from diffusing to the functional layer, and effectively improves the reliability and service life of the device.

Description

Technical Field

[0001] The utility model particularly relates to an epitaxial structure of an ultraviolet optoelectronic device and an optoelectronic device, belonging to the technical field of semiconductor devices. Background Art

[0002] GaN and AlGaN thin film materials have excellent characteristics such as large bandgap width, direct bandgap structure, stable chemical bonds, high breakdown voltage, strong piezoelectric effect, etc., so they have broad application prospects in optoelectronics, power electronics, and communications. AlGaN-based deep ultraviolet light-emitting devices and detection devices with AlN as the bottom layer can be widely used in disinfection, purification, medical treatment, communications and other fields, and the market prospects are very large.

[0003] The use of III-V or II-VI compound semiconductors or light-emitting devices such as laser diodes can achieve various colors such as red, green, blue and ultraviolet due to the development of thin film growth technology, and by using fluorescent materials or combined colors, effective white light can be achieved by using fluorescent materials. Compared with traditional light sources such as fluorescent lamps, incandescent lamps, etc., these light-emitting devices also have the advantages of low power consumption, semi-permanent life, fast response time, safety and environmental friendliness. In particular, the hole concentration of p-type (Al) GaN materials plays a very important role in the performance of optoelectronic devices. However, for p-AlGaN with an Al component of more than 50%, its Mg activation energy is nearly 200meV higher than that of p-GaN materials, which means that the Mg activation efficiency in p-AlGaN is very low, and the hole concentration that can be generated is low. In addition, the effective mass of the hole itself is large and the mobility is low, which will inevitably lead to a high resistivity of the p-AlGaN material and poor lateral expansion of the current in the p-type layer, resulting in high junction temperature and poor reliability of the device.

[0004] At the same time, during the vertical growth of the epitaxial structure corresponding to the initial growth stage, crystal defects are generated at the boundary where the epitaxial structure merges with the AlN island. Crystal defects are generated in various forms, such as "line dislocations" that penetrate to the surface of the optoelectronic device, "point defects", or the above-mentioned "mixed" defects, which seriously affect the reliability of the device. In particular, when the "threading dislocation" extends from the sapphire substrate to the surface of the device, it passes through the light-emitting quantum well of the functional layer. Therefore, the "threading dislocation" becomes a current path for leakage current, etc. When a high voltage such as ESD is applied instantaneously, the functional layer is destroyed or the optical power is reduced, which becomes a fundamental reason for seriously affecting reliability.

[0005] Poor reliability and short life are one of the main bottlenecks for the widespread application of AlGaN-based deep ultraviolet optoelectronic devices. Therefore, it is crucial to develop a method to effectively improve the reliability of deep ultraviolet optoelectronic devices. The main technical solution for reducing the existing defect density such as dislocations is to improve the crystal quality of the underlying AlN epitaxial thin film. Generally, a two-step growth scheme similar to GaN epitaxial growth is adopted, such as CN 109065438 A. First, an AlN nucleation layer is grown on the substrate by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE) growth or sputtering. Secondly, AlN is grown at high temperature after high temperature annealing in MOCVD. Due to the low surface migration ability of Al atoms, the two-step growth of AlN has a very limited effect on the crystal quality. Therefore, some surfactants such as Ga, In, etc. are often added during the growth process, such as patents CN 105543969A and CN 103695999A. In addition, it is also possible to pulse NH by continuously introducing an Al source while introducing NH 3 To increase the surface mobility of Al atoms and improve the crystal quality of AlN grown by the two-step method, as shown in patent CN 106252211 A.

[0006] In addition, there are some other technical solutions, such as the alternating growth of AlN at high and low temperatures (CN 107083539 A) and the alternating growth of AlN at high and low V / III ratios (CN 104392909 A). This type of technical solution promotes the alternating evolution of epitaxial surface roughening and flattening during the growth process by alternating certain growth conditions. In this way, some dislocations will be bent by the mirror force of some inclined growth crystal planes, promoting the interaction and even annihilation between dislocations, and no longer extending upward, thereby reducing the dislocation density in the subsequently grown AlN. In addition, AlON can also be grown on AlN or AlGaN film, and then the formed AlON can be used in the next step of epitaxial growth to further block and annihilate penetrating dislocations, thereby improving the crystal quality. At the same time, there is no problem of difficult merging of AlN lateral epitaxy.

[0007] However, the above-mentioned existing technical solutions for reducing dislocation density all remain at the epitaxial layer below the active area. In the actual growth process of optoelectronic devices, some dislocations and point defects will also be generated during the growth of p(Al)GaN materials above the active area. Moreover, due to the closer distance to the active area, the device is more likely to diffuse into the functional layer when operating at high current and high temperature, thereby resulting in reduced device optical power and reliability degradation. Utility Model Content

[0008] The main purpose of the utility model is to provide an epitaxial structure of an ultraviolet optoelectronic device and an optoelectronic device, thereby overcoming the deficiencies in the prior art.

