Deep Ultraviolet LED with Modulation-Doped Electron Blocking Layer Structure and Preparation Method

Abstract

The present invention discloses a deep ultraviolet LED with a modulation-doped electron blocking layer structure and a preparation method thereof. The deep ultraviolet LED with the modulation-doped electron blocking layer structure includes a sapphire substrate, an AlN intrinsic layer, an n-type AlGaN electron injection layer, a quantum well active layer, a modulation-doped electron blocking layer, and a p-type AlGaN hole injection layer which are sequentially stacked. The modulation-doped electron blocking layer includes a plurality of first blocking layers and second blocking layers which are alternately arranged; both the first blocking layer and the second blocking layer contain Mg doping, and the Mg doping concentration of the first blocking layer is greater than that of the second blocking layer; or both the first blocking layer and the second blocking layer do not contain Mg doping, and Mg doping is carried out at the interface between the first blocking layer and the second blocking layer. By modulating the doping of the electron blocking layer, the present invention improves the Mg doping efficiency, effectively prevents Mg from diffusing into the active region, and improves the light emission efficiency of the deep ultraviolet LED.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor optoelectronics, and particularly to a deep ultraviolet LED with a modulation-doped electron blocking layer structure and a preparation method thereof. Background Art

[0002] As an outstanding representative of wide-bandgap semiconductor materials, group-III nitrides have enabled high-efficiency solid-state light source devices such as blue and green light-emitting diodes (hereinafter referred to as LEDs for short), lasers, etc., and have achieved great success in applications such as flat panel displays and white light illumination. In the past decade, people have expected to apply such high-efficiency light-emitting materials to the ultraviolet band to meet the growing demand for ultraviolet light sources. At present, traditional ultraviolet light sources are mainly mercury lamps, which have disadvantages such as large volume, high power consumption, high voltage, and environmental pollution, and are not conducive to their application in daily life and special environments. Therefore, people are urgently hoping to develop a high-efficiency semiconductor ultraviolet light source device to replace the traditional mercury lamp. Existing research shows that AlGaN in group-III nitrides is the best candidate material for preparing semiconductor ultraviolet light source devices. AlGaN-based ultraviolet LEDs have many advantages such as non-toxic environmental protection, small and portable, low power consumption, low voltage, easy integration, long life, and wavelength tunability, and are expected to make breakthrough progress and wide applications in the next few years, and gradually replace traditional ultraviolet mercury lamps.

[0003] Currently, Al x Ga 1-x The bandgap width of N materials can be continuously adjusted in the range from 3.4 eV (GaN) to 6.2 eV (AlN) by changing the Al component, and light emission in the spectral range from 365 nm to 200 nm can be achieved. Among them, the band-edge emission wavelength of GaN is about 360 nm, which is usually used as a division mark for the emission band of nitride ultraviolet light-emitting diodes (hereinafter referred to as UV-LEDs for short). The active region of UV-LEDs with an emission wavelength greater than 360 nm adopts a GaN / InGaN quantum well (QWs) structure similar to that of blue LEDs. Related research began as early as the 1990s, and has now been successfully commercialized, and the external quantum efficiency (EQE) has also exceeded 40%, reaching a level comparable to that of blue LEDs.

[0004] However, for ultraviolet LEDs with emission wavelengths less than 360 nm, an AlGaN quantum well structure is mainly used as the active region. The electron overflow effect is one of the main reasons for the low efficiency of deep ultraviolet LEDs based on high-Al-component AlGaN. In an LED, the concentration of electrons is high and the migration rate is fast, while the concentration of holes is low and the migration rate is slow. Currently, due to the difficulty of effectively matching and recombining electrons and holes, the recombination efficiency of electrons and holes is restricted, and an ideal light output power cannot be obtained. Moreover, the Mg doping concentration and doping efficiency in high-Al-component AlGaN materials are often low. As the Mg doping concentration increases, Mg will diffuse into the quantum well active layer during the growth process, thus greatly reducing the light emission efficiency of deep ultraviolet devices. Therefore, a new ultraviolet LED solution needs to be proposed to solve the problems existing in the prior art. Summary of the Invention

[0005] The object of the present invention is to provide a deep ultraviolet LED with a modulation-doped electron blocking layer structure and a preparation method thereof, which are used to solve the problem of low efficiency of deep ultraviolet LEDs caused by low Mg doping concentration and doping efficiency in high-Al-component AlGaN materials in the prior art.

