Semiconductor laser devices and methods for producing thereof

Abstract

A vertical-cavity surface-emitting laser (VCSEL) includes a substrate having a first main surface and a second main surface opposite the first main surface with a first reflector structure formed above the first main surface of the substrate. A second reflector structure is formed above the first main surface of the substrate and a multijunction active region formed above the first main surface of substrate between the first reflector structure and the second reflector structure. The multi-junction active region includes a core region configured to generate laser light through stimulated emission and a cladding region laterally surrounding the core region. The cladding region is configured to laterally confine electrical current and optical light vertically traveling in the VCSEL to the core region.

Description

[0001] SEMICONDUCTOR LASER DEVICES AND METHODS FOR PRODUCING THEREOF

[0002] Field

[0003] This present disclosure generally relates to semiconductorbased lasers and methods for producing thereof .

[0004] Background

[0005] FIG . 1 shows a diagram of a typical vertical cavity surface emitting laser (VCSEL ) 100 . The VCSEL 100 includes a p-type distributed Bragg reflector ( DBR) 105 at the top, and a n- type DBR 110 at the bottom .

[0006] The reflector structures , e . g . , the DBRs or DBR mirrors 105 and 110 can be based on an AlGaAs / GaAs material system . That is , the DBR mirrors 105 and 110 can each include alternating layers . For a first layer 112 can be a layer of Aluminum Gallium Arsenide (AlGAas ) and a second layer 114 can be a layer of Gallium Arsenide ( GaAs ) .

[0007] The VCSEL 100 can include an active region that is principally made of a p-i-n j unction, which can include multiple quantumwells (MQWs ) that generate photons . FIG . 1 shows a MQWs or MQWs region 120 . Electrical and optical confinement in the VCSEL 100 can be achieved by using an oxide layer 130 , which can be situated above ( and sometimes below) the active region . The oxide layer 130 can typically be an aluminum oxide layer (A12O3) . The oxide layer 130 can include an aperture region 150 . In many instances , the aperture region 150 can be formed from a semiconductor layer or material .

[0008] These layers are typically grown on the GaAs substrate 140 and using a Metalorganic Chemical Vapor Deposition (MOCVD) technique . As shown in FIG. 1, the VCSEL 100 includes ohmic contacts at the top, also called the anode 165 and the ohmic contacts at the bottom, also called the cathode 160. The ohmic contacts 160, 165 are placed for injecting current flow into the device .

[0009] The VCSEL 100 is configured, when biased, to emit a light beam 170 (shown in FIG. 2) .

[0010] The axes depicted in FIG. 1 show the typical directions at which the epitaxial layers are grown and based on. In other words, the

[0001] direction (e.g., vertical direction) shows the growth direction, while the

[0110] direction (e.g., a lateral direction) and the [1-10] are the directions at which the VCSEL 100 is typically fabricated at.

[0011] In FIG. 1, the outer or peripheral region of the VCSEL 100, designated by reference number 180. The outer region 180can include or be considered a cladding area or region of the VCSEL 100. The area or region between the dashed lines designed by reference number 155 can be considered the core area or region of the VCSEL. The designations of the core region 155 and the outer region 180 can apply to other VCSELs described herein.

[0012] FIG. 2 shows the VCSEL 100 of FIG. 1, when biased. By biasing or injecting current into the VCSEL 100, the current 190 flows from the top anode contact 165 to the bottom cathode contact 160. The oxide aperture 130 provides lateral electrical confinement of the current 190. That is, current is prevented from flowing through the oxidized A12O3regions and instead has to flow within and through the un-oxidized central regions, e.g., the aperture region 150.

[0013] The predominant path of least resistance for vertical current flow 190 is along the edges of the oxide apertures, as illustrated in FIG . 2 . This route of fers the shortest and least resistance for current passage .

[0014] The situation worsens or exacerbates with an increase in the inj ected current or when the diameters of the optical apertures exceed 10 micrometers . Under these conditions , current crowding occurring at the oxide aperture edges leads to the excitation of multiple transverse optical modes . These modes emit light at signi ficantly wider angles compared to modes excited from the central regions of the optical aperture . As shown, the emitted light beam 170 from the VCSEL 100 has a l / eA2 beam width of Wo(beam widths herein are perpendicular and intersecting beam axis ) .

[0015] Consequently, the far- field beam divergence tends to increase with either a rise in the inj ected current or an enlargement of the si ze of the optical aperture . This increased divergence angle poses a challenge for various applications that require delivering a speci fic optical power within a precise footprint .

[0016] Brief Description of the Drawings

[0017] In the drawings , like reference characters generally refer to the same parts throughout the di f ferent views . The drawings are not necessarily to scale , emphasis instead generally being placed upon illustrating the principles of the disclosure . In the following description, various aspects of the disclosure are described with reference to the following drawings , in which :

[0018] FIG . 1 shows a cross-section view of a typical vertical cavity surface emitting laser (VCSEL ) ;

[0019] FIG . 2 shows the VCSEL of FIG . 1 when biased;

[0020] FIGS . 3A and 3B each show cross-sectional views of VCSELS ; FIG . 4 shows a cross-sectional view of a multi j unction VCSEL ;

[0021] FIGS . 5A-5C show examples of a multi j unction VCSEL ;

[0022] FIG . 6 shows an example of a multi j unction VCSEL according to at least one aspect of the present disclosure ;

[0023] FIG . 7 shows a flow diagram of a method according to at least one aspect of the present disclosure ;

[0024] FIG . 8 shows an example of a multi j unction active region structure ;

[0025] FIG . 9 shows an example of a multi j unction active region structure ;

[0026] FIG . 10 show an example of a multi j unction VCSEL according to at least one aspect of the present disclosure ;

[0027] FIG . 11 show an example of a multi j unction VCSEL according to at least one aspect of the present disclosure ;

[0028] FIG . 12 shows an array of multi j unction VCSELs ;

[0029] FIG . 13 shows an array of multi j unction VCSELs according to at least one aspect of the present disclosure .

