KR20180112664A - Vertical Cavity Surface Emitting Lasers - Google Patents

Abstract

A vertical cavity surface emitting laser is disclosed. The vertical cavity surface emitting laser includes a substrate; a lower reflective layer disposed on the substrate; a laser cavity disposed on the lower reflective layer; an oxide layer disposed on the laser cavity and including a first hole disposed in a center thereof; an upper reflective layer disposed on the oxide layer and the first hole; and a first electrode disposed on the upper reflective layer. The upper reflective layer comprises a base layer closest to the oxide layer and the first hole. In the base layer, the thickness of a region disposed on the first hole is larger than the thickness of a region disposed on the oxide layer. It is possible to obtain the uniform diameter of an oxide aperture.

Description

{Vertical Cavity Surface Emitting Lasers}

An embodiment relates to a vertical cavity surface emitting laser.

Significant advances in commercially available vertical cavity surface emitting lasers (VCSELs) have been achieved by the introduction of oxide apertures.

The oxide aperture is formed by exposing AlGaAs layer to a high-temperature N ₂ and H ₂ O mixed gas atmosphere and diffusing H ₂ O molecules inside the AlGaAs layer, resulting in a chemical reaction with the AlGaAs material, AlO _x : As. & Lt _; / RTI >

This chemical oxidation process depends on processing conditions such as the Al content of the AlGaAs layer, the water vapor content, and the temperature of the reaction chamber, and thus it is difficult to precisely control the shape and size of the oxide aperture in the lateral direction. Therefore, there is a problem that it is difficult to uniformly form an oxide aperture on the same wafer.

Currently, the formation of oxide apertures is precisely controlled using an expensive commercial manufacturing process apparatus, but the fundamental problem can not be solved yet, and only the production cost is increased. Further, even when such a precise apparatus is used, there is a problem that an error of 1 占 퐉 or more occurs. [M. Grabherr, D. Wiedenmann, R. Jaeger, and R. King, "Fabrication and performance of tunable single-mode VCSELs in the 750 to 1000 nm range," Proc. SPIE 5737, 120-128 (2005)). Since the diameter of the oxide opening of a typical VCSEL device is about 3 to 10 mu m, a process error of 1 mu m can significantly deteriorate the yield of the device.

In addition, there is a problem in that the efficiency of the operation is extremely reduced because the oxidation process must be carried out one by one for precise control.

The embodiment provides a vertical cavity surface emitting laser with uniform oxide aperture diameter.

The embodiment provides a method of manufacturing a vertical cavity surface emitting laser capable of easily and accurately controlling oxide openings by automatically terminating the formation of an oxide aperture.

The problems to be solved in the embodiments are not limited to these, and the objects and effects that can be grasped from the solution means and the embodiments of the problems described below are also included.

A vertical cavity surface emitting laser according to an embodiment of the present invention includes a substrate; A lower reflective layer disposed on the substrate; A laser cavity disposed on the lower reflective layer; An oxide layer disposed on the laser cavity and including a first hole disposed in the center; An upper reflective layer disposed on the oxide layer and the first hole; And a first electrode disposed on the upper reflective layer, wherein the upper reflective layer includes a base layer disposed closest to the oxide layer and the first hole, and the base layer includes a region disposed on the first hole, Is thicker than the thickness of the region disposed on the oxide layer.

According to the embodiment, the oxidation process for forming the oxide openings is automatically terminated, which can improve the instability of the wet oxidation process.

In addition, it is easy to adjust the oxide aperture size by using a low-cost wet oxidation process apparatus. Also, several tens of wafers can be processed simultaneously in one process.

Thus, the manufacturing process of the vertical cavity surface emitting laser can be simplified and the process productivity can be greatly improved. In addition, the size adjustment yield of the oxide aperture can be greatly improved.

The various and advantageous advantages and effects of the present invention are not limited to the above description, and can be more easily understood in the course of describing a specific embodiment of the present invention.

