Semiconductor laser and display device thereof

Abstract

The invention discloses a semiconductor laser and a display device thereof. The semiconductor laser comprises a first semiconductor layer, a second semiconductor layer and an active layer located between the first semiconductor layer and the second semiconductor layer. A first waveguide layer is arranged between the first semiconductor layer and the active layer, and a second waveguide layer is arranged between the second semiconductor layer and the active layer; an electron blocking layer is arranged between the second waveguide layer and the second semiconductor layer, one side, close to the second semiconductor layer, of the electron blocking layer comprises at least one part of a P-type doped layer, and the component of the P-type doped layer is larger than 1E19cm <-3 >; the P-type doping concentration of the side, close to the second semiconductor layer, of the electron blocking layer is higher than the P-type doping concentration of the side, away from the second semiconductor layer, of the electron blocking layer, and it is avoided that P-type doping diffuses to the second waveguide layer, and consequently light absorption of the second waveguide layer rises.

Description

Technical Field

[0001] This application relates to the field of semiconductor-related technologies, and in particular to a laser diode and its display device. Background Technology

[0002] Gallium nitride (GaN) and its constituent group III nitrides are direct-transition wide-bandgap semiconductor materials with broad energy bands, making them ideal materials for fabricating lasers ranging from the ultraviolet to the green light band. GaN-based blue-green lasers offer advantages such as small size, high integration, high brightness, and high resolution. The distribution of the light field and the photon confinement capability are key factors affecting the performance of GaN-based blue-green lasers.

[0003] In traditional gallium nitride-based blue-green lasers, the electron blocking layer plays a role in suppressing electron overflow while also accommodating hole injection. P-type doping, such as magnesium doping, acts as the main P-type hole-providing layer in the electron blocking layer.

[0004] However, due to the poor activation efficiency of magnesium, the doping concentration is too low and cannot effectively provide enough hole concentration, which affects the luminous efficiency. On the other hand, the excessively high doping concentration will cause optical absorption, which will affect the brightness of the laser. Furthermore, the device will be affected by heat during long-term operation, which will cause trace amounts of magnesium to diffuse into the active layer, forming non-radiative recombination defects and leading to light decay. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a semiconductor laser, primarily a blue-green laser, with an output wavelength of 430 nm to 550 nm. An electron blocking layer is provided, comprising aluminum gallium nitride (AGaN) and / or aluminum indium gallium nitride (AIGaN). The aluminum concentration in the electron blocking layer varies, utilizing this variation to restrict the diffusion of p-type doping, primarily limiting magnesium diffusion. The electron blocking layer includes a p-type doped layer near the second semiconductor layer, with a p-type doping concentration of not less than 1E19 cm⁻¹. -3 The P-type doping concentration on the side of the electron blocking layer closer to the second semiconductor layer is higher than that on the side farther away from the second semiconductor layer, ensuring that the P-type doping provides sufficient holes. Calculations show that in the photon confinement region, the high magnesium doping concentration of the electron blocking layer is the main source of photon absorption. By placing the high P-type doping concentration region away from the second waveguide layer, the optical absorption of the second waveguide layer is reduced, thus improving the light extraction efficiency.

[0006] According to the present invention, preferably, it further includes a high-aluminum barrier layer disposed between the second waveguide layer and the electron barrier layer. The aluminum composition of the high-aluminum barrier layer is more than twice that of the electron barrier layer, or it is disposed on the side of the electron barrier layer closer to the second waveguide layer, and the aluminum composition of the high-aluminum barrier layer is more than twice that of other regions of the electron barrier layer. This increased aluminum composition further restricts the diffusion of P-type doping from the electron barrier layer to the second waveguide layer. Preferably, the high-aluminum barrier layer is a non-P-type doped layer.