[0009] In order to achieve the above-mentioned utility model purpose, the technical solution adopted by the utility model includes:

[0010] On the one hand, the utility model provides a stacked structure, comprising an n-type semiconductor structure layer, a functional layer and a p-type semiconductor structure layer which are sequentially stacked along a selected direction, wherein the p-type semiconductor structure layer comprises an electron blocking layer, a hole transport layer and a contact layer which are stacked along the selected direction; the p-type semiconductor structure layer also comprises a black line layer, wherein the black line layer is arranged between the hole transport layer and the contact layer, the electron blocking layer, the hole transport layer and the black line layer are all formed of a III-group nitride semiconductor material containing Al, the contact layer is formed of a III-group nitride semiconductor material containing Al and / or not containing Al, and the band gap of the black line layer is higher than the band gap of the contact layer.

[0011] Furthermore, the thickness of the black line layer is 0.1-10 nm.

[0012] Furthermore, the thickness of the black line layer is 0.3nm-2.0nm.

[0013] Furthermore, the molar content of the Al component of the black line layer is 0.3-1.0.

[0014] Furthermore, the molar content of the Al component of the black line layer is 0.5-0.9.

[0015] Furthermore, the band gap of the black line layer is higher than the band gap of the hole transport layer.

[0016] Furthermore, the functional layer is an active layer, and the active layer includes a well layer and a barrier layer. The components of the well layer are arranged so that the active layer can emit light in the deep ultraviolet band.

[0017] Furthermore, the band gap of the contact layer is lower than the band gap of the well layer in the functional layer, and the band gap of the hole transport layer is higher than the band gap of the well layer in the functional layer.

[0018] Furthermore, the molar content of the Al component of the contact layer is 0≤Al≤0.4.

[0019] In a more specific embodiment, the contact layer includes a first contact layer and a second contact layer, the second contact layer is closer to the functional layer than the first contact layer, the second contact layer is an AlInGaN contact layer containing Al or an AlGaN contact layer, the first contact layer is an AlInGaN contact layer containing Al or a GaN contact layer not containing Al, and the band gap of the first contact layer is higher than the band gap of the second contact layer.

[0020] Furthermore, the thickness of the first contact layer is 5nm-30nm, and the thickness of the second contact layer is 3nm-20nm.

[0021] Furthermore, the molar content of the Al component in the first contact layer decreases in a stepwise or gradually manner along the direction from the functional layer to the contact layer.

[0022] Furthermore, the contact layer is a superlattice structure.

[0023] Furthermore, the black line layer is also arranged inside the contact layer.

[0024] In a more specific embodiment, the black line layer is also disposed between the first contact layer and the second contact layer.

[0025] Furthermore, the molar content of the Al component of the hole transport layer gradually decreases along the direction from the functional layer to the contact layer.

[0026] In a more specific embodiment, the stacked structure further includes: a spacer layer, which is arranged between the hole transport layer and the electron blocking layer, between the electron blocking layer and the functional layer, or inside the electron blocking layer, and the band gap of the spacer layer is larger than the band gap of the electron blocking layer.

[0027] Further, the molar content of the Al component of the spacer layer is greater than the molar content of the Al component of the black line layer, the molar content of the Al component of the spacer layer is 0.8-1.0, and the thickness of the spacer layer is 0.2nm-20nm;

[0028] On the other hand, the utility model further provides a light-emitting device, wherein the light-emitting device comprises the stacked structure.

[0029] On the other hand, the utility model further provides an optoelectronic device, wherein the optoelectronic device comprises the stacked structure.

[0030] Furthermore, the optoelectronic device may be a deep ultraviolet optoelectronic device. Furthermore, the optoelectronic device may be a photodetector or the like.

[0031] Compared with the prior art, the stacked structure provided by the utility model can effectively block the impurities, vacancies and other defects of the low-temperature contact layer from diffusing to the functional layer. It should be noted that the use of a high-temperature contact layer will cause the surface morphology of the sample to deteriorate and the Mg incorporation efficiency to decrease. Therefore, a medium-low temperature contact layer is often used during growth, but medium-low temperature growth will introduce defects such as impurities and vacancies. The black line layer with a high Al component can effectively block the defects from diffusing to the quantum well functional layer. This aspect can effectively improve the reliability and service life of ultraviolet light-emitting devices or other optoelectronic devices. For solving the problem of ultraviolet optoelectronic devices, it can especially greatly improve the aging performance and service life of deep ultraviolet light-emitting devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of a UV-LED stacked structure provided in a typical implementation case of the utility model;

[0033] Figure 2 This is a TEM image of a hole transport layer and a black line layer in a UV-LED stacked structure provided in a typical implementation case of the utility model;

[0034] Figure 3 This is a Tofsims data diagram of a UV-LED stacked structure provided in a typical implementation case of the utility model;

[0035] Figure 4 The aging residual radiation flux data of LED chips formed by a UV-LED stacking structure provided in a typical implementation case of the utility model and a UV-LED stacking structure in the prior art that does not include a black line layer are compared;

[0036] Figure 5 It is a structural schematic diagram of another UV-LED stacking structure provided in a typical implementation case of the utility model. DETAILED DESCRIPTION

[0037] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the utility model after long-term research and extensive practice. The technical solution, its implementation process and principle, etc. will be further explained in conjunction with the accompanying drawings and specific implementation cases. Unless otherwise specified, the semiconductor vapor phase epitaxial growth equipment and processes such as MOCVD (metal organic chemical vapor deposition) used in the embodiments of the utility model are known to those skilled in the art.

