FR3074372A1 - GAIN STRUCTURE, PHOTONIC DEVICE COMPRISING SUCH STRUCTURE AND METHOD FOR PRODUCING SUCH A GAIN STRUCTURE - Google Patents

Abstract

The invention relates to a gain structure (10) for forming, with a counter-reaction structure (15), a so-called hybrid laser (16). The gain structure (10) comprises: a dielectric layer (350); first, second and third semiconductor regions (311, 321, 331) succeeding each other in two-to-two contact along the thickness of said dielectric layer (350). The first and third semiconductor regions (311, 331) each have a first portion (312, 332) in contact with the second semiconductor region (321) and a second portion (313, 333) extending from the first portion (312, 332) in a direction opposite to the second semiconductor region (321), the gain structure (10) further comprising a first and a second electrical contact (510, 530) in contact with the second portion (313, 333). ) respectively of the first and the third semiconductor zone (311, 331).

Description

GAIN STRUCTURE, PHOTONIC DEVICE COMPRISING SUCH A STRUCTURE, AND METHOD FOR MANUFACTURING SUCH A GAIN STRUCTURE

DESCRIPTION

TECHNICAL AREA

The invention relates to the field of optoelectronics and photonics devices, such as lasers and semiconductor optical amplifiers.

A more specific subject of the invention is a gain structure intended to form a laser, with a feedback structure, or a semiconductor optical amplifier, a photonic device comprising such a gain structure, and methods of manufacturing such a gain structure and such a photonic device.

PRIOR STATE OF THE ART

Photonic devices comprising a laser or an optical semiconductor amplifier generally include:

at least one waveguide, a gain structure comprising a gain medium, at least one transition zone between the waveguide and the second semiconductor zone.

Photonic devices comprising a laser are distinguished from that comprising a semiconductor optical amplifier in that the phonic device further comprises a feedback structure to form an oscillating cavity, the feedback structure possibly being at both ends of the structure to gain (case of a distributed Bragg grating laser better known under the acronym DBR) or distributed in the gain structure (case of a distributed feedback laser also better known under its acronym DFB).

The term “gain structure” is understood above and in the rest of this document to be a structure made of semiconductor materials, generally III-V semiconductor, adapted to provide light emission which can in particular be stimulated in order to provide optical amplification. or, when the structure is coupled to an optical feedback structure, a laser type emission. Such a gain structure comprises at least one gain medium, which is the material in which the light emission is generated, and, on both sides, a first and second zone each having a conductivity type opposite to that on the other to authorize an electric pumping of the gain medium. In a conventional application, whether this relates to lasers with semiconductor materials or semiconductor optical amplifiers, in particular for the wavelength ranges of infrared and in particular at wavelengths 1310 nm and 1550 nm , the first and second zones and the gain medium can be formed by epitaxial growth on substrates of indium phosphide InP or gallium arsenide GaAs. Indeed, the small mesh difference of these materials with their quaternary alloys makes it possible to provide first and second zones and a gain medium of good crystalline quality.

The gain medium of such a gain structure may include a stack of quantum wells and barrier layers providing light emission or optical amplification. As an alternative to quantum wells, the gain medium can also include quantum dots. In order to form such quantum wells, or quantum dots, and in a conventional configuration of such a laser or of an optical semiconductor amplifier, the gain medium can comprise at least two semiconductor materials of the III-V semiconductor type. Each of these at least two materials can thus be selected, for example, from the group comprising indium phosphide InP, gallium arsenide GaAs, indium arsenide InAs, gallium-indium phosphide-indium InGaAsP, gallium-indiumaluminum arsenide InGaAlAs, aluminum-gallium arsenide AIGaAs and indium arsenide-phosphide InAsP and their alloys. Likewise, the first and second zones can be produced in at least one III-V semiconductor material, said material being able to be selected from the group comprising indium phosphide InP, gallium arsenide GaAs, arsenide indium InAs, gallium arsenide-indium phosphide InGaAsP, gallium-indium-aluminum arsenide InGaAlAs, arsenide-indium aluminum nitride InGaAsN, aluminum-gallium arsenide AIGaAs and arsenide indium phosphide InAsP and their alloys, one of the first and second zones being of a first type of conductivity in which the majority carriers are the electrons, the other being of a second type of conductivity in which the majority carriers are the holes.

The expression “optical feedback structure” is understood above and in the rest of this document to be an optical structure produced in a waveguide and making it possible to form an oscillating guiding cavity comprising the gain medium. Thus, the optical field goes back and forth in the waveguide of the cavity between the ends of this same oscillating cavity, this to generate a stimulated emission from the gain medium.

In the case of a laser called Distributed Feedback Laser (known by the acronym DFB laser), the optical feedback structure is constituted by a distributed reflector, such as a Bragg grating. , under or in the gain structure, forming a selective wavelength mirror.

In the case of a laser called a distributed Bragg grating (or Distributed Bragg Reflector Laser in English - known by the acronym DBR laser), the feedback structure is made up of reflectors arranged in the waveguide, on the other hand and the other of the gain structure.

In the case of an optical amplifier, the gain structure is not associated with a feedback structure; it allows the optical amplification of an incoming optical signal.

It should be noted that a laser formed by this type of gain structure associated with a feedback structure or that an optical amplifier formed by means of this same type of gain structure is said to be hybrid if the laser or the amplifier optics associates a gain structure made from III-V semiconductor materials with a feedback structure and / or a waveguide made from one or more materials different from those of the gain structure, such as base materials silicon for example silicon or silicon dioxide SiO ₂ .

For more information on photonic devices comprising a so-called hybrid laser and those comprising a hybrid optical amplifier, the reader is referred respectively to the work of Duprez H. and his coauthors discussed below and to the work of Kaspur P. and his coauthors published in November 2015 in the scientific journal “IEEE photonics technology” volume 27 number 22 page 2383 to 2386. In this type of 'hybrid' device, the input / output waveguide of the laser or amplifier is a guide 'wave in semiconductor material, such as silicon Si, placed under the active structure, and the coupling between the waveguide and the active structure is done by' adiabatic coulpers'. Another type of hybrid laser, based on an end-to-end coupling between the active structure and a waveguide made of dielectric material SiOx, is described in T. Fujii and his coauthors published in 2015 in the scientific journal "IET Optoelectronics »volume 9 number 4 pages 151 to 157. For more information on end-to-end coupling, reference is made to the description of the work of T. Fujii and these co-authors presented in the second part of this section.

In photonic devices, the gain structure can be either of the “vertical” type or of the “lateral” type, this terminology of “vertical” and “lateral” being relative to the surface of the substrate. Thus, in the first case, that is to say a gain structure of the “vertical” type, the first zone, the gain medium and the second zone consist of a stack of layers, said “vertical” stack being oriented perpendicular to the surface of the photonic device substrate. In the second case, that is to say a gain structure of the "lateral" type, the first zone, the gain medium, and the second zone follow one another in a direction parallel to the surface of the substrate of the photonic device.

It will be noted that, more generally, in this document the relative terms of “vertical” and “lateral” and “longitudinal”, even when it does not apply to the type of gain structure, are relative to the substrate. The “vertical”, “lateral”, and “longitudinal” directions correspond respectively to a direction perpendicular to the surface of the substrate, the “lateral” direction, to a direction lying in the plane of the surface of the substrate perpendicular to the direction of propagation. of light in the gain structure and in a direction lying in the plane of the surface of the substrate parallel to the direction of propagation of light in the gain structure.