1 is a conceptual diagram of a laser device according to an embodiment of the present invention,
Fig. 2 is a partially enlarged view of Fig. 1,
3 is a view showing a method of forming an oxide opening in a conventional semiconductor device,
4 is an example showing the process of filling the first hole with the epitaxial growth on the first hole,
5 is a graph showing the growth rate of the epitaxial growth on the first hole,
Fig. 6 is a first modification of Fig. 2,
Fig. 7 is a second modification of Fig. 2,
Fig. 8 is a third modification of Fig. 2,
9 is a graph of reflectance of a laser device according to an embodiment of the present invention,
10 is a graph showing the refractive index and the electric field intensity of a laser device according to an embodiment of the present invention,
11A to 11K are views showing a method of manufacturing a laser device according to an embodiment of the present invention,
12A to 12C are views showing a method of manufacturing a laser device according to another embodiment of the present invention.

The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated and described in the drawings. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terms including ordinal, such as second, first, etc., may be used to describe various elements, but the elements are not limited to these 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 a first component, and similarly, the first component may also be referred to as a second component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations 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 to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings, wherein like or corresponding elements are denoted by the same reference numerals, and redundant description thereof will be omitted.

FIG. 1 is a conceptual diagram of a laser device according to an embodiment of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 3 is a view showing a method of forming an oxide opening in a conventional semiconductor device.

1 and 2, a laser device according to an embodiment includes a substrate 10, a lower reflective layer 20 disposed on the substrate 10, a laser cavity 30 disposed on the lower reflective layer 20, An oxide layer 51 including a first hole h1 disposed at the center, an oxide layer 51 and an upper reflective layer 40 disposed on the first hole h1, an upper reflective layer 40 disposed on the upper reflective layer 40, One electrode 71, and a second electrode 11 disposed under the substrate 10.

The semiconductor structure of the laser device may be formed using a metal-organic chemical vapor deposition (MOCVD) method, a liquid phase epitaxy (LPE) method, a molecular beam epitaxy (MBE) But is not limited thereto.

The substrate 10 may be a semi-insulating or conductive substrate. Illustratively, the substrate 10 is a GaAs substrate 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 the present invention 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 techniques such as MOCVD, MBE, and the like.

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

The first lower reflection layer 21 and the second lower reflection layer 22 have effective optical thicknesses (effective optical thickness = target light wavelength / (4 x refractive index of the material)) of about 1/4 of the wavelength of light generated by the VCSEL Lt; / RTI > It is also desirable to have a reflectance of about 100% for high internal reflection of the VCSEL.

The reflectivity of the lower reflective layer 20 depends on the refractive index difference between the first lower reflective layer 21 and the second lower reflective layer 22 and the number of layers stacked on the first lower reflective layer 21 and the second lower reflective layer 22 . Therefore, in order to obtain a high reflectance, the larger the difference in the refractive index and the smaller the number of layers, the better.

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

The laser cavity 30 may be designed to provide sufficient optical gain. Illustratively, the laser cavity 30 according to the embodiment can center a well layer having a suitable thickness and composition ratio to emit light at a wavelength band of about 850 nm or 980 nm. However, the wavelength range of the laser output by the well layer is not particularly limited.

The laser cavity 30 may include a first semiconductor layer (not shown) disposed under the active layer and a second semiconductor layer (not shown) disposed over 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 the present invention is not limited thereto. The first semiconductor layer and the second semiconductor layer may not be doped with a dopant. Illustratively, 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. Illustratively, oxide layer 51 may be doped with a p-type dopant at a concentration of about 10 < ¹⁸ > cm <" ³ >

The oxide layer 51 may include a semiconductor compound containing aluminum, for example, AlAs, AlGaAs, InAlGaAs, or the like. The first hole h1 may be disposed at the center of the oxide layer 51 according to the embodiment. That is, the oxide layer 51 may have a donut shape in which a hole is formed at the center. The oxide layer 51 may have a relatively high resistance and a relatively low refractive index. Therefore, the current can be injected into the first hole h1, so that laser light can be collected at the center of the device. That is, the first hole h1 can pass current and light.