[0038] See also Figure 1A UV-LED stacked structure, i.e., an epitaxial structure of an ultraviolet photoelectronic device, comprises a buffer layer 120, a transition layer 130, an n-type electron layer 140, a functional layer 150, an electron blocking layer 160, a p-type hole transport layer 170 and a p-type contact layer 190 which are sequentially stacked on a substrate 110 along a selected direction, wherein the conductivity type of the electron layer 140 is n-type, and the conductivity types of the electron blocking layer 160, the hole transport layer 170 and the contact layer 190 are p-type, and the selected direction may be a longitudinal direction or a thickness direction of the UV-LED stacked structure.

[0039] Specifically, the substrate 110 may be a conductive or insulating substrate, and the material of the substrate 110 may be any one of GaN, ZnO, AlN, sapphire, SiC, Si, or a combination of two or more thereof. The substrate 110 may be wet processed to remove surface impurities, or may be a patterned substrate (the pattern may be circular, rhombic, hexagonal, etc.), but is not limited thereto.

[0040] Specifically, the buffer layer 120 and the transition layer 130 are mainly used to buffer the lattice mismatch between the electronic layer 140 and the substrate 110 and improve the crystal quality. The buffer layer 120 and the transition layer 130 can be removed together with the substrate in the subsequent device manufacturing process. The material of the buffer layer 120 and the transition layer 130 can be AlN, AlGaN and other group III nitride semiconductor materials.

[0041] Specifically, the electronic layer 140 is mainly used to generate electrons. The material of the electronic layer 140 is a group III nitride semiconductor material, and the n-type impurities doped therein may be Si, Ge, tin, selenium, tellurium, etc. For example, the electronic layer 140 may be Al x Ga y N layer (0≤x≤1, 0≤y≤1, 0≤x+y≤1), for example, the material of the electronic layer 140 can be any one of AlN, AlGaN, InAlGaN or a combination of two or more thereof.

[0042] Specifically, the functional layer 150 is an area where electrons and holes recombine, and light having a wavelength corresponding to its band gap can be generated as the electrons and holes recombine; the functional layer 150 can be a single quantum well structure or a multi-quantum well structure. More specifically, the material of the functional layer 150 can be Al x Ga y N(0≤x≤1, 0≤y≤1, 0≤x+y≤1).

[0043] Specifically, the electron blocking layer (EBL) 160 has a conventionally high Al content, and the molar content of the Al component is between 0.6 and 1.0. The electron blocking layer (EBL) 160 and the hole transport layer 170 are mainly used to generate holes and inject the holes into the functional layer 150. More specifically, the materials of the electron blocking layer (EBL) 160 and the hole transport layer 170 can be Al x Ga y N(0≤x≤1, 0≤y≤1, 0≤x+y≤1), illustratively, the material of the electron blocking layer (EBL) 160 and the hole transport layer 170 can be AlN, AlGaN, InGaN, InAlGaN, AlInN and other Al-containing Group III nitride semiconductor materials, and the p-type impurities of the electron blocking layer (EBL) 160 and the hole transport layer 170 can be Mg, Zn, Ca, Sr and the like.

[0044] Specifically, the molar content of the Al component in the hole transport layer 170 is 0.2-0.8, the molar content of the Al component in the hole transport layer 170 is greater than 0.45, preferably 0.45-0.8, and the molar content of the Al component in the hole transport layer 170 gradually decreases along the direction toward the contact layer 190, and the decrease range is 10-40%, preferably 20%. The molar content of the Al component can be a slow linear decrease, a gradient slow decrease, or a decrease in other functional forms.

[0045] Specifically, the contact layer 190 is mainly used to form an ohmic contact with the metal electrode. The conductivity type of the contact layer 190 is p-type. The material of the contact layer 190 can be an Al-free Group III nitride semiconductor material and / or a low Al component Group III nitride semiconductor material. Exemplarily, the material of the contact layer 190 can be any one of AlN, AlGaN, AlInN, AlInGaN, GaN, or a combination of two or more thereof. Specifically, the thickness of the contact layer 190 is 5nm-50nm.

[0046] Specifically, the UV-LED stacked structure also includes a black line layer 180, which is arranged between the hole transport layer 170 and the contact layer 190 along a selected direction. The conductivity type of the black line layer 180 is p-type. Exemplarily, the material of the black line layer 180 can be any one or more of AlN, AlGaN, AlInN, and AlInGaN, and the p-type impurity of the black line layer 180 can be at least one of Mg, Zn, Ca, Sr, etc.

