Ultraviolet laser with superlattice structure

Abstract

The ultraviolet laser with the superlattice structure comprises a substrate, a buffer layer, a lower limiting layer, a lower waveguide layer, an active layer, an upper waveguide layer, an electron blocking layer, an upper limiting layer, a hole injection layer and a P-type contact layer which are sequentially stacked from bottom to top, and a P-type electrode is arranged on the P-type contact layer; the N-type electrode is arranged on the lower limiting layer; wherein the upper waveguide layer comprises a first superlattice structure layer, and the first superlattice structure layer comprises a plurality of Ba1Alb1Inc1Ga1-a1-b1-c1N potential barrier layers and a plurality of Bu1Alv1Inw1Ga1-u1-v1-w1N potential well layers, and the Ba1Alb1Inc1Ga1-a1-b1-c1N potential barrier layers and the Bu1Alv1Inw1Ga1-u1-v1-w1N potential well layers are arranged alternately. According to the ultraviolet laser, the upper waveguide layer with the superlattice structure layer is introduced, electrons are effectively prevented from being leaked to the P side, the injection efficiency of carriers is improved, the internal quantum efficiency is improved, and therefore the performance of the ultraviolet laser is improved.

Description

Technical Field

[0001] The invention relates to the technical field of lasers, and in particular to an ultraviolet laser with a superlattice structure. Background Art

[0002] Compared with traditional ultraviolet lasers such as excimer ultraviolet lasers and crystal frequency-doubled ultraviolet lasers, Group III nitride semiconductor ultraviolet lasers have the advantages of adjustable wavelength, high beam quality, fast modulation speed, small size, and environmental protection. They have important applications in scientific research, environmental testing, industry, and medical care.

[0003] At present, the research on GaN-based blue-violet lasers is developing rapidly, and the performance of the devices has been improved, which is specifically reflected in the reduction of threshold and the increase of power. However, with the decrease of excitation wavelength, the material epitaxy and device preparation of AlGaN-based ultraviolet lasers are becoming more and more difficult, the device threshold is high, and it is difficult to achieve continuous lasing with electric pumping at room temperature. Low internal quantum efficiency is the main reason for the high threshold of the device. Compared with blue lasers and all-solid-state lasers, the internal quantum efficiency of ultraviolet lasers is lower. Among them, insufficient hole injection and severe electron leakage are the main reasons for the low internal quantum efficiency. The low internal quantum efficiency seriously affects the performance of the laser. Summary of the invention

[0004] In view of this, the present invention provides an ultraviolet laser with a superlattice structure, which is used to solve the problem that the existing ultraviolet laser has low internal quantum efficiency caused by unbalanced carrier injection, thereby affecting its performance.

[0005] An embodiment of the present invention provides an ultraviolet laser having a superlattice structure, comprising:

[0006] A substrate, a buffer layer, a lower confinement layer, a lower waveguide layer, an active layer, an upper waveguide layer, an electron blocking layer, an upper confinement layer, a hole injection layer and a P-type contact layer are sequentially stacked from bottom to top;

[0007] A P-type electrode is disposed on the P-type contact layer; and

[0008] An N-type electrode is disposed on the lower limiting layer;

[0009] The upper waveguide layer includes a first superlattice structure layer, and the first superlattice structure layer includes a plurality of B a1 Al b1 In c1 Ga 1-a1-b1-c1 N barrier layers and multiple B u1 Al v1 In w1 Ga 1-u1-v1-w1N potential well layer, 0≤a1≤1, 0≤b1≤1, 0≤c1≤1, 0≤u1≤1, 0≤v1≤1, 0≤w1≤1.

[0010] According to an embodiment of the present invention, the B a1 Al b1 In c1 Ga 1-a1-b1-c1 The thickness of the N barrier layer is less than or equal to 5 nm and greater than or equal to the thickness of a single atomic layer;

[0011] The B u1 Al v1 In w1 Ga 1-u1-v1-w1 The thickness of the N potential well layer is less than or equal to 5 nm and greater than or equal to the thickness of a single atomic layer.

[0012] According to an embodiment of the present invention, the B a1 Al b1 In c1 Ga 1-a1-b1-c1 The bandgap width of the N barrier layer is larger than that of the B u1 Al v1 In w1 Ga 1-u1-v1-w1 The bandgap width of the N potential well layer.