[0006] To solve the above technical problems, the first solution provided by the present invention is: a deep ultraviolet LED with a modulation-doped electron blocking layer structure, which includes a sapphire substrate, an AlN intrinsic layer, an n-type AlGaN electron injection layer, a quantum well active layer, a modulation-doped electron blocking layer, and a p-type AlGaN hole injection layer arranged in a stacked manner in sequence. The modulation-doped electron blocking layer includes a plurality of first blocking layers and second blocking layers arranged alternately; both the first blocking layer and the second blocking layer contain Mg doping, and the Mg doping concentration of the first blocking layer is greater than that of the second blocking layer; or, both the first blocking layer and the second blocking layer do not contain Mg doping, and Mg doping is performed at the interface between the first blocking layer and the second blocking layer.

[0007] Preferably, the first blocking layer and the second blocking layer are Mg-doped AlGaN structures with the same composition, and the Al component percentage is 50-100%, and the number of periods is 2-100.

[0008] Preferably, the doping concentration of the first blocking layer is 10 17 ~10 21 cm -3 , and the thickness is 0.1-50 nm; the doping concentration of the second blocking layer is 10 14 ~10 19 cm -3 , and the thickness is 0.1-100 nm.

[0009] Preferably, the modulation-doped electron blocking layer is Alx Ga 1-x N / Al y Ga 1-y N superlattice structure, the number of periods of the superlattice structure is 1 to 50; Al in the superlattice structure x Ga 1-x N and Al y Ga 1-y There are two film layers of N, one film layer is the first barrier layer, and the other film layer is the second barrier layer, where x is 70 to 100%, y is 60 to 90%, and x is not equal to y.

[0010] Preferably, when both the first barrier layer and the second barrier layer are doped with Mg, the doping concentration of the first barrier layer is 10 17 ~10 21 cm -3 , and the thickness is 0.1 to 50 nm; the doping concentration of the second barrier layer is 10 14 ~10 19 cm -3 , and the thickness is 0.1 to 100 nm.

[0011] Preferably, when neither the first barrier layer nor the second barrier layer is doped with Mg, during the growth of each first barrier layer or the second barrier layer, magnesium cyclopentadienide is not introduced, and after the growth of the first barrier layer or the second barrier layer is completed, the supply of the raw materials for depositing AlGaN is interrupted, and magnesium cyclopentadienide is introduced at the interface between the first barrier layer and the second barrier layer for Mg doping.

[0012] To solve the above technical problems, the second solution provided by the present invention is: A method for preparing a deep ultraviolet LED having a modulation-doped electron blocking layer structure as described in the foregoing first solution, the steps of which sequentially include:

[0013] (1) Growing an AlN intrinsic layer: Growing a low-temperature buffer layer in the AlN intrinsic layer on a sapphire substrate at 400 to 800 °C, with a thickness of 10 to 50 nm; raising the temperature to 1200 to 1400 °C, and growing an AlN intrinsic layer on the low-temperature buffer layer in the AlN intrinsic layer, and the total thickness of the AlN intrinsic layer is 500 to 4000 nm.

[0014] (2) Growing an n-type AlGaN electron injection layer: Lowering the temperature to 800 to 1200 °C, and growing an n-type AlGaN electron injection layer on the AlN intrinsic layer, where the Al component percentage is 20 to 90%, with a thickness of 500 to 4000 nm, and using Si as the n-type dopant.

[0015] (3) Growing the quantum well active layer: Cooling down to 700 - 1100 °C, growing the quantum well active layer on the n-type AlGaN electron injection layer, where the barrier thickness in the quantum well active layer is 5 - 30 nm, the Al composition percentage of the barrier is 20 - 100%, the well thickness is 0.1 - 5 nm, and the Al composition percentage of the well is 0.1 - 80%.

[0016] (4) Growing the modulation-doped electron blocking layer.

