WO2019194406A1

WO2019194406A1 - Vertical-cavity surface-emitting laser

Info

Publication number: WO2019194406A1
Application number: PCT/KR2019/001610
Authority: WO
Inventors: 최원진; 김동환; 김극
Original assignee: 주식회사 레이아이알
Priority date: 2018-04-02
Filing date: 2019-02-11
Publication date: 2019-10-10

Abstract

Disclosed in an embodiment is a vertical-cavity surface-emitting laser comprising: a substrate; a lower reflective layer disposed on the substrate; a laser cavity including an active layer disposed on the lower reflective layer; an oxide layer disposed on the laser cavity; an upper reflective layer disposed on the oxide layer; a plurality of first holes formed in the upper reflective layer and the oxide layer; and upper electrodes disposed in the plurality of first holes and on the upper reflective layer, wherein the oxide layer includes a plurality of light transmitting regions spaced apart from each other, and the plurality of first holes are disposed so as to surround the light transmitting region on a plane.

Description

Vertical cavity surface emission laser

Embodiments relate to a vertical cavity surface emitting laser.

Vertical Cavity Surface Emitting Laser (VCSEL) is capable of narrow spectrum single longitudinal mode oscillation, and the radiation angle of the beam is small, resulting in high coupling efficiency.

Recently, research into a technique for manufacturing a light source matrix by patterning such a vertical cavity surface emitting laser (VCSEL) into a two-dimensional array has been actively conducted. Irradiating the light source matrix patterned in the form of such a two-dimensional array to the object and analyzing the pattern of the reflected light can construct a three-dimensional image of the object.

The photoelectric conversion efficiency of a typical VCSEL is about 34 to 40% so that when driven, about 60 to 66% of the power energy applied to the VCSEL is converted to heat. As a result, the internal temperature of the VCSEL is increased, and the light efficiency is greatly decreased when driving a high current.

The increase in the internal temperature of the VCSEL is caused by self-heating caused by Joule heat, and it is essential to reduce the series resistance of the device in order to reduce self-heating. Moreover, a 10-degree increase in junction temperature can reduce the lifetime of the device by more than 50%.

Therefore, it is important to reduce the resistance of the device in order to realize a high efficiency long life VCSEL device.

In the case of forming a plurality of emitters of the laser in the form of an array, if the array is formed by a conventional manufacturing method, the contact area of the semiconductor layer that can contact the ohmic electrode is inevitably small, which causes a problem of increasing the contact resistance. Therefore, there is a limit to lowering the operating voltage.

The embodiment discloses a vertical cavity surface emitting laser that can widen the contact area of the ohmic electrode to lower the contact resistance.

The embodiment discloses an excellent vertical cavity surface emitting laser having a high photoelectric conversion efficiency and high light output radiation by increasing the density of a unit light emitting region (emitter) emitting a laser.

The problem to be solved in the examples is not limited thereto, and the object or effect that can be grasped from the solution means or the embodiment described below will also be included.

According to one aspect of the present invention, a vertical cavity surface emitting laser comprises: a substrate; A lower reflective layer disposed on the substrate; A laser cavity including an active layer disposed on the lower reflective layer; An oxide layer disposed on the laser cavity; An upper reflective layer disposed on the oxide layer; A plurality of first holes formed in the upper reflective layer and the oxide layer; And an upper electrode disposed inside the plurality of first holes and on the upper reflective layer, wherein the oxide layer includes a plurality of light transmitting regions spaced apart from each other, and the plurality of first holes cover the light transmitting region on a plane. It may be arranged to surround.

According to an embodiment, the contact area of the ohmic electrode may be widened, thereby lowering the contact resistance and the operating voltage.

In addition, the density of the light-transmitting region emitting the laser is increased, so the photoelectric conversion efficiency is excellent, and the light output emission value can be improved.

Various and advantageous advantages and effects of the present invention are not limited to the above description, and will be more readily understood in the course of describing specific embodiments of the present invention.

1 is a plan view of a vertical cavity surface emitting laser according to one embodiment of the invention,

2 is an enlarged view of a part of FIG. 1;

3 is a cross-sectional view along the A-A direction of FIG.

4 is a cross-sectional view along the B-B direction of FIG.

5 is a cross-sectional view taken along the C-C direction of FIG.

6 is a cross-sectional view taken along the D-D direction of FIG. 1;

7 is a cross-sectional view taken along the E-E direction of FIG.

8 and 9 are views showing a process of oxidizing the oxide layer exposed to the outside by the first hole,

10A is a plan view of the upper electrode of FIG. 1,

FIG. 10B is a plan view illustrating a region in which the upper electrode and the upper reflective layer of FIG. 1 are electrically connected;

11 is a plan view showing a conventional laser structure,

12A is a partial cross-sectional view of a conventional laser structure,

FIG. 12B is a plan view illustrating a region in which the upper electrode and the upper reflective layer of FIG. 11 are electrically connected;

13A to 13D are views for explaining a method of manufacturing a vertical cavity surface emitting laser according to one embodiment of the present invention;

14A to 14E are various modifications of the first hole,

15 is a top view of a vertical cavity surface emitting laser according to another embodiment of the present invention,

16 is a partially enlarged view of FIG. 15;

17 is a cross-sectional view taken along the line F-F in FIG. 15,

18 is a cross-sectional view taken along the G-G direction of FIG. 15;

19 is a cross-sectional view taken along the line H-H in FIG. 15;

20 is a cross-sectional view taken along the line I-I of FIG. 15;

21A is a top view of the upper electrode of FIG. 15,

FIG. 21B is a plan view illustrating a region in which the upper electrode and the upper reflective layer of FIG. 15 are electrically connected;

22A to 22E illustrate a method of manufacturing a vertical cavity surface emitting laser according to another exemplary embodiment.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated and described in the drawings. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms including ordinal numbers, such as second and first, may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the second component may be referred to as the first component, and similarly, the first component may also be referred to as the second component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings, and the same or corresponding components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted.