[0013] According to an embodiment of the present invention, the first superlattice structure layer is located on top of the upper waveguide layer; or

[0014] The first superlattice structure layer is located at the bottom of the upper waveguide layer; or

[0015] The first superlattice structure layer is located in the middle of the upper waveguide layer; or

[0016] The first superlattice structure layer extends from the bottom of the upper waveguide layer to the top of the upper waveguide layer.

[0017] According to an embodiment of the present invention, the lower waveguide layer includes a second superlattice structure layer, and the second superlattice structure layer includes a plurality of B a2 Al b2 In c2 Ga 1-a2-b2-c2 N barrier layers and multiple B u2 Al v2 In w2 Ga 1-u2-v2-w2 N potential well layer, 0≤a2≤1, 0≤b2≤1, 0≤c2≤1, 0≤u2≤1, 0≤v2≤1, 0≤w2≤1.

[0018] According to an embodiment of the present invention, the B a2 Al b2 Inc2 Ga 1-a2-b2-c2 The thickness of the N barrier layer is less than or equal to 5 nm and greater than or equal to the thickness of a single atomic layer;

[0019] The B u2 Al v2 In w2 Ga 1-u2-v2-w2 The thickness of the N potential well layer is less than or equal to 5 nm and greater than or equal to the thickness of a single atomic layer.

[0020] According to an embodiment of the present invention, the B a2 Al b2 In c2 Ga 1-a2-b2-c2 The bandgap width of the N barrier layer is larger than that of the B u2 Al v2 In w2 Ga 1-u2-v2-w2 The bandgap width of the N potential well layer.

[0021] According to an embodiment of the present invention, the second superlattice structure layer is located on top of the lower waveguide layer; or

[0022] The second superlattice structure layer is located at the bottom of the lower waveguide layer; or

[0023] The second superlattice structure layer is located in the middle of the lower waveguide layer; or

[0024] The second superlattice structure layer extends from the bottom of the lower waveguide layer to the top of the lower waveguide layer.

[0025] According to an embodiment of the present invention, an average alloy composition of the upper waveguide layer is the same as an average alloy composition of the lower waveguide layer.

[0026] According to an embodiment of the present invention, the thickness of the upper waveguide layer is 20-200 nm;

[0027] The thickness of the lower waveguide layer is 20-200 nm.

[0028] The ultraviolet laser with a superlattice structure provided by the embodiments of the present invention can at least achieve the following technical effects: by introducing an upper waveguide layer with a first superlattice structure layer, it can effectively prevent electrons from leaking to the P side, improve the injection efficiency of carriers, and improve the internal quantum efficiency, thereby improving the performance of the ultraviolet laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0030] Figure 1The schematic diagram of the structure of the ultraviolet laser according to the embodiment of the present invention is shown;

[0031] FIG2( a ) schematically shows one of the structural diagrams of the upper waveguide layer according to an embodiment of the present invention;

[0032] FIG2( b ) schematically shows a second structural schematic diagram of the upper waveguide layer according to an embodiment of the present invention;

[0033] FIG2( c ) schematically shows a third structural diagram of the upper waveguide layer according to an embodiment of the present invention;

[0034] FIG2( d ) schematically shows a fourth structural diagram of the upper waveguide layer according to an embodiment of the present invention;

[0035] FIG3 (a) schematically shows one of the structural diagrams of the lower waveguide layer according to an embodiment of the present invention;

[0036] FIG3( b ) schematically shows a second structural diagram of the lower waveguide layer according to an embodiment of the present invention;

[0037] FIG3( c ) schematically shows a third structural diagram of the lower waveguide layer according to an embodiment of the present invention;

[0038] FIG3( d ) schematically shows a fourth structural diagram of the lower waveguide layer according to an embodiment of the present invention;

[0039] FIG4 (a) schematically shows a comparison of hole concentration distribution in the quantum well region of the active layer corresponding to the upper waveguide layer having a fixed composition and the upper waveguide layer in FIG2 (b);

[0040] FIG4( b ) schematically shows a comparison of the electron leakage degree of an upper waveguide layer having a fixed composition and an upper waveguide layer having the upper waveguide layer in FIG2( b );

[0041] Reference numerals:

[0042] 1: substrate; 2: buffer layer; 3: lower confinement layer; 4: lower waveguide layer; 41: second superlattice structure layer; 411: second barrier layer; 412: second potential well layer; 42: second alloy layer; 421: first second alloy layer; 422: second second alloy layer; 5: active layer; 6: upper waveguide layer; 61: first superlattice structure layer; 611: first barrier layer; 612: first potential well layer; 62: first alloy layer; 621: first first alloy layer; 622: second first alloy layer; 7: electron blocking layer; 8: upper confinement layer; 9: hole injection layer; 10: P-type contact layer; 11: P-type electrode; 12: N-type electrode. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "include", "comprises", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0045] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] Combine the following Figure 1 4( b ) to 4( b ) illustrate the ultraviolet laser having a superlattice structure of the present invention.