[0017] (5) Growing the p-type AlGaN hole injection layer: Growing the p-type AlGaN hole injection layer on the modulation-doped electron blocking layer at 700 - 1100 °C, where the Al composition percentage is 0.1 - 100%, the thickness is 1 - 50 nm, and Mg is used as the p-type dopant.

[0018] Preferably, in the step of growing the modulation-doped electron blocking layer, at 700 - 1100 °C, the first blocking layer and the second blocking layer are alternately grown. The first blocking layer and the second blocking layer are Mg-doped AlGaN structures with the same composition, and the Al composition percentage of both is 50 - 100%. The number of periods is 2 - 100. When growing the first blocking layer, the flow rate of bis(cyclopentadienyl)magnesium is 1 - 10000 SCCM, and the growth thickness of the first blocking layer is 0.1 - 50 nm. When growing the second blocking layer, the flow rate of bis(cyclopentadienyl)magnesium is 0.1 - 500 SCCM, and the growth thickness of the second blocking layer is 0.1 - 100 nm.

[0019] Preferably, in the step of growing the modulation-doped electron blocking layer, at 700 - 1100 °C, the first blocking layer and the second blocking layer are alternately grown, and form an Mg-doped Al x Ga 1-x N / Al y Ga 1-y N superlattice structure. The number of periods of the superlattice structure is 1 - 50, where x is 70 - 100%, y is 60 - 90%, and x is not equal to y. When growing the first blocking layer, the flow rate of bis(cyclopentadienyl)magnesium is 1 - 10000 SCCM, and the growth thickness of the first blocking layer is 0.1 - 50 nm. When growing the second blocking layer, the flow rate of bis(cyclopentadienyl)magnesium is 0.1 - 500 SCCM, and the growth thickness of the second blocking layer is 0.1 - 100 nm.

[0020] Preferably, in the step of growing the modulation-doped electron blocking layer, at 700 - 1100 °C, the first blocking layer and the second blocking layer are alternately grown, and form an undoped Al x Ga 1-x N / Al y Ga 1-yN superlattice structure, the number of periods of the superlattice structure is 1 to 50, where x is 70 to 100%, y is 60 to 90%, and x is not equal to y; during the growth of each first barrier layer or second barrier layer, no magnesium cyclopentadienyl is introduced. After the growth of each first barrier layer or second barrier layer is completed, the supply of the raw materials for depositing AlGaN is interrupted, and 1 to 10,000 SCCM of magnesium cyclopentadienyl is introduced at the interface between the first barrier layer and the second barrier layer for Mg doping, and the doping time is 1 to 200 s.

[0021] The beneficial effects of the present invention are as follows: Different from the prior art, the present invention provides a deep ultraviolet LED with a modulation-doped electron blocking layer structure and a preparation method. By modulating the doping of the electron blocking layer, the doping efficiency of Mg is improved, the diffusion of Mg into the active region is effectively prevented, and the luminous efficiency of the deep ultraviolet LED is improved. Description of the Drawings

[0022] Figure 1 is a schematic structural diagram of an embodiment of a deep ultraviolet LED with a modulation-doped electron blocking layer structure in the present invention;

[0023] Figure 2 is a comparison diagram of the optical output power of the deep ultraviolet LED samples of Examples 1 to 3 and Comparative Example 1 in the present invention. Detailed Embodiments

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] For the first solution proposed in the present invention, please refer to Figure 1 , Figure 1 is a schematic structural diagram of an embodiment of a deep ultraviolet LED with a modulation-doped electron blocking layer structure in the present invention. The deep ultraviolet LED with a modulation-doped electron blocking layer structure in the present invention includes a sapphire substrate 1, an AlN intrinsic layer 2, an n-type AlGaN electron injection layer 3, a quantum well active layer 4, a modulation-doped electron blocking layer 5, and a p-type AlGaN hole injection layer 6 that are sequentially stacked. On the side of the p-type AlGaN hole injection layer 6 away from the modulation-doped electron blocking layer 5, there is also a p-type GaN contact layer 7.