An example of implementation of a vertical active structure to form a lll-V hybrid laser on Silicon is for example described by Duprez H. and his coauthors in their work published in 2015 in the scientific journal "Optics Express" volume 23 number 7 pages 8489 to 8497.

This gain structure 30 described comprises, as shown in FIG. 1 of their publication included in this document:

a stack of first, second and third semiconductor zones made of III-V materials 31, 32, 33, said “vertical” stack being oriented perpendicular to the surface of the substrate of the photonic device succeeding one another.

The first and third semiconductor zones 31, 33 are respectively of a first and of a second type of conductivity opposite to each other and the second semiconductor zone 32 forms a gain medium capable of emitting light under the effect of the electric pumping of the first and third semiconductor zones 31, 33. The gain structure 30 further comprises a first and a second electrical contact 51, 53 in contact with the first and third semiconductor zones 31, 33 respectively.

This gain structure 30 is assembled with a guide layer facing the third semiconductor zone. The guiding layer 20 comprises a silicon waveguide 21, at least one transition zone 22A, 22B and the optical feedback structure 23.

The gain structure 30, which has a relatively high refractive index, of the order of 3.5, can be left in the air or encapsulated in a dielectric material with a relatively low refractive index, between 1.5 to silicon dioxide SiO ₂ and 2 for silicon nitride SiN _x . It has a number of drawbacks. Indeed, the first semiconductor zone 31 must meet two conflicting constraints:

be fine enough to guarantee good vertical optical confinement of the optical mode in the second semiconductor zone 32, that is to say the gain medium, be thick enough for the electrical contact making 51 by means of a metal to be sufficiently distant from the optical field so as to minimize the losses by absorption in the metallic contact, a minimum thickness of 2 μm being thus generally necessary for the first semiconductor zone 31.

However, such a thickness of the first semiconductor zone 31 is particularly problematic. First, it reduces the vertical confinement of the optical field in the gain medium. Secondly, since the step of forming this first semiconductor zone 31 is generally carried out during an epitaxial deposition, such a thickness makes this step relatively long and costly to implement. In addition, such a thickness of the first semiconductor zone 31 also complicates the supply of the second electrical contact 53. Indeed, the need to have a thickness of approximately 2 μm makes it difficult to make electrical contact due to the high topology , this being especially the case if this electrical contact is of the planar type). It would therefore be desirable to provide a gain structure whose first semiconductor zone has a thickness less than or equal to 700 nm.

We have described above the implementation of a vertical gain structure to form a hybrid laser, and highlighted the problems associated with it. These problems are of course identical for a vertical type laser structure which is not hybrid.

It is also known from the work T. Fujii and his co-authors published in 2015 in the scientific journal "IET Optoelectronics" volume 9 number 4 pages 151 to 157 to use gain structures of the lateral type.

Such gain structures include, as illustrated in FIG. 1 of the publication by T. Fujii and his co-authors taken up in FIG. 2A and a side section view of which is shown diagrammatically in FIG. 2B, a first, a second and a third semiconductor zone 31, 32, 33 made of materials III-V which follow one another along a dielectric layer 1 disposed on the surface of the substrate supporting the gain structure 30.

In the same way as for the gain structure proposed by Duprez H. and his coauthors, the first and the third semiconductor zone 31, 33 have a conductivity type opposite to each other and the second semiconductor zone 32 is suitable to emit light.

Figure 2C shows the end-to-end coupling according to the work of T. Fujii and his co-authors. With such an end-to-end coupling between the gain structure 30 and the guiding layer 20, the output waveguide 21 is housed in the guiding layer made of silicon dioxide. The transition zone between the gain structure 10 and the waveguide 21 includes an InP waveguide 22 (InP tapered waveguide), structured in a point and opening into the waveguide 21. The waveguide InP 22 at the tip is structured in a layer in which the third semiconductor zone 33 has also been structured. It should be noted that it is also possible to provide a laser or a non-hybrid amplifier, by producing the waveguide 21 in part. in one of the layers having participated in the formation of the gain structure 30, in particular the layer having made it possible to form the third semiconductor zone 33.

These gain structures 30 offer the advantage of having a reduced thickness, typically of the order of 400 to 250 nm, vis-à-vis the gain structures of the vertical type as proposed by Duprez H. and his co-authors. Indeed, the electrical contacts 51, 53 are provided on either side of the hybrid waveguide and are therefore sufficiently distant from the waveguide so as not to generate losses by absorption of the optical field. It is therefore not necessary for the first semiconductor zone 31 to have a significant thickness. Thus making electrical contact is facilitated.

However, this ease of manufacture is obtained at the expense of reduced lateral confinement of the optical field in the second semiconductor zone 32. In fact, the second semiconductor zone 32 is surrounded laterally by the first and third semiconductor zones 31, 33 which have, as the second semiconductor zone 32, a relatively high refractive index, generally of the order of 3.5. Thus the optical mode is weakly confined in the second semiconductor zone 32 and extends at least partially in the first and third semiconductor zones 31, 33. We also note, with such a gain structure, the appearance of electrical leakage paths due to two layers of indium phosphide InP 36A, 36B flanking the second semiconductor zone 32.

Thus, at present there is no gain structure which makes it possible to obtain good optical confinement, both lateral and vertical, of the gain medium without any complexity in its manufacture and therefore a drastic increase in time and manufacturing costs.

STATEMENT OF THE INVENTION

The invention aims to at least partially remedy these problems and thus aims to provide a gain structure having a lateral confinement of the optical field in the gain medium which is not reduced, as is the case for the structure with gain proposed by T. Fujii and his co-authors, this by limiting the possible electrical leaks in this lateral structure and keeping the benefit of a thin structure, and therefore minimizing the topology to facilitate the manufacture of electrical contacts.

To this end, the invention relates to a gain structure intended for forming a photonic device comprising at least one of a laser and an optical amplifier, the gain structure comprising:

a dielectric layer comprising at least one dielectric material, a first, a second and a third semiconductor zone housed in the dielectric layer and succeeding each other in pairs by two along the thickness of said dielectric layer, in which the first and the third semiconductor zone are respectively of a first and of a second type of conductivity opposite to each other and in which the second semiconductor zone forms a gain medium capable of emitting light.

The first and third semiconductor zones each have a first portion in contact with the second semiconductor zone and a second portion extending from the first portion along the dielectric layer in a direction opposite to the second semiconductor zone, the structure at gain further comprising a first and a second electrical contact in contact with the second portion of respectively the first and the third semiconductor zone on the end portion of said portion which is opposite from the second semiconductor zone.

With such a division of the first and the third semiconductor zone, it is possible to provide for each of the first and the third zone:

a first portion having a small thickness promoting vertical optical confinement in the gain medium, and

- A second portion adapted to provide good ohmic contact without impact on optical losses, since this second portion extends beyond the gain medium.

In the same way, such a vertical configuration allows:

-to limit the current leaks observed for the gain structure proposed by T. Fujii and his co-authors and

- Provide good lateral optical confinement in the gain medium since the latter is surrounded by a dielectric material generally of low index relative to the second semiconductor zone.