Referring to FIG. 3, the laser structure can oxidize by exposing the sidewalls of the oxide layer 51. Oxidation can progress gradually to the center of the sidewall. The oxidized outer portion 1a is increased in resistance and the unoxidized central portion 1b can function as an oxide aperture for passing current or light.

However, the degree of oxidation of the oxidized layer 51 can be greatly affected by various conditions such as the composition of the semiconductor compound contained in the oxidized layer 51, the orientation of the compound, the thickness of the layer, and the oxidation process. That is, it is very difficult to precisely control the oxide aperture.

Referring again to FIGS. 1 and 2, in the embodiment, even if the oxidation conditions are changed, if the oxidation layer 51 in which the first holes h1 are formed is oxidized, there is no region to be oxidized any more. This is because the upper reflective layer 40 disposed inside the first hole h1 is not well oxidized even when exposed to oxygen. That is, the upper reflection layer 40 disposed inside the first hole h1 can serve as a stopper of the oxidation reaction for automatically terminating the oxidation.

Therefore, there is an advantage that an oxide opening corresponding to the diameter of the first hole h1 can be provided without precisely controlling the degree of oxidation. Therefore, the manufacturing process can be simplified and the yield can be improved. In addition, even when several tens of wafers are oxidized by one oxidation process, uniform oxide openings can be produced, and the production speed can be increased.

Therefore, the oxidation layer 51 according to the embodiment can change the conditions so that the oxidation reaction occurs well. Illustratively, as the thickness of the oxide layer 51 increases, as the aluminum composition increases, as the doping concentration increases, oxidation reaction may occur more easily.

The thickness of the oxide layer 51 may be 50 Å to 5000 Å. When the thickness of the oxide layer 51 is less than 50 angstroms, there is a problem that the process time becomes too long because the oxidation rate is very low. When the thickness is greater than 5000 angstroms, cracks occur at the end of the oxide opening due to shrinkage after oxidation there is a problem.

The doping concentration of the oxide layer 51 may be 1 x 10 ¹⁵ cm ^-3 to 1 x 10 ²⁰ cm ^-3 . When the doping concentration of the oxide layer 51 is less than 1 x 10 ¹⁵ cm ^-3 , there is a problem that the oxidation rate is lowered and the process becomes longer. When the doping concentration is larger than 1 × 10 ²⁰ cm ^-3 , And / or there is a high risk of increased optical losses.

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 that the oxidation rate is slow and the process becomes long.

A capping layer 52 may be disposed on the oxide layer 51. The capping layer 52 can prevent the oxide layer 51 from being exposed to the external environment during or after the process. As described above, the oxidation layer 51 can be designed to have a high aluminum composition and a high doping concentration so that the oxidation layer 51 can be easily oxidized. Thus, in the absence of the capping layer 52, the oxide layer 51 may be already oxidized before proceeding with the oxidation process. The growth of the upper reflective layer may be difficult because the semiconductor layer is difficult to grow on the oxidized layer 51 already oxidized. Accordingly, the capping layer 52 can prevent the oxide layer 51 from being oxidized in advance before the oxidation process.

The oxide layer 51 according to the regrown layer of the upper reflective layer 40 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 a semiconductor layer 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.

The capping layer 52 may be formed of one or more layers selected from one or more of GaAs, AlGaAs, InAlGaAs, AlGaAsSb, AlGaAsP, GaInP, InGaAsP, and AlInGaP.

If the capping layer 52 comprises aluminum, the aluminum composition of the capping layer 52 may be less than the aluminum composition of the oxide layer 51. [ Illustratively, the aluminum composition of the capping layer 52 may be between 0% and 60%. If the aluminum composition of the capping layer 52 is greater than 60%, the surface of the capping layer 52 may be exposed to the air during the process and may be oxidized. Even after forming the upper reflective layer 40, There is a problem that the capping layer 52 is oxidized at the same time.

