Semiconductor optoelectronic devices

Abstract

This disclosure relates to a semiconductor optoelectronic device (10) comprising a junction (12) consisting of a stack of layers defining an N-doped region, an intermediate region, and a P-doped region, at least one modulation layer of the N-doped region and / or the P-doped region and / or the intermediate region, formed by a plurality of sublayer stacks, each sublayer being different from other sublayers of the same stack by the characteristics of the material of the sublayer, the characteristics being called distinguishing features, the thickness of the sublayer and the distinguishing features being selected to reduce photon absorption in the corresponding region, the only difference being that each modulation layer is replaced by a non-modulation layer with the same thickness as the modulation layer and having the same characteristics except for the distinguishing features, compared to a semiconductor optoelectronic device called a reference device.

Description

Technical Field

[0001] This disclosure relates to a semiconductor optoelectronic device, such as a semiconductor laser. Background Technology

[0002] High-power semiconductor lasers are used in many applications, such as telecommunications.

[0003] Since the 1990s, the power of semiconductor lasers has been steadily increasing. In this article, the term "power" refers to the reliable power of a laser, that is, the power a laser can provide over its lifetime (typically 10-15 years). Therefore, this reliable power is often different from the maximum power. Today, such lasers are single-mode with power exceeding 1W, whereas in the 1990s, power was around 150mW.

[0004] Developing higher-power semiconductor lasers is of interest in order to meet the needs of different applications.

[0005] Increasing the power of such lasers involves reducing the internal losses of the laser cavity. In fact, the efficiency of a laser (defined as power per unit injected current) depends on two parameters: the number of charge carriers injected into the active region and the internal losses. Since the parameters related to the charge carriers injected into the active region have been optimized, increasing the efficiency depends on the ability to reduce the internal losses of the laser cavity.

[0006] The challenge is to reduce internal losses to maintain high efficiency, and thus to use a longer cavity for the laser. Indeed, with a longer cavity, the laser operates at a lower current density because the injection is distributed across the entire length of the cavity. The temperature in the active region is also lower because the larger cavity reduces thermal resistance. Furthermore, the laser's conversion efficiency—the ratio between the generated optical power and the injected electrical power—is improved.

[0007] Therefore, since the 1990s, the length of laser cavities has continued to increase, from 1.2-1.5 mm in the 1990s to 4-5 mm currently.

[0008] Because internal losses depend on the doping level of the semiconductor layer, techniques for reducing losses involve lowering the doping level and placing the light field in regions with minimal absorption and thus minimal loss. However, this technique is limited because the doping level of the material cannot be reduced beyond the material's remaining doping level. Summary of the Invention

[0009] The purpose of this disclosure is to provide an alternative for further reducing internal losses in semiconductor optoelectronic devices (e.g., semiconductor lasers) to improve the efficiency and reliability of such devices.

[0010] Therefore, the subject of this specification is a semiconductor optoelectronic device including a junction capable of emitting or absorbing light, the junction being formed by a stack of layers defining N-doped regions, intermediate regions and P-doped regions along a stacking direction;

[0011] At least one modulation layer of N-doped region and / or P-doped region and / or intermediate region is formed by multiple sub-layer stacks stacked on top of each other along the stacking direction;

[0012] Each sublayer stack includes at least two sublayers, wherein each sublayer has a thickness along the stacking direction and is made of at least one material, and each sublayer is distinguished from other sublayers in the same stack by at least one feature of the at least one material of the sublayer, the at least one feature being called a distinguishing feature;

[0013] Each stack of modulation layers is identical to the previous stack, or differs from the previous stack at most in a bounded variation in the composition of at least one material in the two corresponding sublayers of the two stacks; the thickness and distinguishing features of the sublayers are selected to reduce the absorption of photons by free carriers (holes, electrons) in the corresponding regions by changing the electro-optic properties of the conduction band and / or valence band, the only difference from the reference semiconductor optoelectronic device being that each modulation layer is replaced by a non-modulation layer, the non-modulation layer having the same thickness as the modulation layer and having the same characteristics except for at least one distinguishing feature, which is consistent or gradually varied in thickness of the non-modulation layer.

[0014] According to a particular embodiment, the device includes one or more of the following features, either individually or in all technically possible combinations:

[0015] - The modulation layer is an N-doped or P-doped layer, the junction is a PIN junction, and the middle region is the intrinsic region;

[0016] - The modulation layer is a layer of N-doped or P-doped regions, each of which includes a core and a cladding, the optical index of the core being greater than that of the cladding, and the modulation layer is a layer of the core or cladding of the respective doped region, advantageously, each of the core and cladding of the doped region includes a modulation layer.

