CN117410826A - Vertical cavity surface emitting laser with improved oxidation confinement structure and method of fabricating the same - Google Patents
Vertical cavity surface emitting laser with improved oxidation confinement structure and method of fabricating the same Download PDFInfo
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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]
- H01S5/18308—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] having a special structure for lateral current or light confinement
- H01S5/18311—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] having a special structure for lateral current or light confinement using selective oxidation
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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
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/068—Stabilisation of laser output parameters
- H01S5/06821—Stabilising other output parameters than intensity or frequency, e.g. phase, polarisation or far-fields
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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
- H01S2304/00—Special growth methods for semiconductor lasers
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Abstract
The invention discloses a vertical cavity surface emitting laser with an improved oxidation limiting structure. It includes a current confinement structure disposed over the active layer; the current limiting structure comprises at least one current limiting layer, and at least one current limiting layer is an improved oxidation limiting layer; the improved oxidation limiting layer comprises a central region and a peripheral region surrounding the central region, wherein the central region is high in aluminum content Al x Ga 1‑x And the As layer is filled with at least one modification structure, wherein the modification structure is a non-stoichiometric semiconductor material with a refractive index higher than that of aluminum oxide or a non-stoichiometric semiconductor material with an air gap in between. The invention also discloses a manufacturing method of the vertical cavity surface emitting laser with the improved oxidation limiting structure. The invention can form a similar noncircular shape by improving the oxidation limiting structureNon-uniform current density effects due to the oxidized pore structure.
Description
Technical Field
The invention relates to a Vertical-Cavity Surface-Emitting Laser (VCSEL) and a manufacturing method thereof, belonging to the technical field of semiconductor lasers.
Background
The vertical cavity surface emitting laser has higher optical power and can well control the transverse mode, so that the vertical cavity surface emitting laser has the advantages of optical communication, gesture sensing sensor, printing and magnetismThe method has great application prospect in the fields of storage and the like. However, because the device structure has the defects of thin active region, short cavity length, small single-layer gain and the like, in order to improve the effective photon limiting capability, an oxidation limiting type DBR (Distributed Bragg Reflector ) structure is adopted as a current limiting structure at present, and is generally called as an oxidation limiting type VCSEL for short. The oxidation limiting VCSEL adopts wet oxidation process to make the peripheral region of DBR layer have high Al content x Ga 1-x Oxidation of As (x.gtoreq.0.95) layer to AlO x A layer (commonly referred to as oxide holes) and a DBR located directly above the active layer with a high aluminum content Al x Ga 1-x The As layer is not oxidized, forming a circular annular current channel, and this oxidation-limited structure has very good lateral control over the current injected into the active region, so that there is little current in the lateral direction. Meanwhile, the oxidation limiting structure can also transversely limit the light emitted by the laser active region to a certain extent, so that the mode of the laser can be reduced under a certain condition, and the laser can be well stabilized due to the reduction of the mode.
The circular oxidation hole structure has symmetry, and current is evenly injected into the active layer through the circular oxidation holes in the working process, and current density is uniform and consistent everywhere. The uniform and symmetrical current density makes the different modes easy to mutually change, and causes the unstable optical power of the laser. The rise and fall times that form the differentiation between different modes in optical communication applications cause eye diagram deterministic jitter, which becomes more severe due to the differential mode delay phenomenon that occurs when a vcsels is coupled to multimode fibers. In theory, the non-circular oxidation hole structure can generate non-uniform current density, and the abnormal unstable mode in the working process of the laser is improved.
In order to generate the oxidation limiting structure of the noncircular oxidation hole, the existing VCSEL laser generally adopts a non (100) crystal face GaAs substrate to grow DBR materials and quantum well materials, and the anisotropy of gains of the materials in different directions of an (n 11) crystal face and the difference of wet oxidation rates in two crystal directions of [ -110] and [ -110] are utilized to cause the noncircular oxidation hole, so that the modal stability of the VCSEL laser is improved. However, the difference of the growth of the material in different directions of the (n 11) crystal face can cause the roughness of the growth surface of the material, cause the mutual penetration of different quantum well materials at the interface, influence the quantum well efficiency and reduce the performance of the laser; and meanwhile, the doping concentration of carbon (C) in the P-DBR can be reduced, so that the threshold current of the VCSEL laser is increased finally, and the reliability of the laser is reduced. In addition, the non (100) crystal face GaAs substrate sheet is relatively expensive, and the chip cutting is relatively difficult.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art and providing a vertical cavity surface emitting laser with an improved oxidation limiting structure, wherein the non-uniform current density effect similar to that caused by a non-circular oxidation hole structure can be formed by improving the oxidation limiting structure.