[0030] Description

[0031] The following detailed description refers to the accompanying drawings that show, by way of illustration, speci fic details and aspects in which the disclosure may be practiced . One or more aspects are described in suf ficient detail to enable those skilled in the art to practice the disclosure . Other aspects may be utili zed and structural , logical , and electrical changes may be made without departing from the scope of the disclosure . The various aspects described herein are not necessarily mutually exclusive , as some aspects can be combined with one or more other aspects to form new aspects . Various aspects are described in connection with methods and various aspects are described in connection with devices. However, it may be understood that aspects described in connection with methods may similarly apply to the devices, and vice versa. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures. Throughout the drawings, it should be noted that proportions are not necessary to scale and that the size of features may be emphasized for ease of illustration.

[0032] FIG. 3A and FIG. 3B respectively show cross-sectional views of VCSELs 300a and VCSEL 300b. The VCSELs 300a and 300b may incorporate features or components similar or identical to those found e.g., in VCSEL 100 depicted in FIG. 1. Consequently, a repeated description of these shared features may be omitted for brevity.

[0033] The VCSELs, 300a and 300b, each incorporate a tunnel junction 330 that provides an optical aperture for VCSEL 300a. The tunnel junction 330 enhances current distribution by shifting it to the center of the optical aperture. This improvement is largely attributable to low resistance characteristics of the tunnel junction 330, which facilitate more effective lateral current spread. As a result, the transverse modes situated at the center of the optical aperture receive increased gain, promoting their excitation. In contrast, this configuration does not favor the support and lasing of wide-angle modes.

[0034] The tunnel junction optical aperture 330 of the VCSEL 300a may be formed through ion implantation. Ion implantation aims to disrupt the crystalline structure and thereby increase the resistivity within a tunnel junction layer situated in the outer region 180 which inhibits lateral current spread into the tunnel junction layer. For instance, H+ ions (protons) can be used to directionally target and from the cladding zones 380 as illustrated in FIG. 3A. An advantage of this approach is the ability to grow the entire epitaxial structure in a single step, eliminating the need for intricate regrowth procedures .

[0035] However, a potential drawback of ion implantation is the risk of lateral diffusion of the implanted ions into the core active region of the optical aperture. This can adversely affect the VCSEL's optical and electrical performance. Additionally, VCSELs such as VCSEL 300a lack a refractive index step between the core and cladding (which is characteristic of a regrowth approach) potentially raising the lasing threshold of the VCSELs.

[0036] FIG. 3B shows a VCSEL 300b including a tunnel junction optical aperture 330 of the VCSEL 300b formed through an epitaxial regrowth technique or process. The regrowth provides an offset between the layers of the active region and the first reflector structure 105. That is, layers of the core region for the first reflector structure 155 and active region are offset from the same or corresponding layers in the peripheral region 180 of the VCSEL 300b.

[0037] Using a regrowth approach includes the growth of an epitaxial structure using a Metal-Organic Chemical Vapor Deposition (MOCVD) technique. The MOCVD continues until the tunnel junction is formed and at which point growth is temporarily halted. Then, conventional UV lithography methods can be employed to selectively remove (e.g., etching) the tunnel junction layer 330 in the cladding areas or outer regions. After removing or etching, epitaxial growth resumes, which culminates in the completion of the entire VCSEL structure, including, e.g., upper Distributed Bragg Reflector (DBR) mirror layers.

[0038] An advantage of this technique is the precise horizontal definition of the optical aperture, effectively preventing lateral current diffusion through the tunnel junction into the cladding regions around the aperture. Additionally, the presence of the tunnel junction layer 330 in the core area 150 of the VCSEL introduces a refractive index contrast between the core and cladding areas, enhancing optical mode confinement within the core active region and facilitating stimulated emission through index guiding.

[0039] The beam widths W2and W2, measured at the l / eA2 intensity points for the emitted light beams from VCSELs 300a and 300b, can have similar values, for example 940 nm for single Junction. The VCSEL 100, for example, can exhibit a beam width Woof approximately 20 degrees. By contrast, for VCSELs 300a and 300bc, the widths W2and W2, can be reduced to approximately or substantially 15 degrees, indicating a narrower beam spread compared to VCSEL 100.

[0040] FIG. 4 depicts a cross-sectional view of a multi unction VCSEL 400. The VCSEL 400 may be similar to the VCSEL 400 but includes multiple junctions or active regions. That is, the multi j unction active region of the VCSEL 400 includes sets each including an oxide layer 130, an aperture region 150 residing within the oxide layer 130, a MQW 120, and a tunnel junction 125.