Furthermore, such cutting into two portions does not increase the thickness of the gain structure, since the second portion extends along the dielectric layer in a direction opposite to the second semiconductor zone. The thickness of the gain structure not being increased, the supply of electrical contacts during the manufacture of the gain structure is therefore facilitated with respect to the gain structure taught by Duprez H. and his co-authors.

The cumulative thickness of the first portion of the first semiconductor zone, of the second semiconductor zone and of the first portion of the third semiconductor zone of the active structure may be less than 1 μιτι, this cumulative thickness being preferably less than 700 nm.

Such a reduced thickness of the stack formed by the first semiconductor zone, of the second semiconductor zone and of the first portion of the third semiconductor zone makes it possible to reduce the manufacturing costs of such a photonic device, this in particular as regards the formation of the first semiconductor zone and the supply of electrical contacts.

The second portion of the third semiconductor zone may extend in a direction opposite to the direction in which the second portion of the first semiconductor zone extends so that the third semiconductor zone has no part opposite the first contact .

In this way, any capacitive effect between the first and third semiconductor zones is avoided, while facilitating the formation of the gain structure since the formation of the first and second contacts is simplified.

This therefore results in good lateral and vertical optical confinement in the gain medium, while allowing optimized connection of both the first and the third semiconductor zone.

The invention further relates to a photonic device comprising:

at least one waveguide, a gain structure according to the invention, at least one transition zone between the waveguide and the gain structure, to form at least one of a laser and an optical amplifier.

Such a photonic device, whether hybrid or not, benefits from the advantages linked to the use of a gain structure according to the invention. Thus, the lateral and vertical confinement of the optical mode in the second semiconductor zone is optimized there, the manufacture of the electrical contacts is facilitated, and the leakage of the injection current is reduced. It therefore follows that such a photonic device comprises a laser or an optical amplifier with an optimized efficiency with respect to the lasers or optical amplifiers of the photonic devices of the prior art.

The photonic device may comprise a substrate, defining a substrate plane, and a guiding layer housing the waveguide, the guiding layer and the gain structure being able to be arranged in the same plane parallel to the substrate plane, the guide wave being coupled to the gain structure according to an end-to-end coupling.

The photonic device may further comprise a guiding layer in which the waveguide is housed, the guiding layer comprising a first and a second face, the gain structure comprising a first and a second face with the third semiconductor zone facing the second face, the guiding layer being assembled by its first face to the second face of the gain structure.

The assembly of the guide layer to the second face of the gain structure can be obtained by means of a dielectric interface layer.

Such configurations allow good optical coupling between the gain structure and the waveguide of the guiding layer, thus limiting optical losses at the level of the optical transition zone (s).

The at least one transition zone can be housed at least partially in one of the gain structure, the guiding layer and the optional dielectric interface layer.

The gain structure can form a semiconductor optical amplifier.

The device may further comprise a fourth semiconductor layer, preferably made of III-V semiconductor material, housing the waveguide and the transition zone, the gain structure being optically coupled to the waveguide by a butt coupling. tip between one end of the second semiconductor zone and one end of the waveguide housed in the fourth semiconductor layer.

The photonic device may further comprise a feedback structure for forming an oscillating cavity comprising at least a part of the second semiconductor zone so as to form a laser connected optically to the waveguide by at least one optical transition zone.

The feedback structure can be housed at least partially in one of the dielectric layer, the guiding layer, a fourth semiconductor layer, preferably III-V, of the photonic device and the optional interface dielectric layer.

With such configurations, the photonic device comprises either a hybrid laser or an optical amplifier.

The invention further relates to a method of manufacturing a gain structure, said method comprising the following steps:

providing a first, a second and a third semiconductor layer forming materials for forming respectively a first portion of a first semiconductor zone, a second semiconductor zone and a third semiconductor zone, the first, second and third successive semiconductor layers in contact in pairs, localized etching of the first and second semiconductor layer in order to respectively form the first portion of the first semiconductor zone and the second semiconductor zone, the first portion of the first semiconductor zone being in contact with the second semiconductor zone, localized etching of the third semiconductor layer in order to form the third semiconductor zone, the third semiconductor zone comprising a first portion in contact with the second semiconductor zone and a second portion extending from the first portion of the a third semiconductor zone opposite the second semiconductor zone, deposition of at least a first dielectric material encapsulating the first portion of the first semiconductor zone, the second semiconductor zone and the third semiconductor zone, partial removal of the first dielectric material so releasing at least partially the first portion of the first semiconductor area, forming a second portion of the first semiconductor area in contact with the first portion of the first semiconductor area, the second portion extending from the first semiconductor area in a direction opposite to the second semiconductor zone, encapsulation of at least the second portion of the first semiconductor zone and the part of the first portion of the first semiconductor zone which is not housed in the first dielectric material, this so to form a dielectric layer comprising at least the first dielectric material, said dielectric layer thus housing the first, second and third successive semiconductor zones in pairs contact along the thickness of said dielectric layer, forming a first and a second electrical contact in contact with the second portion of the first and third semiconductor regions, respectively, on an end portion of said portion which is opposite from the second semiconductor region.

Such a method allows the formation of a gain structure according to the invention benefiting from the advantages which are linked to it.

The step of forming the second portion of the first semiconductor zone can include the following substeps:

deposition of a layer of a semiconductor material of the second portion of the first semiconductor zone in contact with the first dielectric material and of the first portion of the first semiconductor zone, localized etching of the first semiconductor material of the second portion in order to form the first semiconductor zone.

It can be provided, between the step of partial removal of the first dielectric material and the step of forming a second portion of the first semiconductor zone; the following steps:

deposition of an intermediate layer in contact with the layer of the first dielectric material and of the first portion of the first semiconductor zone the material of the intermediate layer being selected from a dielectric material and a semiconductor material, arrangement of an opening in the layer intermediate to release at least partially the first portion of the first semiconductor zone, and the step of forming the second portion of the first semiconductor zone comprising the following substeps:

deposition of a layer of the semiconductor material of the first semiconductor zone in contact with the intermediate layer and of the first portion of the first semiconductor zone, localized etching of at least the layer of semiconductor material of the first semiconductor zone in order to form the second portion of the first semiconductor zone and therefore to form the first semiconductor zone.

The localized etching step of the first and second semiconductor layer comprises the following substeps:

formation of a hard mask covering the part of the first semiconductor layer intended to form the first portion of the first semiconductor zone, etching of the first and second semiconductor layers, the parts of the first and of the second semiconductor layer, corresponding respectively to the first portion of the first semiconductor zone and the second semiconductor zone, being protected by the hard mask.

The invention further relates to a method of manufacturing a photonic device comprising a gain structure, in which the gain structure is manufactured according to a manufacturing method according to the invention, which device further comprising: at least one guide wave, at least one transition zone between the waveguide and the second semiconductor zone.

