CN112117638A - Vertical resonant cavity surface emitting laser structure - Google Patents
Vertical resonant cavity surface emitting laser structure Download PDFInfo
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- CN112117638A CN112117638A CN201910544607.9A CN201910544607A CN112117638A CN 112117638 A CN112117638 A CN 112117638A CN 201910544607 A CN201910544607 A CN 201910544607A CN 112117638 A CN112117638 A CN 112117638A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
- H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
- H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
- H01S5/18344—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] characterized by the mesa, e.g. dimensions or shape of the mesa
- H01S5/18352—Mesa with inclined sidewall
Abstract
A Vertical Cavity Surface Emitting Laser (VCSEL) structure is provided, wherein an ion implantation region of a gas furnace-shaped structure is arranged in a second mirror layer around an optical window, so that a plurality of conductive channels are reserved between the inner edge and the outer edge of the ion implantation region, and the aperture (namely the aperture of the optical window) at the inner edge of a metal layer is enlarged without loss of resistance. Not only can the shading effect be removed and the function of frequency spectrum width suppression be retained, but also various photoelectric characteristics such as transmission eye pattern and photoelectric curve linearity are improved, and the high-speed transmission characteristic is better optimized.
Description
Technical Field
The present invention relates to a vertical cavity surface emitting laser structure, and more particularly, to a vertical cavity surface emitting laser structure which controls mode, limits current and improves eye pattern by disposing an ion implantation region of a gas furnace structure around an optical window.
Background
Vertical Cavity Surface Emitting Laser (VCSEL) is one of the light Emitting Laser diodes, and is mainly applied to the area network due to its low power and price, and has the advantages of high speed and low price. The VCSEL light emitting and detecting material is generally gallium arsenide (GaAs) or indium phosphide (InP), and is usually fabricated into an epitaxial wafer by Metal Organic Chemical Vapor Deposition (MOCVD). In contrast to the conventional side-emitting laser, the mirror surface required for the resonant cavity and the photons to resonate back and forth in the resonant cavity is not a natural lattice fracture surface formed by the process, but is formed during the epitaxial growth of the device structure.
A general VCSEL structure generally includes a light emitting active layer, a resonant cavity, and a Bragg Reflector (DBR) with high reflectivity on top and bottom. When photons are generated in the light emitting active layer, they are convenient to oscillate back and forth in the resonant cavity, and if they reach population inversion (population inversion), laser light is formed on the surface of the VCSEL device. The VCSEL adopts a surface emitting type, laser light is conical, and can be easily coupled with the optical fiber without an additional optical lens. For the basic structure, manufacturing method and operation method of the conventional VCSEL, reference may be made to the contents of US 4,949,350 and US 5,468,656.
The present invention is to improve the structure and manufacturing method of the above-mentioned prior VCSEL, and to control the mode, limit the current and improve the eye diagram by setting the original gas furnace frame-shaped ion implantation region around the optical window, so that the light shape is more stable and the drop point is reduced, the linearity of the photoelectric curve is improved, and the same or even lower resistance value can be maintained.
Disclosure of Invention
Accordingly, the primary objective of the present invention is to provide a vertical cavity surface emitting laser structure, which can control the mode, limit the current and improve the eye pattern by disposing an ion implantation region of an original gas furnace structure around the light window, so that the light shape is more stable, the drop point is reduced, the linearity of the photoelectric curve is improved, and the same or even lower resistance value can be maintained.