1 is a plan view of a vertical cavity surface emitting laser according to an embodiment of the present invention, and FIG. 2 is a partially enlarged view of FIG. 1.

1 and 2, in the vertical cavity surface emitting laser according to the embodiment, a plurality of light-transmitting regions 53 arranged in a matrix form are disposed, and the plurality of first holes P1 define the light-transmitting regions 53. It may be arranged to surround. As described later, the plurality of first holes P1 may serve to expose the oxide layer to enable the oxidation process.

In the matrix form, a plurality of light-transmitting regions 53 may be spaced apart from each other in a horizontal direction to form one line, and a plurality of lines may be arranged in a vertical direction.

When power is applied to the matrix laser devices, laser light may be emitted through the light-transmitting region 53. Therefore, there is an advantage that can output a plurality of laser light from one laser device.

3 is a cross-sectional view taken along the AA direction of FIG. 1, FIG. 4 is a cross-sectional view taken along the BB direction of FIG. 1, FIG. 5 is a cross-sectional view taken along the CC direction of FIG. 1, FIG. 6 is a cross-sectional view taken along the DD direction of FIG. 1, and FIG. EE direction cross section.

3 to 5, a vertical cavity surface emitting laser according to an embodiment includes a substrate 10, a lower reflective layer 20 disposed on the substrate 10, and an active layer disposed on the lower reflective layer 20. The laser cavity 30, the oxide layer 51 disposed on the laser cavity 30, the upper reflective layer 40 disposed on the oxide layer 51, the inside and the upper reflective layer 40 of the plurality of first holes P1. It may include an upper electrode 60 disposed on).

In the conventional structure, the upper reflective layer 40 and the oxide layer 51 are divided into a plurality of light emitters (emitters), whereas the upper reflective layer 40 in the present embodiment has a plurality of first holes P1 formed therein. In one layer, the oxide layer 51 is also different in that it forms one layer in which a plurality of first holes P1 are formed.

The substrate 10 may be a semi-insulating or conductive substrate 10. For example, the substrate 10 may be a GaAs substrate having a high doping concentration, and the doping concentration may be about 1 × 10 ¹⁷ cm ⁻³ to about 1 × 10 ¹⁹ cm ⁻³ . If necessary, a buffer layer such as an AlGaAs or GaAs thin film may be further disposed on the substrate 10, but is not limited thereto.

The lower reflective layer 20 may include a distributed Bragg reflector (DBR) having an n-type superlattice structure. The lower reflective layer 20 may be epitaxially deposited on the substrate 10 by a technique such as MOCVD, MBE, or the like.

The lower reflective layer 20 may perform an internal reflection function in the VCSEL structure. In the lower reflective layer 20, a plurality of first lower reflective layers 21 and a plurality of second lower reflective layers 22 may be alternately stacked. Both the first lower reflective layer 21 and the second lower reflective layer 22 may be AlGaAs or AlGaAsP, but the aluminum composition of the first lower reflective layer 21 may be higher.

The first lower reflective layer 21 and the second lower reflective layer 22 may have an effective optical thickness that is about 1/4 of the wavelength of light generated by the VCSEL. It is also desirable to have a reflectance of about 100% for high internal reflection of the VCSEL.

The reflectance of the lower reflecting layer 20 may depend on the difference in refractive index between the first lower reflecting layer 21 and the second lower reflecting layer 22, and the number of stacked layers of the first lower reflecting layer 21 and the second lower reflecting layer 22. Can be. Therefore, in order to obtain high reflectance for securing high quality VCSEL characteristics, the larger the difference in refractive index and the smaller the number of stacked layers, the better.

The laser cavity 30 may include one or more well layers and a barrier layer. The well layer may be any one selected from GaAs, AlGaAs, AlGaAsSb, InAlGaAs, AlInGaP, GaAsP or InGaAsP, and the barrier layer may be AlGaAs, InAlGaAs, InAlGaAsP, AlGaAsSb, GaAsP, AlGaAsP, GaInP, InGaAP Can be selected.

The laser cavity 30 can be designed to have sufficient optical gain. In an exemplary embodiment, the laser cavity 30 may have a well layer having a thickness and composition ratio suitable for emitting light in a wavelength band of about 800 nm to a wavelength of 900 nm. However, the wavelength band of the laser which the well layer outputs is not particularly limited.

The laser cavity 30 may include a first semiconductor layer (not shown) disposed below the active layer and a second semiconductor layer (not shown) disposed above the active layer. The first semiconductor layer may be an n-type semiconductor layer and the second semiconductor layer may be a p-type semiconductor layer, but is not limited thereto. The first semiconductor layer and the second semiconductor layer may not be doped with a dopant. For example, the first semiconductor layer and the second semiconductor layer may be AlGaAs, but are not limited thereto.