[0041] In conventional multi j unction VCSELs, each active junction includes its own oxide layer to provide lateral electrical and optical confinement. Moreover, (Esaki) tunnel junctions 125 provide vertical electrical coupling between the active regions. Accordingly, the optical aperture 150 is based on formation of an oxide layer 130, and the tunnel junction 125 is used to provide electrical coupling between vertically adjacent junctions.

[0042] FIGS. 5A-5C respectively show multi j unction VCSELs 500a-500c. These VCSELs may incorporate features or components similar or identical to those found other VCSELs described herein and thus the same reference numbers may be used to refer to such shared features. The VCSEL 500a of FIG. 5A can be the same as the VCSEL 400, except FIG. 5A includes a representation of current flow 190.

[0043] The VCSEL 500b of FIG. 5B is another multi j unction VCSEL where the optical apertures 330 are based on tunnel junctions. Ion implantation in the outer region 180 or cladding zones areas 380 is used to form tunnel- unction-based optical apertures 330. A tunnel junction 125 (e.g., Esaki tunnel junction) is also included in the core region. Like the VCSEL 300a, the cladding zone 380 provides electrical and optical confinement to the core region.

[0044] The VCSEL 500c of FIG. 5C is a multi j unction VCSEL where the optical apertures 330 are based on tunnel junction and they are made using regrowth techniques described herein, e.g., in connection with VCSEL 300b. That is, layers of the core region for the first reflector structure 155 and multi j unction active region are offset from the same or corresponding layers in the peripheral region 180 of the VCSEL 500c.

[0045] Due to improved current spreading for the tunnel- j unctionbased optical aperture, a narrower divergence angle is expected for VCSELs 500b and 500c that that of an oxideconfined multi j unction VCSEL, e.g., VCSEL 500a.

[0046] FIG. 6 shows a multi j unction VCSEL 600 according to at least one exemplary embodiment of the present disclosure. The VCSEL 600 may incorporate features or components similar or identical to those found other VCSELs described herein and thus the same reference numbers may be used to refer to such shared features.

[0047] The VCSEL 600 includes a substrate 140 including a first main surface 140a and a second main surface 140, which is faces in an opposite direction to the first main surface 140a. As in other VCSEL described herein, the VCSEL 600 includes a first reflector structure 105 formed above the first main surface 140a of the substrate 140 and a second reflector structure 110 also formed above the first main surface of the substrate. The first and second reflector structures 105, 110 may DBRs, as described herein, e.g., based on AlGaAs / GaAs material system.

[0048] Situated between the first reflector structure 105 and the second reflector structure 110 there is a multi j unction active region (MAR) . The core region or part 155 (see FIG. 1) of the multi j unction active region MAR is configured to generate laser light through stimulated emission.

[0049] The cladding region 380, located in the outer region 180, laterally surrounds (in

[0110] direction) the core region of the multi unction active region MAR. The cladding region 380 is configured to laterally confine electrical current 190 and optical light 170 vertically traveling in the VCSEL to the core region. That is, the cladding region of the multi unction active region MAR includes electrically resistive material which can serve to laterally confine electrically current to the core region of the multi unction active region MAR.

[0050] In the example of FIG. 6, the core region of the multi j unction active region MAR of the VCSEL 600 includes a plurality of multiple-quantum-wells (MQW) regions 120 and a plurality of tunnel junction regions 125, 330. The core region of the multi unction active region MAR can include, for example spacers or spacer material. Further, the core region of the multi unction active region MAR may be free of or without oxide layers, e.g., oxide aperture layers. This contrasts with the VCSEL 400 of FIG. 4.

[0051] Instead, the VCSEL 600 can include oxide layers solely arranged outside (e.g., above and below) of the multi unction active region MAR. For instance , the VCSEL 600 includes a first oxide layer 130a is arranged between the first reflector structure 105 and the multi j unction active region MAR . Similarly, a second oxide layer 130b is arranged between the multi j unction active region MAR and the second reflector structure 110 and the multi j unction active region MAR . The first and second oxide layers 130a and 130b may be made of aluminum oxide in at least one example . In some case , the first and second oxide layers 130a and 130b may be located directly on the multi j unction active region MAR .

[0052] The multi j unction active region MAR may include one or more epitaxially grown semiconductor layers extending laterally ( along

[0110] direction) and extend in both the core region and the cladding region . That is , the epitaxially grown semiconductors layers reach both the core region 155 and the cladding region 180 sections of the multi j unction active region MAR .

[0053] At least some or all of the epitaxially grown semiconductor layers may be implanted with ions , e . g . , protons , laterally outside of the core region to form the electrically resistive cladding region 380 . In other words , the cladding region 380 corresponds to portions or sections of the epitaxial semiconductor layers residing outside of the multi j unction active region outside the core region that have been implanted with ions .

[0054] The VCSEL 600 can be considered as a result of a hybrid approach . The oxide layers 130a and 130b are formed around the multi j unction active region ( e . g . , above and below) for providing a proper refractive index step between the cladding region 180 and the core region 155 of the VCSEL 600 . The presence of the oxide layers 130a, 130b helps reduce the occurrence of some unwanted optical modes and also provides a refractive index contrast between the core and cladding regions of the VCSEL . Further, the core region 155 of the multi j unction active region MAR of the VCSEL 600 includes tunnel j unctions instead of oxide layers . This can overall improve the current spreading through the apertures and provide an index guided stimulated emission in the VCSEL 600 .