[0026] Specifically, the modulation-doped electron blocking layer 5 includes a plurality of first barrier layers 51 and second barrier layers 52 arranged alternately. The doping methods of the modulation-doped electron blocking layer include the following two:

[0027] First, both the first barrier layer and the second barrier layer contain Mg doping, and the Mg doping concentration of the first barrier layer is greater than that of the second barrier layer. This doping method can be further divided into two cases according to the substrate selection:

[0028] 1) When the first barrier layer and the second barrier layer are Mg-doped AlGaN structures with the same composition, the Al component percentage is 50-100%, and the number of periods is 2-100; among them, the Mg doping concentration of the first barrier layer is greater than that of the second barrier layer, and the doping concentration of the first barrier layer is 10 17 ~10 21 cm -3 , and the thickness is 0.1-50 nm; the doping concentration of the second barrier layer is 10 14 ~10 19 cm -3 , and the thickness is 0.1-100 nm.

[0029] 2) The modulation-doped electron blocking layer is an Al x Ga 1-x N / Al y Ga 1-y N superlattice structure, and the number of periods of the superlattice structure is 1-50; in the superlattice structure, Al x Ga 1-x N and Al y Ga 1-y N two film layers, one film layer is the first barrier layer, and the other film layer is the second barrier layer, where x is 70-100%, y is 60-90%, and x is not equal to y; among them, when both the first barrier layer and the second barrier layer are Mg-doped, the doping concentration of the first barrier layer is 10 17 ~10 21 cm -3 , and the thickness is 0.1-50 nm; the doping concentration of the second barrier layer is 10 14 ~10 19 cm -3 , and the thickness is 0.1-100 nm.

[0030] Second, both the first barrier layer and the second barrier layer do not contain Mg doping, and Mg doping is carried out at the interface between the first barrier layer and the second barrier layer. In this doping method, when each of the first barrier layer and the second barrier layer does not contain Mg doping, magnesium cyclopentadienyl is not introduced during the growth of each of the first barrier layer or the second barrier layer. After the growth of the first barrier layer or the second barrier layer is completed, the supply of the raw materials for depositing AlGaN is interrupted, and magnesium cyclopentadienyl is introduced at the interface between the first barrier layer and the second barrier layer for Mg doping. Different from the previous method, this method is superlattice interface doping.

[0031] In this embodiment, the MOCVD method is used in the preparation process of the deep ultraviolet LED with a modulation-doped electron blocking layer structure. Si is used as the n-type dopant in the n-type AlGaN electron injection layer, and Mg is used as the p-type dopant in the p-type AlGaN hole injection layer and the p-type GaN contact layer. In addition, the n electrode 9 is disposed on the n-type AlGaN electron injection layer 3 and the p electrode 8 is disposed on the p-type GaN contact layer 7 by conventional methods, which will not be elaborated herein.

[0032] For the second solution proposed by the present invention, the steps of the preparation method of the deep ultraviolet LED with a modulation-doped electron blocking layer structure include:

[0033] (1) Growing an AlN intrinsic layer. In this step, a low-temperature buffer layer in the AlN intrinsic layer is grown on the sapphire substrate at 400 - 800 °C, with a thickness of 10 - 50 nm; the temperature is raised to 1200 - 1400 °C, and the AlN intrinsic layer is grown on the low-temperature buffer layer in the AlN intrinsic layer, and the total thickness of the AlN intrinsic layer is 500 - 4000 nm.

[0034] (2) Growing an n-type AlGaN electron injection layer. In this step, the temperature is lowered to 800 - 1200 °C, and the n-type AlGaN electron injection layer is grown on the AlN intrinsic layer, where the Al component percentage is 20 - 90%, the thickness is 500 - 4000 nm, and Si is used as the n-type dopant.

[0035] (3) Growing a quantum well active layer with a gradually changing composition. In this step, the temperature is lowered to 700 - 1100 °C, and the quantum well active layer is grown on the n-type AlGaN electron injection layer. The barrier thickness in the quantum well active layer is 5 - 30 nm, the Al component percentage of the barrier is 20 - 100%, the well thickness is 0.1 - 5 nm, and the Al component percentage of the well is 0.1% - 80%.

