Gallium nitride laser

Abstract

This disclosure provides a gallium nitride-based laser, comprising: an N-type electrode (1), on which a substrate (2), a buffer layer (3), an N-type aluminum gallium nitride lower confinement layer (4), an N-type aluminum gallium nitride lower waveguide layer (5), an active region (6), a P-type aluminum gallium nitride upper waveguide layer (7), a P-type electron blocking layer (8), a P-type aluminum gallium nitride upper confinement layer (9), a P-type ohmic contact layer (10), and a P-type electrode (11) are sequentially stacked. The P-type aluminum gallium nitride upper confinement layer (9) is graded-doped, with the concentration of the graded doping gradually increasing along the direction from the P-type electron blocking layer (8) to the P-type ohmic contact layer (10). The threshold current and output power of the gallium nitride-based laser are significantly improved, and the electro-optic conversion efficiency is high.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of semiconductor lasers, and particularly relates to a gallium nitride-based laser. BACKGROUND

[0002] Gallium nitride (GaN) based semiconductor materials include GaN, indium nitride (InN), aluminum nitride (AlN) and their ternary and quaternary alloy compounds, with a forbidden band width continuously adjustable from 0.7 eV to 6.2 eV, and a light emission spectrum covering from infrared to deep ultraviolet waveband, which is the preferred material for preparing GaN-based ultraviolet lasers. GaN-based ultraviolet lasers have high beam quality, fast modulation speed, high power density and other advantages due to their unique high spatial and practical coherence, and can be widely applied to various fields such as precision laser processing, high-density storage, medical diagnosis, sterilization and disinfection, and gas sensing.

[0003] However, for AlGaN ultraviolet lasers, as the Al component in the AlGaN material increases, the difficulty of material epitaxy and device preparation increases. On the one hand, the epitaxial growth process is imperfect, and as the Al component increases, there is a more serious lattice mismatch phenomenon during the growth process, making it difficult to grow high-quality AlGaN materials, thereby causing large internal loss of the laser. On the other hand, due to the high activation energy of the dopant, it is difficult to achieve high P-type conductivity in p-type AlGaN, and the doping efficiency is low. The ionization energy of the dopant acceptor in P-AlGaN increases with the increase of the Al component, resulting in a very high resistivity of P-AlGaN and a very high operating voltage of the laser, which increases the threshold of the device under current injection and reduces the efficiency. These problems limit the performance improvement of GaN-based ultraviolet lasers. SUMMARY

[0004] Therefore, the present disclosure provides a gallium nitride-based laser, which comprises an N-type electrode, and a substrate, a buffer layer, an N-type aluminum gallium nitride lower confinement layer, an N-type aluminum gallium nitride lower waveguide layer, an active region, a P-type aluminum gallium nitride upper waveguide layer, a P-type electron blocking layer, a P-type aluminum gallium nitride upper confinement layer, a P-type ohmic contact layer and a P-type electrode are sequentially stacked on the N-type electrode; wherein the P-type aluminum gallium nitride upper confinement layer is gradually doped with magnesium, and the gradually doped magnesium concentration gradually increases in a direction from the P-type electron blocking layer to the P-type ohmic contact layer.

[0005] According to an embodiment of the present disclosure, the P-type aluminum gallium nitride upper confinement layer is gradually doped with magnesium, and the gradually doped magnesium concentration gradually increases in a direction from the P-type electron blocking layer to the P-type ohmic contact layer.

[0006] 3. The gallium nitride-based laser according to claim 2, wherein the gradually doped magnesium concentration gradually increases in a direction from the P-type electron blocking layer to the P-type ohmic contact layer, from 2 x 1018cm-3 to 2 x 1020cm-3.24 / cm 3 linearly changes to 2x10 25 / cm 3 .

[0007] According to an embodiment of the present disclosure, the material of the N-type electrode is Ti / Al / Ti / Au material.

[0008] According to an embodiment of the present disclosure, the buffer layer is an N-GaN buffer layer.