The technical scheme adopted by the invention specifically solves the technical problems as follows:
the vertical cavity surface emitting laser with improved oxidation limiting structure includes current limiting structure over the active layer; the current limiting structure comprises at least one current limiting layer, and at least one current limiting layer is an improved oxidation limiting layer; the improved oxidation limiting layer comprises a central region and a peripheral region surrounding the central region, wherein the central region is high in aluminum content Al x Ga 1-x The As layer is filled with at least one modification structure, the modification structure is a non-stoichiometric semiconductor material with a refractive index higher than that of aluminum oxide or a non-stoichiometric semiconductor material with an air gap in the middle, the refractive index of the modification structure is higher than that of aluminum oxide, and the volume ratio of the modification structure in the space of the peripheral region is 18-45%.
Preferably, the non-stoichiometric semiconductor material is ZnO x 、HfO x Or ZrO(s) x 。
Preferably, the current confinement structure comprises a plurality of current confinement layers.
Further preferably, the high aluminum content Al in the plurality of current confinement layers x Ga 1-x The radius of the As layer increases with the direction away from the active layer.
Preferably, the trim structure communicates with an outer edge of the peripheral region.
Preferably, the vertical cavity surface emitting laser of the improved oxidation confinement structure is grown using a (100) crystal plane GaAs substrate.
A method of fabricating a vertical cavity surface emitting laser having an improved oxidation confinement structure as described above, comprising:
etching the epitaxial wafer to form Al with high aluminum content x Ga 1-x An active region mesa with the As layer exposed;
an oxidation step of adding Al with high aluminum content x Ga 1-x Al in the As-layer peripheral region x Ga 1-x As is oxidized to aluminum oxide, and Al in the middle region x Ga 1-x As is not oxidized, thereby forming an oxidation-limiting layer;
further comprises:
and an oxidation limiting layer modification step of removing part of aluminum oxide in at least one oxidation limiting layer and filling the modification structure to form an improved oxidation limiting layer.
Preferably, a portion of the aluminum oxide in the at least one oxidation-limiting layer is removed using an acid or alkali etch process.
Preferably, the modified structure is filled using an ALD (atomic layer deposition) or MLD (molecular layer deposition) process.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
the invention is based on the existing oxidation limiting structure, carries out local improvement modification on the oxidation limiting layer, removes the aluminum oxide part of the peripheral area of the traditional oxidation limiting layer and fills the non-stoichiometric semiconductor material with the refractive index higher than that of the aluminum oxide; because the semiconductor material has weak conductivity, the current injected into the active layer through the peripheral area generates local micro-leakage, the possibility that the current density injected into the active layer is uniform is eliminated, and the mode of the laser is stabilized; meanwhile, as the refractive index of the semiconductor material is larger than that of aluminum oxide, the light limiting capacity of the modified peripheral region on the laser is weaker than that of the unmodified peripheral region, the non-uniform current density effect similar to that of a non-circular oxide hole structure is formed, and the (100) crystal face GaAs substrate which is low in cost and easy to process can be adopted.
Drawings
FIG. 1 is a top view of a VCSEL with an improved oxidation confinement structure in accordance with the present invention;
FIGS. 2-5 are schematic cross-sectional views of a VCSEL having different modified structures along the A-A direction;
FIG. 6 is a schematic cross-sectional view of a VCSEL with an improved oxidation confinement structure along the B-B direction in accordance with the present invention;
fig. 7-26 are schematic views of the fabrication process of the vertical cavity surface emitting laser of the improved oxidation confinement structure of the present invention.
The reference numerals in the drawings have the following meanings:
1. a GaAs substrate; 2. a buffer layer; 3. an N-type DBR; 4. an active layer; 5. a P-type DBR; 6. a current limiting structure; 6-1, high aluminum content Al x Ga 1-x An As layer; 6-2, an aluminum oxide layer; 6-3, modifying the structure; 7. A current limiting channel; 8. a dielectric layer; 9. a P-type metal; 10. an N-type metal; 11. and a light exit window.
