Method for producing optoelectronic devices

Abstract

Title: Method for producing optoelectronic devices The invention relates to a method for manufacturing a first optoelectronic device operating at a wavelength λ1 and a second optoelectronic device operating at a wavelength λ2 > λ1, the first device comprising a first stack comprising a first encapsulation layer (10) of thickness e10 and layers (11, 12, 13, 14, 15) of thickness e1i (i = 1…n), and the second device comprising a second stack comprising a second encapsulation layer (20) of thickness e20 and layers (21, 22, 23, 24, 25) of thickness e2i (i = 1…n), the method comprising: • Forming the second stack by sizing the thicknesses e20 and e2i as a function of λ2, • Forming the first stack by sizing the thicknesses e1i by homothety and adjust the thickness e10 so that the stacks have the same height, • Carry out the same technological step (E3, E4, E5,E6) on the stacks. Figure for the abstract: Fig.1,

Description

Title of the invention: Method for producing optoelectronic devices Technical field

[0001] The present invention relates to the field of optoelectronics. It can be implemented for the production of light-emitting components, in particular in the mid-infrared (MIR) range. It finds a particularly advantageous application in the production of quantum cascade laser sources emitting at different wavelengths. STATE OF THE ART

[0002] The mid-infrared (MIR) domain has a relatively wide spectral range, covering in particular wavelengths between 4 pm and 10 pm. The manufacture of monochromatic MIR light sources over this spectral range generally requires a dedicated manufacturing line for each wavelength. This makes it possible to adjust the structure of each MIR source to optimize the operation of these sources. A MIR source emitting at 4 pm is thus structurally different from a MIR source emitting at 10 pm. A MIR source typically comprises a stack of optically active layers based on III-V materials, intended in particular to emit, propagate and / or confine light radiation. Depending on the desired emission wavelength, the thicknesses of these layers can be very different from one MIR source to another.

[0003] The manufacturing processes for these MIR sources are therefore complex and expensive to implement. One challenge is to simplify the manufacturing processes for these MIR sources to develop a technological sector compatible with the microelectronics industry for a wide range of wavelengths.

[0004] An objective of the present invention is to meet at least part of this need.

[0005] In particular, an object of the present invention is a method for manufacturing optoelectronic devices operating at different wavelengths, which is less expensive and / or which has better industrial compatibility with existing methods. Such a method is advantageously implemented to produce different optoelectronic devices operating at different wavelengths.

[0006] Other objects, features and advantages of the present invention will become apparent from a consideration of the following description and accompanying drawings. It is understood that other advantages may be incorporated. SUMMARY

[0007] To achieve this objective, according to one embodiment, a method is provided for manufacturing at least a first optoelectronic device operating at a first wavelength XI and a second optoelectronic device operating at a second wavelength X2 > XI.

[0008] The first optoelectronic device comprises a first stack along a z direction on a first substrate and the first stack comprises a first lower encapsulation layer of thickness e10 along the z direction and a plurality of first layers of thickness e11 (i = 1.. .m) along the z direction. The second optoelectronic device comprises a second stack along the z direction on a second substrate and the second stack comprises a second lower encapsulation layer of thickness e20 along the z direction and a plurality of second layers of thickness e2i (i = 1.. .n) along the z direction. The second layers of thickness e2i have optical functions similar to those of the first layers of thickness e11.

[0009] Advantageously, the method comprises the following steps: - Form the second stack on the second substrate, by sizing the thicknesses e20 and e2i according to the second wavelength X2, - Form the first stack on the first substrate, by sizing the thicknesses elO and eli according to: [Math 1] eli = with 0.7 < ai < 1.3 ÀZ [Math 2] In . .eli-2^. - Carry out at least one additional technological step on the first and second stacks, for example etching the first and second stacks to the same depth along z, so as to obtain the first and second optoelectronic devices.

[0010] In this method, the first and second stacks are dimensioned so as to advantageously have the same height. The first and second stacks can thus be advantageously structured by one or more common technological steps. Etching patterns can be defined via common photolithography parameters for both stacks (thickness of the resins, focal plane, etc.). The first and second stacks can then be etched by the same etching process. Passivation and subsequent contact formation can also be carried out in the same way on both stacks.

[0011] Typically, the steps of forming the first and second stacks are carried out separately. The first stack may be formed by epitaxy on a substrate donor before being transferred to the first substrate. The second stack can be formed by epitaxy on another donor substrate before being transferred to the second substrate. After formation of the first and second stacks, a certain number of common technological steps can be carried out on these two stacks. This makes it possible to design a common technological process for the production of the first and second optoelectronic devices. The first and second stacks can advantageously be part of the same technological batch. According to one example, the first stack on the first substrate forms a first wafer of this technological batch and the second stack on the second substrate forms a second wafer of this technological batch. When equipment in the microelectronics industry receives such a technological batch, each wafer of the technological batch is treated in the same way by the equipment.The cost of the process for producing the first and second optoelectronic devices is advantageously reduced.