[0047] like Figure 1 As shown, the ultraviolet laser with a superlattice structure provided by the embodiment of the present invention includes a substrate 1, a buffer layer 2, a lower confinement layer 3, a lower waveguide layer 4, an active layer 5, an upper waveguide layer 6, an electron blocking layer 7, an upper confinement layer 8, a hole injection layer 9 and a P-type contact layer 10 stacked in sequence from bottom to top; a P-type electrode 11 is arranged on the P-type contact layer 10; and an N-type electrode 12 is arranged on the lower confinement layer 3. Among them, the upper waveguide layer 6 includes a first superlattice structure layer 61, and the first superlattice structure layer 61 includes a plurality of B a1 Al b1 In c1 Ga 1-a1-b1-c1 N barrier layers and multiple B u1 Al v1 In w1 Ga 1-u1-v1-w1 N potential well layer, 0≤a1≤1, 0≤b1≤1, 0≤c1≤1, 0≤u1≤1, 0≤v1≤1, 0≤w1≤1.

[0048] Specifically, the ultraviolet laser includes a stacked substrate 1, a buffer layer 2, a lower confinement layer 3, a lower waveguide layer 4, an active layer 5, an upper waveguide layer 6, an electron blocking layer 7, an upper confinement layer 8, a hole injection layer 9 and a P-type contact layer 10. A P-type electrode 11 is disposed on the P-type contact layer 10, a step is formed on the lower confinement layer 3, and an N-type electrode 12 is disposed on the lower confinement layer 3.

[0049] A buffer layer 2, a lower confinement layer 3, a lower waveguide layer 4, an active layer 5, an upper waveguide layer 6, an electron blocking layer 7, an upper confinement layer 8, a hole injection layer 9 and a P-type contact layer 10 are sequentially formed on a substrate 1 by an epitaxial growth process. The material, thickness, function, etc. of each layer are described in detail below.

[0050] The material of the substrate 1 includes sapphire, silicon carbide, aluminum nitride, gallium oxide, silicon, etc. The substrate 1 is used to provide support and heat dissipation functions.

[0051] The buffer layer 2 is formed on the substrate 1. The material of the buffer layer 2 is a group III nitride, including , , , , , , The thickness of the buffer layer 2 is in the range of 0.1 to 1 micrometer. The buffer layer 2 can be a single layer structure or a composite structure consisting of a low temperature nucleation layer, a two-dimensional material insertion layer and a high temperature template. The buffer layer 2 is used to improve lattice matching and reduce lattice defects.

[0052] The lower limiting layer 3 is formed on the buffer layer 2. The material of the lower limiting layer 3 is a group III nitride, including , , , , , , The alloy composition of the lower confinement layer 3 can be fixed or can vary along the growth direction, using the polarization effect to generate carriers and affect their transport. The lower confinement layer 3 can be N-type doped, and the dopant includes silicon. The distribution of the dopant along the growth direction can be uniform or variable to improve the conductivity. The thickness of the lower confinement layer 3 ranges from 0.1 to 20 microns and is used to confine carriers and light fields.

[0053] The lower waveguide layer 4 is formed on the lower confinement layer 3, and has a thickness ranging from 20 to 200 nanometers, providing the functions of lower light guidance and carrier transport. The lower waveguide layer 4 can be composed of an alloy layer as a whole, or can be composed of an alloy layer and a superlattice structure layer, or can be composed of a superlattice structure layer as a whole.

[0054] The active layer 5 is formed on the lower waveguide layer 4 and is the core area of ​​laser light emission. The structure of the active layer 5 can be a double heterojunction or a single quantum well or a multi-quantum well. The material of the active layer 5 is a group III nitride, including , , , , , , etc. The wavelength of the UV laser can be optimized by adjusting the alloy composition. The quantum barrier can be undoped or doped to reduce the polarization field and improve the recombination efficiency. The bandgap of the quantum barrier is greater than the bandgap of the quantum well.