The thickness of the capping layer 52 may range from 2.5 A to 5000 A. When the thickness of the capping layer 52 is 2.5 angstroms or less, the capping layer 52 is too thin to effectively block the penetration of oxygen. When the thickness of the capping layer 52 is 5000 angstroms or more, There is a problem that it is difficult to form a uniform and uniform interface.

The first intermediate layer 81 and the second intermediate layer 82 may be disposed between the laser cavity 30 and the oxide layer 51. [ The first intermediate layer 81 may have the same composition as the base layer 41 or the first upper reflective layer 42a. The second intermediate layer 82 may have the same composition as the second upper reflective layer 42b. Illustratively, the base layer 41 may be GaAs or AlGaAs, the first intermediate layer 81 may be GaAs, and the second intermediate layer 82 may be AlGaAs.

The first intermediate layer 81 can protect the laser cavity 30 during the oxidation process of the oxide layer 51. [ Therefore, the aluminum composition of the first intermediate layer 81 may be smaller than that of the second intermediate layer 82. Illustratively, the thickness of the first intermediate layer 81 may be 1 nm to 30 nm, but is not limited thereto.

Generally, when the oxidation layer 51 is oxidized, the material becomes amorphous and the film quality may be somewhat lowered. Accordingly, if the amorphized layer having a somewhat lower film quality is directly bonded to the laser cavity where light is generated, the reliability of the device may be deteriorated. Accordingly, the second intermediate layer 82 can be formed before the oxide layer to prevent the amorphized layer from directly contacting the laser cavity.

The upper reflective layer 40 may be disposed on the oxide layer 51 and the upper portion of the first hole h1. The upper reflective layer 40 includes an oxide layer 51 and a base layer 41 disposed on the first hole h1, a plurality of first upper reflective layers 42a disposed on the base layer 41, (42b).

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

The upper reflective layer 40 may be doped to have a different polarity from the lower reflective layer 20. Illustratively, 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.

The upper reflective layer 40 may have fewer layers than the lower reflective layer 20 to reduce the reflectivity from the VCSEL so that the emission direction of the laser light is opposite to that of the substrate 10. [ That is, the reflectance of the upper reflective layer 40 may be smaller than that of the lower reflective layer 20. [

The reflectance of the upper reflective layer 40 can be designed based on the thickness from the second intermediate layer 82 to the uppermost surface of the upper reflective layer 40. [ In this case, the first region S1 is an opening region (In-Phase region) in which light is distributed and amplified, and the outer region S2 of the first region S1 is a region anti-phase region). The diameter of the first region S1 may be the diameter of the region where the upper reflective layer 40 is exposed through the second hole h2 of the ohmic layer 61. [

According to the embodiment, the diameter of the first hole h1 may be larger than the diameter of the first region S1. Since most of the laser light is distributed in the first region S1, the end of the first hole h1 does not affect the light distribution and the light multiplying region. Accordingly, optical scattering and light absorption at the end of the first hole h1 can be minimized. Therefore, the light efficiency can be increased, and the lifetime of the device can be improved as compared with the conventional structure.

If the diameter of the first hole h1 is disposed inside the first region S1 or the diameter thereof is the same, light may be scattered or absorbed at the end of the first hole h1.

The diameter of the first region S1 may be 6% to 98% of the diameter of the first hole h1 based on 100% of the diameter of the first hole h1. The diameter of a typical oxide opening is about 3 to 15 占 퐉. At this time, when the diameter is less than 6%, the diameter of the first region S1 becomes 1 탆 or less, and the light output may drop sharply. If the diameter is larger than 98%, the end of the first hole h1 The light may be scattered or absorbed.

The upper surface 41a of the base layer 41 of the upper reflective layer 40 may have a flat surface. That is, the base layer 41 covers the first hole h1, so that the top surface can be flat. According to this structure, since the plurality of first upper reflective layer 42a and the second upper reflective layer 42b are disposed on the flat base layer 41, the reliability can be improved.

