Vertical cavity surface emitting laser with grating structure

Abstract

The invention provides a vertical cavity surface emitting type laser with a grating structure. The vertical cavity surface emitting type laser comprises a circuit substrate, a light emitting composite layer and the grating structure. The light-emitting composite layer is located on the circuit substrate and comprises a first Bragg reflector, a light-emitting layer and a second Bragg reflector. The grating structure is located on the first Bragg reflector. The grating structure comprises a contact layer and a protection layer. The contact layer comprises a body and a plurality of convex parts, the convex parts are located on the body, and a groove is formed between every two adjacent convex parts. The protective layer is located on the contact layer, covers each convex part and each groove, and is provided with an undulating surface corresponding to the structure of each convex part and each groove.

Description

Technical Field

[0001] This application relates to a vertical cavity surface-emitting laser, and more particularly to a vertical cavity surface-emitting laser with a grating structure. Background Technology

[0002] Semiconductor lasers have advantages such as small size, light weight, low cost, and high energy conversion efficiency, and are therefore widely used in electronic products.

[0003] In existing semiconductor laser technologies, vertical-cavity surface-emitting lasers (VCSELs) have been developed and applied in various fields, including fiber optic communication systems, consumer electronics scanning systems (such as iris recognition for smartphones and tablets), 3D printing, biometric sensing, and laser projection displays. It is evident that the future demand for VCSELs will be considerable.

[0004] Therefore, how to provide a structurally robust and high-performance vertical cavity surface-emitting laser has become one of the important issues that this field seeks to address. Summary of the Invention

[0005] The technical problem to be solved by this application is to provide a vertical cavity surface-emitting laser with a grating structure, which includes: a circuit board, a light-emitting composite layer, a contact layer and a protective layer.

[0006] A light-emitting composite layer is located on the circuit board. The light-emitting composite layer includes a first Bragg reflector, a light-emitting layer, and a second Bragg reflector, with the first and second Bragg reflectors located on opposite sides of the light-emitting layer. A contact layer is located on the first Bragg reflector and has a grating structure. The grating structure includes a body and multiple protrusions located on the body, with a groove formed between adjacent protrusions. An electrode layer is located on the contact layer and has light-emitting holes, with at least a portion of the grating structure exposed through the light-emitting holes. A protective layer covers the electrode layer and the grating structure. The protective layer corresponds to the shape of each protrusion and each groove, and has a surface with varying elevations.

[0007] According to one feasible embodiment, the protective layer is an aluminum oxide layer, a silicon dioxide layer, a silicon nitride layer, or a magnesium fluoride layer.

[0008] According to one feasible embodiment, the distance between the centers of two adjacent protrusions is less than the wavelength of the light emitted by the light-emitting composite layer.

[0009] According to a feasible embodiment, the groove has a depth of 10 nm or more in the vertical direction and is less than or equal to twice the wavelength of the light-emitting composite layer.

[0010] According to one feasible embodiment, the thickness of the contact layer in the vertical direction is 10 nm to 10 μm.

[0011] According to a feasible embodiment, the protective layer has a thickness of 1 nm or more in the vertical direction and is less than or equal to 0.4 times the distance between two adjacent protrusions.

[0012] According to one feasible embodiment, in the horizontal direction, the ratio of the width of the groove to the distance between the centers of two adjacent protrusions is 0.1-0.9.

[0013] According to a feasible embodiment, viewed from above, a plurality of protrusions and a plurality of recesses extend along a first direction, and the light-emitting aperture defines a centerline passing through the center point of the light-emitting aperture. The centerline is parallel to a second direction, which is orthogonal to the first direction. The centerline divides the grating structure exposed in the light-emitting aperture into a first part and a second part. The first part and the second part are not symmetrical about the centerline.

[0014] According to a feasible embodiment, the ratio of the projected areas of the first part and the second part projected along a light-emitting direction is greater than or equal to 10%.

[0015] According to one feasible embodiment, the first Bragg reflector is a P-type Bragg reflector or an N-type Bragg reflector.