[0036] (4) Growing a modulation-doped electron blocking layer. Specifically, the following three growth methods are included, and any one of them can be selected for growing the modulation-doped electron blocking layer:

[0037] a) At 700 - 1100 °C, the first blocking layer and the second blocking layer are alternately grown. The first blocking layer and the second blocking layer are Mg-doped AlGaN structures with the same composition, and the Al component percentage of both is 50 - 100%. The number of periods is 2 - 100; when the first blocking layer is grown, the flow rate of bis(cyclopentadienyl)magnesium is 1 - 10000 SCCM, and the growth thickness of the first blocking layer is 0.1 - 50 nm; when the second blocking layer is grown, the flow rate of bis(cyclopentadienyl)magnesium is 0.1 - 500 SCCM, and the growth thickness of the second blocking layer is 0.1 - 100 nm.

[0038] b) At 700 - 1100 °C, the first barrier layer and the second barrier layer are grown alternately to form Mg-doped Al x Ga 1-x N / Al y Ga 1-y N superlattice structure, the number of periods of the superlattice structure is 1 - 50, where x is 70 - 100%, y is 60 - 90%, and x is not equal to y; when the first barrier layer is grown, the flow rate of magnesium bis(cyclopentadienyl) is 1 - 10000 SCCM, and the growth thickness of the first barrier layer is 0.1 - 50 nm; when the second barrier layer is grown, the flow rate of magnesium bis(cyclopentadienyl) is 0.1 - 500 SCCM, and the growth thickness of the second barrier layer is 0.1 - 100 nm.

[0039] c) At 700 - 1100 °C, the first barrier layer and the second barrier layer are grown alternately to form undoped Al x Ga 1-x N / Al y Ga 1-y N superlattice structure, the number of periods of the superlattice structure is 1 - 50, where x is 70 - 100%, y is 60 - 90%, and x is not equal to y; during the growth of each first barrier layer or second barrier layer, magnesium bis(cyclopentadienyl) is not introduced. After the growth of each first barrier layer or second barrier layer is completed, the supply of the raw materials for depositing AlGaN is interrupted, and 1 - 10000 SCCM of magnesium bis(cyclopentadienyl) is introduced at the interface between the first barrier layer and the second barrier layer for Mg doping, and the doping time is 1 - 200 s.

[0040] (5) Grow the p-type AlGaN hole injection layer. In this step, at 700 - 1100 °C, the p-type AlGaN hole injection layer is grown on the pulse-doped electron blocking layer, the Al component percentage is 0.1 - 100%, the thickness is 1 - 50 nm, and Mg is used as the p-type dopant.

[0041] In this embodiment, after the p-type AlGaN hole injection layer is grown, a p-type GaN contact layer can be further grown. Specifically, at 400 - 900 °C, the p-type GaN contact layer is grown on the p-type AlGaN hole injection layer, the thickness is 1 - 20 nm, and Mg is used as the p-type dopant.

[0042] Since the method for fabricating the deep ultraviolet LED with a modulation-doped electron blocking layer structure in the second solution is used to fabricate the deep ultraviolet LED with a modulation-doped electron blocking layer structure in the aforementioned first solution, the structures and functions of the deep ultraviolet LEDs with a modulation-doped electron blocking layer structure in the two solutions should be consistent.

[0043] Furthermore, the mechanism of the above-mentioned deep ultraviolet LED with a modulation-doped electron blocking layer structure is elaborated. In the prior art, the Mg doping concentration and doping efficiency in high-Al-component AlGaN materials are often low. In order to obtain a p-type AlGaN hole injection layer with high activation efficiency, it is often necessary to introduce an extremely high concentration of Mg during the growth of the AlGaN material. However, as the Mg doping concentration increases, Mg will diffuse into the quantum well active layer during the growth process, resulting in a large loss of Mg in the p-type AlGaN hole injection layer, and serving as defects to capture the electron-hole pairs entering the active region, thereby greatly weakening the activation efficiency of the p-type AlGaN hole injection layer, and further reducing the luminous efficiency of the deep ultraviolet device. In the present invention, the electron blocking layer is modulation-doped, and two blocking layers with high and low periodic doping are arranged alternately, or the superlattice interface is doped, greatly reducing the concentration difference of Mg between the electron blocking layer and the p-type AlGaN hole injection layer, thereby preventing Mg from diffusing into the active region, and finally achieving a significant improvement in the luminous efficiency of the deep ultraviolet LED device.