[0012] According to another aspect of the invention, a system is provided for manufacturing at least one first optoelectronic device operating at a first wavelength X1 and a second optoelectronic device operating at a second wavelength X2 > XL. The system comprises at least one first substrate carrying a first stack in a z direction and a second substrate carrying a second stack in the z direction. The first stack comprises a first lower encapsulation layer of thickness e10 in the z direction and a plurality of first layers of thickness e11 (i = 1.. .n) in the z direction. The second stack comprises a second lower encapsulation layer of thickness e20 in the z direction and a plurality of second layers of thickness e2i (i = 1.. .n) in the z direction. The second layers of thickness e2i and the first layers of thickness e11 have similar optical functions.

[0013] Advantageously, the thicknesses elO, e20 and eli, e2i verify the following relationships: [Math 3] = eliÿaiwith °>7 ai [Math 4] Al 0 - e20 + L^eli - L(= / 71 /

[0014] The first and second stacks thus have substantially the same height along z.

[0015] According to an example, this system corresponds to a technological batch of the microelectronics industry, in which the first stack on the first substrate forms a first plate and the second stack on the second substrate forms a second plate. Such a batch can advantageously be processed by common technological steps, to form first and second optoelectronic devices. Different ironies. The above-mentioned advantages of the process apply mutatis mutandis.

[0016] According to another aspect of the invention, a device is provided comprising a first stack and a second stack structured on the same support. The first stack comprises a first lower encapsulation layer of thickness el0 in a z direction and at least: - a first active layer of thickness el 1 along z, intended to emit or receive radiation having a first wavelength XI, and - a first upper encapsulation layer of thickness el2 along z.

[0017] The second stack comprises a second lower encapsulation layer of thickness e20 in the z direction and at least: - a second active layer of thickness e21 along z, intended to emit or receive radiation having a second wavelength X2 > XI, and - a second upper encapsulation layer of thickness e22 along z.

[0018] Advantageously, the thicknesses el 1, el2 verify the following relationships: [Math 5] e!2 = will elect with 0.7 < «2 < 1.3 [Math 6] el 1 = e2L“.al with 0.7 £ al < 1.3 * a2 * "

[0019] Advantageously, the first and second stacks have substantially the same height h along z. BRIEF DESCRIPTION OF THE FIGURES

[0020] The aims, objects, as well as the characteristics and advantages of the invention will emerge more clearly from the detailed description of embodiments thereof which are illustrated by the following accompanying drawings in which:

[0021] [Fig.l] [Fig.l] illustrates in cross-section an optoelectronic device according to an embodiment of the present invention.

[0022] [Fig.2A][Fig.2B] Figures 2A, 2B respectively illustrate in cross-section a second and a first optoelectronic device according to an embodiment of the present invention.

[0023] [Fig.3A][Fig.3B] Figures 3A, 3B illustrate in cross-section a simulated distribution of the light radiation propagating in the second and first optoelectronic devices of the embodiment illustrated in Figures 2A, 2B.

[0024] [Fig.4] [Fig.4] illustrates a variation in effective index and a variation in losses optical as a function of wavelength, simulated for different optoelectronic devices emitting at different wavelengths, according to an embodiment of the present invention.

[0025] [Fig.5] [Fig.5] illustrates a variation of the normalized coupling constant as a function of wavelength, simulated for different optoelectronic devices emitting at different wavelengths, according to an embodiment of the present invention.

[0026] [Fig.6] [Fig.6] illustrates a process flow comprising technological steps common to the production of different optoelectronic devices emitting at different wavelengths, according to an embodiment of the present invention.

[0027] The drawings are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications. In particular, on the schematic diagrams, the thicknesses of the different layers and portions, and the dimensions of the patterns are not representative of reality. DETAILED DESCRIPTION

[0028] Before commencing a detailed review of embodiments of the invention, optional features which may possibly be used in combination or alternatively are set out below:

[0029] According to one example, the at least one same technological step of the production method comprises one or more steps taken from: etching along z of a waveguide pattern, passivation, formation of an upper electrical contact, formation of a lower electrical contact, metallization. Advantageously, all these steps can be carried out both on the first stack and on the second stack. Some of the methods for producing the first and second optoelectronic devices are common. This makes it possible to design a partly generic technological process for producing different optoelectronic devices emitting at different wavelengths, in particular in the mid-infrared range.

[0030] According to one example, the plurality of first layers of thickness eli comprises at least one first active layer of thickness el 1 along z, intended to emit or receive radiation having the first wavelength X1, and a first upper encapsulation layer of thickness el2 along z. According to one example, the plurality of second layers of thickness e2i comprises at least one second active layer of thickness e21 along z, intended to emit or receive radiation having the second wavelength X2, and a second upper encapsulation layer of thickness e22 along z. The first and second stacks comprise similar layers typically having the same functions. In particular, each A stack comprises an active layer sandwiched between encapsulation layers. Encapsulation layers may also be referred to as "cladding layers" or "cover layers"; encapsulation layers are typically translated as "cladding layers" in English.