[0055] The upper waveguide layer 6 is formed on the active layer 5, with a thickness ranging from 20 to 200 nanometers, and provides the functions of upper light guide and carrier transport. The upper waveguide layer 6 can be composed of a superlattice structure layer and an alloy layer, and the upper waveguide layer 6 can also be composed of a superlattice structure layer as a whole. The upper waveguide layer 6 is generally not P-type doped or weakly doped to reduce optical loss. The superlattice structure layer in the upper waveguide layer 6 is defined as a first superlattice structure layer 61.

[0056] The first superlattice structure layer 61 includes B a1 Al b1 In c1 Ga 1-a1-b1-c1 N barrier layer and B u1 Al v1 In w1 Ga 1-u1-v1-w1 N potential well layer, multiple B a1 Al b1 In c1 Ga 1-a1-b1-c1 N barrier layers and multiple B u1 Al v1 In w1 Ga 1-u1-v1-w1 The N potential well layers are alternately grown to form the first superlattice structure layer 61. a1 Al b1 In c1 Ga 1-a1-b1-c1 The N barrier layer is referred to as the first barrier layer 611. u1 Al v1 In w1 Ga 1-u1-v1-w1 The N potential well layer is referred to as the first potential well layer 612. The alloy composition of the first barrier layer 611 can be fixed or can change along the growth direction, and the alloy composition of the first potential well layer 612 can be fixed or can change along the growth direction, and three-dimensional hole gas is generated by polarization or the polarization field is used to enhance hole transport.

[0057] The bandgap of the first barrier layer 611 is greater than the bandgap of the first potential well layer 612. The average bandgap of the upper waveguide layer 6 is less than the bandgap of the upper confinement layer 8 and greater than the bandgap of the active region light emitting layer.

[0058] The electron blocking layer 7 is formed on the upper waveguide layer 6. The material of the electron blocking layer 7 is a group III nitride, including , , , , , , The alloy composition of the electron blocking layer 7 can be fixed or can vary along the growth direction. The electron blocking layer 7 can be undoped to reduce non-radiative recombination caused by defects. The electron blocking layer 7 can also be P-type doped to promote the transport of holes. The thickness of the electron blocking layer 7 ranges from 1 to 50 nanometers, and is used to block electrons from overshooting to the P side.

[0059] The upper limiting layer 8 is formed on the electron blocking layer 7. The material of the upper limiting layer 8 is a group III nitride, including , , , , , , The alloy composition of the upper confinement layer 8 can be fixed or can change along the growth direction, so as to polarize and induce three-dimensional hole gas and improve the light field distribution. The upper confinement layer 8 can be doped or undoped. When it is undoped or weakly doped, it is beneficial to reduce the loss in the device. The thickness of the upper confinement layer 8 ranges from 0.01 to 1 micron. The upper confinement layer 8 is used to confine carriers and light fields.

[0060] The hole injection layer 9 is formed on the upper confinement layer 8. The material of the hole injection layer 9 is a group III nitride, including , , , , , , The alloy composition of the hole injection layer 9 can be fixed or can change along the growth direction, and a three-dimensional hole gas is generated by using the polarization effect. The hole injection layer 9 is P-type doped to provide effective injection of holes. The thickness of the hole injection layer 9 ranges from 0.01 to 1 micron. The hole injection layer 9 is used to provide effective injection of holes.

[0061] The P-type contact layer 10 is formed on the hole injection layer 9 . The P-type contact layer 10 uses heavily doped P-type III-group nitride or a tunnel junction structure to provide a low-resistance metal-semiconductor contact.

[0062] The P-type electrode 11 is formed on the P-type contact layer 10 and forms a low-resistance metal-semiconductor contact with the P-type contact layer 10. The N-type electrode 12 is formed on the lower confinement layer 3 and forms a low-resistance metal-semiconductor contact with the lower confinement layer 3. The N-type electrode 12 is not connected to the lower waveguide layer 4.