[0016] One of the beneficial effects of this application is that the vertical-cavity surface-emitting laser with a grating structure provided by this application can maximize the difference in refractive index between the grating structure and the external environment through the technical solutions of "the contact layer has a grating structure, the grating structure includes a body and a plurality of protrusions, the plurality of protrusions are located on the body, and a groove is formed between two adjacent protrusions", "the electrode layer is located on the contact layer, the electrode layer has an emission aperture, at least a part of the grating structure is exposed in the emission aperture", and "the protective layer covers the electrode layer and the grating structure, the protective layer corresponds to the shape of each protrusion and each groove, and the protective layer has a surface with high and low undulations". This greatly improves the density of states (DOS) of the vertical-cavity surface-emitting laser with a grating structure during operation, and enhances and stabilizes the polarization effect of the internal components of the vertical-cavity surface-emitting laser with a grating structure.

[0017] Furthermore, by employing a technical solution that involves "multiple protrusions and multiple recesses extending along a first direction, a center line defined passing through the center point of the light-emitting aperture, the center line being parallel to a second direction, and the second direction being orthogonal to the first direction. The center line divides the grating structure exposed in the light-emitting aperture into a first part and a second part, the first part and the second part not being symmetrical about the center line," a better polarization extinction ratio is achieved compared to a structure where the first part and the second part are symmetrical about the center line.

[0018] The other effects and embodiments of this application are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the external appearance of a vertical cavity surface-emitting laser with a grating structure according to an embodiment of this application;

[0021] Figure 2 for Figure 1 Side view of the embodiment shown;

[0022] Figure 3 An image of a vertical cavity surface-emitting laser with a grating structure according to an embodiment of this application, viewed under an electron microscope.

[0023] Figure 4 for Figure 3 Cross-sectional view of the embodiment shown;

[0024] Figure 5 This is a top view of a vertical cavity surface-emitting laser with a grating structure according to an embodiment of this application. Detailed Implementation

[0025] The following specific embodiments illustrate the implementation of the "vertical cavity surface-emitting laser with grating structure" disclosed in this application. Those skilled in the art can understand the advantages and effects of this application from the content disclosed in this specification. This application can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this application. Furthermore, the accompanying drawings are for simple illustration only and are not depictions of actual dimensions, as stated in advance. The following embodiments will further describe the relevant technical content of this application in detail, but the disclosed content is not intended to limit the scope of protection of this application.

[0026] Please see Figures 1 to 4 , Figure 1 This is a schematic diagram of the appearance of a vertical cavity surface-emitting laser with a grating structure according to an embodiment of this application. Figure 2 for Figure 1 Side view of the embodiment shown. Figure 3 This is an image of a vertical cavity surface-emitting laser with a grating structure according to an embodiment of this application under an electron microscope. Figure 4 for Figure 3 Cross-sectional view of the embodiment shown.

[0027] A vertical-cavity surface-emitting laser Z with a grating structure includes a circuit board 1, a light-emitting composite layer 2, a contact layer 3, an electrode layer 4, and a protective layer 5. Figure 1 and Figure 2 In this embodiment, electrode layer 4 is omitted. The light-emitting composite layer 2 is located on the circuit substrate 1. The light-emitting composite layer 2 includes a first Bragg reflector 21, a light-emitting layer 22, and a second Bragg reflector 23, with the first Bragg reflector 21 and the second Bragg reflector 23 located on opposite sides of the light-emitting layer 22. A grating structure 3 is located on the first Bragg reflector 21. The contact layer 3 has a grating structure 31, which includes a body 311 and multiple protrusions 312. The multiple protrusions 312 are located on the body 311, and a groove 313 is formed between two adjacent protrusions 312. Figure 3 As shown, electrode layer 4 is located on contact layer 3, and electrode layer 4 has light-emitting aperture 41. At least a portion of grating structure 31 is exposed through light-emitting aperture 41 (or see...). Figure 5 Another electrode layer is disposed at the bottom of the circuit board 1. The electrode layer is made of a conductive material, such as a metal material, which is not limited in this application. The protective layer 5 covers the electrode layer 4 and the grating structure 31. Corresponding to the structure of each protrusion 312 and each groove 313, the surface of the protective layer 5 presents a textured surface with high and low undulations.