[0047] Specifically, the black line layer 180 is formed of an Al-containing group III nitride semiconductor material, and the molar content of the Al component in the black line layer 180 is greater than the molar content of the Al component in the contact layer 190; further, the molar content of the Al component in the black line layer is higher than the molar content of the Al component in the entire hole transport layer and the resistance blocking layer, which can prevent the entry of defects; according to different material systems, the molar content of the Al component in the black line layer is 0.3-1.0, preferably 0.5-0.9.

[0048] The utility model provides a UV-LED stacked structure, which introduces a black line layer with a higher Al component, and appears as a higher Al component line in the Z contrast imaging of a cross-sectional transmission electron microscope, so it can be called a "black line layer", such as Figure 2 The black line layer in the utility model has the following functions: the black line layer with high Al content can increase the diffusion barrier of impurity atoms and vacancies and other defects, effectively preventing impurities and vacancies in the contact layer from diffusing to the functional layer, thereby significantly improving the reliability and service life of the device.

[0049] In order to control the contact layer grown at a relatively low temperature from diffusing into the functional layer due to defects and impurities, it is understandable that the material of the contact layer 190 may be GaN or AlGaN or AlInGaN, wherein the molar content of the Al component of the contact layer 190 is 0-0.4, and the molar content of the Al component in the portion of the contact layer 190 relatively close to the black line layer 180 is higher than the molar content of the Al component in another portion relatively far away from the black line layer 180; specifically, the contact layer 190 in contact with the black line layer 180 may be a single-layer structure, or a multi-layer structure formed by two or more different materials, such as the contact layer 190 close to the black line layer 180 is an AlGaN or AlInGaN contact layer with a relatively high band gap, and the contact layer far away from the black line layer 180 is a GaN or AlInGaN contact layer with a relatively low band gap; more specifically, the molar content of the Al component in the Al-containing contact layer 190 gradually decreases or decreases in a gradient along the direction from the functional layer to the contact layer.

[0050] In order to better prevent defects from entering the functional layer when the contact layer is grown at low temperature, the black line layer 180 can also be arranged inside the contact layer 190 while taking into account the hole injection efficiency. The black line layer 180 can block the defects of the contact layer 190, that is, the black line layer can also be arranged inside the contact layer to form a double or triple black line layer; specifically, the black line layer can be arranged between the AlGaN contact layer or AlInGaN contact layer with a relatively high band gap and the GaN contact layer or AlInGaN contact layer with a relatively low band gap. In order to avoid blocking hole injection and reduce the voltage increase, the thickness of the black line layer 180 is controlled at 0.2nm-10nm. If the thickness of the black line layer 180 is less than 0.2nm, its ability to block impurities and defects will be weakened, the blocking effect will be poor, and the effect of improving device aging will be weakened; and excessively increasing the thickness of the black line layer 180 will not only have limited improvement on its effect of blocking impurities and defects, but will also cause an increase in longitudinal resistance, resulting in a gradual increase in the operating voltage of the device. When the thickness of the black line layer 180 is greater than 10nm, the operating voltage of the device will increase rapidly, and it will also cause excessive mismatch with the contact layer to generate new dislocations, thereby affecting other performances of the device. In addition, if the thickness of the black line layer 180 is too large, it will also affect the growth of the subsequent contact layer, which may deteriorate the aging performance of the device and affect the service life of the device. The thickness of the black line layer 180 can be preferably controlled at 0.3nm-2nm to obtain the expected best comprehensive performance.

[0051] Specifically, the black line layer 180 may be formed by in-situ growth on the surface of the formed structural layer after the hole transport layer 170 is grown by a vapor phase epitaxial growth process, by increasing the flow rate of the Al source and / or reducing the flow rate of other group III sources (such as Ga sources, the same below); or, the black line layer 180 may be formed by in-situ growth on the surface of the formed structural layer after the hole transport layer 170 is grown by a vapor phase epitaxial growth process, by stopping the supply of the group III source so that the group III atoms other than Al are desorbed from the surface of the formed structural layer. The black line layer 180 formed in this way is stacked in layers along a selected direction between the hole transport layer 170 and the contact layer 190 or inside the contact layer 190.

[0052] Specifically, disposing the black line layer 180 in the contact layer 190 grown at a relatively low temperature can more effectively improve the anti-aging advantage of the device and increase the life of the device.

[0053] Further, if Figure 5As shown, a spacer layer 1801 is stacked inside the electron blocking layer 160, between the electron blocking layer 160 and the functional layer 150, and between at least one group of structures in the electron blocking layer 160 and the hole transport layer 170. The molar content of the Al component in the spacer layer 1801 is higher than the molar content of the Al component in any one of the electron blocking layer 160, the functional layer 150, and the hole transport layer; further, the molar content of the Al component in the spacer layer 1801 is 0.8-1.0, and the thickness is controlled at 0.1nm-20nm, more preferably 0.2-5nm. The spacer layer 1801 can effectively prevent the overflow of electrons at high temperatures and improve the anti-aging performance of the device, thereby further improving the life and reliability of the device;

[0054] More preferably, when the spacer layer and the black line layer exist at the same time, the molar content of the Al component of the black line layer is set to be lower than the molar content of the Al component of the spacer layer. This can effectively prevent the invasion of defect impurities and improve the crystal quality while minimizing the increase in the operating voltage. The utility model patent will be described in detail in conjunction with the embodiments below.