[0063] Figure 4(a) and 4(b) The differences in hole concentration distribution and electron leakage in the quantum well region of the active layer of the upper waveguide layer with a fixed composition and the upper waveguide layer 6 with the first superlattice structure layer 61 in FIG. 2( b) are compared. The upper waveguide layer with a fixed composition is 50 nm Al 0.45 Ga 0.55 N upper waveguide layer, the upper waveguide layer 6 in FIG2(b) comprises 25 nm of Al 0.45 Ga 0.55 N layer and 25nm Al 0.49 Ga 0.51 N / A 0.41 Ga 0.59 N superlattice structure layer. Figure 4(a) and 4(b) The long dashed line corresponds to the upper waveguide layer having a fixed component, and the dot-dash line corresponds to the upper waveguide layer 6 having the first superlattice structure layer 61 .

[0064] Depend on Figure 4(a) and 4(b) It can be seen that the average hole concentration in the quantum well of the ultraviolet laser with the first superlattice structure layer 61 in the upper waveguide layer 6 is increased by 20%, and the electron current leakage ratio is reduced from 82% to 71%. This is because the multiple quantum barriers of the upper waveguide layer 6 with the first superlattice structure layer 61 enhance the electron blocking and effectively prevent the electrons from leaking to the P side.

[0065] In the embodiment of the present invention, by introducing the upper waveguide layer 6 having the first superlattice structure layer 61, electrons are effectively prevented from leaking to the P side, and the carrier injection efficiency is improved, the internal quantum efficiency is increased, and thus the performance of the ultraviolet laser is improved.

[0066] In an optional embodiment, B a1 Al b1 In c1 Ga 1-a1-b1-c1 The bandgap width of the N barrier layer is larger than that of the B u1 Al v1 In w1 Ga 1-u1-v1-w1 The bandgap width of the N potential well layer, that is, the bandgap width of the first potential barrier layer 611 is greater than the bandgap width of the first potential well layer 612. The barrier material with a larger bandgap width and the potential well material with a smaller bandgap width are alternately arranged to form the first superlattice structure layer 61, which can effectively improve the blocking barrier of electrons.

[0067] The thickness of the first barrier layer 611 is less than or equal to 5 nm, and greater than or equal to the thickness of a single atomic layer; the thickness of the first potential well layer 612 is less than or equal to 5 nm, and greater than or equal to the thickness of a single atomic layer. The sub-nanometer level first superlattice structure layer 61 forms a microstrip, and holes are transported into the quantum well by tunneling, thereby increasing the hole concentration in the quantum well. The upper waveguide layer 6 with the first superlattice structure layer 61 effectively solves the problems of insufficient hole injection and serious electron leakage, which is beneficial to improving the internal quantum efficiency of the ultraviolet laser, reducing the device threshold current density and increasing the output power.

[0068] As shown in Figures 2(a), 2(b), 2(c) and 2(d), in an optional embodiment, depending on the proportion of the first superlattice structure layer 61 in the entire upper waveguide layer 6 and the position of the first superlattice structure layer 61 in the entire upper waveguide layer 6, the structure of the upper waveguide layer 6 includes the following four structural forms.

[0069] The first superlattice structure layer 61 is located at the top of the upper waveguide layer 6; or the first superlattice structure layer 61 is located at the bottom of the upper waveguide layer 6; or the first superlattice structure layer 61 is located in the middle of the upper waveguide layer 6; or the first superlattice structure layer 61 extends from the bottom of the upper waveguide layer 6 to the top of the upper waveguide layer 6. The non-superlattice structure portion in the upper waveguide layer 6 is defined as the first alloy layer 62.

[0070] For example, as shown in FIG2( a ), the upper waveguide layer 6 is composed of a first superlattice structure layer 61 , and a plurality of first barrier layers 611 and a plurality of first potential well layers 612 are alternately grown to form the upper waveguide layer 6 . The bottom layer and the top layer of the upper waveguide layer 6 are both first barrier layers 611 .

[0071] For example, as shown in FIG2(b), the upper waveguide layer 6 is composed of a first superlattice structure layer 61 and a first alloy layer 62. The upper portion of the upper waveguide layer 6 is the first superlattice structure layer 61, and the lower portion is the first alloy layer 62. Specifically, the first alloy layer 62 is formed on the active layer 5, the first superlattice structure layer 61 is formed on the first alloy layer 62, and the electron blocking layer 7 is formed on the first superlattice structure layer 61. The material of the first alloy layer 62 is a group III nitride, including , , , , , , The alloy composition of the first alloy layer 62 may be fixed or may vary along the growth direction.