Such a method makes it possible to manufacture a photonic device comprising a gain structure according to the invention and therefore benefiting from the advantages which are linked to it.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood on reading the description of exemplary embodiments, given for purely indicative and in no way limiting, with reference to the appended drawings in which:

Figure 1 is a resumption of Figure 1 of the work of Duprez H. and his co-authors published in 2015 in the scientific journal "Optics Express" which shows a first prior art of the invention according to a longitudinal section of a hybrid laser implementing an active structure of the 'vertical' type, Figures 2A to 2C are respectively a resumption of Figure 1 of the work of T. Fujii and his co-authors published in 2015 in the scientific journal "IET Optoelectronics", a side section view schematic corresponding to this same figure extracted from these same works and a perspective view of an end-to-end coupling in accordance with the teaching of this same document, Figure 3 illustrates a schematic side sectional view of a structure with gain according to a first embodiment of the invention, FIGS. 4A to 4M illustrate by means of side section views the main steps of a method of manufacturing a gain structure according to the pre mier embodiment of the invention, FIGS. 5A to 5F illustrate by means of side section views the main steps of a method of manufacturing a gain structure according to a second embodiment of the invention, the figures 6A to 6G illustrate by means of side sectional views the main steps of a method of manufacturing a gain structure according to a third embodiment of the invention, FIG. 7 illustrates a side sectional view of a structure gain according to a fourth embodiment in which a first and a third semiconductor zone has no portion facing one another, FIGS. 8A and 8B respectively illustrate a view in longitudinal section and in side section of an example of a photonic device comprising a gain structure according to the invention coupled to a feedback structure to form a hybrid laser, FIG. 9 illustrates a view in longitudinal section of a example of a photonic device comprising a gain structure according to the invention forming a semiconductor optical amplifier.

Identical, similar or equivalent parts of the different figures have the same reference numerals so as to facilitate the passage from one figure to another.

The different parts shown in the figures are not shown on a uniform scale, to make the figures more readable.

The different possibilities (variants and embodiments) must be understood as not being mutually exclusive and can be combined with one another.

The expression “lateral section” and “longitudinal section” respectively means above and in the rest of this document a section along a plane perpendicular to the direction of propagation of the guided optical field and a section along a plane parallel to the direction of propagation of the guided optical field perpendicular to the surface of the substrate.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

FIG. 3 illustrates a gain structure 10 according to a first embodiment, said gain structure 10 being adapted to be assembled with a guiding layer, not illustrated in FIG. 3 and which is described in the rest of this document in connection with FIGS. 8A and 8B, this so as to form a photonic device 1 comprising a laser of the hybrid type.

It will of course be noted that if the majority of the embodiments described below refer to photonic devices comprising at least one hybrid laser III-V with guiding silicon layer, as described in connection with FIG. 8, the invention applies in an identical manner to photonic devices comprising a III-V hyrbid laser with a guiding layer made of dielectric materials, or a non-hybrid laser, that is to say with a guiding layer made of III-V materials, but also to a device comprising at least one optical amplifier with semiconductor, hybrid or not. Indeed, the gain structure 10 according to the invention being adapted to form both a laser and an optical amplifier, a person skilled in the art is able to apply the teaching of this majority of embodiments to photonic devices comprising at least one optical amplifier, hybrid or not. What is more, the invention also covers photonic devices comprising at least one laser and at least one semiconductor optical amplifier at least one, or even each, of them comprising a gain structure 10 according to the invention.

The gain structure 10 according to this first embodiment comprises: a dielectric layer 350 comprising a dielectric material, a first, a second and a third semiconductor zone made of semiconductor materials III-V 311, 321, 331 housed in the dielectric layer 350 and succeeding each other in contact two by two along the thickness of said dielectric layer 350, a first and a second electrical contact 510, 530 in contact respectively with the second portion 313, 333 of respectively the first and the third semiconductor zone 311, 331.

The dielectric layer 350 is an encapsulation layer for encapsulating the active parts of the gain structure 10, namely the first, second and third semiconductor zones 310, 320, 330. The dielectric layer is produced in at least one dielectric material, such as for example silicon dioxide SiO ₂ , silicon nitride SiN _x or a silicon nitride oxide SiOyNx. Thus, in a practical application of this first embodiment of the invention, the dielectric layer 350 is made of silicon dioxide SiO ₂ .

The first, second and third semiconductor zones 311, 321, 331 are all three made of semiconductor materials preferably of the III-V type. Thus, the material or materials of the first, second and third semiconductor zones 311, 321, 331 can for example be selected from the group comprising indium phosphide InP, gallium arsenide GaAs, indium arsenide

InAs, gallium-indium arsenide-phosphide InGaAsP, gallium-indiumaluminum arsenide InGaAlAs, aluminum-gallium arsenide AIGaAs and indium arsenide-phosphide InAsP and their alloys. It should be noted that, of course, these examples of materials are provided only by way of example, those skilled in the art being able to extrapolate the teaching of this document to other semiconductor materials with direct gap.

The first and third semiconductor zones 311, 331 are respectively of a first and of a second type of conductivity opposite to each other, the first type of conductivity being one of a P doping and an N doping , the second type of conductivity being the other among P doping and N doping.

According to a first practical application of this first embodiment, the first and the third semiconductor zone 311, 331 are both made of gallium arsenide GaAs. The first zone has a P doping and the second zone has an N doping. According to a second practical application of this first embodiment, the first and the third semiconductor zone 311, 331 are both made of indium phosphide InP.

As illustrated in FIG. 3, the first and third semiconductor zones 311, 331 each have a first portion 312, 332 in contact with the second semiconductor zone 321 and a second portion 313, 333 extending from the first portion 312 , 332 along dielectric layer 350 in a direction opposite to the second semiconductor zone 321.

Thus in this first embodiment, the first semiconductor zone 311 has a first portion 312 in contact with a first face of the second semiconductor zone 321 and forms a first layer. Thus, according to the practical application of this first embodiment, the first portion 312 of the first semiconductor zone 311 can be made of gallium arsenide GaAs.

The second portion 313 of the first semiconductor zone 311 is in the form of a semiconductor layer in contact with the first portion 312 extending from the latter along the dielectric layer in a direction opposite to the second semiconductor zone 321. It can be noted, as shown in FIG. 3, that if the second portion 313 of the first semiconductor zone 311 extends in a direction opposite to the second semiconductor zone 321, such an extension does not exclude that the second portion 313 also extends in part on either side of the first portion 312 of the first semiconductor zone 311.

The second portion 313 of the first semiconductor zone 311 is preferably made of the same material as the first portion 312 of the first semiconductor zone.

The third semiconductor zone 331 is in the form of a single layer, a first portion 332 of which is in contact with a second face of the second semiconductor zone 321 and a second portion 333 extends from the first portion 332 to the opposite of the second semiconductor zone 321.

According to an advantageous possibility of the invention, the second portion 333 of the third semiconductor zone 331 extends in a direction different from the second portion 313 of the first semiconductor zone 311, preferably opposite to that of the second portion 313 of the first semiconductor zone 311. Such an arrangement makes it possible to facilitate the formation of the first and second electrical contacts 510, 530.

In this first embodiment, the first portion 332 and the second portion 333 of the third semiconductor zone 331 are both formed from the same material. Thus, according to the practical application of this first embodiment, the first and the second portion 332, 333 of the third semiconductor zone 331 are both made of gallium arsenide GaAs.

The second semiconductor zone 321 forms a gain medium capable of emitting light. Thus, to form such a gain medium, the second semiconductor zone 312 may for example comprise a stack of quantum wells and barrier layers or a plurality of quantum dots and barrier layers.