To achieve the above object, the present invention provides a vertical cavity surface emitting laser structure, which comprises: a substrate, a first mirror layer on the substrate, an active layer on the first mirror layer, a second mirror layer on the active layer and having an upper surface, an oxide layer sandwiched in the second mirror layer and having a central through hole, a boss region, a trench, a metal layer and an ion implantation region;
the bump region is located on the substrate and is composed of at least a portion of the first mirror layer, the active layer, the second mirror layer and the oxide layer; a light window is arranged in the center of the top surface of the boss area, and the light window corresponds to the central through hole;
the groove surrounds at least one part of the outer periphery of the boss area; the groove at least penetrates through the second mirror layer, the oxide layer and the active layer from top to bottom of the top surface of the boss region and extends into the first mirror layer; and, fill a dielectric material in the ditch groove;
the metal layer is positioned on the top surface of the boss area, surrounds the outer periphery of the optical window and has at least one inner edge part contacting the upper surface of the second mirror layer; the diameter of the light window is defined by the inner diameter of the inner edge part of the metal layer;
the ion implantation region is at least positioned in the boss region; the ion implantation region is an insulation region formed by implanting a plurality of non-conductive particles into the second mirror layer; the ion implantation region extends from the upper surface of the second mirror layer downward into the second mirror layer to a predetermined depth, and the ion implantation layer in the mesa region is located between the light window and the trench and surrounds at least a portion of the outer periphery of the light window; the ion implantation region has a circular arc inner edge, a circular arc outer edge, and at least one conductive channel extending outward from the circular arc inner edge toward the circular arc outer edge by a predetermined length from a top view, such that an outer end of the conductive channel at least exceeds the outer side of the inner edge of the metal layer; the non-conductive particles are not injected into the conductive channel, so that the metal layer above the conductive channel is directly contacted with the upper surface of the second mirror layer; the diameter of the arc-shaped inner edge of the ion implantation area is smaller than the inner diameter of the inner edge part of the metal layer, namely, the diameter of the arc-shaped inner edge is smaller than the diameter of the optical window.
In one embodiment, the non-conductive particles are protons (Proton) or oxygen ions.
In one embodiment, the diameter of the arc-shaped inner edge of the ion implantation region is smaller than that of the central through hole of the oxide layer; the inner diameter of the optical window is larger than the diameter of the central through hole of the oxide layer.
In one embodiment, the ion implantation region has a plurality of conductive channels, and each of the conductive channels penetrates between the arc-shaped inner edge and the arc-shaped outer edge; from a top view, the plurality of conductive channels cut the ion implantation region into a plurality of separate fan-shaped regions resembling a gas hob structure.
In one embodiment:
the vertical resonant cavity surface emitting laser structure further comprises an insulating layer and a light emitting layer; the insulating layer covers at least a part of the outer surface of the boss area, and the metal layer is exposed out of the insulating layer; the light-emitting layer is located on the light window on the top surface of the boss area;
the first mirror layer is an n-type Distributed Bragg Reflector (DBR), and the second mirror layer is a p-type DBR;
the first mirror layer and the second mirror layer are made of materials containing aluminum gallium arsenide (AlGaAs) with different aluminum mole percentages, and the oxide layer has the aluminum with the highest relative mole percentage in the second mirror layer;
the oxide layer extends horizontally from the inner periphery of the trench toward the center of the boss region to the outer edge of the central through hole; and
the dielectric material is a polymer material with low dielectric properties.
In one embodiment: the diameter of the central through hole of the oxide layer is between 5 μm and 15 μm; the inner diameter of the inner edge portion of the metal layer is between 8 μm and 20 μm; the predetermined depth of the ion implantation region is between 1 μm and 4 μm; the diameter of the circular arc inner edge of the ion implantation area is between 4 μm and 14 μm; the diameter of the arc-shaped outer edge of the ion implantation area is between 20 and 40 mu m; the width of the conductive channel of the ion implantation region is between 1 μm and 5 μm.
Drawings
For a better understanding of the nature and technical aspects of the present invention, reference should be made to the following detailed description of the invention, which is to be read in connection with the accompanying drawings and which are provided for purposes of illustration and description only and are not intended to be limiting.