[0072] For example, as shown in FIG2(c), the upper waveguide layer 6 is composed of a first superlattice structure layer 61 and a first alloy layer 62. The upper portion of the upper waveguide layer 6 is the first alloy layer 62, and the lower portion is the first superlattice structure layer 61. Specifically, the first superlattice structure layer 61 is formed on the active layer 5, the first alloy layer 62 is formed on the first superlattice structure layer 61, and the electron blocking layer 7 is formed on the first alloy layer 62. The material of the first alloy layer 62 is a group III nitride, including , , , , , , The alloy composition of the first alloy layer 62 may be fixed or may vary along the growth direction.

[0073] For example, as shown in FIG2(d), the upper waveguide layer 6 is composed of a first superlattice structure layer 61 and two alloy layers. The upper waveguide layer 6 is divided into three regions. The lower portion of the upper waveguide layer 6 is the first first alloy layer 621, the middle portion of the upper waveguide layer 6 is the first superlattice structure layer 61, and the upper portion of the upper waveguide layer 6 is the second first alloy layer 622. Specifically, the first first alloy layer 621 is formed on the active layer 5, the first superlattice structure layer 61 is formed on the first first alloy layer 621, the second first alloy layer 622 is formed on the first superlattice structure layer 61, and the electron blocking layer 7 is formed on the second first alloy layer 622. The materials of the first first alloy layer 621 and the second first alloy layer 622 are group III nitrides, including , , , , , , The alloy components of the first first alloy layer 621 and the second first alloy layer 622 may be fixed or may vary along the growth direction.

[0074] As shown in FIG. 3( a ), FIG. 3( b ), FIG. 3( c ) and FIG. 3( d ), in an optional embodiment, the lower waveguide layer 4 includes a second superlattice structure layer 41 , and the second superlattice structure layer 41 includes a plurality of B a2 Al b2 In c2 Ga 1-a2-b2-c2 N barrier layers and multiple B u2 Al v2 In w2 Ga 1-u2-v2-w2 N potential well layer, 0≤a2≤1, 0≤b2≤1, 0≤c2≤1, 0≤u2≤1, 0≤v2≤1, 0≤w2≤1.

[0075] Specifically, the lower waveguide layer 4 may include a superlattice structure layer, or may not include a superlattice structure layer. In the case where the lower waveguide layer 4 includes a superlattice structure layer, the superlattice structure layer in the lower waveguide layer 4 is defined as a second superlattice structure layer 41. Preferably, the average alloy composition of the lower waveguide layer 4 is the same as the average alloy composition of the upper waveguide layer 6.

[0076] The second superlattice structure layer 41 includes B a2 Al b2 In c2 Ga 1-a2-b2-c2 N barrier layer and B u2 Al v2 In w2 Ga 1-u2-v2-w2 N potential well layer, multiple B a2 Al b2 In c2 Ga 1-a2-b2-c2 N barrier layers and multiple B u2 Al v2 In w2 Ga 1-u2-v2-w2 The N potential well layers are alternately grown to form the second superlattice structure layer 41. a2 Al b2 In c2 Ga 1-a2-b2-c2 The N barrier layer is referred to as the second barrier layer 411. u2 Al v2 In w2 Ga 1-u2-v2-w2 The N potential well layer is referred to as the second potential well layer 412. The alloy composition of the second barrier layer 411 can be fixed or can change along the growth direction. The alloy composition of the second potential well layer 412 can be fixed or can change along the growth direction. The polarization field is used to regulate the transport behavior of electrons. The lower waveguide layer 4 can be doped with silicon in an appropriate amount to suppress point defects, or undoped to reduce light absorption loss.

[0077] The bandgap width of the second barrier layer 411 is greater than the bandgap width of the second potential well layer 412. The average bandgap width of the lower waveguide layer 4 is smaller than the bandgap width of the lower confinement layer 3.

[0078] The thickness of the second barrier layer 411 is less than or equal to 5 nm, and greater than or equal to the thickness of a single atomic layer; the thickness of the second potential well layer 412 is less than or equal to 5 nm, and greater than or equal to the thickness of a single atomic layer. The barrier material with a larger bandgap width and the potential well material with a smaller bandgap width are alternately grown to form a superlattice structure layer, which can effectively improve the blocking barrier of electrons. The lower waveguide layer 4 with the second superlattice structure layer 41 can reduce the electrons injected into the active layer 5, making the electron-hole distribution more balanced.