[0055] The use of the cladding region 380 can provide better electrical current and optical light confinement in the core region 155 of the VCSEL 600 while at the same time the oxide layers 130a, 130b can provide a better refractive index stepping properties . As a result , the divergence angle of the optical light improves . For example , the VCSEL 600 can have a full-width l / eA2 beam divergence angle less than 25 degrees .

[0056] FIG . 7 shows a method 700 for producing a VCSEL, such as or similar to VCSEL 600 , according to at least one exemplary embodiment of the present disclosure .

[0057] The method 700 includes , at 710 , forming a first reflector structure above a first main surface of a semiconductor substrate .

[0058] At 720 , the method 700 further includes forming a multi unction active region, the multi unction active region including : a core region configured to generate laser light through stimulated emission and a cladding region laterally surrounding the core region, the cladding region configured to laterally confine electrical current and optical light vertically traveling in the VCSEL to the core region .

[0059] At 730 , the method 700 further includes forming a second reflector structure above the multi unction active region .

[0060] At 740 , the method 700 further includes forming at least one oxide layer on the multi unction active region so that the multi j unction active region is arranged between the first reflector structure and the second reflector structure .

[0061] According to at least one example , forming the multi j unction active region includes forming a plurality of tunnel j unction regions , forming a plurality of multiple-quantum-wells (MQWs ) regions , and forming the cladding region by implanting ions in an outer region of the tunnel j unction regions . Further, the area inside of the outer region or the cladding region corresponds to the core region of the multi j unction active region .

[0062] According to at least one example , forming the multi j unction active region further includes forming the plurality of tunnel j unction regions and the plurality of MQW regions so that the plurality tunnel j unction regions alternate along a vertical direction with the plurality of MQW regions . (Unless stated otherwise herein, a vertical direction can be perpendicular to a main surface of a substrate , e . g . , along

[0001] direction in some embodiments ) .

[0063] Implanting ions in the outer region of the tunnel j unction causes formation of an electrically resistive region in the outer region of the tunnel j unction . In at least one example , implanting ions in the outer region includes implanting protons in the outer region .

[0064] Forming at least one oxide layer on the multi j unction active region can include forming a first oxide layer between the multi j unction active region and the first reflector structure . The first oxide layer can include a peripheral region and an aperture region . The peripheral region of the first oxide layer can be arranged above the cladding region, and wherein the aperture region of the first oxide layer can be arranged above the core region . Forming at least one oxide layer on the multi j unction active region can also include forming a second oxide layer between the multi j unction active region and the second reflector structure , the second oxide layer comprising a peripheral region and an aperture region, wherein the peripheral region of the second oxide layer is laterally arranged below the cladding region, wherein the aperture region of the second oxide layer is laterally arranged below the core region .

[0065] FIG . 8 shows a cross-sectional view of an example of a multi j unction active region structure 800 , or section thereof . For example , the structure 800 may at least be included within a core region of a VCSEL . The structure 800 may be used or implemented in one or more of the VCSELs described herein . FIG . 8 shows the spacing of the components or elements of the structure 800 .

[0066] Vertically starting from the top of the structure 800 , a first j unction includes an oxide layer 130 or tunnel j unction layer 330 , which is located at a vertical location corresponding to a null of the standing wave ( a standing wave of an optical field formed inside the laser cavity) . Vertically below in the first active j unction is the MQW layer 120 . The MQW layer 120 is situated at the peak of the standing wave , located at the (vertical ) distance of multiple odd integers of quarterwave from the top oxide layer 130 . Located below the MQW layer 120 is a tunnel j unction 125 . The tunnel j unction 125 is situated at another null of the standing wave in order to minimi ze the internal absorption .

[0067] The distance between the j unction JI to the tunnel j unction 125 is also multiple odd integers of quarter-wave . These three layers again repeat for the lower or bottom j unctions ( J2 , J3 ) in a similar manner . Accordingly, the next oxide layer 130 ( or tunnel j unction 330 ) can be located at another location corresponding the null of the optical field, and therefore, the shortest distance from the above tunnel junction 125 is multiple integers of half wavelength (X / 2) .

[0068] Therefore, in short, the minimum distance between one MQW layer 120 the next MQW layer (along

[0001] ) direction is one wavelength X.

[0069] FIG. 9 shows a multi j unction active region structure 900 according to an exemplary embodiment of the present disclosure. The structure 900 may be implemented or incorporated in the various VCSELs described herein.

[0070] The structure 900 can, for example, combine the function of an oxide layer and the tunnel junction into a single layer. That is, the structure 900 can have so each tunnel junction 125 acts or serves as both an optical aperture and the low resistance junction providing electrical coupling between adjacent active junctions e.g., J1-J3.

[0071] Accordingly, for the structure 900, the vertical spacing between can be reduced in comparison to the corresponding spacing of the structure 800 of FIG. 8. For the structure 900, a minimum distance between the two neighboring active junctions reduces to a half wavelength distance (X / 2) .