[0009] According to an embodiment of the present disclosure, the active region is formed by alternately stacking quantum barrier layers and quantum well layers, and the outermost two layers of the active region are quantum barrier layers.

[0010] According to an embodiment of the present disclosure, the materials of the quantum barrier layers and the quantum well layers are both aluminum gallium nitride, and the content of aluminum and gallium in the quantum barrier layers is different from the content of aluminum and gallium in the quantum well layers.

[0011] According to an embodiment of the present disclosure, the P-type electron blocking layer is a superlattice structure.

[0012] According to an embodiment of the present disclosure, the material of the P-type electron blocking layer is formed by alternately growing multiple periods of aluminum gallium nitride with different components.

[0013] According to an embodiment of the present disclosure, the material of the P-type ohmic contact layer is gallium nitride, and the material of the P-type electrode is Pd / Pt / Au. BRIEF DESCRIPTION OF DRAWINGS

[0014] The above and other objects, features and advantages of the present disclosure will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which:

[0015] Figure 1 A structure diagram of a gallium nitride-based laser provided by an embodiment of the present disclosure is schematically shown.

[0016] Figure 2 A power-current curve diagram of a gallium nitride-based laser provided by an embodiment of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0017] To make the objectives, technical solutions and advantages of the present disclosure clearer, the present disclosure is further described in detail below with reference to specific embodiments and drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present disclosure.

[0018] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the term "includes" and tenses of the term "includes", such as "including", "includes" or "include", means "including, but not limited to".

[0019] In the present disclosure, unless specifically defined otherwise, the terms "mount", "connect", "connection", "fixed", and the like, should be given their broadest possible interpretation in accordance with the principles of equivalency such that, for example, "connection" can be either direct or indirect, "fixed" can be either removable or integral, "attached" can be either mechanically or electrically attached, and "coupled" can be either mechanical, electrical, or communicative coupled. It is further noted that, as used in this specification, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

[0020] In the description of the present disclosure, it should be understood that the terms "longitudinal", "length", "circumferential", "front", "back", "left", "right", "top", "bottom", "inner", "outer", and the like mean the orientation or positional relationship shown by the drawings based on the orientation or positional relationship shown by the drawings, and are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the referred subsystem or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present disclosure.

[0021] Throughout the drawings, identical elements are denoted by the same or similar reference numbers. When it may cause confusion in understanding the present disclosure, conventional structures or configurations will be omitted. Also, the shape, size, positional relationship of the components in the drawings do not reflect the actual size, scale and actual positional relationship. In addition, in the claims, any reference signs located between parentheses should not be construed as limiting the claims.

[0022] Similarly, in order to simplify the present disclosure and help understand one or more of the various disclosed aspects, in the above description of exemplary embodiments of the present disclosure, various features of the present disclosure are sometimes grouped together in a single embodiment, figure or description thereof. The description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present disclosure. In the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0023] In addition, the terms "first", "second", etc. are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or an indicated number of technical features. Thus, features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present disclosure, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0024] In the context of the present disclosure, when a layer / element is referred to as being located "on" another layer / element, the layer / element can be directly located on the other layer / element, or there can be an intermediate layer / element between them. In addition, if a layer / element is located "on" another layer / element in one orientation, it can be located "under" the other layer / element when the orientation is reversed.

[0025] The purpose of the present disclosure is to provide a high-efficiency GaN-based ultraviolet laser based on graded doping, by using a Mg-graded-doped AlGaN layer in the p-type confinement layer near the quantum well, optimizing the doping concentration distribution of the P-type confinement layer can greatly reduce the series resistance of the device, thereby improving the electro-optical conversion efficiency of the device. The following will be described in detail in conjunction with the accompanying drawings.

[0026] Figure 1 The structure of the gallium nitride-based laser provided by the embodiment of the present disclosure is schematically shown.

[0027] As shown in Figure 1 The gallium nitride-based laser may, for example, include an N-type electrode 1, a substrate 2, a buffer layer 3, an N-type aluminum gallium nitride lower confinement layer 4, an N-type aluminum gallium nitride lower waveguide layer 5, an active region 6, a P-type aluminum gallium nitride upper waveguide layer 7, a P-type electron blocking layer 8, a P-type aluminum gallium nitride upper confinement layer 9, a P-type ohmic contact layer 10, and a P-type electrode 11 formed in sequence on the N-type electrode 1.