The oxide layer 51 may be disposed on the laser cavity 30. The oxide layer 51 may be doped with the same kind of dopant as the upper reflective layer 40. For example, the oxide layer 51 may be doped with a p-type dopant at a concentration of about 10 ¹⁸ cm ^−3, but is not limited thereto.

The oxide layer 51 may include a semiconductor compound containing aluminum, for example, AlAs, AlGaAs, InAlGaAs, or the like. In the oxide layer 51 according to the exemplary embodiment, the non-oxidized light transmissive region 53 may be disposed in the center. That is, the oxide layer 51 may have an oxide region having a polygonal shape in which a transmissive region 53 is formed at the center.

The oxide layer 51 may have a relatively high resistance while having a relatively low refractive index. Thus, current can be injected into the light-transmitting region 53 so that laser light can be collected at the center of the device.

An intermediate layer 43 may be disposed between the laser cavity 30 and the oxide layer 51. The intermediate layer 43 may include a first intermediate layer and a second intermediate layer. The first intermediate layer may have the same composition as the first upper reflective layer 41. In addition, the second intermediate layer may have the same composition as the second upper reflective layer 42. In exemplary embodiments, the first intermediate layer may be GaAs, and the second intermediate layer may be AlGaAs.

In general, when the oxide layer 51 is oxidized, the material may be amorphous and the film quality thereof may be somewhat degraded. As a result, when the amorphous layer, which has a somewhat poor film quality, is directly bonded to the laser cavity 30 in which light is generated, device reliability may be deteriorated. Therefore, the second intermediate layer may be formed before the oxide layer 51 to prevent the amorphous layer from directly contacting the laser cavity 30.

The upper reflective layer 40 may be disposed on the oxide layer 51. The upper reflective layer 40 may include a plurality of first upper reflective layers 41 and second upper reflective layers 42.

The first upper reflective layer 41 may have a composition of AlGaAs, and the second upper reflective layer 42 may have a composition of GaAs. Thus, the aluminum composition of the first upper reflective layer 41 may be higher than the second upper reflective layer 42.

The upper reflective layer 40 may be doped to have a different polarity than the lower reflective layer 20. For example, if the lower reflective layer 20 and the substrate 10 are doped with an n-type dopant, the upper reflective layer 40 may be doped with a p-type dopant.

In order for the radiation direction of the laser light to be in the opposite direction of the substrate 10, the upper reflective layer 40 may have fewer layers than the lower reflective layer 20 to reduce the reflectance from the VCSEL. That is, the reflectance of the upper reflective layer 40 may be smaller than the lower reflective layer 20.

The upper electrode 60 may be disposed on the upper reflective layer 40, and the lower electrode 11 may be disposed below the substrate 10. However, the present invention is not limited thereto, and the lower electrode 11 may be disposed in the exposed area after exposing the upper portion of the substrate 10. The upper electrode 60 may be a P-type ohmic electrode, and the lower electrode 11 may be an N-type ohmic electrode. The upper electrode 60 may be electrically connected to the pad electrode 101.

The upper electrode 60 and the lower electrode 11 are indium tin oxide (ITO), indium zinc oxide (IZO), indium zinc tin oxide (IZTO), indium aluminum zinc oxide (IZAO), indium gallium zinc oxide (IGZO), IGTO (indium gallium tin oxide), AZO (aluminum zinc oxide), ATO (antimony tin oxide), GZO (gallium zinc oxide), IZON (IZO Nitride), AGZO (Al-Ga ZnO), IGZO (In-Ga ZnO) , ZnO, IrOx, RuOx, NiO, RuOx / ITO, Ni / IrOx / Au, or Ni / IrOx / Au / ITO, Ag, Ni, Cr, Ti, Al, Rh, Pd, Ir, Sn, In, Ru, It may be formed including at least one of Mg, Zn, Pt, Au, Hf, but is not limited to these materials.

In exemplary embodiments, the upper electrode 60 may have a plurality of metal layers (eg, Ti / Pt / Au). At this time, the thickness of Ti may be about 100 to 400 ohms strong and the thickness of Au may be 3,000 to 20,000 ohms strong, but is not limited thereto.

The lower electrode 11 may have a plurality of metal layers (eg, AuGe / Ni / Au). In this case, the thickness of AuGe may be 1,000 ohms strong, the thickness of Ni may be 100 ohms strong, and the thickness of Au may be 2,000 ohms strong, but is not limited thereto.

An ohmic layer 44 may be further disposed between the upper electrode 60 and the upper reflective layer 40. The ohmic layer 44 may include a material having a bandgap equal to or lower than the energy of the emitted laser light while having a bandgap equal to or lower than that of the GaAs substrate 10 for low ohmic resistance.

For example, the ohmic layer may be selected from AlInGaAs, InGaAs, GaAs, AlInGaAsSb, AlInGaAsPSb, InGaAsP, InGaAsPSb, GaAsSb, InGaAsSb, InAsSb, AlGaAsSb, AlGaAsP, and AlGaInAsP.