[0044] The performance and effect of the above-mentioned deep ultraviolet LED with a modulation-doped electron blocking layer structure are characterized by specific examples below.

[0045] Example 1

[0046] In this example, the steps for preparing a deep ultraviolet LED with a modulation-doped electron blocking layer structure are as follows:

[0047] (1) At 700 °C, a low-temperature buffer layer in the AlN intrinsic layer is grown on a sapphire substrate, with a thickness of 20 nm; the temperature is raised to 1200 °C, and an AlN intrinsic layer is grown on the low-temperature buffer layer in the AlN intrinsic layer, and the total thickness of the AlN intrinsic layer is 800 nm.

[0048] (2) The temperature is lowered to 1000 °C, and an n-type AlGaN electron injection layer is grown on the AlN intrinsic layer, with a thickness of 1000 nm.

[0049] (3) The temperature is lowered to 850 °C, and a quantum well active layer is grown on the n-type AlGaN electron injection layer. Among them, the AlGaN quantum well layer is Al 0.4 Ga 0.6 N, and the thickness of each quantum well layer is 5 nm; the AlGaN barrier layer is Al 0.5 Ga 0.5 N, and the thickness of each barrier layer is 5 nm. After 5 cycles of alternating growth, a quantum well active layer is obtained.

[0050] (4) At 750 °C, the first blocking layer and the second blocking layer are alternately grown, and an Mg-doped Al x Ga 1-x N / Al y Ga 1-y An AlGaN / GaN superlattice structure with 5 periods, where x is 80% and y is 70%. When growing the first barrier layer, the flow rate of bis(cyclopentadienyl)magnesium is 2000 SCCM and the growth thickness is 20 nm. When growing the second barrier layer, the flow rate of bis(cyclopentadienyl)magnesium is 200 SCCM and the growth thickness is 50 nm, obtaining a modulation-doped electron blocking layer.

[0051] (5) At 800 °C, grow a p-type AlGaN hole injection layer on the modulation-doped electron blocking layer with an Al composition percentage of 20% and a thickness of 20 nm, and use Mg as the p-type dopant. At 800 °C, grow a p-type GaN contact layer on the p-type AlGaN hole injection layer with a thickness of 10 nm, and use Mg as the p-type dopant.

[0052] Example 2

[0053] This example is based on the preparation steps of Example 1, only adjusting step (4) in Example 1, and keeping the other steps the same as in Example 1. The adjusted step (4) is as follows:

[0054] At 750 °C, alternately grow the first barrier layer and the second barrier layer. The first barrier layer and the second barrier layer are Mg-doped AlGaN structures with the same composition and an Al composition percentage of 70%. The number of periods of the superlattice structure is 5. When growing the first barrier layer, the flow rate of bis(cyclopentadienyl)magnesium is 2000 SCCM and the growth thickness is 20 nm. When growing the second barrier layer, the flow rate of bis(cyclopentadienyl)magnesium is 200 SCCM and the growth thickness is 50 nm, obtaining a modulation-doped electron blocking layer.

[0055] Example 3

[0056] This example is based on the preparation steps of Example 1, only adjusting step (4) in Example 1, and keeping the other steps the same as in Example 1. The adjusted step (4) is as follows:

[0057] At 750 °C, alternately grow the first barrier layer and the second barrier layer to form an undoped Al x Ga 1-x N / Al y Ga 1-yN superlattice structure, where x is 80% and y is 70%; during the growth of each first barrier layer or second barrier layer, magnesium cyclopentadienyl is not introduced. After the growth of each first barrier layer or second barrier layer is completed, the supply of the raw materials for depositing AlGaN is interrupted, and 2000 SCCM of magnesium cyclopentadienyl is introduced for Mg doping at the interface between the first barrier layer and the second barrier layer. The doping time is 40 s. After repeating the growth for 5 cycles, a modulation-doped electron blocking layer is obtained.