Detailed Description
Aiming at the defects of the prior art, the solution idea of the invention is to take the existing oxidation limiting structure as the basis, carry out local improvement modification on the oxidation limiting layer, remove the aluminum oxide part of the peripheral area of the traditional oxidation limiting layer and fill the non-stoichiometric semiconductor material with the refractive index higher than that of the aluminum oxide, so as to generate the non-uniform current density effect similar to that of a non-circular oxidation hole structure.
The invention provides a vertical cavity surface emitting laser with an improved oxidation limiting structure, which comprises a current limiting structure arranged on an active layer; the current limiting structure comprises at least one current limiting layer, and at least one current limiting layer is an improved oxidation limiting layer; the improved oxidation-limiting layer includes a central region and a periphery surrounding the central regionA region with a high aluminum content Al x Ga 1-x The As layer is filled with at least one modification structure, the modification structure is a non-stoichiometric semiconductor material with a refractive index higher than that of aluminum oxide or a non-stoichiometric semiconductor material with an air gap in the middle, the refractive index of the modification structure is higher than that of aluminum oxide, and the volume ratio of the modification structure in the space of the peripheral region is 18-45%.
Preferably, the non-stoichiometric semiconductor material is ZnO x 、HfO x Or ZrO(s) x 。
Preferably, the current confinement structure comprises a plurality of current confinement layers.
Further preferably, the high aluminum content Al in the plurality of current confinement layers x Ga 1-x The radius of the As layer increases with the direction away from the active layer.
From a manufacturing process point of view, it is preferred that the modification structure communicates with the outer edge of the peripheral region.
The invention can use a GaAs substrate with a non (100) crystal face or a GaAs substrate with a (100) crystal face; preferably, the vertical cavity surface emitting laser of the improved oxidation confinement structure is grown using a (100) crystal plane GaAs substrate.
In order to simplify the manufacturing process, the invention further provides the following technical scheme based on the traditional oxidation limiting VCSEL manufacturing process:
the method for manufacturing the vertical cavity surface emitting laser with the improved oxidation limiting structure comprises the following steps:
etching the epitaxial wafer to form Al with high aluminum content x Ga 1-x An active region mesa with the As layer exposed;
an oxidation step of adding Al with high aluminum content x Ga 1-x Al in the As-layer peripheral region x Ga 1-x As is oxidized to aluminum oxide, and Al in the middle region x Ga 1-x As is not oxidized, thereby forming an oxidation-limiting layer;
further comprises:
and an oxidation limiting layer modification step of removing part of aluminum oxide in at least one oxidation limiting layer and filling the modification structure to form an improved oxidation limiting layer.
Preferably, a portion of the aluminum oxide in the at least one oxidation-limiting layer is removed using an acid or alkali etch process.
For the convenience of public understanding, the following detailed description of the technical scheme of the invention is provided with reference to the accompanying drawings:
fig. 1, 2 and 6 show the basic structure of a particular embodiment of a vertical cavity surface emitting laser of the present invention with improved oxidation confinement structure, comprising: the light emitting diode comprises a GaAs substrate 1, a buffer layer 2, an N-type DBR3, an active layer 4, a P-type DBR 5, a dielectric layer 8, P-type metal 9, N-type metal 10 and a light emitting window 11; a current confinement structure 6 is provided in the P-type DBR 5 above the active layer 4; the current confinement structure 6 in this embodiment includes upper and lower current confinement layers, the central regions of both of which are high aluminum content Al x Ga 1-x As layer 6-1, high aluminum content Al of two current confinement layers x Ga 1-x The region between the As layers 6-1 forms a current limiting channel 7; high aluminum content Al in upper current confinement layer x Ga 1-x The radius of the As layer is larger than that of the Al with high aluminum content in the lower current limiting layer x Ga 1-x Radius of the As layer; the lower current confinement layer in this embodiment is a conventional oxidation confinement layer, and its peripheral region is made of AlO x The aluminum oxide layer 6-2 is formed, the upper current confinement layer is a modified oxidation confinement layer, the peripheral region is the aluminum oxide layer 6-2 filled with at least one modification structure 6-3, the modification structure 6-3 is a non-stoichiometric semiconductor material with higher refractive index than aluminum oxide (such as ZnO x 、HfO x Or ZrO(s) x Etc.), i.e. to modify part of the AlO in the peripheral region of the oxidation-limiting layer x Is filled and replaced by a modified structure composed of a non-stoichiometric semiconductor material with a higher refractive index than aluminum oxide; the volume ratio of the modification structure in the peripheral area space of the upper current limiting layer is 18-45%.