[0017] -At least one distinguishing feature is the degree of doping of at least one material in the sublayer;

[0018] - The doping level of each sublayer differs from that of other sublayers in the same stack by at least one percent;

[0019] - The average doping degree of the modulation layer is less than or equal to the doping degree of the corresponding non-modulation layer;

[0020] - The doping level of one of the sublayers of each stack is the residual doping level of at least one material used to make that sublayer;

[0021] - The thickness of each sublayer of the stack is less than the thickness of the other sublayer, where the doping level is greater than that of the other sublayer.

[0022] -At least one distinguishing feature is the composition of at least one material in the sublayer;

[0023] - At least one material in each sublayer contains chemical elements from columns III and V, or columns II and VI, or columns IV of the periodic table;

[0024] - The thickness of each sublayer stack is between 1 nanometer and 100 nanometers, preferably greater than or equal to 5 nanometers, and advantageously greater than or equal to 10 nanometers;

[0025] - Select the thickness of each sublayer stack to reduce the absorption of photons by free carriers in the corresponding region compared to the reference electronics;

[0026] - By changing the electro-optic properties of the conduction band and / or valence band, it is possible to redistribute the oscillation intensity of spurious intraband transitions between different polarizations of photons circulating in the optoelectronic device at the onset of free carrier absorption of photons, and in particular, to transfer most of the oscillation intensity of intraband transitions to polarizations orthogonal to the polarization of laser emission.

[0027] - The alteration of the electro-optic properties of the conduction and valence bands occurs by generating a substantially two-dimensional modulation layer that produces discrete subbands in the conduction and valence bands.

[0028] - Each sublayer of each stack does not contain gallium nitride.

[0029] This specification also relates to a semiconductor optoelectronic device, including a PIN junction capable of emitting or absorbing light, the PIN junction being formed from a stack of layers defining N-doped regions, intrinsic regions and P-doped regions along a stacking direction;

[0030] At least one of the N-doped and P-doped regions, called a modulation layer, is formed by a stack of multiple sub-layers stacked on top of each other along the stacking direction;

[0031] Each sublayer stack includes at least two sublayers, wherein each sublayer has a thickness along the stacking direction and is made of at least one material, and each sublayer is distinguished from other sublayers in the same stack by at least one feature of the at least one material of the sublayer, the at least one feature being called a distinguishing feature;

[0032] Each stack of modulation layers is identical to the previous stack, or differs from the previous stack at most in the bounded variation of the composition of at least one material in the two corresponding sublayers of the two stacks; the thickness and distinguishing features of the sublayers are selected to reduce photon absorption in the corresponding doped regions, and the only difference from the reference semiconductor optoelectronic device is that each modulation layer is replaced by a non-modulation layer, which has the same thickness as the modulation layer and the same features except for at least one distinguishing feature, which is consistent or gradually varies in thickness of the non-modulation layer. Attached Figure Description

[0033] Other features and advantages of this disclosure will become apparent from the following description of embodiments of this disclosure, given by way of example only, and with reference to the following drawings:

[0034] Figure 1 This is a schematic cross-sectional view of an example of a semiconductor laser according to a first example of an embodiment;

[0035] Figure 2 This is a schematic cross-sectional view of an example of a semiconductor laser according to a second example of an embodiment; and

[0036] Figure 3 This is a schematic cross-sectional view of an example of a semiconductor laser according to a third example of an embodiment. Detailed Implementation

[0037] The longitudinal direction is defined in the following description. The stacking direction and the transverse direction are also defined. The stacking direction is perpendicular to the longitudinal direction and is contained within a plane that is transverse to the longitudinal direction. The stacking direction is perpendicular to the so-called longitudinal propagation direction of light. The transverse direction is perpendicular to both the longitudinal and stacking directions. Figures 1 to 3 In the diagram, the vertical direction, the stacking direction, and the horizontal direction are represented by the Y-axis, Z-axis, and X-axis, respectively.

[0038] In the following text, a semiconductor laser 10 comprising a PIN junction 12 capable of emitting or absorbing light is considered. The laser is preferably a high-power laser, i.e., capable of emitting or absorbing a laser beam with a power greater than 500 mW. Preferably, the laser cavity has a length greater than 3 mm and less than 10 mm.