[0031] According to an example, the plurality of first layers of thickness eli further comprises a first lower optical confinement layer of thickness el3 interposed between the first lower encapsulation layer and the first active layer, and a first upper optical confinement layer of thickness el4 interposed between the first upper encapsulation layer and the first active layer. According to an example, the plurality of second layers of thickness e2i further comprises a second lower optical confinement layer of thickness e23 interposed between the second lower encapsulation layer and the second active layer, and a second upper optical confinement layer of thickness e24 interposed between the second upper encapsulation layer and the second active layer, with: [Math 7] 61 1 = e2Ü|.6 / l with 0.7 < al < 1.3 Az [Math 8] 6'12 = e22^.a2 with 0.7 < «2 < 1.3 [Math 9] 613 = e23.^.a3 with 0.7 < «3 < 1.3 [Math 10] 614= e2^.a4 with 0.7 S a4 < 1.3 AZ [Math 11] 610 = e20 + e21 + 622 + 623+624 - <612 + el 1 + el3 + 614)

[0032] According to one example, the plurality of first layers of thickness eli further comprises a first stop layer of thickness el5 under the first lower encapsulation layer. According to one example, the plurality of second layers of thickness e2i further comprises a second stop layer of thickness e25 under the second lower encapsulation layer. According to one example, the thicknesses el5, e25 are such that: [Math. 12] 6'15 = 625.11 ,a5 with 0.7 < «5 < 1.3 AZ This makes it possible to avoid an evanescent wave phenomenon by the first stopping layer of thickness el5.

[0033] According to one example, the first and second stacks are etched according to the same depth h along z to form first and second protruding structures, respectively having a first width W1 along an x direction and a first length L1 along a y direction, and a second width W2 along the x direction and a second length L2 along the y direction, the method further comprising, before etching the first and second stacks: - Determine the second width W2 and the second length L2 as a function of the second wavelength X2, - Determine the first width W1 and the first length L1 according to: [Math 13] W1 with °'7 - aw - 1 >3 [Math 14] L1 = L2^.aL with 0.7 < aL £ 1.3

[0034] According to an example, the method further comprises a first etching configured to form a first grating having a first depth on the first stack carried by the first substrate, and independently a second etching configured to form a second grating having a second depth on the second stack carried by the second substrate. This typically makes it possible to produce distributed feedback lasers, called DFB for “Distributed FeedBack”. The first and second gratings are wavelength-specific. They are typically formed by independent first and second etchings.

[0035] According to one example, the first and second wavelengths X1, X2 are chosen in the mid-infrared range between 2 pm and 15 pm, preferably between 4 pm and 10 pm.

[0036] According to one example, the first stack is bordered by first trenches of depth h in the z direction and forms a first projecting structure, and the second stack is bordered by second trenches of the same depth h in the z direction and forms a second projecting structure.

[0037] According to an example, the plurality of first layers of thickness eli comprises at least one first active layer of thickness el 1 along z, intended to emit or receive radiation having the first wavelength X1, and a first upper encapsulation layer of thickness el2 along z, and the plurality of second layers of thickness e2i comprises at least one second active layer of thickness e21 along z, intended to emit or receive radiation having the second wavelength X2, and a second upper encapsulation layer of thickness e22 along z, with: [Math 15] el 2 = e22^.a2 with 0.7 < «2 < 1.3 AZ [Math 16] 611 = with 0.7 < «1 < 1.3

[0038] According to an example, the first projecting structure has a first width W1 in an x direction and a first length L1 in a y direction, and the second projecting structure has a second width W2 in the x direction and a second length L2 in the y direction, the first and second widths W1, W2 and the first and second lengths L1, L2 satisfying the following relationships: [Math 17] Wl = W2^.aw with 0.7 < aw < 1.3 [Math 18] Ll = L2^.aL with 0.7 < aL < 1.3.

[0039] According to one example, the first and second substrates are based on silicon and the first and second stacks are based on III-V materials, the first and second stacks respectively comprising first and second optical isolation layers configured to avoid optical coupling at wavelengths X1 and X2 with the first and second substrates.

[0040] According to one example, the first and second optoelectronic devices correspond to first and second distributed feedback quantum cascade lasers.

[0041] Unless incompatibility exists, it is understood that all of the above optional features and / or the indicated variants may be combined so as to form an embodiment which is not necessarily illustrated or described. Such an embodiment is obviously not excluded from the invention. The features of one aspect of the invention, for example the system, the device or the method, may be adapted mutatis mutandis to another aspect of the invention.

[0042] It is specified that, in the context of the present invention, the terms "on", "overcomes", "covers", "underlying", "facing" and their equivalents do not necessarily mean "in contact with". Thus, for example, the deposition of a first layer on a second layer does not necessarily mean that the two layers are directly in contact with each other, but means that the first layer at least partially covers the second layer by being either directly in contact with it, or by being separated from it by at least one other layer or at least one other element.

[0043] A layer may also be composed of several sub-layers of the same material or of different materials.

[0044] A substrate, a stack, a layer, “based” on a material A, is understood to mean a substrate, a stack, a layer comprising this material A only or this material A and possibly other materials, for example alloying elements and / or doping elements. Thus, a silicon-based substrate is understood to mean, for example, a Si or doped Si substrate, or SiGe. An InP-based layer is understood to mean, for example, an InP, doped InP layer, or InP alloys. A silicon nitride SiN passivation layer may, for example, comprise non-stoichiometric silicon nitride (SixNy), or stoichiometric silicon nitride (Si3N4).