Figures 1, 3 and 6 illustrate the basic structure of another embodiment of a VCSEL of the improved oxidation confinement structure of the present invention,it comprises the following steps: the light emitting diode comprises a GaAs substrate 1, a buffer layer 2, an N-type DBR3, an active layer 4, a P-type DBR 5, a dielectric layer 8, P-type metal 9, N-type metal 10 and a light emitting window 11; a current confinement structure 6 is provided in the P-type DBR 5 above the active layer 4; the current confinement structure 6 in this embodiment includes upper and lower current confinement layers, the central regions of both of which are high aluminum content Al x Ga 1-x As layer 6-1, high aluminum content Al of two current confinement layers x Ga 1-x The region between the As layers 6-1 forms a current limiting channel 7; high aluminum content Al in upper current confinement layer x Ga 1-x The radius of the As layer is larger than that of the Al with high aluminum content in the lower current limiting layer x Ga 1-x Radius of the As layer; the lower current confinement layer in this embodiment is a conventional oxidation confinement layer, and its peripheral region is made of AlO x The aluminum oxide layer 6-2 is formed, the upper current confinement layer is a modified oxidation confinement layer, the peripheral region is the aluminum oxide layer 6-2 filled with at least one modification structure 6-3, and the modification structure 6-3 is a non-stoichiometric semiconductor material (such as ZnO) with air gap in between and higher refractive index than aluminum oxide x 、HfO x Or ZrO(s) x Etc.), i.e. in the present embodiment, part of AlO in the peripheral region of the oxidation-limiting layer is modified x Filling and replacing the aluminum oxide with a modified structure formed by a non-stoichiometric semiconductor material with an air gap having a higher refractive index than aluminum oxide; the volume ratio of the modification structure in the peripheral area space of the upper current limiting layer is 18-45%.
Fig. 1, 4 and 6 show the basic structure of another embodiment of the vertical cavity surface emitting laser of the improved oxidation confinement structure of the present invention, comprising: the light emitting diode comprises a GaAs substrate 1, a buffer layer 2, an N-type DBR3, an active layer 4, a P-type DBR 5, a dielectric layer 8, P-type metal 9, N-type metal 10 and a light emitting window 11; a current confinement structure 6 is provided in the P-type DBR 5 above the active layer 4; the current confinement structure 6 in this embodiment includes upper and lower current confinement layers, the central regions of both of which are high aluminum content Al x Ga 1-x As layer 6-1, high aluminum content Al of two current confinement layers x Ga 1-x As layer 6The region between-1 forms a current confinement channel 7; high aluminum content Al in upper current confinement layer x Ga 1-x The radius of the As layer is larger than that of the Al with high aluminum content in the lower current limiting layer x Ga 1-x Radius of the As layer; both current confinement layers in this embodiment are modified oxidation confinement layers, the peripheral region is an aluminum oxide layer 6-2 filled with at least one modified structure 6-3, the modified structure 6-3 in this embodiment is a non-stoichiometric semiconductor material with a higher refractive index than aluminum oxide (e.g. ZnO x 、HfO x Or ZrO(s) x Etc.), i.e. to modify part of the AlO in the peripheral region of the oxidation-limiting layer x Is filled and replaced by a modified structure composed of a non-stoichiometric semiconductor material with a higher refractive index than aluminum oxide; the volume ratio of the modification structure in the peripheral area space of the two current limiting layers is 18-45%.