Referring to FIG. 6, the insulating layer 80 may be disposed in the first hole P1 to prevent the upper electrode 60 from directly contacting the laser cavity 30. Therefore, current may be injected into the laser cavity 30 only through the light transmission region 53 of the oxide layer 51 so that light may be concentrated. In addition, the insulating layer 80 may be disposed between the light transmissive region 53 and the second hole to prevent the light transmissive region 53 from being exposed to the outside.

The first hole P1 may be formed through the upper reflective layer 40 and the oxide layer 51. Therefore, the oxide layer 51 may be exposed to the outside and oxidized through the first hole P1. By controlling the oxidation time, the diameter of the light transmissive region 53 can be controlled.

Referring to FIG. 7, an area in which the first hole P1 is not formed may be electrically connected to the upper electrode 60 to form one layer. In addition, the insulating layer 80 may be removed in the region where the first hole P1 is not formed, thereby increasing the area in which the upper electrode 60 and the upper reflective layer 40 are electrically connected.

The series resistance of the VCSEL device can be composed of the sum of the contact resistance and the semiconductor layer resistance, and the contact resistance which greatly affects the series resistance of the device is inversely proportional to the contact area. Therefore, the operating voltage can be lowered automatically if the contact resistance can be lowered. Therefore, it is possible to lower the increase in the internal temperature of the VCSEL, so that the photoelectric conversion efficiency is high, the emission of high output light is possible, and the lifetime can be improved.

8 and 9 are views illustrating a process of oxidizing an oxide layer exposed to the outside by the first hole of an embodiment.

Referring to FIG. 8, when the oxide layer 51 exposed by the first hole P1 is exposed to water vapor, oxidation proceeds along the shape of the first hole P1. Subsequently, when the oxidized regions meet each other, as shown in FIG. 9, a light transmissive region 53 is formed therein. This structure has an advantage of increasing the density of the transmissive region 53 because neighboring transmissive regions share the oxidized region. That is, the area of the light transmissive region 53 may be relatively increased by minimizing the oxidized region. Therefore, the maximum light output value per unit chip can be increased.

FIG. 10A is a plan view of the upper electrode of FIG. 1, and FIG. 10B is a plan view showing a region in which the upper electrode and the upper reflective layer of FIG. 1 are electrically connected.

Referring to FIG. 10A, the upper electrode 60 may include a plurality of second holes 62. In addition, referring to FIG. 10B, an area in which the upper electrode 60 and the upper reflective layer 40 are in electrical contact may be a remaining area except for the first hole P1 and the second hole 62. That is, according to the exemplary embodiment, an area in which the upper electrode 60 and the upper reflective layer 40 are electrically connected to each other may increase, thereby lowering the contact resistance.

FIG. 11 is a plan view illustrating a conventional laser array structure, FIG. 12A is a partial cross-sectional view of a conventional laser array, and FIG. 12B is a plan view illustrating a region in which the upper electrode and the upper reflective layer of FIG. 11 are electrically connected.

Referring to FIGS. 11 and 12A, the conventional laser structure may partition the plurality of light emitting parts (emitters) by isolating the plurality of upper reflective layers ET1 by mesa etching. In this case, the area 105a in which the ohmic electrode 105 contacts the upper reflective layer ET1 is small, resulting in a large contact resistance. Outside the plurality of light emitting parts, the ohmic electrode 105 is not electrically connected to the upper reflective layer 103 by the insulating layer 104.

Referring to FIG. 12B, the contact area 105a connecting the ohmic electrode 105 and the upper reflective layer 103 may be the sum of a plurality of ring-shaped areas. Compared with FIG. 10B, it can be seen that the contact area is very small (in the conventional structure, the area in contact with the ohmic electrode is about 29% of the total area of the chip).

13A to 13D are views for explaining a method of manufacturing a vertical cavity surface emitting laser according to an embodiment of the present invention.

Referring to FIG. 13A, the lower reflective layer 20, the laser cavity 30, the intermediate layer 43, the oxide layer 51, and the upper reflective layer 40 may be sequentially grown on the substrate 10. Each layer configuration may include all of the above-described features. Metal-Organic Chemical Vapor Deposition (MOCVD), Liquid Phase Epitaxy (LPE), Molecular Beam Epitaxy (MBE), etc. It is not limited.

Referring to FIG. 13B, a plurality of first holes P1 penetrating the upper reflective layer 40 and the oxide layer 51 may be formed. The number of the first holes P1 is not particularly limited. The shape of the plurality of holes is not particularly limited. Various shapes, such as a cross shape, a polygon shape, and a radial shape, may be selectively applied to the first hole P1. However, since oxidation proceeds along the plurality of first holes P1 to form a uniform light-transmitting region 53, the shape of the first holes P1 may be advantageously symmetrical with respect to an imaginary line passing through the center thereof. Can be.

Side surfaces of the oxide layer 51 may be exposed by the plurality of first holes P1. Therefore, when the oxide layer 51 is exposed to the N ₂ and H ₂ O mixed gas in an environment of high temperature (about 300 ° C. or more), oxidation may proceed from the side. Thereafter, oxidation may be performed until the light-transmitting region 53 has a desired diameter.

Referring to FIG. 13C, when the oxidation process is completed, the insulating layer 80 may be formed in the first hole P1 and on the upper reflective layer 40. The insulating layer 80 may be at least one of SiO ₂ , Si ₃ N ₄ , SiON, Ta ₂ O ₅ , HfO ₂ , benzocyclobutene (BCB), and polyimide, but is not limited thereto.