Thus, according to a first practical application of the invention, the second semiconductor zone 321 comprises a plurality of quantum dots made of indium arsenide InAs and barrier layers made of gallium arsenide GaAs. According to a second practical application of the invention, the second semiconductor zone 321 comprises a stack of quantum wells and barrier layers of gallium phosphide arsenide and indium InGaAsP.

It should be noted that, according to an advantageous possibility of the invention, the cumulative thickness of the first, second and third semiconductor zones 311, 321, 331 is less than 1 μm, this cumulative thickness being preferably less than 700 nm, even 400 nm. Thus, according to the practical application of the invention, the first portion 312 of the first semiconductor zone 311 has a thickness of 140 nm, the third semiconductor zone 331 having a thickness of 110 nm. The second semiconductor zone 321 has a thickness of 120 nm. In this way, with a second portion 313 of the first semiconductor zone less than 300 nm, the first, second and third semiconductor zones 311, 321, 331 have a cumulative thickness less than 700 nm.

The first and second electrical contacts 510, 530 are electrical contacts taken laterally on either side of the waveguide and illustrate a possibility of connection according to the invention. Other possibilities, known to those skilled in the art, are of course conceivable without departing from the scope of the invention. Thus according to this possibility illustrated in FIG. 3, the first and second electrical contacts 510, 530 each comprise a via which extends through the dielectric layer 350 and a contact pad on the surface of the dielectric layer 350. The first electrical contact 510 is in contact with the second portion 313 of the first semiconductor zone 311 on an end portion of said second portion 313 which is opposite to the second semiconductor zone 321. Likewise, the second electrical contact 530 is in contact with the second portion 333 of the third semiconductor zone 331 to an end portion of said second portion 333 which is opposite to the second semiconductor zone 321.

By end part of each of the second portions 313, 333 of the first and of the third semiconductor zone 311, 331 it is understood above and in the rest of this document, a part of said portion 313, 333 representing less than 1/3 of the total length in the direction in which said portion 313 extends,

333.

Such a gain structure 10 can be formed, as illustrated in FIGS. 4A to 4N, by means of a method comprising the following steps:

providing a first, a second and a third semiconductor layer 310, 320, 330 of respective materials respectively intended to form respectively the first portion 312 of the first semiconductor zone 311, the second semiconductor zone 321 and the third semiconductor zone 331, said first, second and third semiconductor layers 310, 320, 330 succeeding each other in pairs and being supplied on a first support 300 adapted for their formation, as illustrated in FIG. 4A, bonding of the first, second and third semiconductor layers 310, 320, 330 / first support 300 on a second support 200 the first and second supports 300, 200 surrounding the first, second and third semiconductor layers 310, 320, 330, as illustrated in FIG. 4B, deletion of the first support 300, as illustrated in FIG. 4C, formation of a first etching mask 220 in contact with the first semiconductor layer 310, said etching mask 220 covering the part of the first semiconductor layer 310 intended to form the first portion and being preferably produced in one of the silicon dioxide SiO ₂ and a silicon nitride SiN _x , as illustrated in FIG. 4D, etching of the first and second semiconductor layers 310,

320, the parts of the first and second semiconductor layer 310, 320 intended to form the first portion 312 of the first semiconductor zone 311 and the second semiconductor zone 321 being protected by the first etching mask 220, the first portion 312 of the first semiconductor zone 311 and the second semiconductor zone 321 thus being formed with the first portion 312 of the first semiconductor zone 311 in contact with the second semiconductor zone

321, as illustrated in FIG. 4E, formation of a second etching mask 230 covering the part of the third semiconductor layer 330 intended to form the second portion

333 of the second semiconductor zone 331 and partially or totally covering the etching mask 220, localized etching of the third semiconductor layer 330 in order to form the third semiconductor zone 331, and the first portion 312, 332 of the first and of the third zone semiconductor 311, 331, the second semiconductor zone 321 being protected by the first etching mask 220 while the second portion 333 of the third semiconductor zone 331 is protected by the second etching mask 230, the third semiconductor zone 331 being thus formed, this comprising a first portion 332 in contact with the second semiconductor region 321 and a second portion 333 extending from the first portion 332 of the third semiconductor region 331 in a direction opposite to the second semiconductor region 321, as illustrated in FIG. 4F, deletion of the second mask 230, as illustrated above FIG. 4G, deposition of at least a first dielectric material 351 enclosing the first portion 312 of the first semiconductor zone 311, the second semiconductor zone 321 and the third semiconductor zone 331 and the first etching mask 220 as illustrated in the figure 4H, the deposited layer of the first dielectric material 351 forming an intermediate layer, planarization step of the first dielectric material 351 in order to make the first mask 220 flush, as illustrated in FIG. 41, selective removal of the first etching mask 220 in order to release a face of the first portion 312 of the first semiconductor zone 311 which is opposite from the second semiconductor zone 321, as illustrated in FIG. 4J taken up by epitaxy of a layer of material 315 of a material intended to form the second portion 313 of the first semiconductor zone 311 in contact with the first portion 312 of the first semiconductor zone 311 and of the layer of the first dielectric material 351, as illustrated in FIG. 4K, the step of resuming epitaxy can be carried out with the following characteristics:

o the material 315 intended to form the second portion 313 of the first semiconductor zone 311 is preferably identical to the material of the first portion of the first semiconductor zone 312, o the growth of the material 315 intended to form the second portion 313 of the first zone semiconductor 311 is preferably done by molecular beam epitaxy better known by its acronym MBE for Molecular Beam epixtaxy, for example at a temperature of 500 ° C., where the growth of material 315 takes place vertically from the free surface of the first portion 312 of the first semiconductor zone 311 with good crystalline quality; it also takes place laterally on either side of the first portion 312 of the first semiconductor zone, from the free surface of the first dielectric material 351, in the form of grains of material 315. The crystalline quality of the epitaxial material 315 at the level of 351 is, starting from the surface 351, less good than starting from the surface 312, but it covers a good crystalline quality when the 2 epitaxial zones (raw zone at the start of 312 and raw zone at the start of 351 ) join ;

partial etching, after an optional planarization step, of the layer of material 315 in order to form the second portion 313 of the first semiconductor zone 311 in contact with the first portion 312 of the first semiconductor zone 311, the second portion 313 extending from the first semiconductor zone 311 in a direction opposite to the second semiconductor zone 321, as illustrated in FIG. 4L, deposition and planarization of a dielectric material, identical or different from the first dielectric material encapsulating the second portion 313 of the first semiconductor zone 311, this so as to form a dielectric layer 350 comprising at least the first dielectric material 351, said dielectric layer 350 thus housing the first, second and third semiconductor zones 311, 321, 331 which succeed one another in pairs contact the along the thickness of said dielectric layer 350, forming a first and second electrical contact 510, 530 in contact with the second portion 313, 333 of the first and third semiconductor zones 311, 331 respectively.

Of course, the skilled person, from the teaching of this document, is able to modify this manufacturing process, and the others described in this document in order to best meet his needs. It will be noted in particular that it is able to adapt the step of forming the first and second electrical contacts in order to use conventional manufacturing techniques for microelectronics and optoelectronics.

Concerning the step of resumption of epitaxy of the layer of material 315, this resumption of epitaxy can be carried out according to a method similar to that described by the work of S. Chen and his co-authors in 2016 in the scientific journal "nature photonics »volume 10 pages 307-311.