[0079] As shown in Figures 3(a), 3(b), 3(c) and 3(d), in an optional embodiment, depending on the proportion of the second superlattice structure layer 41 in the entire lower waveguide layer 4 and the position of the second superlattice structure layer 41 in the entire lower waveguide layer 4, the structure of the lower waveguide layer 4 includes the following four structural forms.

[0080] The second superlattice structure layer 41 is located at the top of the lower waveguide layer 4; or the second superlattice structure layer 41 is located at the bottom of the lower waveguide layer 4; or the second superlattice structure layer 41 is located in the middle of the lower waveguide layer 4; or the second superlattice structure layer 41 extends from the bottom of the lower waveguide layer 4 to the top of the lower waveguide layer 4.

[0081] For example, as shown in FIG3( a ), the lower waveguide layer 4 is composed of a second superlattice structure layer 41 , and a plurality of second barrier layers 411 and a plurality of second potential well layers 412 are alternately grown to form the lower waveguide layer 4 . The bottom layer and the top layer of the lower waveguide layer 4 are both second barrier layers 411 .

[0082] For example, as shown in FIG3( b ), the lower waveguide layer 4 is composed of a second superlattice structure layer 41 and a second alloy layer 42. The upper portion of the lower waveguide layer 4 is the second superlattice structure layer 41, and the lower portion is the second alloy layer 42. Specifically, the second alloy layer 42 is formed on the lower confinement layer 3, the second superlattice structure layer 41 is formed on the second alloy layer 42, and the active layer 5 is formed on the second superlattice structure layer 41. The material of the second alloy layer 42 is a group III nitride, including , , , , , , The alloy composition of the second alloy layer 42 may be fixed or may vary along the growth direction.

[0083] For example, as shown in FIG3(c), the lower waveguide layer 4 is composed of a second superlattice structure layer 41 and a second alloy layer 42, the upper portion of the lower waveguide layer 4 is the second alloy layer 42, and the lower portion is the second superlattice structure layer 41. Specifically, the second superlattice structure layer 41 is formed on the lower confinement layer 3, the second alloy layer 42 is formed on the second superlattice structure layer 41, and the active layer 5 is formed on the second alloy layer 42. The material of the second alloy layer 42 is a group III nitride, including , , , , , , The alloy composition of the second alloy layer 42 may be fixed or may vary along the growth direction.

[0084] For example, as shown in FIG3(d), the lower waveguide layer 4 is composed of a second superlattice structure layer 41 and two alloy layers. The lower waveguide layer 4 is divided into three regions. The lower portion of the lower waveguide layer 4 is the first second alloy layer 421, the middle portion of the lower waveguide layer 4 is the second superlattice structure layer 41, and the upper portion of the lower waveguide layer 4 is the second second alloy layer 422. Specifically, the first second alloy layer 421 is formed on the lower confinement layer 3, the second superlattice structure layer 41 is formed on the first second alloy layer 421, the second second alloy layer 422 is formed on the second superlattice structure layer 41, and the active layer 5 is formed on the second second alloy layer 422. The materials of the first second alloy layer 421 and the second second alloy layer 422 are group III nitrides, including , , , , , , The alloy components of the first second alloy layer 421 and the second second alloy layer 422 may be fixed or may vary along the growth direction.

[0085] The lower waveguide layer 4 having the above four structural forms can partially block the electrons entering the active layer 5, thereby making the injection of electrons and holes more balanced.

[0086] In summary, the upper waveguide layer 6 and the lower waveguide layer 4 of the ultraviolet laser of the present invention both include superlattice structure layers. Barrier materials with larger bandgap width and potential well materials with smaller bandgap width are alternately arranged to form superlattice structure layers, which can effectively improve the blocking barrier of electrons.

[0087] The lower waveguide layer 4 having the second superlattice structure layer 41 can reduce the electrons injected into the active layer 5, making the electron-hole distribution more balanced; the upper waveguide layer 6 having the first superlattice structure layer 61 can significantly reduce electron leakage, and the sub-nanometer superlattice structure layer forms a microstrip, and holes are easily tunneled and transported into the quantum well, which is conducive to improving the hole injection level, thereby improving the internal quantum efficiency of the laser, reducing the threshold and increasing the output power. In addition, due to the enhanced hole transport of the upper waveguide layer 6, the parasitic luminescence of the upper waveguide layer 6 is reduced. The ultraviolet laser of the present invention reduces electron leakage and improves the injection efficiency of carriers by forming a superlattice structure layer in the upper waveguide layer 6 and the lower waveguide layer 4, thereby improving the internal quantum efficiency and achieving higher performance.