[0007] According to the present invention, preferably, considering both the effect of hole injection and the avoidance of the restriction of hole movement by high alumina, especially the restriction of hole movement towards the active layer, the composition of the high alumina barrier layer includes In. y Al x Ga (1-x-y) N, where x is 0.5 to 1, y is 0 to 0.2, the thickness of the high-aluminum barrier layer is no greater than 0.003 μm, and the quantum efficiency within the product is improved by using a transient doping process.

[0008] According to the present invention, preferably, the thickness of the P-type doped layer in the electron blocking layer is 0.001 μm to 0.01 μm to enhance the diffusion suppression effect.

[0009] According to the present invention, preferably, the electron blocking layer has a first P-type doping concentration peak, the electron blocking layer has an aluminum concentration peak, the peak value of the first P-type doping concentration peak is located on the side of the aluminum concentration peak of the electron blocking layer close to the second semiconductor layer, and the diffusion of P-type impurities is prevented by delaying doping relative to the aluminum peak, and the peak doping concentration of the first P-type doping concentration peak is not lower than the P-type doping concentration in other regions of the electron blocking layer.

[0010] According to the present invention, preferably, the electron blocking layer has a second P-type doping concentration peak, which is located between the first P-type doping concentration peak and the second waveguide layer. The second P-type doping concentration peak is affected by the position of the aluminum concentration peak, and the distance between the second P-type doping concentration peak and the aluminum concentration peak is less than 50 angstroms.

[0011] According to the present invention, preferably, the electron blocking layer has a second P-type doping concentration peak, the peak value of the second P-type doping concentration peak is located on the side of the peak value of the aluminum peak of the electron blocking layer that is close to the second waveguide layer, and the second P-type doping concentration peak plays a buffering role for P-type doping diffusion, further preventing P-type doping from diffusing to the second waveguide layer.

[0012] According to the present invention, preferably, the distance between the peak of the first P-type doping concentration peak and the second waveguide layer is 0.005 μm to 0.02 μm, with the upper limit being to increase hole injection efficiency and the lower limit being to prevent Mg diffusion to the second waveguide layer. The distance between the peak of the first P-type doping concentration peak and the surface of the electron blocking layer near the second semiconductor layer is 0 μm to 0.01 μm.

[0013] According to the present invention, preferably, the peak value of the first P-type doping concentration peak is higher than the peak value of the second P-type doping concentration peak, and the peak concentration of the second P-type doping concentration peak is not less than 1E19 cm⁻¹. -3 Doping maximizes hole injection efficiency while also slowing down or buffering dopant diffusion.

[0014] According to the present invention, preferably, the surface P-type doping concentration of the electron blocking layer near the second waveguide layer is not less than 1E19. cm -3 High concentrations of P-type doping are used to slow down or buffer the diffusion of P-type doping.

[0015] According to the present invention, preferably, the P-type doping concentration of the second waveguide layer is not greater than 1E19 cm⁻¹. -3 .

[0016] According to the present invention, preferably, the electron blocking layer has a trough in the P-type doping concentration, wherein the P-type doping concentration of the trough is less than 70% of the highest P-type doping concentration in the electron blocking layer, and the P-type doping concentration of the trough is 7E18cm. -3 The actual doping settings below can be implemented at 5E18cm. -3 The following section utilizes the valley effect to limit the diffusion of P-type doping.

[0017] In this invention, a display device is also provided, including a display light source, wherein the display light source employs the aforementioned semiconductor laser.

[0018] The beneficial effects of this invention include at least: moving the high concentration region of P-type doping away from the second waveguide layer, reducing the optical absorption of the second waveguide layer, and controlling the P-type doping concentration of the second waveguide layer to be no greater than 1E19 cm⁻¹. -3 By using localized doping techniques to control the location of Mg doping at the end of the electron blocking layer, the same hole injection efficiency can be obtained, and the diffusion of P-type doping to the active layer can also be slowed down. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a cross-sectional schematic diagram of a laser diode according to Embodiment 1 of this application; Figure 2 This refers to the component test data of a laser diode according to Embodiment 1 of this application; Figure 3 This is a cross-sectional schematic diagram of a laser diode according to Embodiment 2 of this application; Figure 4 The above refers to the component test data of a laser diode according to Embodiment 2 of this application; Figure 5 A cross-sectional photograph of a laser diode according to Embodiment 2 of this application; Figure 6 This refers to the component test data of a laser diode according to Embodiment 3 of this application; Figure 7 This is a diagram showing the improvement in light efficiency according to Embodiment 3 of this application.