[0028] The light-emitting layer 22 includes an active region and an oxide layer (current-limiting layer, not shown in the figure), the oxide layer having a limiting aperture. In some embodiments, the first Bragg reflector 21 is a P-type Bragg reflector or an N-type Bragg reflector. The second Bragg reflector 23 is the corresponding Bragg reflector. For example, the first Bragg reflector 21 is a P-type Bragg reflector, and the second Bragg reflector 23 is an N-type Bragg reflector. The first Bragg reflector 21 is an N-type Bragg reflector, and the second Bragg reflector 23 is a P-type Bragg reflector.

[0029] The grating structure 31 of the contact layer 3 can be patterned using nanoimprint lithography or deep ultraviolet (DUV) imaging. Protrusions 312 and grooves 313 (grating structure 31) are then fabricated in the contact layer 3 via etching (e.g., ICP dry etching). The protective layer 5 is then completed using vapor deposition (e.g., atomic layer deposition, ALD). The semiconductor can be epitaxially formed and can be doped or undoped. In some embodiments, the contact layer 3 is gallium arsenide. In some embodiments, the protective layer 5 is an oxide layer, such as, but not limited to, an aluminum oxide layer. According to some embodiments, the protective layer can also be a silicon dioxide layer (SiO2), a silicon nitride layer (SiNx), or a magnesium fluoride layer (MgF2). By designing the shape (corresponding to the protrusion 312 and the concave portion, having a surface with varying heights) and thickness of the protective layer 5, the refractive index difference between the contact layer 3 and the external environment (e.g., air) is maximized, thereby significantly increasing the density of states (DOS) of the grating-structured vertical cavity surface-emitting laser during operation, enhancing and stabilizing the polarization effect of the internal components of the grating-structured vertical cavity surface-emitting laser.

[0030] In some embodiments, the distance W1 between the centers of two adjacent protrusions 312 (see...) Figure 2 The depth H of the groove 313 in the vertical direction D3 is 10 nm or more, and is less than or equal to twice the wavelength of the light-emitting composite layer 2. In some embodiments, the thickness T1 of the contact layer 3 in the vertical direction D3 is 10 nm to 10 μm. In other embodiments, the thickness T2 of the protective layer 5 in the vertical direction D3 is 1 nm or more, and is less than or equal to 0.4 times the distance W1 between two adjacent protrusions 312. Furthermore, in some embodiments, the ratio of the width W2 of the groove 313 to the distance W1 between the centers of two adjacent protrusions in the horizontal direction D4 is 0.1-0.9. At least one of the above structural conditions can enhance the aforementioned technical effects. This application does not limit the aforementioned structural and emission wavelength conditions to be met in order to achieve the aforementioned effect of maximizing the difference in refractive index between the contact layer 3 and the external environment, improving the energy state density of the vertical cavity surface-emitting laser with grating structure during operation, and enhancing and stabilizing the component polarization of the vertical cavity surface-emitting laser with grating structure.

[0031] Please see Figure 5 This is a top view of a vertical-cavity surface-emitting laser with a grating structure according to an embodiment of this application. Figure 5As shown, viewed from above, multiple protrusions 312 and multiple recesses extend along the first direction D1. A center line L is defined passing through the center point C of the light-emitting aperture 41. The center line L is parallel to the second direction D2, which is orthogonal to the first direction D1. The center line L divides the grating structure 31 exposed in the light-emitting aperture 41 into a first part a1 and a second part a2. The first part a1 and the second part a2 are not symmetrical about the center line L. Based on this structure, compared to a structure where the first part a1 and the second part a2 are symmetrical about the center line L, Figure 5 The embodiments shown have a good polarization extinction ratio (PER), and in some embodiments, the polarization extinction ratio is about 3 to 4.

[0032] Furthermore, according to some embodiments, the aforementioned structure where the first portion a1 and the second portion a2 are not symmetrical about the center line L indicates that the projected areas of the first portion a1 and the second portion a2 along the light-emitting direction (such as the vertical direction D3) are different. In some embodiments, the ratio of the projected areas is greater than or equal to 10%.

[0033] "Beneficial effects of the embodiments"

[0034] The vertical-cavity surface-emitting laser with a grating structure provided in this application can maximize the difference in refractive index between the grating structure and the external environment through the following technical solutions: "the contact layer has a grating structure, the grating structure includes a body and multiple protrusions, the multiple protrusions are located on the body, and a groove is formed between two adjacent protrusions", "the electrode layer is located on the contact layer, the electrode layer has an emission aperture, and at least one part of the grating structure is exposed in the emission aperture", and "the protective layer covers the electrode layer and the grating structure, the protective layer corresponds to the shape of each protrusion and each groove, and the protective layer has a surface with high and low undulations". This will greatly improve the energy density of states of the vertical-cavity surface-emitting laser with a grating structure during operation and enhance and stabilize the polarization effect of the internal components of the vertical-cavity surface-emitting laser with a grating structure.