[0045] Several embodiments of the invention implementing successive steps of the manufacturing method are described below. Unless explicitly stated, the adjective "successive" does not necessarily imply, even if this is generally preferred, that the steps follow one another immediately, intermediate steps being able to separate them.

[0046] Furthermore, the term “step” means the carrying out of a part of the method, and can designate a set of sub-steps.

[0047] Furthermore, the term "step" does not necessarily mean that the actions carried out during a step are simultaneous or immediately successive. Certain actions of a first step may in particular be followed by actions linked to a different step, and other actions of the first step may be repeated subsequently. Thus, the term step does not necessarily mean unitary and inseparable actions in time and in the sequence of phases of the process.

[0048] A preferably orthonormal reference frame, comprising the axes x, y, z is shown in the attached figures. When a single reference frame is shown on the same sheet of figures, this reference frame applies to all the figures in this sheet.

[0049] In the present patent application, the thickness of a layer is taken along a direction normal to the main extension plane of the layer. Thus, a layer typically has a thickness along z. The relative terms "on", "overcomes", "under", "underlying", "intercalated", "above", "below" refer to positions taken along the z direction. This list of terms is not exhaustive. Other relative terms can be easily specified as needed, by referring to the accompanying drawings.

[0050] The terms "vertical", "vertically" refer to a direction along z. The terms "horizontal", "horizontally", "lateral", "laterally" refer to a direction in the xy plane. Unless explicitly stated, thickness, height and depth are measured along z.

[0051] An element located "perpendicular to" or "in line with" another element means that these two elements are both located on the same line perpendicular to a plane in which a lower or upper face of a substrate mainly extends, that is to say on the same line oriented vertically in the figures.

[0052] The present invention finds as its preferred field of application a scalable platform for manufacturing QCL quantum cascade lasers in the mid-infrared (MIR) spectral range.

[0053] The optoelectronic devices according to the present invention typically emit monochromatic or quasi-monochromatic light radiation, each having a main wavelength. The main wavelength is the only wavelength emitted by a monochromatic laser, or the wavelength mainly emitted by a quasi-monochromatic laser.

[0054] In the context of the present invention, the light radiation is typically guided and / or confined so as to ensure its propagation along a main propagation direction, taken along the x axis in the accompanying drawings. The light radiation is preferably coherent and monochromatic. The light radiation preferably propagates according to a single optical propagation mode, typically the transverse electric (TE00) or transverse magnetic (TM00) fundamental optical mode.

[0055] To guide and / or confine the light radiation, the first and second stacks are typically structured to form first and second protruding structures, respectively. In the following, the first protruding structure typically corresponds to a portion of the first stack. The second protruding structure typically corresponds to a portion of the second stack.

[0056] The terms “substantially”, “approximately”, “of the order of” mean “to within 10%” or, when it is an angular orientation, “to within 10°” and preferably “to within 5°”. Thus, a direction substantially normal to a plane means a direction having an angle of 90+10° relative to the plane.

[0057] [Fig.l] generically illustrates an optoelectronic device according to the invention. The numerical references beginning with the number 1 relate to a first optoelectronic device. The numerical references beginning with the number 2 relate to a second optoelectronic device. The first and second optoelectronic devices typically comprise the same elements. There is a functional correspondence between two elements of the same nature. The alphanumeric references beginning with a letter followed by the number 1 relate to dimensions of the first optoelectronic device. The alphanumeric references beginning with a letter followed by the number 2 relate to dimensions of the second optoelectronic device. The dimensions of the elements of the first optoelectronic device are typically different from those of the elements of the second optoelectronic device.The first optoelectronic device is configured to operate at a first wavelength Xp. The second optoelectronic device is configured to operate at a second wavelength X2.

[0058] The first optoelectronic device typically comprises, in stacking along z: - A first substrate 110, preferably based on silicon. - A first layer of bonding 111, for example based on SiO2. - A first optical insulation layer 16, typically based on InP. - A first etching stop layer 15 of thickness eis, for example based on InGaAs. - A first lower encapsulation layer 10 of thickness ei0, for example based on InP. - A first lower optical confinement layer 13 thick, for example based on InGaAs. - A first active layer 11 of thickness, comprising for example multiple quantum wells based on ternary AlInAs, GalnAs or quaternary of the GalnAsP or AlGalnAs type. This first active layer 11 is preferably configured to emit a first light radiation of wavelength Xp - A first upper optical confinement layer 14 of thickness ei4, for example based on InGaAs. - A first upper encapsulation layer 12 of thickness ei2, for example based on InP. According to one possibility, the first upper encapsulation layer 12 can be structured in the form of a network 120. Such a network 120 is typically presented, in a known manner, in the form of trenches regularly spaced along x. The trenches of the network 120 have a depth di along z and are distributed according to a network pitch Pi along x. The depth di and the network pitch pi depend on the wavelength Xb

[0059] The stack of layers 16, 15, 10, 13, 11, 14, 12 forms a first stack. This first stack is preferably based on III-V materials. It can be formed by epitaxy on a donor substrate, for example based on InP, then possibly transferred to the first substrate 110, for example based on silicon. A first bonding layer 111, for example based on silicon oxide, can thus be intercalated between the first substrate 110 and the first stack. During epitaxy, the stack is typically in the form of planar layers extending over the entire surface of the donor substrate. This stack is then structured in order to produce the first optoelectronic device.