[0021] Illustration: 100, Substrate; 210, First semiconductor layer; 220, Second semiconductor layer; 300, Active layer; 310, Well layer; 320, Barrier layer; 410, First waveguide layer; 420, Second waveguide layer; 500, Electron blocking layer; 510, P-type doped layer; 520, High-alumina blocking layer. Detailed Implementation

[0022] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or operated through other different specific embodiments, and various details in this application can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application.

[0023] The composition of each layer contained in this application can be analyzed by any suitable method, such as secondary ion mass spectrometry (SIMS); the thickness of each layer can be analyzed by any suitable method, such as transmission electron microscopy (TEM) or scanning electron microscopy (SEM), in conjunction with, for example, the depth position of each layer on a SIMS spectrum.

[0024] See Figure 1In a first embodiment of the present invention, a gallium nitride-based laser diode is provided, comprising a substrate 100, the substrate 100 being made of materials including but not limited to gallium nitride. An N-type first semiconductor layer 210, a P-type second semiconductor layer 220, and an active layer 300 located between the two are fabricated on the substrate 100. The fabrication method may include chemical vapor deposition. The active layer 300 is composed of a complex number of periodically stacked well layers 310 and barrier layers 320. As an example, the well layer 310 comprises indium gallium nitride, the barrier layer 320 comprises gallium nitride, a first waveguide layer 410 is included between the first semiconductor layer 210 and the active layer 300, and a second waveguide layer 420 is included between the second semiconductor layer 220 and the active layer 300. In this invention, the primary focus is on excitation wavelengths in the 430nm to 550nm band.

[0025] An electron blocking layer 500 is disposed between the second waveguide layer 420 and the second semiconductor layer 220. The electron blocking layer 500 includes aluminum gallium nitride. The electron blocking layer 500 restricts the movement of electrons from the active layer 300 to the second semiconductor layer 220, thereby increasing the electron concentration in the active layer 300 to trap electrons in the active layer 300 and improve recombination efficiency. The aluminum concentration in the electron blocking layer 500 is variable, and the concentrated distribution of P-type doping is controlled by the variable aluminum concentration.

[0026] Specifically, the first waveguide layer 410 includes Al x1 In y1 Ga 1-x1-y1 The values ​​of N and x1 range from 0 to 0.1, and the values ​​of y1 range from 0 to 0.2. The preferred aluminum concentration in the first waveguide layer 410 is 3 × 10⁻⁶. 16 ~5×10 17 cm -3 The preferred concentration of indium is 2 × 10⁻⁶. 20 ~4×10 20 cm -3 The refractive index of the first waveguide layer 410 is preferably 2.4 to 2.6. Doping the first waveguide layer 410 with a trace amount of aluminum can effectively reduce its lattice constant, thereby matching the first semiconductor layer 210. The second waveguide layer 420 comprises aluminum indium gallium nitride or indium gallium nitride, including Al... x2 In y2 Ga 1-x2-y2 The values ​​of N and x2 range from 0 to 0.1, and the values ​​of y2 range from 0 to 0.2. The preferred aluminum concentration in the second waveguide layer 420 is 3 × 10⁻⁶. 16 ~5×10 17 cm -3 The preferred concentration of indium is 2 × 10⁻⁶. 20 ~4×10 20 cm -3The first waveguide layer 410 and the second waveguide layer 420 serve as photon confinement capabilities.