Fig. 1, 5 and 6 show the basic structure of a further embodiment of the vertical cavity surface emitting laser of the improved oxidation confinement structure of the present invention, comprising: the light emitting diode comprises a GaAs substrate 1, a buffer layer 2, an N-type DBR3, an active layer 4, a P-type DBR 5, a dielectric layer 8, P-type metal 9, N-type metal 10 and a light emitting window 11; a current confinement structure 6 is provided in the P-type DBR 5 above the active layer 4; the current confinement structure 6 in this embodiment includes upper and lower current confinement layers, the central regions of both of which are high aluminum content Al x Ga 1-x As layer 6-1, high aluminum content Al of two current confinement layers x Ga 1-x The region between the As layers 6-1 forms a current limiting channel 7; high aluminum content Al in upper current confinement layer x Ga 1-x The radius of the As layer is larger than that of the Al with high aluminum content in the lower current limiting layer x Ga 1-x Radius of the As layer; both current confinement layers in this embodiment are modified oxide confinement layers, the peripheral region is an aluminum oxide layer 6-2 filled with at least one modified structure 6-3, the modified structure 6-3 in this embodiment is a non-stoichiometric semiconductor material with an air gap in between having a refractive index higher than that of aluminum oxide (e.g. ZnO x 、HfO x Or ZrO(s) x Etc.), i.e. in the present embodiment, part of AlO in the peripheral region of the oxidation-limiting layer is modified x Quilt toolFilling substitution of a modified structure formed by a non-stoichiometric semiconductor material with an air gap having a higher refractive index than aluminum oxide; the volume ratio of the modification structure in the peripheral area space of the two current limiting layers is 18-45%.
The above four embodiments are described by taking a current confinement structure including two current confinement layers as an example, and a single current confinement layer or more current confinement layers may be actually provided as needed to form the current confinement structure of the present invention; when there are two or more current confinement layers, all of the current confinement layers may be provided as the improved oxidation confinement layers, or only a part of the current confinement layers may be provided as the improved oxidation confinement layers; as long as at least one of the current confinement layers is said modified oxidation confinement layer, i.e. falls within the scope of the invention as claimed. In addition, the modified structures in the modified oxidation-limiting layer may be both non-stoichiometric semiconductor materials having a refractive index higher than that of aluminum oxide, or both non-stoichiometric semiconductor materials having an air gap having a refractive index higher than that of aluminum oxide, or a combination of both modified structures.
For ease of understanding, the preferred fabrication process of the VCSEL with the improved oxidation confinement structure described above is described in further detail below; the preferred manufacturing process is improved based on the traditional oxidation-limited VCSEL manufacturing process and specifically comprises the following steps:
step 1, selecting epitaxial wafer with section as shown in FIG 7, arranging two high aluminum content Al on the active layer x Ga 1-x As layer, and the two high aluminum content Al x Ga 1-x The aluminum content of the As layer decreases progressively along the direction away from the active layer (or the aluminum content of the upper high aluminum content AlxGa1-xAs layer is equal to the aluminum content of the lower high aluminum content AlxGa1-xAs layer, and the thickness of the upper high aluminum content AlxGa1-xAs layer is larger than that of the lower high aluminum content AlxGa1-xAs layer); coating photoresist on the surface of the epitaxial wafer, wherein the thickness of the photoresist is 5-15 um; exposing and developing the photoresist to obtain a circular photoresist mask, see fig. 8;
step 2, etching the epitaxial wafer obtained in the step 1 by adopting an ICP dry etching process, wherein etching gas is Cl 2 +BCl 3 Or Cl 2 +SiCl 4 Etching to 1-10 pairs of N-DBR under the active layer to obtain high aluminum content Al to be oxidized x Ga 1-x The As layer is exposed, see fig. 9; removing the photoresist to obtain an active region platform, see fig. 10;
step 3, oxidizing the high-aluminum content Al by adopting a wet oxidation process x Ga 1-x Oxidation of Al to AlO at the periphery of the As layer x While the middle region has high aluminum content Al x Ga 1-x As is not oxidized, high aluminum content Al x Ga 1-x The As layer is converted into a central area with high aluminum content Al x Ga 1-x An As layer and an oxidation-limited layer of an aluminum oxide layer in the peripheral region, thereby obtaining an active region mesa having an oxidation-limited structure, see fig. 11; due to the high aluminum content Al in the upper layer x Ga 1-x The Al content of the As layer is lower than that of the lower layer x Ga 1- x Aluminum content of As layer (or aluminum content of upper high aluminum content AlxGa1-xAs layer is equal to aluminum content of lower high aluminum content AlxGa1-xAs layer and upper high aluminum content AlxGa1-xAs layer is thicker than lower high aluminum content AlxGa1-xAs layer), in oxidation process, upper high aluminum content Al x Ga 1-x The oxidation depth of the outer ring of the As layer is smaller, so that the radius of the unoxidized part of the central area of the upper oxidation limiting layer is larger than that of the unoxidized part of the central area of the lower oxidation limiting layer;