The base layer 41 includes a region disposed on the oxide layer 51 and a region disposed in the first hole h1 and the thickness d2 of the region disposed in the first hole h1 is smaller than the thickness d2 of the oxide layer 51. [ May be thicker than the thickness (d3) of the region disposed on the substrate.

The ratio d3 / h1 of the maximum thickness d3 of the base layer 41 to the maximum diameter of the first holes h1 may be 0.001 to 0.3. If the thickness is out of this range, the thickness of the base layer 41 may deviate from an appropriate range and the performance of the device may be deteriorated.

The sum of the thickness of the base layer 41 disposed in the first hole and the thickness of the first intermediate layer 81 can satisfy 1, 3, 5, 7, 9, 11 QWOT (Quarter-Wave Optical Thickness). Illustratively, if the target wavelength is 980 nm, the thickness of 1 QWOT may be approximately 69.47 nm. However, it is not necessarily limited to this, and it may have an effective optical thickness that is at least one of 1/4 3/4, 5/4, 7/4, 9/4, and 11/4 of the optical wavelength. That is, the base layer 41 and the first intermediate layer 81 may function as one second upper reflective layer 42b. Therefore, the base layer 41 and the first intermediate layer 81 may have the same composition. Illustratively, the base layer 41 and the first intermediate layer 81 may be GaAs. As a result, the base layer 41 may not be oxidized even if the oxidation layer 51 is oxidized.

The first electrode 71 may be disposed on the upper reflective layer 40 and the second electrode 11 may be disposed on the lower portion of the substrate 10. However, the present invention is not limited to this, and it may be arranged in the exposed region after exposing the upper portion of the substrate 10 of the second electrode 11.

The first electrode 71 and the second electrode 11 may be formed of one selected from the group consisting of ITO (indium tin oxide), IZO (indium zinc oxide), IZTO (indium zinc tin oxide), IAZO (indium aluminum zinc oxide), IGZO ), IGTO (indium gallium tin oxide), AZO (aluminum zinc oxide), ATO (antimony tin oxide), GZO (gallium zinc oxide), IZON (IZO Nitride), AGZO ZnO, ZnO, IrOx, RuOx, NiO, RuOx / ITO, Ni / IrOx / Au or Ni / IrOx / Au / ITO, Ag, Ni, Cr, Ti, Al, Rh, Pd, Ru, Mg, Zn, Pt, Au, and Hf. However, the present invention is not limited to these materials.

Illustratively, the first electrode 71 may have a plurality of metal layers (e.g., Ti / Pt / Au). At this time, the thickness of Ti may be about 100 to 400 angstroms, and the thickness of Au may be 3000 to 20000 angstroms, but not always limited thereto.

The second electrode 11 may have a plurality of metal layers (e.g., AuGe / Ni / Au). At this time, the thickness of AuGe may be 1000 angstroms, the thickness of Ni may be 100 angstroms, and the thickness of Au may be 2000 angstroms, but not always limited thereto.

An ohmic layer 61 may be further disposed between the first electrode 71 and the upper reflective layer 40. The ohmic layer 61 may include a material having a band gap equal to or lower than that of the GaAs substrate 10 and having a band gap equal to or lower than the energy of the emitted laser light for low ohmic resistance. For example, the ohmic layer 61 may be selected from AlInGaAs, InGaAs, GaAs, AlInGaAsSb, AlInGaAsPSb, InGaAsP, InGaAsPSb, GaAsSb, InGaAsSb, InAsSb, AlGaAsSb, AlGaAsP and AlGaInAsP. The diameter of the second hole (h2) of the ohmic layer (61) may be smaller than the diameter of the first hole (h1). That is, since the ohmic layer 61 is disposed in an area where no light is distributed, it may not affect the light output.