Referring to FIG. 13D, an upper electrode 60 may be formed on the insulating layer 80. In this case, the ohmic electrode may be inserted into the via hole of the insulating layer 80 to electrically connect the upper reflective layer 40 and the upper reflective layer 40.

The upper electrode 60 may have a plurality of metal layers (eg, Ti / Pt / Au). At this time, the thickness of Ti may be about 100 to 1,000 ohms strong and the thickness of Au may be 3,000 to 200,000 ohms strong, but is not limited thereto.

14A to 14E illustrate various modifications of the first hole.

Various shapes, such as a cross shape, a polygon shape, and a radial shape, may be selectively applied to the first hole P1. However, since oxidation proceeds along the plurality of first holes P1 to form a uniform light-transmitting region 53, the shape of the first holes P1 may be advantageously symmetrical with respect to an imaginary line passing through the center thereof. Can be.

Referring to FIG. 14A, the first hole P1 may have a shape in which three extension portions radially extend from the center. In such a structure, the light transmitting region 53 may have a hexagonal shape. That is, the shape of the transmissive area 53 may be determined according to the shape of the first hole P1 to have the same shape.

14B and 14C, the first hole P1 may have a rectangular or square shape. In this case, the light transmission area 53 may have a square shape.

Referring to FIG. 14D, the first hole P1 may have a triangular shape. In this case, the light transmitting region 53 may also have a triangular shape.

In addition, referring to FIG. 14E, the first hole P1 may have a hexagonal shape. In this case, the light transmitting region 53 may also have a hexagonal shape. However, the present invention is not limited thereto, and the first hole and the light transmissive area may have various polygonal structures, such as a pentagonal shape and an octagonal shape.

FIG. 15 is a plan view of a vertical cavity surface emitting laser according to another embodiment 2) of the present invention, and FIG. 16 is a partially enlarged view of FIG. 15.

15 and 16, in the vertical cavity surface emitting laser according to the embodiment, a plurality of through holes 54 arranged in a matrix form are disposed, and a plurality of first holes P2 is formed through the through holes 54. It may be arranged to surround. The through hole 54 may function as an emitter from which the oxide layer is removed, and may form a light transmitting region through which the laser light is emitted. As will be described later, the plurality of first holes P2 expose the oxide layer 51 to perform an oxidation process.

The diameter of the through hole 54 may be larger than the diameter of the first hole P2. For example, when the size of the array chip is 750un x 780um, the diameter of the through hole 54 may be 3um to 100um, and the diameter of the first hole P2 may be 2um to 5um. The number of through holes 54 may be 200 to 400, and the number of first holes P2 may be 50 to 300, but is not limited thereto.

The area of the first hole P2 may be 0.1% to 50% of the area of the through hole 54. If the area is smaller than 0.1%, the area of the first hole P2 may be too small, and the oxidation process of the oxide layer 51 may be lengthened. If the area is larger than 50%, the through hole 54 may be reduced to give light. The output may be degraded.

However, the present invention is not limited thereto, and the diameter of the first hole P2 may be larger than that of the through hole 54. In addition, the shape of the first hole P2 may have various shapes in addition to the circular shape.

FIG. 17 is a sectional view taken along the F-F direction of FIG. 15, FIG. 18 is a sectional view taken along the G-G direction of FIG. 15, FIG. 19 is a sectional view taken along the H-H direction of FIG. 15, and FIG. 20 is a sectional view taken along the I-I direction of FIG. 15.

The substrate 10 may be a semi-insulating or conductive substrate 10. For example, the substrate 10 may be a GaAs substrate 10 having a high doping concentration, and the doping concentration may be about 1 × 10 ¹⁷ cm ⁻³ to 1 × 10 ¹⁹ cm ⁻³ . If necessary, a buffer layer such as an AlGaAs or GaAs thin film may be further disposed on the substrate 10, but is not limited thereto.

The lower reflective layer 20 may include a distributed Bragg reflector (DBR) having an n-type superlattice structure. The lower reflective layer 20 may be epitaxially deposited on the substrate 10 by the above-described techniques such as MOCVD and MBE.

The reflectance of the lower reflecting layer 20 may depend on the difference in refractive index between the first lower reflecting layer 21 and the second lower reflecting layer 22 and the number of stacked layers of the first lower reflecting layer 21 and the second lower reflecting layer 22. Can be. Therefore, in order to obtain high reflectance for securing high quality VCSEL characteristics, the larger the difference in refractive index and the smaller the number of stacked layers, the better.

The laser cavity 30 may include one or more well layers and a barrier layer. The well layer may be selected from GaAs, AlGaAs, AlGaAsSb, InAlGaAs, AlInGaP, GaAsP, or InGaAsP, and the barrier layer may be AlGaAs, InAlGaAs, InAlGaAsP, AlGaAsSb, GaAsP, AlaAsP, GaInP, InGaAP, InGaAP Can be selected.

The laser cavity 30 can be designed to provide sufficient optical gain. In an exemplary embodiment, the laser cavity 30 may have a well layer having a thickness and composition ratio suitable for emitting light in a wavelength band of about 800 nm or a wavelength of 900 nm. However, the wavelength band of the laser which the well layer outputs is not particularly limited.