FIG. 1 is a schematic cross-sectional view of one embodiment of a VCSEL structure of applicants' prior invention;
FIG. 2A is a schematic top view showing the relative positions of the inner edge of the metal layer, the inner edge of the ion implantation region, the outer edge of the ion implantation region, and the periphery of the central through hole of the oxide layer in the VCSEL structure embodiment shown in FIG. 1;
FIG. 2B is a cross-sectional view A-A as shown in FIG. 2A, schematically illustrating a cross-sectional structure of the mesa region in the VCSEL structure embodiment shown in FIG. 1;
FIG. 3A is a schematic top view showing the relative positions of the inner edge of the metal layer, the inner edge of the ion implantation region, the outer edge of the ion implantation region, and the periphery of the central through hole of the oxide layer in an embodiment of the VCSEL structure of the present invention;
FIG. 3B is a cross-sectional view B-B as shown in FIG. 3A, schematically illustrating a cross-sectional B-B structure of the mesa region in an embodiment of the VCSEL structure of the present invention;
FIG. 3C is a cross-sectional view, taken along line C-C as shown in FIG. 3A, schematically illustrating the cross-sectional structure of the mesa region in an embodiment of the VCSEL structure of the present invention;
FIGS. 4A, 4B and 4C are schematic diagrams of an Eye Diagram (Eye Diagram), a photo-electric graph of output optical power versus current (L-I) and a spectral characteristic graph of output optical intensity versus wavelength, respectively, measured according to the current VCSEL structure (8 μm optical window aperture) shown in FIGS. 2A and 2B;
FIGS. 5A, 5B and 5C are graphs of the transmission Eye Diagram (Eye Diagram), the output optical power vs. current (L-I) and the output optical intensity vs. wavelength spectrum measured according to the VCSEL structure (optical window aperture 11 μm) of the present invention as shown in FIGS. 3A, 3B and 3C, respectively.
List of reference numerals: 20-substrate; 21. 41, 51 to a first mirror layer; 22. 42, 52-activation layer; 23. 43, 53 to the second mirror layer; 231. 431, 531 to oxide layer; 4311. 5311 the periphery of the central through hole; 24. 44, 54-ion implantation layer (region); 441. 541-inner edge of ion implantation area; 442. 542 to the outer edge of the ion implantation area; 240-upper surface; 25. 45, 55-insulating layer; 26. 46, 56 dielectric material; 27. 47, 57-metal layer; 471. 571 to the inner edge of the metal layer; 270 to the first contact layer; 271 to 273 parts of a second contact layer; 2710 to the top surface; 274. 474, 574 to a light emitting layer; 30-boss area; 300. 400, 500-optical window; 31-a first trench; 32-second groove; 321. 331-bottom; 33 to third trenches.
Detailed Description
The invention relates to a vertical resonant cavity surface emitting laser structure, which is mainly characterized in that an ion implantation area with a gas furnace-shaped structure is arranged in a second mirror layer around an optical window, so that a plurality of conductive channels are reserved between the inner edge and the outer edge of the ion implantation area, the aperture of the inner edge of a metal layer (namely the aperture of the optical window) can be amplified without losing resistance, the functions of shading effect removal and spectrum width inhibition can be reserved, various photoelectric characteristics such as linearity of a transmission eye diagram and a photoelectric curve are improved, and high-speed transmission characteristics are better optimized.
FIG. 1 is a schematic cross-sectional view of an embodiment of a VCSEL structure of the applicant's prior invention.
In this embodiment, the vcsel structure is configured on a laser chip substrate mainly made of Gallium Arsenide (GaAs) or indium phosphide (InP), and the substrate sequentially includes: a substrate 20, a first mirror layer 21 on the substrate 10, an Active Region 22 (QW) on the first mirror layer 21, and a second mirror layer 23 on the Active layer 22. An Oxide Layer 231(Oxide Layer) is sandwiched in the second mirror Layer 23. In the present embodiment, the first mirror layer 21 is an n-type Distributed Bragg Reflector (DBR) layer, which may also be referred to as a lower mirror layer, and the second mirror layer 23 is a p-type DBR layer, which may also be referred to as an upper mirror layer. The materials of the first mirror layer 21 and the second mirror layer 23 include a multi-layer structure of aluminum gallium arsenide (AlGaAs) with different aluminum mole percentages, and the oxide layer 231 has the aluminum with the highest mole percentage in the second mirror layer 23. Thus, during the oxidation process, the oxide layer 231 can form insulating alumina (Al2O3) during the oxidation process.
In addition, the substrate further comprises: a Mesa Region 30(Mesa), a first Trench 31(Isolation Trench), a second Trench 32, a third Trench 33, a Dielectric Material 26(Dielectric Material), a first Contact Layer 270(Contact Layer), second Contact layers 271-273, an ion-implanted Layer 24(Implant Region), an insulating Layer 25 (insulating Layer), and a light-emitting Layer 274(Power Output Layer).