[0060] In particular, the stack of layers 16, 15, 10, 13, 11, 14, 12 is at least partly etched along z so as to form a first structure 1 projecting from the optical insulation layer 16. This first projecting structure 1 notably allows to confine and / or guide the first light radiation of wavelength Xi emitted by the first active layer 11. In this example, the first light radiation propagates mainly along x. The first optoelectronic device thus has a first characteristic dimension W1 along y.

[0061] The first optoelectronic device typically comprises one or more passivation layers 100, 100' on the sides of the first projecting structure 1. The first optoelectronic device typically comprises a first lower electrical contact 101 configured to inject charge carriers, for example electrons, into the first active layer 11 via the first lower encapsulation layer 10, and a first upper electrical contact 102 configured to inject charge carriers, for example holes, into the first active layer 11 via the first upper encapsulation layer 12. The first optoelectronic device is for example a first distributed feedback quantum cascade laser, emitting at the wavelength Xb

[0062] The second optoelectronic device typically comprises, in stacking along z: - A second substrate 210, preferably silicon-based. - A second bonding layer 211, for example based on SiO2. - A second optical isolation layer 26, typically based on InP. - A second etching stop layer 25 with a thickness of e25, for example based on InGaAs. - A second lower encapsulation layer 20 of thickness e20, for example based on InP. - A second lower optical confinement layer 23 of thickness e23, for example based on InGaAs. - A second active layer 21 of thickness e2b comprising for example multiple quantum wells based on ternary AlInAs, GalnAs or quaternary of the GalnAsP or AlGalnAs type. This second active layer 21 is preferably configured to emit a second light radiation of wavelength X2. - A second upper optical confinement layer 24 of thickness e24, for example based on InGaAs. - A second upper encapsulation layer 22 of thickness e22, for example based on InP. According to one possibility, the second upper encapsulation layer 22 can be structured in the form of a network 220. Such a network 220 is typically presented, in a known manner, in the form of trenches regularly spaced along x. The trenches of the network 220 have a depth d2 along z and are distributed according to a network pitch p2 along x. The depth d2 and the grating pitch p2 depend on the wavelength X2.

[0063] The stack of layers 26, 25, 20, 23, 21, 24, 22 forms a second stack. This second stack is preferably based on III-V materials. It can be formed by epitaxy on a donor substrate, for example based on InP, then possibly transferred to the second substrate 210, for example based on silicon. A second bonding layer 211, for example based on silicon oxide, can thus be intercalated between the second substrate 210 and the second stack. During epitaxy, the stack is typically in the form of planar layers extending over the entire surface of the donor substrate. This stack is then structured in order to produce the second optoelectronic device.

[0064] In particular, the stack of layers 26, 25, 20, 23, 21, 24, 22 is at least partly etched so as to form a second structure 2 projecting from the optical insulation layer 26. This second projecting structure 2 makes it possible in particular to confine and / or guide the second light radiation of wavelength X2 emitted by the second active layer 21. In this example, the second light radiation propagates mainly along x. The second optoelectronic device thus has a second characteristic dimension W2 along y.

[0065] The second optoelectronic device typically comprises one or more passivation layers 200, 200' on the sides of the second projecting structure 2. The second optoelectronic device typically comprises a second lower electrical contact 201 configured to inject charge carriers, for example electrons, into the second active layer 21 via the second lower encapsulation layer 20, and a second upper electrical contact 202 configured to inject charge carriers, for example holes, into the second active layer 21 via the second upper encapsulation layer 22. The second optoelectronic device is for example a second distributed feedback quantum cascade laser, emitting at the wavelength X2.

[0066] An object of the present invention is to enable the first and second optoelectronic devices to be manufactured by a partly common technological process. The principle adopted in the context of the development of the present invention relates to a dimensioning of the layers of the first and second stacks making it possible to obtain the same height h for the first and second protruding structures 1, 2 of the first and second optoelectronic devices. In particular, the present invention relates to rules for dimensioning the thickness of the etch stop layer, the lower encapsulation layer, the lower optical confinement layer, the active layer, the upper optical confinement layer, the upper encapsulation layer, for each protruding structure 1, 2.

[0067] According to one embodiment, a first step consists in determining what is the minimum height h allowing all of the optoelectronic devices to operate. In practice, the minimum height h typically corresponds to the optoelectronic device having the longest operating wavelength. In the example illustrated, the second wavelength X2 is greater than the first wavelength Xb. The thicknesses e25, e20, e23, e2b e24, e22 of the layers 25, 20, 23, 21, 24, 22 are therefore first fixed so that the second optoelectronic device has the optical properties required for the second wavelength X2. In this case, e25 + e20 + e23 + e2i + e24 + e22 = h. The thicknesses e^, ei0, en, en, eM, ei2 of the layers 15, 10, 13, 11, 14, 12 are then calculated from the thicknesses e25, e20, e23, e2b e24, e22 of the layers 25, 20, 23, 21, 24, 22.This calculation typically consists of applying a homothety for the thicknesses e^, en, en, eM, ei2 of the layers 15, 13, 11, 14, 12, and compensating for the difference in height with respect to h by varying the thickness ei0 of the layer 10. The first lower encapsulation layer 10 has a thickness compensation role and is therefore similar to a buffer layer. The homothety factor depends on the wavelengths Xb X2. .