The oxide layer 51 may include a semiconductor compound containing aluminum, for example, AlAs, AlGaAs, InAlGaAs, or the like. In the oxide layer 51 according to the embodiment, the through hole 54 may be disposed at the center thereof. The shape of the through hole 54 may have a circular, elliptical, and polygonal shape. The oxide layer 51 may have a donut shape with a hole formed in the center thereof.

The oxide layer 51 may have a relatively high resistance while having a relatively low refractive index. Therefore, the current can be injected into the through hole 54 so that the laser light can be collected at the center of the device. That is, the through hole 54 may pass current and light. Therefore, the through hole 54 may perform the function of the light transmitting area.

According to the embodiment, when all of the oxide layer 51 having the through hole 54 is oxidized, there is no longer a region to be oxidized. This is because the upper reflective layer 40 disposed inside the through hole 54 has a relatively low aluminum composition and does not oxidize well even when exposed to oxygen. That is, the upper reflective layer 40 disposed inside the through hole 54 may serve as a stopper of the oxidation reaction to automatically terminate the oxidation.

Therefore, there is an advantage that the oxide opening can correspond to the size and shape of the through hole 54 without precisely controlling the degree of oxidation. Thus, the manufacturing process can be simplified and the yield can be improved. In addition, it is possible to simultaneously form a uniform oxide aperture.

The aluminum composition of the oxide layer 51 may be 80% to 100%. When the aluminum composition of the oxide layer 51 is 80% or less, there is a problem in that the oxidation rate is slow and the process is long.

The capping layer 52 may be disposed on the oxide layer 51. The capping layer 52 may prevent the oxide layer 51 from being exposed to the external environment during or after the process.

As described above, the oxide layer 51 may be designed to have a high composition of aluminum and a high doping concentration so that the oxide layer 51 may be easily oxidized. Thus, in the absence of the capping layer 52, the oxide layer 51 may already be oxidized before proceeding with the oxidation process.

Since the growth of the semiconductor layer is difficult on the already oxidized oxide layer 51, the growth of the upper reflective layer 40 may be difficult. Therefore, the capping layer 52 can prevent the oxide layer 51 from being oxidized before the oxidation process.

The oxide layer 51 according to the embodiment may include a semiconductor compound containing aluminum, for example, AlAs, AlGaAs, InAlGaAs, or the like. That is, the oxide layer 51 according to the embodiment may include arsenic (As) so that the upper reflective layer 40 can be grown thereon.

The capping layer 52 may be selected from at least one of GaAs, AlGaAs, InAlGaAs, AlGaAsSb, AlGaAsP, GaInP, InGaAsP, and AlInGaP, but is not limited thereto.

In addition, the capping layer 52 may be composed of one or more layers by selecting one or more materials from GaAs, AlGaAs, InAlGaAs, AlGaAsSb, AlGaAsP, GaInP, InGaAsP, and AlInGaP.

When the capping layer 52 includes aluminum, the aluminum composition of the capping layer 52 may be smaller than the aluminum composition of the oxide layer 51. For example, the aluminum composition of the capping layer 52 may be 0% to 60%. When the aluminum composition of the capping layer 52 is greater than 60%, a problem may occur that the surface of the capping layer 52 is exposed to air during oxidation, and may be oxidized, even after the upper reflective layer 40 is formed. There may be a problem that the capping layer 52 is oxidized together when the 51 is oxidized.

The thickness of the capping layer 52 may be 2.5 kPa to 5000 kPa. If the thickness of the capping layer 52 is 2.5 μs or less, the capping layer 52 may be too thin to effectively block oxygen penetration. If the thickness is 5000 μs or more, the step may be too large when the upper reflective layer 40 is regrown. There is a problem that it becomes large and difficult to form a uniform interface.

An intermediate layer 43 may be included between the laser cavity 30 and the oxide layer 51. The intermediate layer 43 may include a first intermediate layer and a second intermediate layer. The configuration of the intermediate layer may be the same as described above.

The upper reflective layer 40 may be disposed inside the through hole 54 and above the oxide layer 51. The upper reflective layer 40 may include a plurality of first upper reflective layers 41 and second upper reflective layers 42 disposed inside the capping layer 52 and / or inside the through holes 54.

The upper electrode 60 may be disposed on the upper reflective layer 40, and the lower electrode 11 may be disposed below the substrate 10. However, the present invention is not limited thereto, and the lower electrode 11 may be disposed in the exposed area after exposing the upper portion of the substrate 10.

In exemplary embodiments, the upper electrode 60 may have a plurality of metal layers (eg, Ti / Pt / Au). At this time, the thickness of Ti may be about 100 to 1,000 ohms strong and the thickness of Au may be 3,000 to 200,000 ohms strong, but is not limited thereto.

The lower electrode 11 may have a plurality of metal layers (eg, AuGe / Ni / Au). In this case, the thickness of AuGe may be 1000 ohms, the thickness of Ni may be 100 ohms, and the thickness of Au may be 2000 ohms, but is not limited thereto.

An ohmic layer may be further disposed between the upper electrode 60 and the upper reflective layer 40. The ohmic layer may include a material having a bandgap equal to or lower than the energy of the emitting laser light while having a bandgap equal to or lower than that of the GaAs substrate 10 for low ohmic resistance. For example, the ohmic electrode may be selected from AlInGaAs, InGaAs, GaAs, AlInGaAsSb, AlInGaAsPSb, InGaAsP, InGaAsPSb, GaAsSb, InGaAsSb, InAsSb, AlGaAsSb, AlGaAsP, and AlGaInAsP.