It can be noted that in a variant not illustrated of this first embodiment, it is also possible to form the layer of material 315 of a material intended to form the second portion 313 of the first semiconductor zone 311 by molecular bonding of the said layer of material 315.

A method according to this variant differs from the manufacturing method according to the first embodiment in that during the planarization step of the first dielectric material 351 in that:

the planarization step of the first dielectric material 351 is carried out in order to make the first portion 312 of the first semiconductor zone flush, there is no step of selective etching of the first etching mask 220, the mask having been previously deleted during the planarization step, there is performed, in place of the epitaxy step of a layer of material 315, a step of molecular bonding of the layer of material 315 in contact with the first material dielectric 351 and the first portion 312.

FIGS. 5A to 5F illustrate the main steps of a method for manufacturing a gain structure 10 according to a second embodiment. A gain structure 10 according to this second embodiment differs from a gain structure 10 according to the first embodiment by the configuration of the second portion 313 of the first semiconductor zone 331, as illustrated in FIG. 5F.

Indeed, as shown in FIG. 5F, in this second embodiment, the second portion 313 of the first semiconductor area 311 is in contact with the first portion 312 of the first semiconductor area 311 both on one side of the latter and over part of its height. Such a configuration, obtained by growth of the second portion 313 of the first semiconductor zone 311 from the first portion 312 of the first semiconductor zone 311.

The method of manufacturing a gain structure 10 according to this second embodiment differs from the method of manufacturing a gain structure 10 according to the first embodiment in that it is provided after the planarization step of the first dielectric material 351 illustrated in FIG. 5A, the following steps: forming a third etching mask 230 partially covering the first etching mask 220 on the side of 331, the first dielectric material 351, the parts of the first dielectric material 351 in view of the second portion 313 of the first semiconductor zone 311 being free of the third etching mask 230, as illustrated in FIG. 5B, partial etching of the first dielectric material 351 in order to release part of the height of the first portion 312 of the first semiconductor zone 311 which is intended to be in contact with the second portion 313 of the first semiconductor zone 311, as illustrated in FIG. 5C, removal of the third etching mask 230, as illustrated in FIG. 5D, removal of the first etching mask 220 in order to release one face of the first portion 312 of the first semiconductor zone 311 which is opposite to the second semiconductor zone 321, as illustrated in FIG. 5E, growth by epitaxy, preferably by vapor phase epitaxy with organometallics (better known by the acronym MOVPE), of the second portion 313 of the first semiconductor zone 311 from the first portion 312 of the first semiconductor zone 311, said growth taking place from the released parts of the first portion 312 of the first semiconductor zone, it extends in a direction opposite to the second semiconductor zone 321, as illustrated in the FIG. 5F, deposition and planarization of a dielectric material, identical or different from the first dielectric material sheet 351 enclosing at least the second portion 313 of the first semiconductor zone 311 this so as to form a dielectric layer 350 comprising at least the first dielectric material 351, said dielectric layer 350 thus housing the first, second and third semiconductor zones 311, 321 , 331 which succeed one another in pairs contact along the thickness of said dielectric layer 350, formation of first and second electrical contacts 510, 530 in contact with the second portion 313, 333 of the first respectively and the third semiconductor zone 311, 331 in an identical manner to the step of the method according to the first embodiment illustrated in FIG. 4M.

FIGS. 6A to 6E illustrate the main steps of a method for manufacturing a gain structure 10 according to a third embodiment. A gain structure 10 according to this third embodiment differs from a gain structure 10 according to the first embodiment by the configuration of the second portion 313 of the first semiconductor zone 331, as illustrated in FIG. 6G, this the latter resting partly on a buffer layer 240 adapted for the formation of said second portion 313 of the first semiconductor zone 311.

As part of the practical application where the second portion 313 of the first semiconductor zone 311 is made of gallium arsenide GaAs, the buffer layer can be made of amorphous or polycrystalline silicon Si or even germanium Ge.

The method of manufacturing a gain structure 10 according to this third embodiment differs from the method of manufacturing a gain structure 10 according to the first embodiment in that it is provided after the planarization step of the first dielectric material 351 illustrated in FIG. 6A, the following steps:

partial etching of the first dielectric material 351 so as to release the first portion 312 of the first semiconductor zone 311 over part of its height, the first portion 312 of the first semiconductor zone 311 having its face opposite to the second semiconductor zone 321 covered by the first etching mask 220, as illustrated in FIG. 6B, selective deposition of a buffer layer 240 in contact with the first dielectric material 351 and the first etching mask 220, said buffer layer 240 forming an intermediate layer, as illustrated in the FIG. 6C, planarization of the buffer layer 240 in order to bring the first etching mask 220 flush, as illustrated in FIG. 6D, selective removal of the first etching mask 220, as illustrated in FIG. 6E, epitaxy of a fourth semiconductor layer 315 made of the material intended to form the second portion 313 of the first semiconductor zone this 311 in contact with the buffer layer 240 and the first portion 312, as illustrated in FIG. 6F, localized etching of the fourth semiconductor layer 315 and of the buffer layer 240 so as to leave only the parts of the corresponding fourth semiconductor layer 315 to the second portion 313 of the first semiconductor zone 311, as illustrated in FIG. 6G, deposition and planarization of a dielectric material, identical or different from the first dielectric material enclosing the second portion 313 of the first semiconductor zone 311, this so forming a dielectric layer 350 comprising at least the first dielectric material, said dielectric layer

350 thus housing the first, second and third semiconductor zones 311, 321, 331 which succeed one another in pairs contact along the thickness of said dielectric layer 350, formation of a first and a second electrical contact 510, 530 in contact with the second portion 313, 333 of respectively the first and the third semiconductor zone 311, 313 in an identical manner to the step of the method according to the first embodiment illustrated in FIG. 4M.

Of course, the skilled person, from the teaching of this document, is able to modify this manufacturing process, and the others described in this document in order to best meet his needs. It will be noted in particular that it is able to adapt the step of forming the first and second electrical contacts in order to use conventional manufacturing techniques for microelectronics and optoelectronics.

In the context of the practical application in which the first semiconductor zone 311 is gallium arsenide GaAs, the step of depositing a fourth semiconductor layer 315 can, in the same way as for the method according to the first and the second embodiment, be carried out by organometallic vapor phase epitaxy (better known under the acronym MOVPE or under the acronym MOCVD for Metalorganic Chemical Vapor Deposition). Alternatively and less advantageously, the step of depositing a fourth semiconductor layer 315 may be a molecular beam epitaxy.

FIG. 7 illustrates a side section view of a gain structure according to a fourth embodiment in which the second portions 313, 333 of the first and third semiconductor zones 311, 331 extend in opposite directions and do not comprise any part opposite each other. Thus a gain structure 10 according to this fourth embodiment is distinguished from a structure according to the first embodiment only in that the second portion 313 has no part opposite the second portion 333 of the third semiconductor zone

331.

A gain structure 10 according to the invention, whether this is according to the first, second, third or fourth embodiment, is in particular adapted to be assembled with a guiding layer in the context of the formation of a device photonics. This assembly between the guiding layer and the gain structure can be carried out

- in end-to-end coupling of the guide layer and the gain structure 10 longitudinally, the guide layer being able to be of dielectric material or of III-V material,

- in 'adiabatic' coupling, the guiding layer being underlying the gain structure 10.