The mesa region 30 is located on the substrate 20 and is formed by at least a portion of the first mirror layer 21, the active layer 22, the second mirror layer 23, and the oxide layer 231. A light window 300 is formed at a center of a top surface of the land region 30. The oxide layer 231 is spaced apart in height from the bottom of the ion implantation layer 24 by a free distance, but may also overlap. The first groove 31 is located in the land area 30 and surrounds at least a portion of the outer periphery of the light window 300. The first trench 31 extends from the top surface of the mesa region 30 through at least the second mirror layer 23, the oxide layer 231, and the active layer 22 from top to bottom, such that the bottom of the first trench 31 is located in the first mirror layer 21. The second groove 32 surrounds at least a portion of the outer periphery of the upper half of the land area 30 and is spaced apart from the first groove 31. The second trench 32 extends at least through the second mirror layer 23 and the oxide layer 231 from top to bottom, such that a bottom 321 of the second trench 32 is located at one of the active layer 22 and the first mirror layer 21. The oxide layer 231 extends horizontally from the inner periphery of the trench 31 toward the center of the land area 30. The third groove 33 surrounds at least a portion of the outer periphery of the lower half of the land area 30 and is recessed downward from the bottom 321 of the second groove 32. Moreover, the third trench 33 penetrates at least the first mirror layer 21 (or the active layer 22 and the first mirror layer 21) from top to bottom, such that a bottom 331 of the third trench 33 is located at the upper surface of the substrate 20.
Preferably, the dielectric material 26 is a polymer material with low dielectric property, and the dielectric material 26 is at least filled in the first trench 31, which can provide the effect of reducing the overall capacitance of the VCSEL structure. In the present embodiment, the dielectric material 26 is a polymer, which can be polyimide, and has a reflection coefficient of 1.5-1.6. By digging the first trench 31 and filling the polymer (dielectric material 26), the area of the semiconductor material with high dielectric constant can be reduced, thereby reducing the capacitance. The first contact layer 270 and the second contact layers 271-273 are part of the metal layer 27. The first contact layer 270 is located on the top surface of the mesa region 30 and contacts an upper surface 240 of the second mirror layer 23. The second contact layers 271, 272, 273 are at least located at the bottom 331 of the third trench 33 and at least contact the substrate 20. The second contact layers 271, 272, 273 extend from the bottom 331 of the third trench 33 along the respective sloped surfaces of the third trench 33 and the second trench 32 up to the upper surface 240 of the second mirror layer 23, such that a top surface 2710 of the second contact layers 271, 272, 273 is located at approximately the same height as the top surface of the first contact layer 270. Therefore, the first contact layer 270 and the second contact layers 271, 272, 273 are not only located on the same surface of the substrate 20, but also located at substantially the same height position, so as to facilitate the subsequent wire bonding process.
The ion implantation layer 24 is located in the second mirror layer 23 and above the active layer 22, and the relative aperture sizes of the oxide layer 231 and the ion implantation 24 can be used to control the optical mode. Wherein the ion implantation belongs to Gain-guided (Gain-guided) and the oxidation belongs to refractive-guided (index-guided) waveguides, and the mixed application of the two can control the optical mode. The ion implantation layer 24 in the mesa region 30 is located between the light window 300 and the first trench 31 and surrounds at least a portion of the outer periphery of the light window 300. The first contact layer 270 is disposed on an upper surface of the ion implantation layer 24. The present invention can be used to control the optical mode and limit the current by the ion implantation region 24 additionally arranged around the optical window 300; in the present embodiment, the ion implantation process may implant non-conductive particles, such as but not limited to: proton (Proton) or oxygen ion with a depth of 2-4 um. In the present embodiment, multiple different energy implantation processes (for example, taking protons as an example, three different energy implantation processes of 100Kev +200Kev +300Kev as examples, and different energy implantation processes if the elements are different) may be added to the same ion implantation process, or a combination of multiple elements (for example, oxygen + boron + hydrogen) may be added, and the amount of the combination may range from 1e14 to 1e15cm-3, taking protons as an example. The insulating layer 25 covers at least a portion of an outer surface of the mesa region 30, and at least a portion of the first contact layer 270 and the second contact layers 271, 272, 273 is exposed outside the insulating layer 25. The light-emitting layer 274 is disposed on the light window 300 on the top surface of the mesa region 30 for controlling light emission, and the principle is to use the refractive index, thickness and optical wavelength of the material of the light-emitting layer 274 to adjust the light emission. In the embodiment, the light emergent layer 274 may be made of Si3N4, SiO2, Si3O4, SiN, SiNO, or the like. In the present embodiment, the light-emitting layer 274 can be made of a dielectric material, and the material composition can be silicon dioxide (SiO2), silicon nitride (SiN), or a mixture of the two materials, and the reflection coefficient is between 1.5 and 2.0.