[0055] Example 1: Growth of UVLED stacked structure on sapphire substrate

[0056] A method for preparing a UV-LED stacked structure comprises the following steps:

[0057] S1: Sputtering AlN bottom layer: Sputtering AlN film with a thickness of 50 nm on the sapphire substrate as the AlN bottom layer; placing the sapphire substrate with the AlN bottom layer formed in the reaction chamber of the MOCVD equipment, raising the temperature in the reaction chamber to 1150°C, and introducing H into the reaction chamber at the same time. 2 and NH 3 , anneal for 10 minutes.

[0058] S2: Growth of AlN hole-forming layer: The growth temperature in the reaction chamber is lowered to 900°C, and trimethylaluminum (TMA) and ammonia (NH 3 ), and control the reaction source (i.e., trimethylaluminum (TMA) and ammonia (NH 3 ), trimethylaluminum (TMA) as Al source, ammonia (NH 3 ) as a nitrogen source) with a V / III ratio increased to 5000, and an AlN hole-forming layer with a thickness of 300 nm was grown on the AlN bottom layer at low temperature and high V / III.

[0059] S3: Growth of AlN merged layer: Raise the growth temperature in the reaction chamber to 1200°C, reduce the V / III ratio of the reaction source to 50, grow an AlN merged layer with a thickness of 450nm on the AlN hole formation layer at high temperature and low V / III, continue to increase the V / III ratio of the reaction source to 200, grow AlN with a thickness of 2 to 4um on the AlN merged layer at high temperature and low V / III, thereby forming an AlN buffer layer.

[0060] S4: Growth of AlN / Al 0.6 Ga 0.4 N transition layer: Lower the growth temperature in the reaction chamber to 1150°C and grow 1nm AlN / 1nm Al on the AlN buffer layer. 0.6 Ga 0.4 N superlattice, 80 pairs in total.

[0061] S5: Growth of n-AlGaN electron layer: The growth temperature in the reaction chamber is lowered to 1100°C, and trimethylaluminum (TMA) and ammonia (NH 3 ) and trimethylgallium (TMGa), in AlN / Al 0.6 Ga 0.4 The n-Al layer with a thickness of 750nm is first grown on the N transition layer. 0.6 Ga 0.4 N layer, then grow n-Al with a thickness of lμm 0.55 Ga 0.45 N layers.

[0062] S6: Growth of MQW functional layer: The growth temperature in the reaction chamber is reduced to 1020°C, and the growth atmosphere is changed to N 2 / H 2 Mixed gas, growing 5 pairs of Al on the n-AlGaN electron layer 0.6 Ga 0.4 N(10nm) / Al 0.45 Ga 0.55 N (1.8nm) superlattice structure, in which the last Al 0.6 Ga 0.4 The thickness of the N layer remains only 1 nm.

[0063] S7: Growth of p-EBL electron blocking layer and p-AlGaN hole transport layer: Increase the growth temperature in the reaction chamber to 1080 °C and change the growth atmosphere to pure H 2 First, a p-Al layer with a thickness of 20 nm and a molar content of 60% Al is grown on the MQW functional layer. 0.75 Ga 0.25The N layer is used as a p-EBL electron blocking layer, and the flow rates of TMAl and TMGa are adjusted to continue growing a p-AlGaN layer with a thickness of 35 nm and a molar content of Al component of 50% as a p-AlGaN hole transport layer.

[0064] S8: Growth of a p-AlGaN black line layer with a high molar content of Al component: After the p-AlGaN hole transport layer is grown on the basis of S7, the flow rate of TMAl introduced into the reaction chamber is rapidly increased and the flow rate of TMGa is reduced, so that a p-AlGaN black line layer with a thickness of 6.45 nm and an Al component of approximately 70% is grown on the p-AlGaN hole transport layer in a relatively short time.

[0065] S9: Growth of low-temperature p-(Al)GaN contact layer: After the black line layer is grown, the TMAl flow rate is gradually changed to zero, transitioning from p-AlGaN to p-GaN. At the same time, the growth temperature in the reaction chamber is reduced to 840°C, and a low-temperature p-GaN contact layer with a thickness of 8nm is continued to be grown. The low-temperature p-GaN contact layer is used to form an ohmic contact with the p metal electrode to reduce the contact resistance. The UVLED stacked structure formed in Example 1 is as follows Figure 1 shown.