step 4, as shown in fig. 12, coating photoresist on the surface of the epitaxial wafer obtained in step 3, wherein the photoresist is distributed on the top of the active region platform and the side wall of the active region platform, wherein the top of the active region platform is covered by the photoresist, the photoresist is coated on all annular side walls of the lower oxidation limiting layer and partial areas in the annular side walls of the upper oxidation limiting layer in the side wall of the active region platform, the photoresist is not coated on the other partial areas in the annular side walls of the upper oxidation limiting layer, so that a corrosion channel of the upper oxidation limiting layer is formed, and the non-photoresist coverage area corresponding to the corrosion channel can be one area or a plurality of scattered areas with different sizes;
step 5, placing the epitaxial wafer obtained in the step 4 in acid liquor (or alkali liquor), and corroding the aluminum oxide layer in the upper oxidation limiting layer from outside to inside through the corrosion channel by adopting an acid corrosion process (or alkali corrosion process), so as to completely or partially corrode the aluminum oxide in the photoresist-free protection area, as shown in fig. 13; the acid corrosion process adopts strong acid solution such as hydrochloric acid, phosphoric acid and the like, the concentration of the acid solution is 0.05-1 mol/L, and the corrosion time is 1-60 min;
step 6, adopting ALD or MLD technology to carry out film plating in the area space of the etched aluminum oxide layer of the active area platform, wherein the film plating material is ZnO x 、HfO x 、ZrO x The non-stoichiometric semiconductor material with an equal refractive index greater than that of aluminum oxide can be used for completely filling the area space etched away the aluminum oxide (shown in fig. 14) or can be used for filling only a part of the area space etched away the aluminum oxide (shown in fig. 15); the film forming process temperature of the embodiment is 80-200 ℃, the film forming pressure is 10-500 Pa, and the metal source is HfCl 4 、ZrCl 4 、ZnCl 4 The oxygen source is H 2 O; then removing the photoresist to form a modified structure completely filled with the non-stoichiometric semiconductor material in the aluminum oxide layer of the upper current confinement layer, as shown in fig. 16, or a modified structure partially filled with the non-stoichiometric semiconductor material, with an air gap in between, as shown in fig. 17;
step 7, coating photoresist on the surface of the epitaxial wafer obtained in the step 6, wherein the photoresist is distributed on the top of the active region platform and the side wall of the active region platform, the top of the active region platform is completely covered by the photoresist, partial areas in the annular side wall of the lower layer oxidation limiting layer are coated with the photoresist, and the other partial areas in the annular side wall of the lower layer oxidation limiting layer are not covered by the photoresist, so that corrosion channels of the lower layer oxidation limiting layer are formed, and the photoresist distribution of the corrosion channels can be consistent with or inconsistent with that of the corrosion channels in the step 4;
step 8, placing the epitaxial wafer obtained in the step 7 in acid liquor (or alkali liquor), and corroding the aluminum oxide layer in the lower oxidation limiting layer from outside to inside through the corrosion channel by adopting an acid corrosion process (or alkali corrosion process), so as to completely or partially corrode the aluminum oxide in the photoresist-free protection area, as shown in fig. 19; the acid corrosion process adopts strong acid solution such as hydrochloric acid, phosphoric acid and the like, the concentration of the acid solution is 0.05-1 mol/L, and the corrosion time is 1-60 min;
step 9, adopting ALD or MLD technology to coat film in the area space of the active area platform where the aluminum oxide layer is corroded, wherein the coating material is ZnO x 、HfO x 、ZrO x The non-stoichiometric semiconductor material with the equal refractive index being larger than the refractive index of the aluminum oxide, and the specific coating material can be the same as or different from the coating material in the step 6; the plating film may completely fill the region space etched away aluminum oxide (as shown in fig. 20), or may fill only a portion of the region space etched away aluminum oxide (as shown in fig. 21); the film forming process temperature of the embodiment is 80-200 ℃, the film forming pressure is 10-500 Pa, and the metal source is HfCl 4 、ZrCl 4 、ZnCl 4 The oxygen source is H 2 O; then removing the photoresist, and forming a modified structure completely filled with the non-stoichiometric semiconductor material in the aluminum oxide layer of the lower current limiting layer, as shown in fig. 22, or a modified structure partially filled with the non-stoichiometric semiconductor material, wherein an air gap is formed between the modified structure and the modified structure, as shown in fig. 23;
step 10, plating a dielectric layer on the surface of the epitaxial wafer obtained in the step 9, wherein the plating process is PECVD or ALD, and the film layer is SiN x 、SiO 2 、SiON、Al 2 O 3 、TiO 2 The film layer can be a single layer or a laminated layer of the film materials, the film thickness is 300-1000 nm, and the water vapor barrier capacity WVTR of the film layer is 1E -1 ~1E -4 See fig. 24;
step 11, etching a metal Via hole on the epitaxial wafer finished in the step 10, wherein etching gas is CF 4 +Ar (or Cl2+BCl3 or Cl2+SiCl 4), or BOE, to give an epitaxial wafer with Via holes, see FIG. 25;
step 12, filling Via holes with deposited metal of the epitaxial wafer obtained in step 11, wherein the metal is Au, pt, ag, al, and the like, see fig. 26;
and step 13, finally, splitting according to the requirement to obtain the vertical cavity surface emitting laser chip or array with the improved oxidation limiting structure.