FIG. 4 is a view showing a process of filling the first hole on the first hole, FIG. 5 is a view showing the growth time of the epitaxially grown on the first hole in conformity with the time in FIG. 4 FIG. 7 is a second modification of FIG. 2, and FIG. 8 is a third modification of FIG.

Referring to FIGS. 4 and 5, the base layer 41 according to the embodiment may include a step SL1 disposed on the first hole during growth on the first hole h1. At this time, the thickness of the region T1 disposed on the first hole h1 may be thicker than the thickness of the region T2 disposed on the oxide layer 51, in the base layer 41. [ As shown in FIG. 5, this thickness difference may be caused by the difference in the growth rate of the epi in the first hole region and the growth rate of the epi in the first hole region. That is, the epi growth rate in the first hole h1 is higher than the first hole h1 and the epi growth rate in the upper region of the oxide layer 51 after the completion of the planarization of the first hole, And the growth rate becomes equal.

Therefore, part of the first upper reflective layer 42a and the second upper reflective layer 42b disposed on the base layer 41 may also have stepped portions SL2 and SL3. However, the stepped portion becomes gradually smaller as the layer is stacked, and after some point, the planarization having a flat surface can be completed.

As shown in FIG. 6, the inner wall of the capping layer 52 may have a protrusion 52a having a longer length in the direction of the center of the side surface than the oxide layer 51. The projecting portion 52a can reduce the exposed area of the inner wall of the oxide layer. The length of the protrusion 52a may be greater than zero and a maximum of 3 um, but is not limited thereto. These protrusions 52a can be formed by the difference in etch rate of the epi layer. The inner wall of the oxide layer 51 may be tilted unintentionally (especially by wet chemical etching using a solution) during the etching process.

Referring to FIG. 7, the capping layer 52 may include an extension 52b extending to the inner wall of the first hole h1 of the oxide layer 51. As shown in FIG. In this case, it is possible to suppress the generation of interface defects between the upper reflective layer 40 and the oxide layer 51 disposed inside the first hole h1.

The minimum thickness of the extension 52b may be between 2.5 and 2000 Angstroms. When the thickness of the extended portion 52b is 2.5 angstroms or less, the occurrence of interface defects between the upper reflective layer 40 and the oxidized layer 51 can not be suppressed. When the thickness of the extended portion 52b is 2000 angstroms or more, A problem may occur in the uniformity of the reflective films grown near the side surface of the oxide layer 51.

The extended portion 52b is formed by forming a capping layer 52 on the oxide layer 51 and then subjecting it to a heat treatment at a high temperature in a PH ₃ atmosphere (InGaP or InGaAsP type material) or an AsH ₃ atmosphere (GaAs type material) Can be formed by moving into the relatively low first hole (h1).

Referring to FIG. 8, a light-transmitting layer 54 may be further disposed in the first hole h1 of the oxide layer 51. In FIG. The light-transmitting layer 54 may be made of a material having a high transmittance so that light emitted from the laser cavity 30 positioned at the center of the active layer can be well emitted. Illustratively, the light-transmitting layer 54 may be selected from semiconductor compounds such as InAlGaAs, InAlGaP, InGaAsP, and ZnSeS, but is not limited thereto.

FIG. 9 is a graph showing the reflectance of a laser device according to an embodiment of the present invention, and FIG. 10 is a graph illustrating a refractive index and an electric field intensity of a laser device according to an embodiment of the present invention.

9 shows that the reflectivity of the upper reflective layer 40 in the first region is about 99.5% at 940 nm to 1040 nm, while the reflectivity is relatively low at 980 nm. Therefore, it can be seen that this laser device can output laser light of about 980 nm.

11A to 11K are views showing a method of manufacturing a laser device according to an embodiment of the present invention.

11A, a substrate 10, a lower reflective layer 20, a laser cavity 30, a second intermediate layer 82, a first intermediate layer 81, an upper reflective layer 40, an oxide layer 51, And a pinning layer 52 can be formed in this order. The characteristic of each layer can be applied as it is.