[0066] Example 2: Growth of UV-LED on sapphire substrate

[0067] A method for preparing a UV-LED stacked structure comprises the following steps:

[0068] S1: Sputtering AlN bottom layer: Sputtering AlN film with a thickness of 50 nm on the sapphire substrate as the AlN bottom layer; placing the sapphire substrate with the AlN bottom layer formed in the reaction chamber of the MOCVD equipment, raising the temperature in the reaction chamber to 1150°C, and introducing H into the reaction chamber at the same time. 2 and NH 3 , anneal for 10 minutes.

[0069] S2: Growth of AlN hole-forming layer The growth temperature in the reaction chamber is lowered to 900°C, and trimethylaluminum (TMA) and ammonia (NH 3 ), and control the reaction source (i.e., trimethylaluminum (TMA) and ammonia (NH 3 ), trimethylaluminum (TMA) as Al source, ammonia (NH 3 ) as a nitrogen source) with a V / III ratio increased to 5000, and an AlN hole-forming layer with a thickness of 300 nm was grown on the AlN bottom layer at low temperature and high V / III.

[0070] S3: Growth of AlN merged layer: Raise the growth temperature in the reaction chamber to 1200°C, reduce the V / III ratio of the reaction source to 50, grow an AlN merged layer with a thickness of 450nm on the AlN hole formation layer at high temperature and low V / III, continue to increase the V / III ratio of the reaction source to 200, grow AlN with a thickness of 2 to 4um on the AlN merged layer at high temperature and low V / III, thereby forming an AlN buffer layer.

[0071] S4: Growth of AlN / Al 0.6 Ga 0.4 N transition layer: Lower the growth temperature in the reaction chamber to 1150°C and grow 1nm AlN / 1nm Al on the AlN buffer layer. 0.6 Ga 0.4 N superlattice, 80 pairs in total.

[0072] S5: Growth of n-AlGaN electron layer: The growth temperature in the reaction chamber is lowered to 1100°C, and trimethylaluminum (TMA) and ammonia (NH 3 ) and trimethylgallium (TMGa), in AlN / Al 0.6 Ga 0.4 The n-Al layer with a thickness of 750nm is first grown on the N transition layer. 0.6 Ga 0.4 N layer, then grow n-Al with a thickness of 1 μm 0.55 Ga 0.45 N layers.

[0073] S6: Growth of MQW functional layer: The growth temperature in the reaction chamber is reduced to 1020°C, and the growth atmosphere is changed to N 2 / H 2 Mixed gas, growing 5 pairs of Al on the n-AlGaN electron layer 0.6 Ga 0.4 N(10nm) / Al 0.45 Ga 0.55 N (1.8nm) superlattice structure, in which the last Al 0.6 Ga 0.4 The thickness of the N layer remains only 1 nm.

[0074] S7: Growth of p-EBL electron blocking layer and p-AlGaN hole transport layer: Increase the growth temperature in the reaction chamber to 1080 °C and change the growth atmosphere to pure H 2 First, a p-Al layer with a molar content of 20 nm thick is grown on the MQW functional layer. 0.75 Ga 0.25The N layer is used as a p-EBL electron blocking layer, and the flow rates of TMAl and TMGa are adjusted to continue growing a p-AlGaN layer with a thickness of 35 nm and a molar content of Al component of 50% as a p-AlGaN hole transport layer.

[0075] S8: Growth of a p-AlGaN black line layer with a high molar content of Al component: After the p-AlGaN hole transport layer is grown on the basis of S7, the TMAl source and the TMGa source are directly turned off, the growth is paused for 1 minute, and the desorption of Ga atoms is utilized to form a p-AlGaN black line layer with a thickness of 0.65 nm and a molar content of Al component of 70% in the surface area of ​​the p-AlGaN hole transport layer in a relatively short time.

[0076] S9: Growth of low-temperature p-(Al)GaN contact layer: After growing the p-AlGaN black line layer with a high Al component, gradually change the flow rate of TMAl to zero, transitioning from p-AlGaN to p-GaN. At the same time, reduce the growth temperature in the reaction chamber to 840°C, and continue to grow an 8nm low-temperature p-GaN contact layer to form an ohmic contact with the p metal electrode to reduce the contact resistance.

[0077] Comparative Example 1

[0078] Comparative Example 1 is basically the same as Example 2, and the same parts of the two are not repeated here. The difference is that:

[0079] In Comparative Example 1, S8 was omitted.

[0080] like Figure 4 As shown, by introducing the p-AlGaN black line layer, the p-AlGaN black line layer with a high Al component can effectively prevent the impurities and defects of the low-temperature contact layer from diffusing to the functional layer and effectively improve the working life. Compared with the LED device without the p-AlGaN black line layer with a high Al component, the operating voltage is 5.4V. Within the aging time of 800h, the light decay of the LED with the p-AlGaN black line layer with a high Al component is only 20%, while the light decay of the p-AlGaN black line layer without a high Al component is as high as 40%.