Although the vcsel structure shown in fig. 1 has the effect of controlling the optical mode and confining the current by disposing the ion implantation layer 24 around the periphery of the optical window 300, the specific design of the ion implantation layer 24 has its disadvantages, which will be described below.
Please refer to fig. 2A and fig. 2B. FIG. 2A is a schematic top view showing the relative positions of the inner edge of the metal layer, the inner edge of the ion implantation region, the outer edge of the ion implantation region, and the periphery of the central through hole of the oxide layer in the VCSEL structure shown in FIG. 1. FIG. 2B is a cross-sectional view A-A as shown in FIG. 2A, schematically illustrating a cross-sectional structure of the mesa region in the VCSEL structure embodiment shown in FIG. 1. In the embodiments of the mesa Region of the vcsel structure shown in fig. 2A and 2B, since the structures, positions, dimensions, and materials of the first mirror layer 41, the active layer 42, the second mirror layer 43, the oxide layer 431, the ion implantation Region 44(Implant Region), the insulating layer 45, the dielectric material 46, the metal layer 47, the light-emitting layer 474, and the optical window 400 are substantially the same as those of the corresponding elements of the embodiment shown in fig. 1, the foregoing description can be directly used, and thus the details will not be repeated.
In the conventional vcsel structure shown in fig. 1, 2A and 2B, the current injection region and the light emitting aperture are defined by oxidation (oxide layer 431) and ion implantation (ion implantation region 44), and the optical mode and the confinement current are controlled by controlling the difference between the central apertures of the oxide layer 431 and the ion implantation region 44, so as to optimize the cut-off between the spectral width and the threshold current. However, since the implanted element in the ion implantation region 44 is a non-conductive element, the inner edge of the connection metal layer 47 must have a smaller aperture than that of the ion implantation region 44 because the other regions are non-conductive except the space of the region located at the inner edge of the ion implantation region 44 where the ion implantation is not performed. Accordingly, the pore sizes of the three are in order: the diameter of the central through hole edge 4311 of the oxide layer 431 is ≧ the diameter of the arc-shaped inner edge 441 of the ion implantation region 44 > the diameter of the inner edge 471 of the metal layer 47, and the diameter of the arc-shaped outer edge 442 of the ion implantation region 44 > the diameter of the central through hole edge 4311 of the oxide layer 431. In this way, the inner edge 471 of the metal layer 47 can directly contact the upper surface of the second mirror layer in the conductive region without ion implantation located at the inner edge of the ion implantation region 44, thereby conducting the current. Since the metal layer 47 is a non-light-transmitting material, the above sequence shows that the design of the device has an essential light-shielding effect, the diameter of the light window 400 is defined by the aperture of the inner edge 471 of the metal layer 47, and the light-shielding effect is also utilized to secondarily suppress the spectrum width. However, such a design can still use high frequency modulation of the electro-optical signal in a narrow process space; however, once the tolerance range is exceeded, the photoelectric curve generates a two-stage slope due to the shading phenomenon, and further high frequency signals are degraded, and no screening is performed from any point measurement parameters, so that the batch eye pattern performance of the product is different, and further improvement space is provided.
In order to overcome the above-mentioned disadvantages of the conventional vcsel structure, the vcsel structure of the present invention reserves a conductive channel by changing the pattern of the ion implantation region, so that the aperture of the metal layer can be enlarged without losing resistance, thereby removing the shading effect and reserving the function of spectral width suppression, and further finding that the two-stage photoelectric curve disappears, various photoelectric characteristics such as linearity are improved, and high-speed transmission characteristics are better optimized.