[0058] Comparative Example 1

[0059] This comparative example is based on the preparation steps of Example 1, only replacing the modulation-doped electron blocking layer with a conventional undoped electron blocking layer, and other steps are the same as those in Example 1.

[0060] The samples in Examples 1 to 3 and Comparative Example 1 were compared, and the optical output power was measured. The results are shown as Figure 2 follows. Specifically, Figure 2 is a comparison chart of the optical output power of the deep ultraviolet LED samples in Examples 1 to 3 and Comparative Example 1 of the present invention. Examples 1 to 3 respectively correspond to three modulation-doped electron blocking layer growth methods in the preparation method of the deep ultraviolet LED with a modulation-doped electron blocking layer structure described above. Example 1 is the high-low period doping method of the superlattice structure, Example 2 is the high-low period doping method of a single substrate, and Example 3 is the grain boundary doping method of the superlattice structure, while Comparative Example 1 is a conventional undoped electron blocking layer. It can be Figure 2 seen that due to the modulation doping treatment of the electron blocking layer, the optical output power of Examples 1 to 3 is significantly improved compared with that of Comparative Example 1. The optical output effect of the sample in Example 3 is the best, and Figure 2 under the condition of 150 mA, the optical output power of the sample in Example 3 is increased by about 75% compared with that of the conventional structure in Comparative Example 1, thus proving that modulating the doping of the electron blocking layer can significantly improve the doping efficiency of Mg, effectively prevent the diffusion of Mg into the active region, and thereby significantly improve the luminous efficiency of the deep ultraviolet LED device.

[0061] Furthermore, the luminous efficiencies of the samples in Examples 1 to 3 were analyzed. First, it can be seen that the luminous efficiencies of Examples 1 and 3 are better than that of Example 2, that is, the superlattice structure can improve the luminous efficiency better than the single substrate; the mechanism lies in that the superlattice structure will cause the bending deformation of the energy band, which can reduce the distance between the Mg energy level and the valence band. The reduction of the distance between the Mg energy level and the valence band means that less energy is required to activate holes in the valence band. Therefore, under the same high and low period doping conditions, the superlattice structure can greatly reduce the Mg activation energy, thus having a higher Mg activation efficiency, further increasing the hole concentration in the device and achieving a better light-emitting effect. Second, it can be seen that the luminous efficiency of Example 3 is better than that of Example 1, that is, grain boundary doping under the superlattice structure can better improve the luminous efficiency; the mechanism lies in that during the general doping process, the Mg doping concentration will decrease sharply with the penetration depth in the AlGaN material, that is, the doping concentration on the AlGaN surface is the highest and decreases towards the inside, and it is easier to obtain a higher doping concentration for surface doping than for internal doping. Therefore, Example 3 strengthens the doping at the interface and cooperates with the superlattice structure to obtain a higher Mg doping concentration, which is more conducive to improving the luminous efficiency of the device.

[0062] Different from the prior art, the present invention provides a deep ultraviolet LED with a modulation-doped electron blocking layer structure and a preparation method thereof. By modulating the doping of the electron blocking layer, the doping efficiency of Mg is improved, the diffusion of Mg into the active region is effectively prevented, and the luminous efficiency of the deep ultraviolet LED is improved.

[0063] The above-described embodiments merely represent the implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A deep ultraviolet LED with a modulation-doped electron blocking layer structure, characterized in that, The deep ultraviolet LED with a modulation-doped electron blocking layer structure includes a sapphire substrate, an AlN intrinsic layer, an n-type AlGaN electron injection layer, a quantum well active layer, a modulation-doped electron blocking layer, and a p-type AlGaN hole injection layer which are sequentially stacked. The modulation-doped electron blocking layer is composed of a plurality of first blocking layers and second blocking layers arranged alternately. Both the first barrier layer and the second barrier layer contain Mg doping. The first barrier layer and the second barrier layer are Mg-doped AlGaN structures with the same composition, and the percentage of Al component is 50-100%, and the number of periods is 2-100. The doping concentration of the first barrier layer is 10 17 ~10 21 cm -3 , and the thickness is 0.1-50 nm. The doping concentration of the second barrier layer is 10 14 ~10 19 cm -3 , and the thickness is 0.1-100 nm; Alternatively, both the first blocking layer and the second blocking layer contain Mg doping, and the modulation-doped electron blocking layer is Al x Ga 1- x N / Al y Ga 1-y N superlattice structure, the number of periods of the superlattice structure is 1 to 50, and in the superlattice structure, Al x Ga 1-x N and Al y Ga 1-y N are two film layers, one film layer is the first blocking layer, and the other film layer is the second blocking layer. Among them, x is 70 to 100%, y is 60 to 90%, and x is not equal to y. When both the first blocking layer and the second blocking layer are doped with Mg, the doping concentration of the first blocking layer is 10 17 ~10 21 cm -3 , the thickness is 0.1 to 50 nm, and the doping concentration of the second blocking layer is 10 14 ~10 19 cm -3 , and the thickness is 0.1 to 100 nm.