[0068] According to a dimensioning example, for a second wavelength X2 = 9.6 pm, the thicknesses e26, e25, e20, e23, e2b e24, e22 of the layers 26, 25, 20, 23, 21, 24, 22 can be fixed such that: - The thickness e26 of the second optical insulation layer 26 is of the order of 6.5 pm, - The thickness e25 of the second stop layer 25 is of the order of 300 nm, - The thickness e20 of the second lower encapsulation layer 20 is the order of 0.7 pm, - The thickness e23 of the second lower optical confinement layer 23 is of the order of 175 nm, - The thickness e2i of the second active layer 21 is of the order of 3.09 pm, - The thickness e24 of the second upper optical confinement layer 24 is of the order of 195 nm, - The thickness e22 of the second upper encapsulation layer 22 is of the order of 0.7 pm.

[0069] According to one possibility, the sizing rules are written, for i = 1.. .n (with n = 5 in the illustrated example): [Math 19] elz = e2L~ .ai with 0.7 < ai < 1.3 [Math 20] In

[0070] ai is preferably of the order of 1. This makes it possible to optimize the optical properties of each stack of layers, for each optoelectronic device. A tolerance of ± 30% on the homothety factor can be applied for each of the thicknesses eh, without the performance of the optoelectronic devices being significantly degraded.

[0071] Alternatively, the homothety factor can be corrected for the refractive index dispersion, according to: [Math 21] eli = e2i — — with the effective index of the layers of the stack at X2'nl wavelengths Xi, X2 respectively.

[0072] The thickness ei6 of the first optical insulation layer 16 is preferably substantially equal to the thickness e26 of the second optical insulation layer 26. The first and second stacks of layers based on III-V materials thus have a substantially identical total height.

[0073] The same homothety can be applied to the other dimensions of the first projecting structure 1, in particular to the width W1 along y and to the length L1 along x (not illustrated on the section yz of the accompanying figures).

[0074] According to one possibility, the sizing rules for the width W1 and the length L1 are written: [Math 22] Wl = W2^.àw- with 0.7 < aw < 1.3 [Math 23] L1 = with 0.7 < aL < 1.3.

[0075] A tolerance of ± 30% on the homothety factor can be applied for each of these dimensions Wl, LL. The performance of the optoelectronic devices remains substantially constant in this range of dimensions.

[0076] Figures 2A, 2B respectively illustrate a second optoelectronic device and a first optoelectronic device comprising second and first protruding structures of the same height h. The second optoelectronic device is sized to operate at a wavelength X2 = 9.6 pm. The first optoelectronic device is sized to operate at a wavelength Xi = 4.2 pm. The thicknesses of the layers 15, 10, 13, 11, 14, 12 of the first protruding structure 1 were sized according to the sizing rules set out above ([Mathl9] and [Math 20]), from the thicknesses of the layers 25, 20, 23, 21, 24, 22 of the second protruding structure 2.

[0077] The width Wl of the first projecting structure 1 was also dimensioned according to the dimensioning rules set out above ([Math 22] and [Math 23]), at from the width W2 of the second projecting structure 2.

[0078] Figures 3A, 3B respectively illustrate the distributions of the second and first light radiations in the second and first optoelectronic devices illustrated in Figures 2A, 2B. It appears that the dimensioning carried out according to the dimensioning rules set out above makes it possible to effectively confine each of the second and first light radiations within the second and first optoelectronic devices. Thus, the first and second optoelectronic devices have the optical properties required for their operation, while advantageously having first and second projecting structures of the same height h.

[0079] Figures 4 and 5 illustrate the variations of certain optical parameters as a function of the wavelength, for an infinite number of optoelectronic devices sized "by homothety", according to the sizing rules stated above. It appears that sizing by homothety makes it possible to obtain effective indices ([Fig.4], curve C1) that are almost constant as a function of the wavelength, between 4.2 pm and 9.6 pm. Sizing by homothety also makes it possible to maintain optical losses ([Fig.4], curve C2) at a very low level for wavelengths between 4.2 pm and 9.6 pm. Sizing by homothety also makes it possible to obtain a normalized coupling constant K* ([Fig.5], curve C3) that is almost constant between 4.2 pm and 9.6 pm.

[0080] In practice, scaling is performed for only a few wavelengths of the MIR wavelength range. For example, the wavelength range is subdivided into intervals of about 500 nm or 1 pm, and scaling is performed for the central wavelengths of these intervals.

[0081] Sizing by homothety makes it possible in particular to manufacture quantum cascade lasers (QCL) with distributed feedback (DFB) emitting in a wide range of MIR wavelengths with satisfactory properties, while advantageously providing a constant device height h. This makes it possible to pool a certain number of technological steps after formation of the different stacks corresponding to the different devices.

[0082] [Fig.6] illustrates a technological process flow corresponding to the manufacture of QCL DFB lasers.