[0081] Example 3

[0082] Embodiment 3 is basically the same as Embodiment 2, and the same parts of the two are not repeated here. The difference is that:

[0083] The growth pause time in S8 of this embodiment is longer, and the thickness of the formed p-AlGaN black line layer is 1.98nm, and the molar content of the Al component is about 72%. At this thickness, the light attenuation amplitude of the device after aging can be maintained at a low level, and the voltage is relatively low, approximately 5.5V.

[0084] Example 4

[0085] Example 4 is basically the same as Example 1, and the same parts of the two are not repeated here. The difference is that:

[0086] In this embodiment S8, by controlling the growth process of the black line layer, the thickness of the AlGaN black line layer is formed to be 7.5nm, and the molar content of the Al component is about 73%. At this thickness, the aging light attenuation of the device is maintained at a low level, but the operating voltage is maintained at approximately 5.8V, but still less than 6V.

[0087] Example 5: Growth of AlGaN-based PiN photodetector on sapphire substrate

[0088] S1: Sputtering AlN bottom layer: Sputtering AlN film with a thickness of 50 nm on the sapphire substrate as the AlN bottom layer; placing the sapphire substrate with the AlN bottom layer formed in the reaction chamber of the MOCVD equipment, raising the temperature in the reaction chamber to 1150°C, and introducing H into the reaction chamber at the same time. 2 and NH 3 , anneal for 10 minutes.

[0089] S2: Growth of AlN hole-forming layer: The growth temperature in the reaction chamber is lowered to 900°C, and trimethylaluminum (TMA) and ammonia (NH 3 ), and control the reaction source (i.e., trimethylaluminum (TMA) and ammonia (NH 3 ), trimethylaluminum (TMA) as Al source, ammonia (NH 3 ) as a nitrogen source) with a V / III ratio increased to 5000, and an AlN hole-forming layer with a thickness of 300 nm was grown on the AlN bottom layer at low temperature and high V / III.

[0090] S3: Growth of AlN merged layer: Raise the growth temperature in the reaction chamber to 1200°C, reduce the V / III ratio of the reaction source to 50, grow an AlN merged layer with a thickness of 450nm on the AlN hole forming layer at high temperature and low V / III, continue to increase the V / III ratio of the reaction source to 200, grow AlN with a thickness of 2 to 4um on the AlN merged layer at high temperature and low V / III, thereby forming an AlN buffer layer.

[0091] S4: Growth of AlN / Al 0.6 Ga 0.4 N transition layer: Lower the growth temperature in the reaction chamber to 1150°C and grow 1nm AlN / 1nm Al on the AlN buffer layer. 0.6 Ga 0.4 N superlattice, 80 pairs in total.

[0092] S5: Growth of n-AlGaN electron layer: The growth temperature in the reaction chamber is lowered to 1100°C, and trimethylaluminum (TMA) and ammonia (NH 3 ) and trimethylgallium (TMGa), in AlN / Al 0.6 Ga 0.4 The n-Al layer with a thickness of 750nm is first grown on the N transition layer. 0.6 Ga 0.4 N layer, then grow n-Al with a thickness of 1 μm 0.55 Ga 0.45 N layers.

[0093] S6: Growth of i-AlGaN structure: Lower the growth temperature of the reaction chamber to 1020°C and change the growth atmosphere to N 2 / H 2 Mixed gas, grow Al with a thickness of 2-3μm on the n-AlGaN electron layer 0.45 Ga 0.55 N layer, the corresponding light absorption wavelength is about 280nm.

[0094] S7: Growth of p-AlGaN hole supply layer: Increase the growth temperature of the reaction chamber to 1080°C and change the growth atmosphere to pure H 2 , a p-AlGaN hole supply layer with a thickness of 350 nm is continuously grown, and the molar content of the Al component of the p-AlGaN hole supply layer is reduced from 60% to 50%.

[0095] S8: Growth of a p-AlGaN black line layer with a high Al component: Based on S7, the TMAl source and the TMGa source are directly turned off, the growth is paused for 1 minute, and the p-AlGaN black line layer with a high Al component is formed in a relatively short time by utilizing the desorption of Ga atoms. The thickness of the p-AlGaN black line layer is 1.94 nm, and the molar content of the Al component is about 70%.

[0096] S9: Growth of low-temperature p-GaN / p-AlGaN contact layer: After the p-AlGaN black line layer is grown, the TMAl flow rate is gradually changed to zero, transitioning from p-AlGaN to p-GaN. At the same time, the growth temperature of the reaction chamber is reduced to 840°C, and a low-temperature p-GaN / p-AlGaN contact layer with a thickness of 8nm is continued to be grown to form an ohmic contact with the p metal electrode to reduce the contact resistance.

[0097] The AlGaN-based PiN photodetector obtained in the implementation case can effectively increase the hole concentration in the p-AlGaN material by combining a black line layer on the basis of p-AlGaN with gradually decreasing composition and utilizing the polarization induced charge formed by the gradual change of the Al composition of the p-AlGaN material. At the same time, the p-AlGaN black line layer with a high Al composition can also effectively prevent impurities and defects in the low-temperature contact layer from diffusing to the functional layer, and effectively improve the aging condition and increase the working life of the device.