[0072] This spacing reduction along the vertical direction does not adversely affect the performance of a VCSEL including such a structure 900. Further, using the structure 900 or similar structure, e.g., with reduced vertical spacing, allows for the ability to add or include more active junctions.

[0073] For many VCSELs, the maximum total number of active junctions is 8. This is because increasing the number of active junctions increases the total cavity length. The increased spacing between the longitudinal lasing modes results in additional lasing wavelengths in addition to the main emission wavelength. Therefore, this increased spacing in many instances is detrimental to the performance of the VCSEL, both impacting the output power and the far field beam divergence.

[0074] In one example, the structure 900 can allow for realizing up to 12-junction VCSEL while maintaining a same cavity length (along a vertical direction) as an 8-junction VCSEL. As such, a 12- junction VCSEL, can scale output power by 50%, which can be extremely useful for various applications, such as, for example automotive LIDAR applications.

[0075] FIG. 10 shows a cross-sectional view of a VCSEL 1000 that is similar to the VCSEL 500b and can include the same or similar elements or components unless otherwise noted. For instance, the VCSEL 1000, like the VCSEL 500b, includes a cladding zones 380 and its core region of the multi unction active region includes tunnel junctions 330 for optical apertures.

[0076] However, the VCSEL 1000, for the multi j unction active region, uses a structure with the same or similar to the structure 900. As such, assuming the VCSEL 500b and the VCSEL 1000 have a same number of junctions in their multi j unction active region, the cavity length of the VCSEL 500b, Lactive(l) , measured along the vertical direction

[0001] , is longer than the corresponding cavity length, Lactive(2) of the VCSEL 1000 Lactive ( 2 ) :

[0077] Lacti e ( 1 ) > Lacti e ( 2 )

[0078] FIG. 11 shows a cross-sectional view of a VCSEL 1100 that is similar to the VCSEL 500c and can include the same or similar elements or components unless otherwise noted. For instance, the VCSEL 1100 can be formed like the VCSEL 500c, e.g., using regrowth techniques. As such, the VCSEL 1100 includes layers of core region of the first reflector structure 105 and the multi j unction active region that are offset with respect to the corresponding layers of the peripheral region 180 of the first reflector structure 105 and the multi j unction active region .

[0079] Compared to the VCSEL 500c, which has a cavity length Lactive(3) (measured along

[0001] direction) , that is longer than the corresponding cavity Lactive(4) of the VCSEL 1100:

[0080] Lactive(3) > Lactive(4) .

[0081] FIG. 12 shows an array of multi j unction VCSELs 1200. More specifically, the array 1200 includes an array of conventional VCSELs 400. As depicted, the array 1200 requires trench etches 1210 between laterally neighboring VCSELs 400 for performing wet oxidation in the fabrication of the VCSELs. Accordingly, the existence of etched trenches increases the VCSEL apertures' pitch (distance between the apertures) , resulting in a VCSEL array with low fill-factor.

[0082] FIG. 13 shows an array of VCSELS 1300. The VCSELs of the array may be VCSELs such as VCSELs 500b or 600, e.g., multi j unction VCSELs with tunnel junction as optical apertures. Notably, the fabrication process for these types of VCSELs (e.g., 500b / 600) eliminates the requirement for trench etching, which enables a significant reduction in the aperture pitch. This facilitates the creation of VCSEL arrays that are more compact, allowing for a denser arrangement of the lasers. Consequently, this denser configuration substantially enhances the total output power density of the array, offering improved performance capabilities.

[0083] Any of the aspects, examples, and / or embodiments described herein may be suitable or appropriately combined.

[0084] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any example or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other examples or designs . For the purposes of the present disclosure, the phrase "A and / or B" means (A) , (B) , or (A and B) . For the purposes of the present disclosure, the phrase "A, B, and / or C" means (A) , (B) , (C) , (A and B) , (A and C) , (B and C) , or (A, B, and C) .

[0085] Reference to "one embodiment" or "an embodiment" in the present disclosure means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase "in one embodiment" or "in an embodiment" are not necessarily all referring to the same embodiment. The appearances of the phrase "for example," "in an example," or "in some examples" are not necessarily all referring to the same example.

[0086] The words "plurality" and "multiple" in the description or the claims expressly refer to a quantity greater than one. The terms "group (of) ", "set [of] ", "collection (of) ", "series (of)", "sequence (of)", "grouping (of)", etc., and the like in the description or in the claims refer to a quantity equal to or greater than one, i.e. one or more. Any term expressed in plural form that does not expressly state "plurality" or "multiple" likewise refers to a quantity equal to or greater than one .

[0087] The term "connected" can be understood in the sense of a (e.g. mechanical, optical and / or electrical) , e.g. direct or indirect, connection and / or interaction. For example, several elements can be connected together mechanically such that they are physically retained (e.g., a plug connected to a socket) and electrically such that they have an electrically conductive path (e.g., signal paths exist along a communicative chain) .

[0088] As used herein, unless otherwise specified the use of the ordinal adjectives "first", "second", "third" etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner.