2. A method for preparing a deep ultraviolet LED having a modulation-doped electron blocking layer structure as described in claim 1, characterized in that, The steps thereof sequentially include: (1) Growing the AlN intrinsic layer: Growing a low-temperature buffer layer of the AlN intrinsic layer on the sapphire substrate at 400 - 800 °C, with a thickness of 10 - 50 nm; heating up to 1200 - 1400 °C and growing the AlN intrinsic layer on the low-temperature buffer layer of the AlN intrinsic layer. The total thickness of the AlN intrinsic layer is 500 - 4000 nm. (2) Growing the n-type AlGaN electron injection layer: Cooling down to 800 - 1200 °C and growing the n-type AlGaN electron injection layer on the AlN intrinsic layer, where the Al component percentage is 20 - 90%, the thickness is 500 - 4000 nm, and Si is used as the n-type dopant. (3) Growing the quantum well active layer: Cooling down to 700 - 1100 °C and growing the quantum well active layer on the n-type AlGaN electron injection layer. In the quantum well active layer, the barrier thickness is 5 - 30 nm, the Al component percentage of the barrier is 20 - 100%, the well thickness is 0.1 - 5 nm, and the Al component percentage of the well is 0.1 - 80%. (4) Growing the modulation-doped electron blocking layer; (5) Growing the p-type AlGaN hole injection layer: Growing the p-type AlGaN hole injection layer on the modulation-doped electron blocking layer at 700 - 1100 °C, where the Al component percentage is 0.1 - 100%, the thickness is 1 - 50 nm, and Mg is used as the p-type dopant.

3. The manufacturing method of the deep ultraviolet LED with a modulation-doped electron blocking layer structure according to claim 2, wherein, In the step of growing the modulation-doped electron blocking layer, the first blocking layer and the second blocking layer are alternately grown at 700 - 1100 °C. The first blocking layer and the second blocking layer are Mg-doped AlGaN structures with the same composition, and the Al component percentage of both is 50 - 100%, and the number of periods is 2 - 100. When growing the first blocking layer, the flow rate of bis(cyclopentadienyl)magnesium is 1 - 10000 SCCM, and the growth thickness of the first blocking layer is 0.1 - 50 nm. When growing the second blocking layer, the flow rate of bis(cyclopentadienyl)magnesium is 0.1 - 500 SCCM, and the growth thickness of the second blocking layer is 0.1 - 100 nm.

4. The preparation method of the deep ultraviolet LED with a modulation-doped electron blocking layer structure according to claim 2, characterized in that, In the step of growing the growth-modulated doped electron blocking layer, the first blocking layer and the second blocking layer are alternately grown at 700-1100 °C to form Mg-doped Al x Ga 1-x N / Al y Ga 1-y N superlattice structure, the number of periods of the superlattice structure is 1-50, where x is 70-100%, y is 60-90%, and x is not equal to y; When growing the first blocking layer, the flow rate of bis(cyclopentadienyl)magnesium is 1 - 10000 SCCM, and the growth thickness of the first blocking layer is 0.1 - 50 nm. When growing the second blocking layer, the flow rate of bis(cyclopentadienyl)magnesium is 0.1 - 500 SCCM, and the growth thickness of the second blocking layer is 0.1 - 100 nm.

Images