Please refer to fig. 3A, fig. 3B and fig. 3C. FIG. 3A is a schematic top view showing the relative positions of the inner edge of the metal layer, the inner edge of the ion implantation region, the outer edge of the metal layer, and the periphery of the central through hole of the oxide layer in an embodiment of the VCSEL structure of the present invention. FIG. 3B is a cross-sectional view B-B as shown in FIG. 3A, schematically illustrating a cross-sectional B-B structure of the mesa region in an embodiment of the VCSEL structure of the present invention. FIG. 3C is a cross-sectional view, taken along line C-C as shown in FIG. 3A, schematically illustrating the cross-sectional structure of the mesa region in an embodiment of the VCSEL structure of the present invention. In the embodiments of the vcsel structure of the present invention shown in fig. 3A, fig. 3B and fig. 3C, the structure, position, dimension and material of the substrate, the first mirror layer 51, the active layer 52, the second mirror layer 53, the upper surface of the second mirror layer 53, the oxide layer 531, the central via of the oxide layer 531, the mesa Region, the top surface of the mesa Region, the optical window, the trench, the ion implantation Region 54(Implant Region), the insulating layer 55, the dielectric material 56, the metal layer 57, the light extraction layer 574 and the optical window 500 are substantially the same as those of the corresponding elements of the embodiment shown in fig. 1, and the description of these elements in fig. 1 can be directly followed.
Specifically, in the embodiments shown in fig. 3A, 3B and 3C, the vcsel structure of the present invention also includes: a substrate (not shown), a first mirror layer 51, an active layer 52, a second mirror layer 53, an oxide layer 531, a mesa region, a trench (filled with dielectric material 56), a metal layer 57, and an ion implantation region 54. The first mirror layer 51 is disposed on the substrate. The active layer 52 is located on the first mirror layer 51. The second mirror layer 53 is disposed on the active layer 52 and has an upper surface. The oxide layer 531 is sandwiched in the second mirror layer 53, and the oxide layer 531 has a central through hole. The mesa region is located on the substrate and is formed by at least a portion of the first mirror layer 51, the active layer 52, the second mirror layer 53 and the oxide layer 531. An optical window 500 is disposed at a center of a top surface of the convex region, and the optical window 500 corresponds to the central through hole. The groove surrounds at least a portion of the outer periphery of the land area. The trench extends from the top surface of the mesa region from top to bottom through at least the second mirror layer 53, the oxide layer 531 and the active layer 52 into the first mirror layer 51; and, the trench is filled with a dielectric material 56. The metal layer 57 is located on the top surface of the convex region and surrounds the outer periphery of the optical window 500, and at least one inner edge 571 is in contact with the upper surface of the second mirror layer 53. A diameter of the optical window 500 is defined by an inner diameter of the inner edge portion 571 of the metal layer 57. The ion implantation region 54 is located at least in the mesa region. A light emitting layer 574 is disposed above the light window 500.
In the present embodiment, the ion implantation region 54 is an insulating region formed by implanting non-conductive particles (such as, but not limited to, protons (Proton) or oxygen ions) into the second mirror layer 53. The ion implantation region 54 extends from the upper surface of the second mirror layer 53 down into the second mirror layer 53 to a predetermined depth, and the ion implantation layer 54 in the mesa region is located between the light window 500 and the trench (where the dielectric material 56 is filled) and surrounds at least a portion of the outer periphery of the light window 500. The ion implantation region 54 has an arc-shaped inner edge 541, an arc-shaped outer edge 542, and at least one conductive channel 543 extending outward from the arc-shaped inner edge 541 toward the arc-shaped outer edge 542 for a predetermined length, such that an outer end of the conductive channel 543 at least extends outward beyond the inner edge 571 of the metal layer 57. In the present embodiment, the ion implantation region 54 has a plurality of the conductive channels 543, and each of the conductive channels 543 penetrates between the arc-shaped inner edge 541 and the arc-shaped outer edge 542. As shown in fig. 3A, from a top view, the conductive channels 543 cut the ion implantation region 54 into separate fan-shaped regions resembling a gas hob structure. The conductive path 543 is not implanted with protons (Proton) and oxygen ions, so it is part of the conductive second mirror layer 53; therefore, as shown in FIG. 3B, in the cross-sectional view taken