[0089] As utilized herein, terms "module", "component," "system," "circuit, " "element, " "slice, " "circuitry, " and the like are intended to refer to a set of one or more electronic components, a computer-related entity, hardware, software (e.g., in execution) , and / or firmware. For example, circuitry or a similar term can be a processor, a process running on a processor, a controller, an object, an executable program, a storage device, and / or a computer with a processing device. By way of illustration, an application running on a server and the server can also be circuitry. One or more circuits can reside within the same circuitry, and circuitry can be localized on one computer and / or distributed between two or more computers. A set of elements or a set of other circuits can be described herein, in which the term "set" can be interpreted as "one or more."

[0090] Such electric or electronic circuitry can be operated by a software application or a firmware application executed by one or more processors. The one or more processors can be internal or external to the apparatus and can execute at least a part of the software or firmware application. As yet another example, circuitry can be an apparatus that provides specific functionality through electronic components without mechanical parts; the electronic components can include one or more processors therein to execute executable instructions stored in computer readable storage medium and / or firmware that confer (s) , at least in part, the functionality of the electronic components. As another example, circuitry or similar term can be implemented in hardware such as application specific integrated circuit (ASIC) , programmable gate array (PGA) , discrete digital circuits, etc.) or in a combination of hardware and software (e.g., a software model executed by a corresponding processor) .

[0091] The term "semiconductor substrate" can mean any construction comprising semiconductor material, for example, a silicon substrate with or without an epitaxial layer, a silicon-on- insulator substrate containing a buried insulator layer, or a substrate with a silicon germanium layer.

[0092] A lateral direction is understood to mean a direction that runs, in particular, parallel to a main extension surface of the component, in particular of a layer. A vertical direction is understood to mean a direction that is oriented, in particular, perpendicular to the main extension surface of the component and / or layer. The vertical direction and the lateral direction are approximately orthogonal to each other.

[0093] Further, spatially relative terms, such as "beneath, " "below, " "lower, " "above, " "upper" and the like, may be used herein for ease of description to describe one element or feature's relationship to another element (s) or feature (s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly .

[0094] The term "data" as used herein may be understood to include information in any suitable analog or digital form, e.g., provided as a file, a portion of a file, a set of files, a signal or stream, a portion of a signal or stream, a set of signals or streams, and the like. Further, the term "data" may also be used to mean a reference to information, e.g., in form of a pointer. The term data, however, is not limited to the aforementioned examples and may take various forms and represent any information as understood in the art .

[0095] As used herein, a signal that is " indicative of" a value or other information may be a digital or analog signal that encodes or otherwise communicates the value or other information in a manner that can be decoded by and / or cause a responsive action in a component receiving the signal . The signal may be stored or buf fered in computer readable storage medium prior to its receipt by the receiving component and the receiving component may retrieve the signal from the storage medium . Further, a "value" that is " indicative of" some quantity, state , or parameter may be physically embodied as a digital signal , an analog signal , or stored bits that encode or otherwise communicate the value .

[0096] Unless otherwise stated, the words "about" and " substantially" as used herein are to be construed as meaning the normal measuring and / or fabrication limitations related to the value or condition which the word "about" or " substantially" modi fies . Unless expressly stated otherwise , the term "embodiment" is used herein to mean an embodiment of the present disclosure .

[0097] As used herein, a signal may be transmitted or conducted through a signal chain in which the signal is processed to change characteristics such as phase , amplitude , frequency, and so on . The signal may be referred to as the same signal even as such characteristics are adapted . In general , so long as a signal continues to encode the same information, the signal may be considered as the same signal . For example , a transmit signal may be considered as referring to the transmit signal in baseband, intermediate , and radio frequencies .

[0098] While the above descriptions and connected figures may depict device components as separate elements , skilled persons will appreciate the various possibilities to combine or integrate discrete features , functions into a single element . Such may include combining two or more components into a single component . Conversely, skilled persons will recogni ze the possibility to separate a single element into two or more discrete elements , such as splitting a single component into two or more separate components .

[0099] It is appreciated that implementations of methods detailed herein are exemplary in nature , and are thus understood as capable of being implemented in a corresponding device . Likewise , it is appreciated that implementations of devices detailed herein are understood as capable of being implemented as a corresponding method . It is thus understood that a device corresponding to a method detailed herein may include one or more components configured to perform each aspect of the related method .

[0100] All acronyms defined in the above description additionally hold in all claims included herein .

[0101] While embodiments of the present disclosure have been described above , it is obvious that further embodiments may be implemented . For example , further embodiments may comprise any subcombination of features recited in the claims or any subcombination of elements described in the examples given above . Accordingly, this spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein .

[0102] While the disclosure has been particularly shown and described with reference to speci fic embodiments , it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims . The scope of the disclosure is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced .

[0103] Reference Numeral List

[0104] 100 VCSEL

[0105] 105 p-type DBR

[0106] 110 n-type DBR

[0107] 112 first layer of 105 / 110

[0108] 114 second layer of 105 / 110

[0109] 120 MQW layer

[0110] 125 tunnel j unction

[0111] 130 , 130a, 130b oxide layer

[0112] 140 substrate

[0113] 150 aperture region

[0114] 155 core region of VCSEL

[0115] 160 cathode

[0116] 165 anode

[0117] 170 light beam

[0118] 180 outer region of VCSEL

[0119] 190 current flow in VCSEL

[0120] 300a, 300b VCSEL

[0121] 330 tunnel j unction optical aperture

[0122] 380 cladding zone

[0123] 400 VCSEL

[0124] 500a, 500b, 500c VCSELs

[0125] 600 VCSEL

[0126] 700 method

[0127] 800 multi j unction active region structure

[0128] 900 multi j unction active region structure

[0129] 1000 VCSEL

[0130] 1100 VCSEL

[0131] 1200 VCSEL array

[0132] 1300 VCSEL array

[0133] MAR multi j unction active region

Claims

CLAIMS1 . A vertical-cavity surface-emitting laser (VCSEL ) comprising : a substrate having a first main surface and a second main surface opposite the first main surface ; a first reflector structure formed above the first main surface of the substrate ; a second reflector structure formed above the first main surface of the substrate ; a multi j unction active region formed above the first main surface of substrate between the first reflector structure and the second reflector structure , the multi- j unction active region comprising : a core region configured to generate laser light through stimulated emission; a cladding region laterally surrounding the core region, the cladding region configured to laterally confine electrical current and optical light vertically traveling in the VCSEL to the core region; and at least one oxide layer .2 . The VCSEL of claim 1 , wherein the at least one oxide layer comprises : a first oxide layer situated between the multi j unction active region and the first reflector structure , the first oxide layer comprising a peripheral region and an aperture region, wherein the peripheral region of the first oxide layer is aligned over the cladding region in a vertical direction defined from the second main surface towards the first main surface of the substrate , and wherein the aperture region of the first oxide layer laterally aligned over the core region in the vertical direction .3 . The VCSEL of claim 1 , wherein the at least one oxide layer comprises :a second oxide layer situated between the mult ij unction active region and the second reflector structure , the second oxide layer comprising a peripheral region and an aperture region, wherein the peripheral region of the second oxide layer is aligned below the cladding region in the vertical direction, and wherein the aperture region of the second oxide layer laterally aligned below the core region in the vertical direction .4 . The VCSEL of claim 1 , wherein the core region of the multi j unction active region comprises : a plurality of multiple-quantum-wells (MQW) regions ; and a plurality of tunnel j unction regions .

5. The VCSEL of claim 4 , wherein in the core region the plurality of MQW regions are arranged to alternate along a vertical direction with the plurality tunnel j unction regions .

6. The VCSEL of any of claims 1 to 5 , wherein the core region is free of any oxide layers .7 . The VCSEL of any of claims 1 to 5 , wherein the cladding region comprises electrically resistive material .8 . The VCSEL of any of claims 1 to 5 , wherein the multi unction active region comprises one or more epitaxially grown semiconductor layers extending laterally through the core region and the cladding region .

9. The VCSEL of claim 8 , wherein the cladding region comprises portions of the epitaxial semiconductor layers residing outside of the core region, wherein the epitaxial semiconductor layers are implanted with ions .

10. The VCSEL of claim 9, wherein the ions are protons.

11. The VCSEL of claim 8, wherein the core region comprises portions of the epitaxial semiconductor layers residing within the core region.

12. The VCSEL of claim 11, wherein the tunnel junction regions comprise the epitaxial layers laterally inside the core region.

13. The VCSEL of any of claims 1 to 5, wherein the first mirror structure comprises a first distributed Bragg reflector (DBR) having a first conductivity type, and wherein the second mirror structure comprises a second DBR having a second conductivity type, wherein the first conductivity type is opposite to the second conductivity type.

14. The VCSEL of claim 13, wherein the first DBR and / or the second DBR comprise alternating layers of aluminum gallium arsenide (AlGaAs) and gallium arsenide (GaAs) .

15. The VCSEL of any of claims 1 to 5, further comprising: an anode disposed over the first main surface of the substrate and disposed on or over the first reflector structure; and a cathode disposed on or over a second surface of the substrate, the second main surface being opposite to the first main surface of the substrate.