[0088] The above is only a specific embodiment of the present invention, but the protection scope of this application is not limited thereto. Any changes or substitutions made within the spirit and principle of the present invention should be included in the protection scope of this application. Therefore, the protection scope of this application should be based on the protection scope of the claims.

Claims

1. An ultraviolet laser having a superlattice structure, characterized in that: include: A substrate, a buffer layer, a lower confinement layer, a lower waveguide layer, an active layer, an upper waveguide layer, an electron blocking layer, an upper confinement layer, a hole injection layer and a P-type contact layer are sequentially stacked from bottom to top; A P-type electrode, disposed on the P-type contact layer; as well as An N-type electrode is disposed on the lower limiting layer; The upper waveguide layer includes a first superlattice structure layer, and the first superlattice structure layer includes a plurality of B a1 Al b1 In c1 Ga 1-a1-b1-c1 N barrier layers and multiple B u1 Al v1 In w1 Ga 1-u1-v1-w1 N potential well layer, 0≤a1≤1, 0≤b1≤1, 0≤c1≤1, 0≤u1≤1, 0≤v1≤1, 0≤w1≤1.

2. The ultraviolet laser according to claim 1, characterized in that: B a1 Al b1 In c1 Ga 1-a1-b1-c1 The thickness of the N barrier layer is less than or equal to 5 nm and greater than or equal to the thickness of a single atomic layer; B u1 Al v1 In w1 Ga 1-u1-v1-w1 The thickness of the N potential well layer is less than or equal to 5 nm and greater than or equal to the thickness of a single atomic layer.

3. The ultraviolet laser according to claim 1, characterized in that: B a1 Al b1 In c1 Ga 1-a1-b1-c1 The bandgap width of the N barrier layer is larger than that of the B u1 Al v1 In w1 Ga 1-u1-v1-w1 The bandgap width of the N potential well layer.

4. The ultraviolet laser according to any one of claims 1 to 3, characterized in that: The first superlattice structure layer is located on top of the upper waveguide layer; or The first superlattice structure layer is located at the bottom of the upper waveguide layer; or The first superlattice structure layer is located in the middle of the upper waveguide layer; or The first superlattice structure layer extends from the bottom of the upper waveguide layer to the top of the upper waveguide layer.

5. The ultraviolet laser according to claim 1, characterized in that: The lower waveguide layer includes a second superlattice structure layer, and the second superlattice structure layer includes a plurality of B a2 Al b2 In c2 Ga 1-a2-b2-c2 N barrier layers and multiple B u2 Al v2 In w2 Ga 1-u2-v2-w2 N potential well layer, 0≤a2≤1, 0≤b2≤1, 0≤c2≤1, 0≤u2≤1, 0≤v2≤1, 0≤w2≤1.

6. The ultraviolet laser according to claim 5, characterized in that: B a2 Al b2 In c2 Ga 1-a2-b2-c2 The thickness of the N barrier layer is less than or equal to 5 nm and greater than or equal to the thickness of a single atomic layer; B u2 Al v2 In w2 Ga 1-u2-v2-w2 The thickness of the N potential well layer is less than or equal to 5 nm and greater than or equal to the thickness of a single atomic layer.

7. The ultraviolet laser according to claim 5, characterized in that: B a2 Al b2 In c2 Ga 1-a2-b2-c2 The bandgap width of the N barrier layer is larger than that of the B u2 Al v2 In w2 Ga 1-u2-v2-w2 The bandgap width of the N potential well layer.

8. The ultraviolet laser according to any one of claims 5 to 7, characterized in that: The second superlattice structure layer is located on top of the lower waveguide layer; or The second superlattice structure layer is located at the bottom of the lower waveguide layer; or The second superlattice structure layer is located in the middle of the lower waveguide layer; or The second superlattice structure layer extends from the bottom of the lower waveguide layer to the top of the lower waveguide layer.

9. The ultraviolet laser according to claim 1, characterized in that: The average alloy composition of the upper waveguide layer is the same as the average alloy composition of the lower waveguide layer.

10. The ultraviolet laser according to claim 1, characterized in that: The thickness of the upper waveguide layer is 20-200 nm; The thickness of the lower waveguide layer is 20-200 nm.

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