[0027] See in combination Figure 2 The electron blocking layer 500 includes a p-type doped layer 510 on the side near the second semiconductor layer 220, the composition of the p-type doped layer 510 being greater than 1E19 cm⁻¹. -3 The P-type doped layer 510 can be disposed on the end face of the electron blocking layer 500 or inside the electron blocking layer 500. The P-type doping concentration of the electron blocking layer 500 closer to the second semiconductor layer 220 is higher than that of the electron blocking layer 500 farther from the second semiconductor layer 220. In this invention, both the electron blocking layer 500 and the second semiconductor layer 220 are P-type doped. In this embodiment, the doping concentration of the P-type doped layer 510 is not lower than that of other regions of the second semiconductor layer 220 and the electron blocking layer 500. The distance between the P-type doped layer 510 and the well layer 310 closest to the second semiconductor layer 220 in the active layer 300 is 0.2 μm to 0.3 μm. Compared with conventional designs, increasing the distance of the high-concentration P-type doped region from the well layer 310 increases the product's aging life.

[0028] The p-type doped layer 510 is located at the end of the electron blocking layer 500 near the second semiconductor layer 220. In this embodiment, the dopant in the p-type doped layer 510 is Mg doped. The thickness of the p-type doped layer in the electron blocking layer 500 is 0.001 μm to 0.01 μm. The total thickness of the electron blocking layer 500 is 0.003 μm to 0.05 μm.

[0029] In this embodiment, through process control, the surface P-type doping concentration of the electron blocking layer 500 near the second waveguide layer 420 is set to be no greater than 1E19 cm⁻¹. -3 Meanwhile, the p-type doping concentration of the second waveguide layer 420 is no greater than 1E19 cm⁻¹. -3 This avoids exacerbating the light absorption problem and reducing the photoelectric conversion efficiency due to the high P-type doping concentration in the second waveguide layer 420.

[0030] See Figure 3In a second embodiment of the present invention, a laser diode is provided. The difference from the first embodiment is that the epitaxial stack further includes a high-alumina barrier layer 520. In this embodiment, the high-alumina barrier layer 520 is non-P-type doped and is disposed between the second waveguide layer 420 and the electron blocking layer 500. The aluminum composition of the high-alumina barrier layer 520 is more than twice that of the electron blocking layer 500. Alternatively, it can be disposed on the side of the electron blocking layer 500 closer to the second waveguide layer 420, with the aluminum composition of the high-alumina barrier layer 520 being more than twice that of other areas of the electron blocking layer 500. The high-alumina barrier layer 520 is configured to control the aluminum composition distribution within the electron blocking layer 500. This includes not only overlapping states where the layers are in contact with each other but also overlapping states with another layer inserted between them. Preferably, since the high-alumina barrier layer 520 is closer to the second waveguide layer 420 than other areas of the electron blocking layer 500, the high-alumina barrier layer 520 is intentionally P-type doped. The aluminum composition distribution of the high-aluminum barrier layer is not continuous, but is achieved by significantly increasing the aluminum composition in a small range. Therefore, it is difficult to distinguish the aluminum composition from that of the electron blocking layer 500 on the SIMS, but a bright layer can appear on the TEM.

[0031] The high-alumina barrier layer 520 of this invention comprises In. y Al x Ga (1-x-y) N, where x is 0.5 to 1 and y is 0 to 0.2, the thickness of the high-aluminum barrier layer 520 is no more than 0.003 μm, and the aluminum composition distribution is strictly controlled, which is beneficial to improving the efficiency of the second semiconductor 220 on the P side injecting holes into the active layer 300.

[0032] See Figure 4 By setting a high-aluminum barrier layer 520, a first P-type doping concentration peak (Mg doping peak 1) is further formed in the electron barrier layer 500. The electron barrier layer 500 has an aluminum concentration peak. The peak value of the first P-type doping concentration peak is located on the side of the electron barrier layer 500 near the aluminum concentration peak of the second semiconductor layer 220. The peak doping concentration of the first P-type doping concentration peak is not lower than the P-type doping concentration in other regions of the electron barrier layer 500.