[0083] The El brick corresponds to the formation of the stack of layers on the substrate. The El brick typically comprises twenty-two steps. This El brick is specific to the device to be manufactured. The twenty-two steps are therefore repeated n times to manufacture n different devices.

[0084] Brick E2 corresponds to the etching of the DFB on the stack of layers. E2 brick typically includes twelve steps. The sizing of the DFB depends on the wavelength. This E2 brick is therefore specific to the device to be manufactured. The twelve steps, some of which can be shared, are therefore repeated n times to manufacture n different devices.

[0085] Brick E3 corresponds to the etching of the stack to form the protruding structure of the devices. Brick E3 typically comprises fourteen steps. Advantageously, the n different devices have, according to the invention, a protruding structure of the same height h. Brick E3 can therefore be carried out only once for all n devices. This brick E3 comprises a set of steps common to the manufacture of the n different devices.

[0086] Brick E4 corresponds to the formation of the lower contact of the devices. Brick E4 typically comprises ten steps. Advantageously, the n different devices have, according to the invention, a protruding structure of the same height h. Brick E4 can therefore be carried out only once for all n devices. This brick E4 comprises a set of steps (for example, spreading of photolithography resin, exposure of the resin at the same focal length, deposition, CMP removal at the same height, etc.) common to the manufacture of the n different devices.

[0087] Brick E5 corresponds to the formation of the upper contact of the devices. Brick E5 typically comprises ten steps. Advantageously, the n different devices have, according to the invention, a protruding structure of the same height h. Brick E5 can therefore be carried out only once for all n devices. This brick E5 comprises a set of steps (for example, spreading of photolithography resin, exposure of the resin at the same focal length, deposition, CMP removal at the same height, etc.) common to the manufacture of the n different devices.

[0088] Brick E6 corresponds to a metallization; this can make it possible, for information purposes, to form metal pads on the electrical contacts on the DFBs and to form routing elements for the output of the lower and upper contacts. Brick E6 typically comprises sixteen steps. Advantageously, the n different devices have, according to the invention, a projecting structure of the same height h. Brick E6 can therefore be carried out only once for all n devices. This brick E6 comprises a set of steps common to the manufacture of the n different devices.

[0089] Unlike conventional process flows in which bricks E1 to E6 are all carried out n times to manufacture n different devices (i.e. a total of n*84 steps), the flow according to the invention makes it possible, according to one example, to pool bricks E3 to E6 (50 steps). Only bricks E1 and E2 (34 steps) remain specific to the n devices to be manufactured. The process flow according to the invention thus makes it possible to advantageously reduce the total number of steps to n*34 + 50.

[0090] From the above, it appears clearly that the present invention advantageously makes it possible to significantly reduce the total number of manufacturing steps of n optoelectronic devices operating at n different wavelengths. The manufacturing time and the manufacturing cost of these n devices are thus advantageously reduced.

[0091] A particular application of the manufacturing method according to the invention relates to the production of quantum cascade lasers (QCL) with distributed feedback (DFB) emitting in a wide range of MIR wavelengths. Other applications can be envisaged. The invention is not limited to the embodiments previously described.

Claims

Claims

1. Method for manufacturing at least a first optoelectronic device operating at a first wavelength X1 and a second optoelectronic device operating at a second wavelength X2 > X1, the first optoelectronic device comprising a first stack in a z direction on a first substrate (110), the first stack comprising a first lower encapsulation layer (10) of thickness e10 in the z direction and a plurality of first layers (11, 12, 13, 14, 15) of thickness e11 (i = 1.. .n) in the z direction, and the second optoelectronic device comprising a second stack in the z direction on a second substrate (210), the second stack comprising a second lower encapsulation layer (20) of thickness e20 in the z direction and a plurality of second layers (21, 22, 23, 24, 25) of thickness e2i (i = 1.. .m) along the z direction, said second layers (21, 22, 23, 24, 25) of thickness e2i having optical functions similar to those of the first layers (11, 12, 13, 14, 15) of thickness eli, the method comprising the following steps: • Forming the second stack on the second substrate (210) by dimensioning the thicknesses e20 and e2i as a function of the second wavelength X2, • Forming the first stack on the first substrate (110) by dimensioning the thicknesses e 10 and eli according to: eli = e2i~mwith el0 = e20 + ^- fe2i-Y- ,eli • Carrying out at least one same technological step (E3, E4, E5, E6) on the first and second stacks, for example an etching of the first and second stacks according to the same depth according to z, so as to obtain the first and second optoelectronic devices.

2. Method according to the preceding claim in which the at least one same technological step (E3, E4, E5, E6) comprises one or more steps taken from: an etching along z of a waveguide pattern, passivation, formation of an upper electrical contact (102, 202), formation of a lower electrical contact (101, 201), metallization.

3. Method according to any one of the preceding claims in which the plurality of first layers of thickness eli comprises at least one first active layer (11) of thickness el 1 along z, intended to emit or receive radiation having the first wavelength X1, and a first upper encapsulation layer (12) of thickness el2 along z, and in which the plurality of second layers of thickness e2i comprises at least one second active layer (21) of thickness e21 along z, intended to emit or receive radiation having the second wavelength X2, and a second upper encapsulation layer (22) of thickness e22 along z.