along line B-B, the metal layer 57 above the conductive via 543 directly contacts the upper surface of the second mirror layer 53, so that the current applied to the metal layer 57 can enter the second mirror layer 53 through the conductive vias 543. In contrast, as shown in FIG. 3C, in the cross-sectional view along the line C-C, except above the conductive path 543, the metal layer 57 in other areas cannot conduct current because its lower surface can only contact the insulated ion implantation region 54. Thus, although the diameter of the optical window 500 is still defined by the inner edge 571 of the metal layer 57, which is opaque, the aperture of the inner edge 571 of the metal layer 57 is no longer required to be smaller than the diameter of the arc-shaped inner edge 541 of the ion implantation region 54. In other words, in the present invention, the diameter of the circular arc inner edge 541 of the ion implantation region 54 is smaller than the inner diameter of the inner edge portion 571 of the metal layer 57, i.e., the diameter of the circular arc inner edge 541 is smaller than the diameter of the optical window 500. Moreover, the diameter of the arc-shaped inner edge 541 of the ion implantation region 54 is smaller than the diameter of the central through hole 5311 of the oxide layer 531, the diameter of the optical window 500 (i.e. the diameter of the inner edge 571 of the metal layer 57) is larger than the diameter of the central through hole 5311 of the oxide layer 531, and the diameter of the arc-shaped outer edge 542 of the ion implantation region 54 is larger than the diameter of the central through hole periphery 5311 of the oxide layer 531. Therefore, the vcsel structure of the present invention is designed to have a top view profile similar to a gas hob of the vcsel structure, so as to leave one or more conductive channels 543 between the inner and outer edges of the vcsel structure 54, confine the current to enter the second mirror layer 53 from the conductive channels 543, and amplify the aperture of the metal layer 57 (i.e. the aperture of the optical window 500) without losing resistance, thereby removing the shading effect and retaining the function of spectral width suppression, and finding that the two-stage photoelectric curve has disappeared, the linearity and other photoelectric characteristics are improved, and the high-speed transmission characteristics are better optimized.
In a preferred embodiment of the present invention, the diameter of the central through hole 5311 of the oxide layer 531 is between 5 μm and 15 μm; the inner diameter of the inner edge portion 571 of the metal layer 57 is between 8 μm and 20 μm; the predetermined depth of the ion implantation region 54 is between 1 μm and 4 μm; the diameter of the arc-shaped inner edge 541 of the ion implantation region 54 is between 4 μm and 14 μm; the diameter of the arc-shaped outer edge 542 of the ion implantation region 54 is between 20 μm and 40 μm; the number of the conductive paths 543 of the ion implantation region 54 is 4, and the width is between 1 μm and 5 μm.
Referring to fig. 4A, 4B and 4C, there are shown a transmission Eye Diagram (Eye Diagram), a photoelectric graph of output light power versus current (L-I) and a spectrum characteristic graph of output light intensity versus wavelength measured according to the existing vcsel structure (optical window aperture 8 μm) shown in fig. 2A and 2B, respectively. Referring to fig. 5A, 5B and 5C, there are shown a transmission Eye Diagram (Eye Diagram), a photoelectric graph of output light power versus current (L-I) and a spectrum characteristic graph of output light intensity versus wavelength, respectively, measured according to the vcsel structure (optical window aperture 11 μm) shown in fig. 3A, 3B and 3C. Comparing fig. 4A and fig. 5A, it can be seen that the vcsel structure of the present invention has a better transmission eye diagram, and the light shape is more stable and the drop point is reduced, so as to provide better high-speed transmission characteristics. As can be seen from comparing fig. 4B and fig. 5A, fig. 4B shows a two-step photoelectric curve, that is, the slope of the curve when the current is less than 10mA is significantly different from the slope of the curve when the current is greater than 10 mA; in contrast, the photoelectric curve in fig. 5B has no two-step photoelectric curve, and has better linearity and better high-frequency signal performance. Therefore, the vertical cavity surface emitting laser structure of the present invention has improved transmission eye pattern, linearity of photoelectric curve and other photoelectric characteristics, better optimized high-speed transmission characteristics, and improved defects of the prior art.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, so that the equivalent technical changes using the description and drawings of the present invention are included in the scope of the present invention.