The improved oxidation limiting layers in the manufacturing process are prepared separately, and in practice, all the oxidation limiting layers can be subjected to acid corrosion (or alkali corrosion) at the same time without photoresist protection, and then the same non-stoichiometric semiconductor material is plated on each etched oxidation limiting layer by using an ALD (atomic layer deposition) or MLD (multi-layer deposition) process, so that all the oxidation limiting layers are converted into the improved oxidation limiting layers at one time.
Claims (9)
1. The vertical cavity surface emitting laser with improved oxidation limiting structure includes current limiting structure over the active layer; the current limiting structure is characterized by comprising at least one current limiting layer, wherein at least one current limiting layer is an improved oxidation limiting layer; the improved oxidation limiting layer comprises a central region and a peripheral region surrounding the central region, wherein the central region is high in aluminum content Al x Ga 1-x The As layer is filled with at least one modification structure, the modification structure is a non-stoichiometric semiconductor material with a refractive index higher than that of aluminum oxide or a non-stoichiometric semiconductor material with an air gap in the middle, the refractive index of the modification structure is higher than that of aluminum oxide, and the volume ratio of the modification structure in the space of the peripheral region is 18-45%.
2. The VCSEL with improved oxidation confinement structure as defined in claim 1 wherein said non-stoichiometric semiconductor material is ZnO x 、HfO x Or ZrO(s) x 。
3. A vertical cavity surface emitting laser according to claim 1, wherein said current confinement structure comprises a plurality of current confinement layers.
4. The improved oxide confinement structure vertical cavity surface emitting laser according to claim 3, wherein high aluminum content Al in said plurality of current confinement layers x Ga 1-x The radius of the As layer increases with the direction away from the active layer.
5. A vertical cavity surface emitting laser according to claim 1, wherein said modified structure communicates with an outer edge of said peripheral region.
6. The improved oxide confinement structure vertical cavity surface emitting laser according to claim 1, wherein said improved oxide confinement structure is grown using a (100) plane GaAs substrate.
7. The method of manufacturing a vertical cavity surface emitting laser with improved oxidation confinement structure as defined in claim 1, comprising:
etching the epitaxial wafer to form Al with high aluminum content x Ga 1-x An active region mesa with the As layer exposed;
an oxidation step of adding Al with high aluminum content x Ga 1-x Al in the As-layer peripheral region x Ga 1-x As is oxidized to aluminum oxide, and Al in the middle region x Ga 1-x As is not oxidized, thereby forming an oxidation-limiting layer;
characterized by further comprising:
and an oxidation limiting layer modification step of removing part of aluminum oxide in at least one oxidation limiting layer and filling the modification structure to form an improved oxidation limiting layer.
8. A method of fabricating a vertical cavity surface emitting laser with improved oxidation confinement structure according to claim 7, wherein a portion of aluminum oxide in at least one of the oxidation confinement layers is removed using an acid or alkali etching process.
9. A method of fabricating a vertical cavity surface emitting laser with improved oxidation confinement structure according to claim 7, wherein said modified structure is filled using ALD or MLD process.
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