[0033] See Figure 5 Transmission electron microscopy reveals a portion of the semiconductor layer sequence, primarily consisting of a second waveguide layer 420, a high-alumina barrier layer 520, an electron blocking layer 500, and a second semiconductor layer 220, from bottom to top. The high-alumina barrier layer 520 exhibits higher brightness than other parts of the electron blocking layer 520, and is located on the side of the electron blocking layer 500 closest to the second waveguide layer 420. In some embodiments, the electron blocking layer 500 has a thickness of 94 angstroms, and the high-alumina barrier layer 520 is brighter than other parts of the electron blocking layer 500.

[0034] See Figure 6 In a third embodiment of the present invention, a second P-type doping concentration peak is provided in the electron blocking layer 500, which is located between the first P-type doping concentration peak and the second waveguide layer 420. The electron blocking layer 500 has a second P-type doping concentration peak (Mg doping peak 2), and the peak value of the second P-type doping concentration peak is located on the side of the peak value of the aluminum peak in the electron blocking layer 500 that is closer to the second waveguide layer 420.

[0035] The distance between the peak of the first P-type doping concentration peak and the second waveguide layer 420 is not less than 0.005 μm, and the distance between the peak of the first P-type doping concentration peak and the surface of the electron blocking layer 500 near the second semiconductor layer 220 is 0 μm to 0.01 μm.

[0036] The peak value of the first P-type doping concentration peak is higher than the peak value of the second P-type doping concentration peak, and the peak concentration of the second P-type doping concentration peak is not less than 1E19 cm⁻¹. -3 The peak position of the second P-type doping concentration is controlled by adjusting the concentration of the first P-type doping layer and the high-aluminum barrier layer during the manufacturing process.

[0037] In some embodiments of this example, a trough 530 of P-type doping concentration is set in the electron blocking layer 500. The P-type doping concentration in the trough is less than 70% of the highest P-type doping concentration in the electron blocking layer 500. The P-type doping concentration in the trough is less than 7E18, and the actual doping concentration can be less than 5E18. The trough is used to limit the diffusion of P-type doping. However, since the P-type doping concentration diffuses, only a clear trough region can be observed in SIMS detection.

[0038] See Figure 7 In this embodiment, the implementation of the solution can significantly reduce the absorption of P-type doping in the second waveguide layer 420, further improve the slope after lasing, and improve the brightness. For example, at a current of 1.5 amperes, the brightness of the product is improved by 20%.

[0039] In a fourth embodiment of this aspect, a display device is provided, including a display light source, wherein the display light source is any of the semiconductor lasers described in the above embodiments.

[0040] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application.

Claims

1. A semiconductor laser, comprising an N-type first semiconductor layer, a P-type second semiconductor layer, and an active layer located between the two for emitting light, the active layer being formed by periodically stacking a plurality of well layers and barrier layers; a first waveguide layer is included between the first semiconductor layer and the active layer, and a second waveguide layer is included between the second semiconductor layer and the active layer; An electron blocking layer is disposed between the second waveguide layer and the second semiconductor layer. The electron blocking layer includes aluminum gallium nitride and / or aluminum indium gallium nitride. Its features are, The electron blocking layer includes a high-alumina blocking layer and a p-type doped layer. The aluminum content of the high-alumina blocking layer is relatively higher than that of other regions of the electron blocking layer. The p-type doped layer is located on the side of the electron blocking layer closest to the second semiconductor layer, and the doping concentration of the p-type doped layer is no lower than that of other regions of the electron blocking layer. The P-type doping concentration on the side of the electron blocking layer closer to the second semiconductor layer is higher than the P-type doping concentration on the side of the electron blocking layer farther from the second semiconductor layer.

2. A semiconductor laser according to claim 1, characterized in that, The doping composition of the P-type doped layer is Mg doping, and the composition of the P-type doped layer is greater than 1E19 cm⁻¹. -3 .