Thus, with such an assembly, the gain structure allows the formation of a photonic device 1, such as those described above in connection with FIGS. 8A, 8B and 9, said device comprising at least one of:

a laser 15 formed by said gain structure 10 in association with a feedback structure 213,

- an optical amplifier formed by said gain structure 10.

FIGS. 8A and 8B illustrate an example of a hybrid IIIV / Silicon device, in which the guide layer 210 is formed on a substrate 200. According to this example, the active structure 10 and the guide layer 210 are assembled during step for bonding the first, second and third semiconductor layers 310, 320, 330 / first support 300 to the second support 200, the second support 200 comprising the guiding layer 210.

FIGS. 8A and 8B illustrate an example of such a photonic device 1 in which the assembly between the gain structure 10 and the guiding layer 210 is obtained by means of a dielectric interface layer 205, such as a layer of silicon dioxide SiO ₂ . Of course, it is also conceivable, according to a possibility not illustrated, that this assembly is obtained without the use of such a dielectric interface layer 205, the gain structure 10 then being assembled directly in contact with the guiding layer 210 .

FIG. 8A represents a view in longitudinal section of the photonic device 1 while FIG. 8B is a view in lateral section at the level of the second semiconductor zone along the axis YY of FIG. 8A.

Such a photonic device 1 comprises, in addition to the gain structure 10 according to the invention:

a waveguide 211 at least one optical transition zone 212A, 212B between the waveguide 211 and the gain structure 10, a feedback structure 213 distribute under at least part of the gain structure 10 to form an oscillating cavity and thus form a hybrid laser 15 optically connected to the waveguide 211 by the optical transition zones 212A, 212B.

Thus, as illustrated in FIG. 8A, the guiding layer 210 comprises a waveguide 211 which is formed of a fifth and sixth semiconductor layer 211A, 211B preferably both made of silicon Si. The waveguide 211 has thus, with the cumulative thickness of the fifth and sixth semiconductor layer 211A, 211B, a thickness suitable for guiding the electromagnetic radiation emitted by the hybrid laser 15. The hybrid laser 15 shown in FIG. 8A is a distributed feedback laser , also known by the acronym DBF, whose optical feedback structure 213 is formed in the guiding layer under the gain structure 10.

As shown in FIGS. 8A and 8B, the sixth semiconductor layer 211B is partially present under the gain structure 10, longitudinally at the input and at the output of the active structure 10, at the transitions 212A, 212B between the waveguides 211 made of Silicon and the hybrid waveguide formed by the assembly 'gain structure 10 / portion of guide layer 210.

Indeed, the thickness of the sixth semiconductor layer 211B is gradually reduced and has, at the level of the first and second transition zones 212A, 212B, a shape adapted to allow an adiabatic transition between the waveguide 211 and the guide. hybrid wave formed by the gain structure 10 and the portion of guiding layer 210 located under the gain structure 10. Thus, each of the ends of the sixth semiconductor layer 211B forms a transition zone 212A, 212B.

The sixth semiconductor layer comprises, as illustrated in FIG. 8A, a Bragg grating distributed under the gain structure 10 and under the second semiconductor zone 321, the Bragg grating being of the “vertical corrugation” type totally etched in the fifth layer semiconductor 211A as a feedback structure 213.

Of course, this example of a photonic device 1 is described by way of example of a photonic device which may include a gain structure 10 according to the invention and is in no way limiting. The skilled person is thus perfectly capable, from the present disclosure, of integrating a gain structure according to the invention, such as that according to the first to the fourth embodiments, into a photonic device known in the art prior or adapted from those known in the prior art to form a laser.

Similarly, it is perfectly conceivable without departing from the scope of the invention that:

the feedback structure is provided by a distributed Bragg grating selected from the group comprising the distributed Bragg grids with lateral corrugations totally etched in the thickness of the fifth semiconductor layer 211A, the Bragg grids distributed with vertical corrugations partially etched in the thickness of the fifth semiconductor layer 211B and the Bragg gratings distributed with vertical corrugations totally etched in the thickness of the sixth semiconductor layer 211B, or at least one of the fifth and sixth semiconductor layers 211A, 211B comprises level of transition zones 212A, 212B, a first and a second mirror so as to form an oscillating cavity comprising the second semiconductor zone 321, the first and second mirror forming the feedback structure.

It may also be noted that it is perfectly conceivable, without departing from the scope of the invention, that each of the transition zones can be formed at least in part in one of the dielectric layer 350, the guiding layer 210 and the possible interface dielectric layer 205.

Likewise, the optical feedback structure, whether provided by a Bragg grating distributed under the second semiconductor region 321, or by first and second mirrors, can also be formed at least in part in the one of the dielectric layer 350, the guiding layer 210 and the optional interface dielectric layer 205.

Of course, this example of a photonic device 1 is described by way of example of a photonic device which may include a gain structure 10 according to the invention and is in no way limiting. A person skilled in the art is thus perfectly capable, from the present disclosure, of integrating a gain structure according to the invention, such as those according to the first to the fourth embodiments, into a photonic device known in the art prior or adapted from those known in the prior art to form a laser.

Thus, in particular, a person skilled in the art is able to combine a gain structure 10 according to the invention with a photonic device as described by T. Kakitsuka and his co-authors in their work published in 2016 in the scientific journal "NTT technical review »volume 14 number 1 pages 1 to 7. Such a coupling, already described in connection with FIG. 2C, could thus be done by means of an end-to-end coupling of one end of the gain structure 10 with a waveguide formed end-to-end with the gain structure 10, the contact zone between the end of the gain structure 10 and the end of the waveguide then forming the transition zone. According to this possibility, the waveguide can have a higher refractive index than the index of the dielectric layer 350, the waveguide 211 being for example made of a silicon oxide SiO _x , a silicon nitride SiN _x , or a silicon nitride oxide SiOyNx, or other dielectric material. The waveguide can also be produced in an III-V semiconductor.

These latter examples are of course given by way of illustration of the possibilities of the invention and are in no way limiting, the gain structure according to the invention possibly being compatible, in fact, with any feedback structure known to those skilled in the art. in the field of photonic devices and with all the configurations of photonic devices compatible with a gain structure of the vertical type.

It should also be noted that a gain structure 10 according to the invention, whether this is according to the first, second or third, fourth embodiment, is also adapted to be assembled with a guiding layer 210 of a photonic device for forming an optical amplifier of said photonic device.

FIG. 9 thus illustrates an example of a photonic device 1 according to such a possibility. Such a photonic device differs from a photonic device 1 such as those illustrated in FIGS. 8A and 8B in that it does not have a feedback structure. Thus, without such a feedback structure, the gain structure is capable of providing optical amplification over a wide range of wavelengths.

Due to the similarities, all of the remarks and other lessons from this document concerning photonic devices comprising a gain structure forming a laser with a feedback structure apply identically to photonic devices comprising a gain structure forming an optical amplifier, with the exception, of course, of lessons concerning feedback structures.