Referring to FIG. 11B, a first hole h1 may be formed at the center of the capping layer 52 and the oxide layer 51 by disposing a first mask on the capping layer 52 and then etching. The first mask 81 may be, but not limited to, SiO ₂ , SixOy, Si ₃ N ₄ , Si _x N _y , SiO _x N _y , Al ₂ O ₃ , TiO ₂ , AlN or a photoresist.

11C and 11D, the upper reflective layer 40 can be re-grown on the oxide layer 51 and the first hole h1. Thus, the oxide layer 51 may be disposed between the lower reflective layer 20 and the upper reflective layer 40. [

The upper reflective layer 40 disposed on the oxide layer 51 may include a base layer 41 covering the first hole h1. The sum of the thicknesses of the base layer 41 and the first intermediate layer 81 can satisfy 1, 3, 5, 7, 9, 11 QWOT (Quarter-Wave Optical Thickness). The plurality of first upper reflective layer 42a and the second upper reflective layer 42b may be disposed on the base layer 41.

The second hole h2 may be formed by removing the region corresponding to the first groove 44 after the entirety of the ohmic layer 61 is formed on the upper reflective layer 40. [ According to the embodiment, most laser light can be emitted through the second hole h2 without being incident on the ohmic layer 61. [ Accordingly, the ohmic layer 61 can use a material having a band gap equal to or lower than that of the GaAs substrate 10 and having a bandgap equal to or lower than the energy of the emission laser light.

11E to 11H, a first electrode 71 is formed on the ohmic layer 61 and a second mask 82 is formed thereon. Thereafter, the second mask 82 is removed to form a border region It can be etched.

Referring to FIG. 11I, the side surface of the oxidized layer 51 can be oxidized. According to the embodiment, since the aperture is formed in which light is already injected by the first hole h1, it is not necessary to precisely control the degree of oxidation of the oxide layer 51. [ That is, when the oxidation layer 51 is completely oxidized, the oxidation process can be automatically terminated.

Illustratively, the oxidation step may be performed by exposing the sample to a reaction tube equipped with a mixed gas atmosphere of N ₂ and H ₂ O at a temperature in the vicinity of 300 ° C. to 450 ° C. for about 30 to 50 minutes, but is not limited thereto. In addition, the oxide layer 51 according to the embodiment can control the thickness, the doping concentration, and the aluminum composition so that the oxidation proceeds rapidly.

Referring to FIG. 11J, the protective layer 90 may be disposed in the etched edge region. The protective layer 90 may be made of various materials capable of protecting the outside of the laser device. Illustratively, the protective layer 90 may be at least one of SiO ₂ , Si ₃ N ₄ , SiON, Ta ₂ O ₅ , HfO ₂ , BCB (benzocyclobutene), and polyimide. Further, the protective layer 90 may be further cured if necessary.

Referring to FIG. 11K, a pad electrode 72 connected to the first electrode 71 may be formed. The second electrode 11 may be formed under the substrate 10.

12A to 12C are views showing a method of manufacturing a laser device according to another embodiment of the present invention.

12A and 12B, a substrate 10, a lower reflective layer 20, a laser cavity 30 in which an active layer is positioned at a center, an upper reflective layer 40, an oxide layer 51, and a capping layer 52 And then the first mask 81 is disposed on the capping layer 52 and then etched to form the first hole h1 in the center of the capping layer 52 and the oxide layer 51. [

The capping layer 52 may be formed on the oxide layer 51 and then the capping layer 52 may be thermally treated to form the extension 52b of the capping layer 52 on the inner wall of the first hole h1. Specifically, when a capping layer 52 is formed on the oxide layer 51 and a high-temperature heat treatment is performed in a PH ₃ atmosphere (InGaP or InGaAsP-based material) or an AsH ₃ atmosphere (GaAs-based material), the capping material at the edge is relatively And the extended portion 52b can be formed by moving to the inside of the first hole h1. At this time, the heat treatment temperature may be 500 ° C to 900 ° C. According to this structure, the extended portion 52b can serve as a stopper for preventing the progress of oxidation.