16. The VCSEL of any of claims 1 to 5, wherein the VCSEL has a full-width l / eA2 beam divergence angle greater than 25 degrees.17 . The VCSEL of any of claims 1 to 5 , wherein the substrate comprises a semiconductor substrate .18 . The VCSEL of claim 17 , wherein the semiconductor substrate is a gallium arsenide substrate .19 . A method for forming a vertical-cavity surface-emitting laser, the method comprising : forming a first reflector structure above a first main surface of a substrate ; forming a multi j unction active region comprising : a core region configured to generate laser light through stimulated emission, and a cladding region laterally surrounding the core region, the cladding region configured to laterally confine electrical current and optical light vertically traveling in the VCSEL to the core region; and forming a second reflector structure above the multi j unction active region; and forming at least one oxide layer on the multi j unction active region so that the multi j unction active region is arranged between the first reflector structure and the second reflector structure .20 . The method of claim 19 , wherein forming the multi j unction active region comprises : forming a plurality of tunnel j unction regions , and forming a plurality of multiple-quantum-wells (MQWs ) regions , and forming the cladding region by implanting ions in an outer region of the tunnel j unction regions , wherein an area inside of the outer region and the cladding region corresponds to the core region of the multi j unction active region .21 . The method of claim 20 ,wherein forming the multi j unction active region further comprises forming the plurality of tunnel j unction regions and the plurality of MQW regions so that the plurality tunnel j unction regions alternate along a vertical direction with the plurality of MQW regions .22 . The method of claim 20 , wherein implanting ions in the outer region of the tunnel j unction comprises forming an electrically resistive region in the outer region of the tunnel j unction .23 . The method of claim 20 , wherein implanting ions in the outer region comprises implanting protons in the outer region .24 . The method of any of claims 19 to 23 , wherein forming at least one oxide layer on the multi j unction active region comprises : forming a first oxide layer between the multi j unction active region and the first reflector structure , the first oxide layer comprising a peripheral region and an aperture region, wherein the peripheral region of the first oxide layer laterally is arranged above the cladding region, wherein the aperture region of the first oxide layer laterally is arranged above the core region .25 . The method of any of claims 19 to 24 , wherein forming at least one oxide layer on the multi j unction active region comprises : forming a second oxide layer between the multi j unction active region and the second reflector structure , the second oxide layer comprising a peripheral region and an aperture region, wherein the peripheral region of the second oxide layer is laterally arranged below the cladding region,wherein the aperture region of the second oxide layer is laterally arranged below the core region .26 . The method of any of claims 19 to 24 , wherein forming the first mirror structure comprises a forming first distributed Bragg reflector ( DBR) having a first conductivity type , and wherein forming the second mirror structure comprises forming a second DBR having a second conductivity type , wherein the first conductivity type is opposite to the second conductivity type .27 . The method of claim 26 , wherein the first DBR and / or the second DBR comprise alternating layers of aluminum gallium arsenide (AlGaAs ) and gallium arsenide ( GaAs ) .28 . The method of any of claims 19 to 24 , further comprising : forming an anode on or over the first main surface of the substrate and disposed on or over the first reflector structure ; and forming a cathode on or over a second surface of the substrate , the second main surface being opposite to the first main surface of the substrate .29 . The method of any of claims 19 to 24 , wherein the substrate comprises a semiconductor substrate .30 . The method of claim 29 , wherein the semiconductor substrate is a gallium arsenide substrate .31 . A vertical-cavity surface-emitting laser (VCSEL ) comprising : a substrate having a first main surface and a second main surface opposite the first main surface ;a first reflector structure formed above the first main surface of the substrate ; a second reflector structure formed above the first main surface of the substrate ; a multi j unction active region formed between the first main surface of substrate between the first reflector structure and the second reflector structure , the multi- j unction active region comprising a core region configured to generate laser light through stimulated emission, the core region comprising : a plurality of multiple-quantum-wells (MQW) regions ; and a plurality of tunnel j unction regions , wherein the plurality of MQW regions alternate with the plurality of tunnel j unctions along a vertical direction of the VCSEL, wherein the vertical direction is perpendicular to first main surface to the substrate .32 . The VCSEL of claim 31 , wherein each of the plurality of tunnel j unction regions is respectively arranged at a location along the vertical direction corresponding to a null of a standing wave of light generated in the VCSEL .33 . The VCSEL of claim 31 , wherein each of the plurality of MQW regions is respectively arranged at a location along the vertical corresponding to a peak of a standing wave of light generated in the VCSEL .34 . The VCSEL of claim 31 , wherein each of the plurality of tunnel j unction regions is separated from a neighboring adj acent MQW region along the vertical direction by a length of one-quarter of a wavelength of the standing wave of light generated in the VCSEL .35 . The VCSEL of claim 31 ,wherein the plurality of tunnel j unction regions and the plurality of MQW regions form a plurality of active regions , and wherein each of the plurality of active regions is separated from a neighboring adj acent active region in the vertical direction by a length of one-hal f the wavelength of the standing wave of light generated by the VCSEL .36 . The VCSEL of claim 31 , wherein each of the plurality of tunnel j unctions regions is separated from an immediate next tunnel j unction region in the vertical direction by a length of one-hal f the wavelength of the standing wave of light generated by the VCSEL37 . The VCSEL of claim 31 to 36 , further comprising : a cladding region laterally surrounding the core region, the cladding region configured to laterally confine electrical current and optical light vertically traveling in the VCSEL to the core region .38 . The VCSEL of claim 37 , wherein the cladding region comprises electrically resistive material .39 . The VCSEL of any of claims 31 to 36 , wherein the multi j unction active region further comprising : an outer region surrounding the core region, the outer region including a plurality of multiple-quantum-wells (MQW) regions and a plurality of tunnel j unction regions respectively corresponding to the plurality of MQW regions and the plurality tunnel j unction regions of the core region, wherein the plurality of MQW regions and the plurality of tunnel j unction regions of the outer region are respectively of fset in a vertical direction from the corresponding plurality of MQW regions and the plurality of tunnel j unction regions of the core region .40 . The VCSEL of any of claims 31 to 36 , wherein the first mirror structure comprises a first distributed Bragg reflector ( DBR) having a first conductivity type , and wherein the second mirror structure comprises a second DBR having a second conductivity type , wherein the first conductivity type is opposite to the second conductivity type .41 . The VCSEL of claim 40 , wherein the first DBR and / or the second DBR comprise alternating layers of aluminum gallium arsenide (AlGaAs ) and gallium arsenide ( GaAs ) .42 . The VCSEL of any of claims 31 to 36 , further comprising : an anode disposed over the first main surface of the substrate and disposed on or over the first reflector structure ; and a cathode disposed on or over a second surface of the substrate , the second main surface being opposite to the first main surface of the substrate .

Images