Claims (15)

1. Gain structure (10) intended for the formation of a photonic device (1) comprising at least one of a laser (15) and an optical amplifier (16), the gain structure (10) comprising: a dielectric layer (350) comprising at least one dielectric material, a first, a second and a third semiconductor zone (311, 321, 331) housed in the dielectric layer (350) and succeeding each other in pairs contact along the thickness of said dielectric layer (350), in which the first and third semiconductor zones (311, 331) are respectively of a first and a second type of conductivity opposite to each other and in which the second semiconductor zone (321) forms a gain medium capable of emitting light, the gain structure (10) being characterized in that the first and third semiconductor zone (311, 331) each comprise a first portion (312, 332) in contact with the second semiconductor zone (321) and a second portion (313, 333) extending from the first portion (312, 332) along the dielectric layer (350) in a direction opposite to the secondsemiconductor zone (321), the gain structure (10) further comprising first and second electrical contacts (510, 530) in contact with the second portion (313, 333) of the first and third semiconductor zones (311, respectively) , 331) to an end part of said portion (311, 331) which is opposite from the second semiconductor zone (321). 2. gain structure (10) according to claim 1, in which the cumulative thickness of the first portion (312) of the first semiconductor zone (311), of the second semiconductor zone (321) and of the first portion (332 ) of the third semiconductor zone (333) is less than 1 μm, this cumulative thickness is preferably less than 700 nm. 3. gain structure (10) according to claim 1 or 2, in which the second portion (333) of the third semiconductor zone (331) extends in a direction opposite to the direction in which the second portion extends ( 313) of the first semiconductor (311) so that the third semiconductor zone (331) has no part opposite the first contact (510). 4. Photonic device (1) comprising: at least one waveguide (211), a gain structure (10) according to any one of claims 1 to 3, at least one transition zone between the waveguide (211) and the gain structure (10) for forming one of a laser (15) and an optical amplifier (15). 5. Photonic device (1) according to claim 4, comprising a substrate, defining a substrate plane, and a guide layer (210) housing the waveguide (211), in which, the guide layer (210) and the gain structure (10) are arranged in the same plane parallel to the substrate plane, the waveguide (211) being coupled to the gain structure (10) in an end-to-end coupling. 6. Photonic device (1) according to claim 4 further comprising a guide layer (210) in which is housed the waveguide (211), in which the guide layer (210) comprises a first and a second face, the gain structure (10) comprising a first and a second face with the third semiconductor zone facing the second face, and in which the guiding layer (210) is assembled by its first face to the second face of the gain structure ( 10). 7. Photonic device (1) according to claim 6, in which the assembly of the guiding layer (210) to the second face of the gain structure is obtained by means of a dielectric interface layer (205). 8. Photonic device (1) according to claim 6 to 7, wherein the at least one transition zone is housed at least partially in one of the dielectric layer (350), the guiding layer (210) and the possible interface dielectric layer (205). 9. Photonic device (1) according to any one of claims 4 to 8, in which the gain structure (10) forms an optical semiconductor amplifier. 10. Photonic device (1) according to any one of claims 4 to 8, in which the photonic device (1) further comprises a feedback structure to form an oscillating cavity comprising at least part of the second semiconductor zone ( 321) so as to form a laser optically connected to the waveguide by at least one optical transition zone. 11. Method for manufacturing a gain structure (10), said gain structure (10) intended for the formation of a photonic device (1) comprising at least one of a laser (15) and an optical amplifier (16), the manufacturing process comprising the following steps: providing a first, a second and a third semiconductor layer (310, 320, 330) formed of materials intended to respectively form a first portion (312) of a first semiconductor zone (311), a second zone semiconductor (321) and a third semiconductor zone (331), the first, second and third semiconductor layers (310, 320, 330) succeeding each other in pairs, localized etching of the first and second semiconductor layers (310, 320 ) in order to respectively form the first portion (312) of the first semiconductor zone (311) and the second semiconductor zone (321), the first portion (312) of the first semiconductor zone (311) being in contact with the second semiconductor zone (321), localized etching of the third semiconductor layer (330) in order to form the third semiconductor zone (331), the third semiconductor zone (331) comprising a first portion ( 332) in contact with the second semiconductor zone (321) and a second portion (333) extending from the first portion (332) of the third semiconductor zone (331) opposite the second semiconductor zone (321 ), deposition of at least a first dielectric material encapsulating the first portion (312) of the first semiconductor zone (311), the second semiconductor zone (321) and the third semiconductor zone (331), partial removal of the first dielectric material so releasing at least partially the first portion (312) of the first semiconductor zone (311), forming a second portion (313) of the first semiconductor zone (311) in contact with the first portion (312) of the first zone semiconductor (311), the second portion (313) extending from the first semiconductor zone (311) in a direction opposite to the second semiconductor zone (321), encapsulating at least the second th portion (313) of the first semiconductor zone (311) and the part of the first portion (312) of the first semiconductor zone (311) which is not housed in the first dielectric material, so as to form a layer dielectric (350) comprising at least the first dielectric material, said dielectric layer (350) thus housing the first, second and third semiconductor zones (311, 321, 331) which succeed one another in pairs contact along the thickness of said dielectric layer (350), forming a first and a second electrical contact (510, 520) in contact with the second portion (313, 333) of respectively the first and the third semiconductor zone (311, 313) on an end portion of said portion (311, 331) which is opposite from the second semiconductor zone (321). 12. Method for manufacturing a gain structure (10) according to claim 12, in which the step of forming the second portion (313, 333) of the first semiconductor zone (310) comprises the following substeps: deposition of a layer of a first semiconductor material of the second portion (313) of the first semiconductor zone (311) in contact with the first dielectric material and of the first portion (312) of the first semiconductor zone (311), etching localized with the layer of the first semiconductor material of the second portion (313) to form the first semiconductor zone. 13. A method of manufacturing a gain structure (10) according to claim 12, in which it is provided, between the step of partial removal of the first dielectric material and the step of forming a second portion of the first area; the following steps: deposition of an intermediate layer (351, 240) in contact with the layer of the first dielectric material and of the first portion (312) of the first semiconductor zone (311), the material of the intermediate layer being selected from a dielectric material and a semiconductor material, arrangement of an opening in the intermediate layer (351, 240) to at least partially release the first portion of the first semiconductor zone (311), and in which the step of forming the second portion (313) of the first semiconductor zone (311) comprises the following sub-steps: deposition of a layer of the semiconductor material of the first semiconductor zone (311) in contact with the intermediate layer (351, 240) and of the first portion (312) of the first semiconductor zone (311), localized etching of at least the layer of semiconductor material of the first semiconductor zone (311) in order to form the second portion (313) of the first semiconductor zone (311) and therefore to form the first semiconductor zone (311). 14. A method of manufacturing a gain structure (10) according to any one of claims 12 to 13, in which the localized etching step of the first and the second semiconductor layer (310, 320) comprises the sub- following steps : formation of a hard mask covering the part of the first semiconductor layer (310) intended to form the first portion (312) of the first semiconductor zone (311), etching of the first and second semiconductor layers (310, 320), the parts of the first and second semiconductor layer (310, 320) corresponding respectively to the first portion (312) of the first semiconductor zone (311) and to the second semiconductor zone (321) being protected by the hard mask. 15. A method of manufacturing a photonic device (1) comprising a gain structure (10), in which the gain structure (10) is manufactured according to a manufacturing method according to any one of claims 12 to 14, which device further comprising: at least one waveguide (211), at least one transition zone between the waveguide (211) and the gain structure (10).