Referring to FIG. 12C, an upper reflective layer 40 may be formed on the oxide layer 51 and the first hole h1. The subsequent process can proceed in the same manner as in Figs. 11E to 10K.

The laser device according to the present embodiment can be used as a light source of 3D face recognition and 3D imaging technology. 3D face recognition and 3D imaging techniques require a light source matrix patterned in a two-dimensional array. The patterned light source matrix in the form of a two-dimensional array can be irradiated onto the object and the pattern of the reflected light can be analyzed. At this time, among the light source matrix patterned in the form of a two-dimensional array, by analyzing the deformed states of the element lights reflected from the curved surface of each shape object, a three-dimensional image of the object can be formed. A VCSEL array according to an embodiment of the present invention can be fabricated by structured light sources patterned in the form of a two-dimensional array. A structured light source patterned in a two- Matrix can be provided.

In addition, the laser device according to the present invention can be used in various fields such as an optical communication device, a CCTV, a night vision for an automobile, a motion recognition, a medical treatment / therapy, a communication device for IoT, Pumping applications, heating processes for bonding plastic films, and the like, can be used as low-cost VCSEL light sources.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (15)

Board;
A lower reflective layer disposed on the substrate;
A laser cavity disposed on the lower reflective layer;
An oxide layer disposed on the laser cavity and including a first hole disposed in the center;
A capping layer disposed over the oxide layer;
An upper reflective layer disposed on the capping layer and the first hole; And
And a first electrode disposed on the upper reflective layer,
Wherein the upper reflective layer comprises a base layer disposed closest to the oxide layer and the first hole,
Wherein the base layer is thicker than the thickness of the region disposed on the first hole and the thickness of the region disposed on the oxide layer.
The method according to claim 1,
Wherein the upper surface of the base layer has a planar surface.
The method according to claim 1,
The upper reflective layer
A plurality of first upper reflective layers and a plurality of second upper reflective layers disposed on the base layer,
The plurality of first upper reflection layers and the second upper reflection layers are alternately arranged,
Wherein the first upper reflective layer has a refractive index higher than that of the second upper reflective layer.
The method of claim 3,
Wherein the base layer has the same composition as the second upper reflective layer.
The method according to claim 1,
Wherein the ratio of the maximum thickness of the base layer to the maximum diameter of the first hole is 0.001 to 0.3.
The method of claim 3,
Wherein the base layer includes a stepped portion disposed on the first hole,
Wherein a portion of the plurality of first upper reflective layers and the second upper reflective layer comprises a step disposed on the first hole.
The method according to claim 1,
Wherein the capping layer is smaller in aluminum composition than the oxide layer.
The method according to claim 1,
Wherein the capping layer comprises at least one layer comprising at least one of GaAs, AlGaAs, InAlGaAs, AlGaAsSb, AlGaAsP, GaInP, InGaAsP, AlInGaP.
8. The method of claim 7,
Wherein the capping layer includes protrusions protruding from the oxide layer toward the center of the first hole.
10. The method of claim 9,
Wherein the length of the projection is greater than zero and less than 3 um.
8. The method of claim 7,
Wherein the capping layer comprises an extension extending into the inner wall of the first hole.
12. The method of claim 11,
Wherein the extension is thinner than the thickness of the capping layer.
The method according to claim 1,
And a first intermediate layer disposed between the oxide layer and the laser cavity,
Wherein the first intermediate layer has the same composition as the base layer.
14. The method of claim 13,
Wherein the first intermediate layer is in contact with the base layer in a first hole.
15. The method of claim 14,
Wherein the sum of the thicknesses of the first intermediate layer and the base layer satisfies at least one of 1, 3, 5, 7, 9, and 11 QWOT (Quarter-Wave Optical Thickness).

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