Referring to FIG. 19, the insulating layer 80 may be disposed in the first hole P2 to prevent the upper electrode 60 from directly contacting the laser cavity. Accordingly, the current is injected into the laser cavity 30 while the current flows through the through hole 54 from the contact area 61 of the semiconductor and the upper electrode 60 in the unit light-transmitting region to concentrate the light in the through hole 54. Can be. In addition, the insulating layer 80 may be disposed between the through hole 54 and the second hole 64 to prevent the through hole 54 from being exposed to the outside.

The first hole P2 may be formed through the upper reflective layer 40 and the oxide layer 51. Therefore, the oxide layer 51 may be exposed to the outside through the first hole P2 to be oxidized. Even if oxidation starts from the periphery of the first hole P2, since the end of the oxidation is terminated in the through hole 54, the shape of the through hole 54 may be determined by the shape of the through hole 54.

Referring to FIG. 20, a region where the first hole P2 is not formed may be electrically connected to the upper electrode 60 layer to form one layer. In addition, the insulating layer 80 may be removed in a region where the first hole P2 is not formed, thereby increasing the area in which the upper electrode 60 and the upper reflective layer 40 are electrically connected. Therefore, the contact resistance can be lowered and the operating voltage can be lowered. As a result, the increase in the internal temperature of the VCSEL can be lowered, so that the photoelectric conversion efficiency can be high, and high power light can be emitted. In addition, the life of the VCSEL or VCSEL array can be improved.

FIG. 21A is a plan view of the upper electrode of FIG. 15, and FIG. 21B is a plan view showing a region in which the upper electrode and the upper reflective layer of FIG. 15 are electrically connected.

Referring to FIG. 21A, the upper electrode 60 may include a plurality of second holes 64. In addition, referring to FIG. 21B, an area in which the upper electrode 60 and the upper reflective layer 40 are electrically connected may be a remaining area except for the first hole P2 and the second hole 64. That is, according to the exemplary embodiment, the contact resistance of the upper electrode 60 and the upper reflective layer 40 may increase to lower the contact resistance.

Referring to FIG. 22A, the lower reflective layer 20, the laser cavity 30, the oxide layer 51, the capping layer 52, and the upper reflective layer 40 may be sequentially grown on the substrate 10. Each layer configuration may include all of the above-described features.

Specifically, after the plurality of through holes 54 are formed in the oxide layer 51 and the capping layer 52, the upper reflective layer 40 may be grown thereon. Therefore, a portion of the upper reflective layer 40 may be disposed in the through hole 54.

The semiconductor structure may be manufactured using metal-organic chemical vapor deposition (MOCVD), liquid phase epitaxy (LPE), molecular beam epitaxy (MBE), or the like. However, the present invention is not limited thereto.

Referring to FIG. 22B, a plurality of first holes P2 penetrating through the upper reflective layer 40, the capping layer 52, and the oxide layer 51 may be formed. The number of the first holes P2 is not particularly limited. The shape of the plurality of holes is not particularly limited. The first hole P2 may be selectively applied in various shapes such as circle shape, cross shape, polygon shape, and radial shape.

Side surfaces of the oxide layer 51 may be exposed by the plurality of first holes P2. Therefore, when the oxide layer 51 is exposed to the N ₂ and H ₂ O mixed gas, the oxidation may proceed from the side. As shown in FIG. 22C, the oxidation process may proceed until all of the oxide layer 51 except for the through hole 54 is oxidized.

Referring to FIG. 22D, when the oxidation process is completed, the insulating layer 80 may be formed inside the first hole P2 and on the upper reflective layer 40. The insulating layer 80 may be at least one of SiO ₂ , Si ₃ N ₄ , SiON, Ta ₂ O ₅ , HfO ₂ , benzocyclobutene (BCB), and polyimide, but is not limited thereto.

Referring to FIG. 22D, an upper electrode 60 may be formed on the insulating layer 80. In this case, the upper electrode 60 may be electrically connected to the upper reflective layer 40 by a via hole formed in the insulating layer 80 in advance. The upper electrode 60 may have a plurality of metal layers (eg, Ti / Pt / Au). At this time, the thickness of Ti may be about 100 to 10,000 ohms strong and the thickness of Au may be 3,000 to 200,000 ohms strong, but is not limited thereto.

Before forming the upper electrode 60, an ohmic layer may be formed. The ohmic layer may be selected from AlInGaAs, InGaAs, GaAs, AlInGaAsSb, AlInGaAsPSb, InGaAsP, InGaAsPSb, GaAsSb, InGaAsSb, InAsSb, AlGaAsSb, AlGaAsP, and AlGaInAsP.

When comparing the characteristics of the conventional technology and the VCSEL array chip to which the first and second technologies are applied, are shown in Table 1 below.