[0098] The utility model uses a black line layer with a high molar content of Al components to be arranged between the hole transport layer and the contact layer to block the impurities and vacancies of the contact layer from diffusing to the functional layer, so as to achieve the purpose of improving the reliability and working life of the device. This technical solution can be used not only for deep ultraviolet light-emitting devices, but also for other ultraviolet or deep ultraviolet optoelectronic devices, such as photodetectors.

[0099] The utility model provides a stacked structure that can effectively block defects such as impurities and vacancies in the low-temperature contact layer from diffusing into the functional layer. It should be noted that the use of a high-temperature contact layer will cause the surface morphology of the sample to deteriorate and the efficiency of Mg incorporation to decrease. Therefore, a medium-low temperature contact layer is often used during growth. However, medium-low temperature growth will introduce defects such as impurities and vacancies. The black line layer with a high Al component can effectively block the defects from diffusing into the quantum well functional layer, which can effectively improve the reliability and service life of the device.

[0100] The implementation method of the stacked structure provided by the utility model is very simple, does not increase the production cost, greatly improves the reliability of the device, and can be used in combination with other methods for increasing the hole concentration of group III nitride materials or used alone.

[0101] It should be understood that the above embodiments are only for illustrating the technical concept and features of the utility model, and their purpose is to enable people familiar with the technology to understand the content of the utility model and implement it accordingly, and they cannot be used to limit the protection scope of the utility model. Any equivalent changes or modifications made according to the spirit of the utility model should be included in the protection scope of the utility model.

Claims

1. An epitaxial structure of an ultraviolet photoelectronic device, comprising an n-type semiconductor structure layer, a functional layer and a p-type semiconductor structure layer stacked in sequence along a selected direction, wherein the p-type semiconductor structure layer comprises an electron blocking layer, a hole transport layer and a contact layer stacked along the selected direction; characterized in that: The p-type semiconductor structure layer also includes a black line layer, which is arranged between the hole transport layer and the contact layer. The electron blocking layer, the hole transport layer and the black line layer are all formed of an Al-containing III-nitride semiconductor material. The contact layer is formed of an Al-containing and / or Al-free III-nitride semiconductor material, and the band gap of the black line layer is higher than the band gap of the contact layer.

2. The epitaxial structure of the ultraviolet photoelectronic device according to claim 1, characterized in that: The thickness of the black line layer is 0.1-10 nm.

3. The epitaxial structure of the ultraviolet photoelectronic device according to claim 2, characterized in that: The thickness of the black line layer is 0.3nm-2.0nm.

4. The epitaxial structure of the ultraviolet photoelectronic device according to claim 1, characterized in that: The band gap of the black line layer is higher than the band gap of the hole transport layer.

5. The epitaxial structure of the ultraviolet photoelectronic device according to claim 1, characterized in that: The functional layer is an active layer, and the active layer includes a well layer and a barrier layer. The composition of the well layer is arranged so that the active layer can emit light in the deep ultraviolet band.

6. The epitaxial structure of the ultraviolet photoelectronic device according to claim 5, characterized in that: The band gap of the contact layer is lower than the band gap of the well layer in the functional layer, and the band gap of the hole transport layer is higher than the band gap of the well layer in the functional layer.

7. The epitaxial structure of the ultraviolet photoelectronic device according to claim 1, characterized in that: The contact layer includes a first contact layer and a second contact layer, the second contact layer is closer to the functional layer than the first contact layer, the second contact layer is an AlInGaN contact layer containing Al or an AlGaN contact layer, the first contact layer is an AlInGaN contact layer containing Al or a GaN contact layer not containing Al, and the band gap of the first contact layer is higher than the band gap of the second contact layer.

8. The epitaxial structure of the ultraviolet photoelectronic device according to claim 7, characterized in that: The thickness of the first contact layer is 5nm-30nm, and the thickness of the second contact layer is 3nm-20nm.

9. The epitaxial structure of the ultraviolet photoelectronic device according to claim 7, characterized in that: The black line layer is also arranged inside the contact layer.

10. The epitaxial structure of the ultraviolet photoelectronic device according to claim 9, characterized in that: The black line layer is disposed between the first contact layer and the second contact layer.

11. The epitaxial structure of the ultraviolet photoelectronic device according to any one of claims 1 to 10, characterized in that: Also includes: A spacer layer is provided between the hole transport layer and the electron blocking layer, between the electron blocking layer and the functional layer, or inside the electron blocking layer, and the band gap of the spacer layer is greater than the band gap of the electron blocking layer.

12. The epitaxial structure of the ultraviolet photoelectronic device according to claim 11, characterized in that: The thickness of the spacer layer is 0.2nm-20nm.

13. A light emitting device, characterized in that include: The epitaxial structure of the ultraviolet photoelectronic device according to any one of claims 1 to 12.

14. An optoelectronic device, characterized in that include: The epitaxial structure of the ultraviolet photoelectronic device according to any one of claims 1 to 12.

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