[0028] In the embodiment of the present disclosure, the N-type electrode 1 can be Ti / Al / Ti / Au material, that is, the N-type electrode 1 is formed by stacking Ti, Al, Ti, and Au, and the thickness of each layer may, for example, be 70 / 50 / 70 / 200 nm, which is set according to actual needs, and the present disclosure does not make any limitation.

[0029] In the embodiment of the present disclosure, the substrate 2 can be selected as a GaN substrate, and the thickness thereof can be 50 μm-150 μm, preferably 100 μm.

[0030] In the embodiment of the present disclosure, the buffer layer 3 may, for example, be an N-GaN buffer layer.

[0031] In the embodiment of the present disclosure, the material of the N-type aluminum gallium nitride lower confinement layer 4 may, for example, be preferably Al 0.55 Ga 0.45N, preferably 2 pm in thickness.

[0032] In the embodiments of the present disclosure, the material of the N-type aluminum gallium nitride lower waveguide layer 5 may, for example, preferably be Al 0.5 Ga 0.5 N, preferably 120 nm in thickness.

[0033] In the embodiments of the present disclosure, the active region 6 may be formed by alternately stacking quantum barrier layers and quantum well layers, and the outermost two layers of the active region are quantum barrier layers. The materials of the quantum barrier layers and the quantum well layers are both aluminum gallium nitride, and the contents of aluminum and gallium in the quantum barrier layers are different from those in the quantum well layers.

[0034] For example, the active region 6 is composed of three AlGaN quantum barrier layers and two GaN quantum well layers alternately stacked. The three AlGaN quantum barrier layers are preferably Al 0.3 Ga 0.7 N, and the thickness of a single quantum barrier layer is preferably 10 nm. The two quantum well layers are preferably Al 0.2 Ga 0.8 N, and the thickness of a single quantum well layer is preferably 3 nm.

[0035] In the embodiments of the present disclosure, the material of the P-type aluminum gallium nitride upper waveguide layer 7 may, for example, preferably be Al 0.5 Ga 0.5 N, preferably 120 nm in thickness.

[0036] In the embodiments of the present disclosure, the P-type electron blocking layer 8 is a superlattice structure. Specifically, the material of the P-type electron blocking layer 8 is formed by alternately growing multiple periods of aluminum gallium nitride with different compositions.

[0037] For example, the material of the P-type electron blocking layer 8 is alternately grown for 20 periods of Al 0.65 Ga 0.35 N and Al 0.75 Ga 0.25 N.

[0038] In the embodiments of the present disclosure, the P-type aluminum gallium nitride upper confinement layer 9 is gradually doped, and the concentration of the gradually doped gradually increases in the direction from the P-type electron blocking layer 8 to the P-type ohmic contact layer 10.

[0039] Specifically, the P-type aluminum gallium nitride upper confinement layer 9 may, for example, be gradually doped with magnesium, and the concentration of the gradually doped magnesium gradually increases in a linear manner in the direction from the P-type electron blocking layer 8 to the P-type ohmic contact layer 10. Preferably, the concentration of the gradually doped magnesium linearly changes from 2 x 1016 / cm2in the direction from the P-type electron blocking layer 8 to the P-type ohmic contact layer 10 to 2 x 1018 / cm2. 24 / cm 3 / cm 25 / cm 3The component of aluminum in the P-type AlGaN upper confining layer 9 is preferably 0.55, and the thickness is preferably 2.3 μm.

[0040] In the embodiments of the present disclosure, the material of the P-type ohmic contact layer 10 can be preferably GaN, and the thickness is preferably 120 nm.

[0041] In the embodiments of the present disclosure, the material of the P-type electrode 11 is preferably Pd / Pt / Au, and the thickness is preferably 30 nm / 50 nm / 80 nm.