[0035] Furthermore, by employing a technical solution that involves "multiple protrusions and multiple recesses extending along a first direction, a center line defined passing through the center point of the light-emitting aperture, the center line being parallel to a second direction, and the second direction being orthogonal to the first direction. The center line divides the grating structure exposed in the light-emitting aperture into a first part and a second part, the first part and the second part not being symmetrical about the center line," a better polarization extinction ratio is achieved compared to a structure where the first part and the second part are symmetrical about the center line.

[0036] The embodiments and / or implementation methods described above are merely preferred embodiments and / or implementation methods for implementing the technology of this application, and are not intended to limit the implementation methods of the technology of this application in any way. Any person skilled in the art may make some modifications or alterations to other equivalent embodiments without departing from the scope of the technical means disclosed in this application, but these should still be regarded as the technology or embodiments that are substantially the same as those of this application.

Claims

1. A vertical-cavity surface-emitting laser with a grating structure, characterized in that, The vertical-cavity surface-emitting laser with a grating structure includes: A circuit board; A light-emitting composite layer is located on the circuit board. The light-emitting composite layer includes a first Bragg reflector, a light-emitting layer and a second Bragg reflector. The first Bragg reflector and the second Bragg reflector are respectively located on both sides of the light-emitting layer. A contact layer is located on the first Bragg reflector. The contact layer has a grating structure, which includes a body and a plurality of protrusions. The plurality of protrusions are located on the body, and a groove is formed between two adjacent protrusions. An electrode layer is located on the contact layer, the electrode layer having a light-emitting aperture, at least a portion of the grating structure being exposed through the light-emitting aperture; and A protective layer covers the electrode layer and the grating structure, the protective layer corresponding to the shape of each of the protrusions and each of the grooves, the protective layer having a surface with undulations.

2. The vertical-cavity surface-emitting laser with a grating structure according to claim 1, characterized in that, The protective layer is an aluminum oxide layer, a silicon dioxide layer, a silicon nitride layer, or a magnesium fluoride layer.

3. The vertical-cavity surface-emitting laser with a grating structure according to claim 1, characterized in that, The distance between the centers of two adjacent protrusions is less than the wavelength of light emitted by the light-emitting composite layer.

4. The vertical-cavity surface-emitting laser with a grating structure according to claim 1, characterized in that, The groove has a depth of more than 10 nm in a vertical direction and is less than or equal to twice the wavelength of the light-emitting composite layer.

5. The vertical-cavity surface-emitting laser with a grating structure according to claim 1, characterized in that, The thickness of the contact layer in a vertical direction is 10 nm to 10 μm.

6. The vertical-cavity surface-emitting laser with a grating structure according to claim 1, characterized in that, The protective layer has a thickness of 1 nm or more in a vertical direction and is less than or equal to 0.4 times the distance between two adjacent protrusions.

7. The vertical-cavity surface-emitting laser with a grating structure according to claim 1, characterized in that, In a horizontal direction, the ratio of the width of the groove to the distance between the centers of two adjacent protrusions is 0.1-0.

9.

8. The vertical-cavity surface-emitting laser with a grating structure according to claim 1, characterized in that, Viewed from above, the plurality of protrusions and the plurality of recesses extend along a first direction. The light-emitting aperture defines a center line passing through the center point of the light-emitting aperture. The center line is parallel to a second direction, which is orthogonal to the first direction. The center line divides the grating structure exposed in the light-emitting aperture into a first part and a second part. The first part and the second part are not symmetrical about the center line.

9. The vertical-cavity surface-emitting laser with a grating structure according to claim 8, characterized in that, The ratio of the projected area of ​​the first part to that of the second part along a light-emitting direction is greater than or equal to 10%.

10. The vertical-cavity surface-emitting laser with a grating structure according to claim 1, characterized in that, The first Bragg reflector is either a P-type Bragg reflector or an N-type Bragg reflector.

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