4. Method according to the preceding claim, in which the plurality of first layers of thickness eli further comprises a first lower optical confinement layer (13) of thickness el3 interposed between the first lower encapsulation layer (10) and the first active layer (11), and a first upper optical confinement layer (14) of thickness el4 interposed between the first upper encapsulation layer (12) and the first active layer (11), and in which the plurality of second layers of thickness e2i further comprises a second lower optical confinement layer (23) of thickness e23 interposed between the second lower encapsulation layer (20) and the second active layer (21), and a second upper optical confinement layer (24) of thickness e24 interposed between the second upper encapsulation layer (22) and the second active layer (21), with: el 1 = Ælll.al with 0.7£ al £1.3 • el2 = e22ÀLa2 with 0.7 £ a2< 1.3 AZ • el3= e23.M.a3 with 0.7 < a3£ 1.3 AZ * e 14 = e24.M .«4 with 0.7 < «4 < 1.3 *À2' • el0 = (e20+e21 + e22 + e23 + e24)-(el2 + ell+el3 + el4).

5. Method according to the preceding claim, in which the plurality of first layers of thickness eli further comprises a first barrier layer (15) of thickness el5 under the first lower encapsulation layer (10), and wherein the plurality of second layers of thickness e2i further comprises a second barrier layer (25) of thickness e25 under the second lower encapsulation layer (20), with: • el 5 - ^25.^5 with 0.7 < a5 < 1.

3.

6. Method according to any one of the preceding claims in which the first and second stacks are etched to the same depth h along z to form first and second protruding structures (1, 2), respectively having a first width W1 along an x direction and a first length L1 along a y direction, and a second width W2 along the x direction and a second length L2 along the y direction, said method further comprising, before etching the first and second stacks (1, 2): • Determining the second width W2 and the second length L2 as a function of the second wavelength X2, • Determining the first width W1 and the first length L1 according to: • with 0.7 < aw < 1.3 • L1 = L2.^.aL with 0.7 < aL < 1.

3.

7. A method according to any preceding claim further comprising a first etching configured to form a first grating (120) having a first depth d1 on the first stack carried by the first substrate (110), and independently a second etching configured to form a second grating (220) having a second depth d2 on the second stack carried by the second substrate (220).

8. Method according to any one of the preceding claims in which the first and second wavelengths XI, 72 are chosen in the mid-infrared range between 2 pm and 15 pm, preferably between 4 pm and 10 pm.

9. System for manufacturing at least a first optoelectronic device operating at a first wavelength 71 and a second optoelectronic device operating at a second wavelength / .2 > XI, the system comprising at least a first substrate (110) carrying a first stack in a z direction comprising a first lower encapsulation layer (10) of thickness elO in the z direction and a plurality of first layers (11, 12, 13, 14, 15) of thickness eli (i = l...n) in the z direction, and a second substrate (210) carrying a second stack in the z direction comprising a second lower encapsulation layer (20) of thickness e20 in the z direction and a plurality of second layers (21, 22, 23, 24, 25) of thickness e2i (i = l...m) along the z direction, said second layers of thickness e2i having optical functions similar to those of the first layers of thickness eli, the thicknesses el0, e20 and eli, e2i verifying the following relationships: • e1 / = with 1 >3 - K—171 610 = ^20 + ^.,62 / -^.^1 / *■+=1 ^ / .= 1 so that the first and second stacks have substantially the same height along z.

10. System according to the preceding claim in which the first stack is bordered by first trenches of depth h in the z direction and forms a first projecting structure (1), and the second stack is bordered by second trenches of the same depth h in the z direction and forms a second projecting structure (2).

11. System according to the preceding claim in which the first projecting structure (1) has a first width W1 in an x direction and a first length L1 in a y direction, and the second projecting structure (2) has a second width W2 in the x direction and a second length L2 in the y direction, the first and second widths Wl, W2 and the first and second lengths Ll, L2 satisfying the following relationships: Wl = WZ^a^ with 0.7 < aw < 1.3 Ll = L2^.ar with 0.7 <al< 1,3.

12. A system according to any one of claims 9 to 11 wherein the plurality of first layers (11, 12, 13, 14, 15) of thickness eli comprises at least one first active layer (11) of thickness el 1 along z, intended to emit or receive radiation having the first wavelength X1, and a first upper encapsulation layer (12) of thickness el2 along z, and in which the plurality of second layers (21, 22, 23, 24, 25) of thickness e2i comprises at least one second active layer (21) of thickness e21 along z, intended to emit or receive radiation having the second wavelength X2, and a second upper encapsulation layer (22) of thickness e22 along z, with: • Al 2 - e22M.a2 with 0.7 < al < 1.3 AZ • ell = e21#alavec0.7 <al< 1,3. az

13. System according to any one of claims 9 to 12 wherein the first and second substrates (110, 210) are based on silicon and wherein the first and second stacks are based on III-V materials, the first and second stacks respectively comprising first and second optical isolation layers (16, 26) configured to avoid optical coupling at wavelengths X1 and X2 with the first and second substrates (110, 210).

14. A system according to any one of claims 9 to 13 wherein the first and second optoelectronic devices correspond to first and second distributed feedback quantum cascade lasers.

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