Claims (6)
1. A vertical cavity surface emitting laser structure comprising:
a substrate;
a first mirror layer on the substrate;
an active layer on the first mirror layer;
a second mirror layer on the active layer and having an upper surface;
an oxide layer sandwiched in the second mirror layer and having a central through hole;
a bump region located on the substrate and composed of at least a portion of the first mirror layer, the active layer, the second mirror layer and the oxide layer; a light window is arranged in the center of the top surface of the boss area, and the light window corresponds to the central through hole;
a groove surrounding at least a portion of the outer periphery of the land area; the groove at least penetrates through the second mirror layer, the oxide layer and the active layer from top to bottom of the top surface of the boss region and extends into the first mirror layer; and, fill a dielectric material in the ditch groove;
a metal layer located on the top surface of the convex area, surrounding the outer periphery of the optical window, and having at least one inner edge portion contacting the upper surface of the second mirror layer; the diameter of the light window is defined by the inner diameter of the inner edge part of the metal layer; and
an ion implantation region at least located in the boss region;
the method is characterized in that:
the ion implantation region is an insulation region formed by implanting a plurality of non-conductive particles into the second mirror layer; the ion implantation region extends from the upper surface of the second mirror layer downward into the second mirror layer to a predetermined depth, and the ion implantation layer in the mesa region is located between the light window and the trench and surrounds at least a portion of the outer periphery of the light window; the ion implantation region has a circular arc inner edge, a circular arc outer edge, and at least one conductive channel extending outward from the circular arc inner edge toward the circular arc outer edge by a predetermined length from a top view, such that an outer end of the conductive channel at least exceeds the outer side of the inner edge of the metal layer; the non-conductive particles are not injected into the conductive channel, so that the metal layer above the conductive channel is directly contacted with the upper surface of the second mirror layer; the diameter of the arc-shaped inner edge of the ion implantation area is smaller than the inner diameter of the inner edge part of the metal layer, namely, the diameter of the arc-shaped inner edge is smaller than the diameter of the optical window.
2. The VCSEL structure of claim 1, wherein the non-conductive particles are protons (Proton) or oxygen ions.
3. The VCSEL structure of claim 1, wherein a diameter of the arc-shaped inner edge of the ion implantation region is smaller than a diameter of the central via of the oxide layer; the diameter of the optical window is larger than the diameter of the central through hole of the oxide layer.
4. The VCSEL structure of claim 1, wherein the ion implantation region has a plurality of the conductive channels, and each of the conductive channels penetrates between the circular arc-shaped inner edge and the circular arc-shaped outer edge; from a top view, the plurality of conductive channels cut the ion implantation region into a plurality of separate fan-shaped regions resembling a gas hob structure.
5. A vertical cavity surface emitting laser structure according to claim 1, wherein:
the vertical resonant cavity surface emitting laser structure further comprises an insulating layer and a light emitting layer; the insulating layer covers at least a part of the outer surface of the boss area, and the metal layer is exposed out of the insulating layer; the light-emitting layer is located on the light window on the top surface of the boss area;
the first mirror layer is an n-type Distributed Bragg Reflector (DBR), and the second mirror layer is a p-type DBR;
the first mirror layer and the second mirror layer are made of materials containing aluminum gallium arsenide (AlGaAs) with different aluminum mole percentages, and the oxide layer has the aluminum with the highest relative mole percentage in the second mirror layer;
the oxide layer extends horizontally from the inner periphery of the trench toward the center of the boss region to the outer edge of the central through hole; and
the dielectric material is a polymer material with low dielectric properties.
6. A vertical cavity surface emitting laser structure according to claim 1, wherein:
the diameter of the central through hole of the oxide layer is between 5 μm and 15 μm;
the inner diameter of the inner edge portion of the metal layer is between 8 μm and 20 μm;
the predetermined depth of the ion implantation region is between 1 μm and 4 μm;
the diameter of the circular arc inner edge of the ion implantation area is between 4 μm and 14 μm;
the diameter of the arc-shaped outer edge of the ion implantation area is between 20 and 40 mu m;
the width of the conductive channel of the ion implantation region is between 1 μm and 5 μm.
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