구조rescue	칩 전체 면적 중 오믹 전극과 접촉하는 면적Area of chip total contact with ohmic electrode	상대 저항 비율Relative resistance ratio
기존 구조Existing structure	29%29%	100%100%
실시예1Example 1	79%79%	73%73%
실시예2Example 2	88%88%	58%58%

The laser device according to the present embodiment may be used as a light source of 3D face recognition and 3D imaging technology. 3D face recognition and 3D imaging techniques require light source matrices patterned in the form of two-dimensional arrays. The light source matrix patterned in the form of such a two-dimensional array can be irradiated onto the object and the pattern of reflected light can be analyzed. In this case, by analyzing the deformed states of the element lights reflected from the curved surface of each object in the light source matrix patterned in the form of a two-dimensional array, it is possible to construct a three-dimensional image of the object. When the VCSEL array is fabricated according to the embodiment of the structured light source patterned in the form of such a two-dimensional array, the light source patterned in the form of a two-dimensional array in which the characteristics of each element light source are uniform. Matrix can be provided. However, the VCSEL required for the application may require high power optical devices with low power consumption while capable of light output of several to several tens of watts and short pulses of 1 to 10 ns or more than 100 MHz. The modulation equivalent circuit of the optical device may be represented as an RC circuit, and in the RC circuit, the characteristic time for determining the modulation rate may be expressed as a product of resistance and capacitance. Therefore, in order to realize a device capable of high-speed modulation and high photoelectric conversion efficiency, it is important to secure low resistance. Therefore, the present invention can provide a solution that is most suitable for providing a light source for 3D face recognition and 3D imaging. In addition, the laser device according to the present invention is an optical communication device, CCTV, night vision for cars, motion recognition. It can be used as a low cost VCSEL light source in many applications such as medical / treatment, communication devices for IoT, thermal tracking cameras, thermal imaging cameras, solid state laser (SOL) pumping, and heating processes for bonding plastic films.

Although described above with reference to the embodiments are only examples and are not intended to limit the present invention, those skilled in the art to which the present invention pertains are not exemplified above within the scope not departing from the essential characteristics of the present embodiment. It will be appreciated that many variations and applications are possible. For example, each component specifically shown in the embodiment can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

Claims

Board;

A lower reflective layer disposed on the substrate;

A laser cavity including an active layer disposed on the lower reflective layer;

An oxide layer disposed on the laser cavity;

An upper reflective layer disposed on the oxide layer;

A plurality of first holes formed in the upper reflective layer and the oxide layer; And

An upper electrode disposed in the plurality of first holes and on the upper reflective layer,

The oxide layer includes a plurality of light transmitting regions spaced apart from each other,

And the plurality of first holes are arranged to surround the light transmitting area on a plane.
The method of claim 1,

The upper electrode includes a plurality of second holes overlapping the plurality of light transmitting regions in a vertical direction.

And wherein the plurality of first holes surround the second hole in a plane.
The method of claim 2,

And wherein the area of the plurality of second holes is greater than the area of the light transmissive area.
The method of claim 2,

An insulating layer disposed between the upper reflective layer and the upper electrode;

And the insulating layer is disposed inside the plurality of second holes.
The method of claim 1,

The oxide layer is connected to each other except for the region where the first hole is formed,

The upper reflective layer is a vertical cavity surface emitting laser connected to each other except for the region where the first hole is formed.
The method of claim 1,

And wherein said oxide layer comprises a plurality of oxidation regions surrounding said transmissive region.
The method of claim 6,

And wherein the plurality of oxidation regions has a shape corresponding to the shape of the first hole.
The method of claim 6,

And wherein each transmissive region is surrounded by the plurality of oxidation regions.
The method of claim 1,

And the area of the upper electrode is between 65% and 85% of the area of the laser cavity.
The method of claim 1,

And the area of the plurality of first holes is 0.1% to 50% of the area of the light transmissive area.
The method of claim 1,

And the first hole has at least one of a cross shape, a polygon shape, a circle shape, and a radial shape.
The method of claim 1,

A capping layer disposed on the oxide layer,

And wherein the aluminum composition of the capping layer is lower than the aluminum composition of the oxide layer.
Board;

A lower reflective layer disposed on the substrate;

A laser cavity including an active layer disposed on the lower reflective layer;

An oxide layer disposed on the laser cavity and including a plurality of through holes;

A capping layer disposed on the oxide layer;

An upper reflective layer disposed on the capping layer;

A plurality of first holes formed in the upper reflective layer and the oxide layer; And

An upper electrode disposed in the plurality of first holes and on the upper reflective layer,

And the plurality of first holes are arranged to surround the transmission holes on a plane.
The method of claim 13,

The upper electrode includes a plurality of second holes overlapping the plurality of through holes in a vertical direction.

And wherein the plurality of first holes surround the second hole in a plane.
The method of claim 14,

And the area of the plurality of second holes is greater than the area of the through holes.
The method of claim 14,

An insulating layer disposed between the upper reflective layer and the upper electrode;

And the insulating layer is disposed inside the plurality of second holes.
The method of claim 13,

The oxide layer is connected to each other except for the region in which the through hole and the first hole are formed.

The upper reflective layer is a vertical cavity surface emitting laser connected to each other except for the region where the first hole is formed.
The method of claim 13,

And wherein the diameter of the first hole is less than the diameter of the through hole.
The method of claim 13,

And wherein the area of the upper electrode is between 65% and 85% of the area of the laser cavity.
The method of claim 13,

And wherein the area of the first hole is between 10% and 40% of the area of the through hole.
The method of claim 13,

And the through hole has at least one of a cross shape, a polygon shape, a circle shape, an elliptical shape, and a radial shape.