[0042] To better illustrate the excellent performance of the GaN-based laser provided by the embodiments of the present disclosure, experimental data is provided below for proof.

[0043] Figure 2 A power-current curve diagram of the GaN-based laser provided by the embodiments of the present disclosure is schematically shown.

[0044] As Figure 2 shown, wherein the curve L1 represents the power-current curve diagram of the P-type upper confining layer with a fixed doping concentration of Mg of 2×10 25 / cm 3 , the curve L2 represents the power-current curve diagram of the P-type upper confining layer with a gradually changing doping concentration of Mg from 1×10 25 / cm 3 to 3×10 25 / cm 3 , and the curve L3 represents the power-current curve diagram of the P-type upper confining layer with a gradually changing doping concentration of Mg from 2×10 24 / cm 3 to 2×10 25 / cm 3 . The inflection points of the curves correspond to the threshold current of the GaN-based laser with different doping methods. By comparing the curve L1, the curve L2 and the curve L3, it can be seen that the gradually changing doping method of Mg in the P-type upper confining layer can greatly improve the threshold current and output power of the GaN-based laser, and improve the electro-optical conversion efficiency of the GaN-based laser.

[0045] According to the gallium nitride-based laser provided by the embodiment of the present disclosure, the P-type upper limiting layer adopts a structure design of Mg gradient doping, and by reasonably setting the content of Mg doping in the P-type upper limiting layer, the series resistance of the gallium nitride-based laser can be obviously reduced, the electron leakage can be inhibited, and the threshold current can be reduced. Meanwhile, the gradient doping can reduce the growth pressure of the Mg activation in the high Al component, so that the number of effective Mg activation is increased, so as to improve the ohmic contact of the P-type layer, and then improve the threshold current and the output power. In combination with the reasonable design of other structure layers, the electro-optical conversion efficiency of the gallium nitride-based laser is improved, and a high-performance gallium nitride-based laser with high electro-optical conversion efficiency is obtained.

[0046] The above specific embodiments further specifically describe the purposes, technical solutions and beneficial effects of the present disclosure, and it should be understood that the above description is only for specific embodiments of the present disclosure and is not used to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A gallium nitride-based laser, comprising: an N-type electrode (1), a substrate (2), a buffer layer (3), an N-type AlGaN lower confining layer (4), an N-type AlGaN lower waveguide layer (5), an active region (6), a P-type AlGaN upper waveguide layer (7), a P-type electron blocking layer (8), a P-type AlGaN upper confining layer (9), a P-type ohmic contact layer (10) and a P-type electrode (11) being sequentially stacked on the N-type electrode (1) ; The P-type aluminum gallium nitride upper limiting layer (9) is gradually doped with magnesium, and the gradually doped magnesium concentration linearly changes from 2×10 24 / cm 3 to 2×10 25 / cm 3 from the P-type electron blocking layer (8) to the P-type ohmic contact layer (10).

2. The gallium nitride-based laser of claim 1, wherein, the material of the N-type electrode (1) is Ti / Al / Ti / Au.

3. The gallium nitride-based laser of claim 1, wherein, the buffer layer (3) is an N-GaN buffer layer.

4. The gallium nitride-based laser of claim 1, wherein, the active region (6) is formed by alternately stacking quantum barrier layers and quantum well layers, and the outermost two layers of the active region are quantum barrier layers.

5. The gallium nitride-based laser of claim 4, wherein, the materials of the quantum barrier layers and the quantum well layers are both AlGaN, and the contents of Al and Ga in the quantum barrier layers are different from those in the quantum well layers.

6. The gallium nitride-based laser of claim 1, wherein, the P-type electron blocking layer (8) is a superlattice structure.

7. The gallium nitride-based laser of claim 6, wherein, the material of the P-type electron blocking layer (8) is formed by alternately growing multiple periods of AlGaN with different compositions.

8. The gallium nitride-based laser of claim 1, wherein, the material of the P-type ohmic contact layer (10) is gallium nitride, and the material of the P-type electrode (11) is Pd / Pt / Au.

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