3. A semiconductor laser according to claim 1, characterized in that, The high-aluminum barrier layer consists of In y Al x Ga (1-x-y) N, where x is between 0.5 and 1, and y is between 0 and 0.

2.

4. A semiconductor laser according to claim 1, characterized in that, The thickness of the P-type doped layer in the electron blocking layer is 0.001 μm to 0.01 μm.

5. A semiconductor laser according to claim 1, characterized in that, The electron blocking layer has a first P-type doping concentration peak and an aluminum concentration peak. The peak value of the first P-type doping concentration peak is located on the side of the electron blocking layer where the peak value of the aluminum concentration peak is close to the second semiconductor layer. The peak doping concentration of the first P-type doping concentration peak is not lower than the P-type doping concentration in other regions of the electron blocking layer.

6. A semiconductor laser according to claim 5, characterized in that, The electron blocking layer has a second P-type doping concentration peak, the peak value of which is located between the first P-type doping concentration peak and the second waveguide layer, and the distance between the second P-type doping concentration peak and the aluminum concentration peak is less than 50 angstroms.

7. A semiconductor laser according to claim 5, characterized in that, The electron blocking layer has a second P-type doping concentration peak. The peak value of the second P-type doping concentration peak is located on the side of the peak value of the aluminum concentration peak in the electron blocking layer that is closer to the second waveguide layer. The peak value of the first P-type doping concentration peak is higher than the peak value of the second P-type doping concentration peak. The peak concentration of the second P-type doping concentration peak is not less than 1E19 cm⁻¹. -3 .

8. A semiconductor laser according to claim 5, characterized in that, The distance between the peak of the first P-type doping concentration peak and the second waveguide layer is not less than 0.005 μm, and the distance between the peak of the first P-type doping concentration peak and the surface of the electron blocking layer near the second semiconductor layer is 0 μm to 0.01 μm.

9. A semiconductor laser according to claim 1, characterized in that, The surface p-type doping concentration of the electron blocking layer near the second waveguide layer is not less than 1E19 cm⁻¹. -3 .

10. A semiconductor laser according to claim 1, characterized in that, The second waveguide layer comprises aluminum indium gallium nitride or indium gallium nitride.

11. A semiconductor laser according to claim 1, characterized in that, The total thickness of the electron blocking layer is 0.003 μm to 0.05 μm.

12. A semiconductor laser according to claim 1, characterized in that, The laser is gallium nitride based and emits light at wavelengths ranging from 430 nm to 550 nm.

13. A semiconductor laser according to claim 1, characterized in that, The high-aluminum barrier layer is unintentionally P-type doped, and the thickness of the high-aluminum barrier layer 520 is no greater than 0.003 μm.

14. A semiconductor laser according to claim 1, characterized in that, The electron blocking layer has a trough in P-type doping concentration, which is below 70% of the highest P-type doping concentration in the electron blocking layer, and the trough P-type doping concentration is 7E18cm. -3 the following.

15. A semiconductor laser according to claim 1, characterized in that, The electron blocking layer exhibits a trough in p-type doping concentration, with the trough below 70% of the highest p-type doping concentration in the electron blocking layer, and a doping concentration of 5E18cm. -3 the following.

16. A semiconductor laser according to claim 1, characterized in that, The doping concentration of the P-type doped layer is not lower than that of the second semiconductor layer, and the P-type doping concentration of the second waveguide layer is not greater than 1E19 cm⁻¹. -3 .

17. A semiconductor laser according to claim 1, characterized in that, The P-type doped layer is located at the end of the electron blocking layer near the second semiconductor layer, and the distance between the P-type doped layer and the well layer closest to the second semiconductor layer in the active layer is 0.2 μm to 0.3 μm.

18. A display device, characterized in that, Includes a display light source, wherein the display light source is a semiconductor laser as described in any one of claims 1 to 17.

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