[0039] Such lasers are suitable for applications such as telecommunications, for example, in erbium-doped fiber amplifiers. For instance, a GaAs (gallium arsenide) laser emits a wavelength of 980 nm.

[0040] The PIN junction 12 consists of a stack of layers along the stacking direction Z.

[0041] Each layer of the stack is a planar layer, meaning that the layer extends between two flat and parallel surfaces.

[0042] Each layer also has a thickness along the stacking direction Z. The thickness of a layer is defined as the distance between the two faces of that layer along the stacking direction Z.

[0043] The stacked layers define N-doped regions, intrinsic region I, and P-doped regions. The term "N-doped region" refers to the region where impurities are introduced to generate excess electrons. The term "intrinsic region" refers to the region without intentionally added impurities; the intrinsic region is the active region of PIN junction I2. Intrinsic region I generates light through electron-hole recombination. The term "P-doped region" refers to the region where impurities are added to generate excess holes.

[0044] Each of the N-doped and P-doped regions comprises a core and a cladding, with the core having a higher optical index than the cladding, thus forming a waveguide. The core of each doped region and the cladding of each doped region correspond to one or more different layers of the stack.

[0045] Figures 1 to 3 This is an example of a stack of layers forming a PIN junction 12. In this example, the layers forming the stack are stacked on the substrate 14 along the stacking direction Z. In the figures, the N-doped region is represented by Z. N The expropriation zone is indicated by Z. I This indicates that the P-doped region is represented by Z. P Indicated. The core of the N-doped region is made of C N This indicates that the core of the P-doped region is composed of C P This indicates that the cladding of the N-doped region is composed of G N This indicates that the cladding of the P-doped region is composed of G P express.

[0046] For example, when the semiconductor laser 10 is a GaAs laser, the substrate 14 is made of GaAs.

[0047] At least one layer, either an N-doped region or a P-doped region, is called a modulation layer and consists of a stack of multiple sublayers along the stacking direction Z. In other words, at least one modulation layer is one of an N-doped region or a P-doped region.

[0048] Each sublayer stack comprises at least two sublayers stacked along the stacking direction Z. Each sublayer stack can be considered as a pattern repeated as many times as the number of sublayer stacks.

[0049] The modulation layer is a core or cladding layer of the doped region in question. Advantageously, the doped region in question includes at least one modulation layer belonging to the core and at least one modulation layer belonging to the cladding.

[0050] Figure 1 An example is shown where only the N-doped region includes a modulation layer, i.e., a modulation layer forming the core of the N-doped region and a modulation layer forming the cladding. Figure 2 An example is shown where only the P-doped region includes a modulation layer, i.e., a modulation layer forming the core of the P-doped region and a modulation layer forming the cladding. Figure 3 Examples are shown of each of the N-doped and P-doped regions including a modulation layer (the modulation layer of each of the core and cladding layers of the P-doped and N-doped regions).

[0051] Sublayer stacks are stacked on top of each other along the stacking direction Z, such that the thickness of all sublayer stacks (the sum of the thicknesses of the sublayers forming the stack) is equal to the thickness of the modulation layer.

[0052] Preferably, the number of sublayer stacks forming the modulation layer is greater than or equal to 10. Therefore, when the thickness of each sublayer stack is between 1 nm and 100 nm, the total thickness of the modulation layer is typically between 10 nm and 10 μm.

[0053] Each sublayer is a planar sublayer, meaning that the sublayer extends between two flat and parallel planes.

[0054] Each sublayer has a thickness along the stacking direction Z. The thickness of a sublayer is defined as the distance between two faces of the sublayer along the stacking direction Z. The thickness of each sublayer is strictly less than the thickness of the corresponding modulation layer. Preferably, the thickness of each sublayer is greater than or equal to 1 nm and less than or equal to 100 nm.

[0055] Preferably, the thickness of each sublayer stack is between 1 nm and 100 nm.

[0056] Each sublayer is made of at least one material.

[0057] Advantageously, at least one material in each sublayer is composed of multiple chemical elements. These chemical elements are elements from the Mendeleev table. Preferably, the elements belong to columns III and V, or columns II and VI, or columns IV of the periodic table. For example, the material is aluminum gallium arsenide (AlGaAs) or indium phosphide (InP), or alloys thereof, such as InGaAsP or InGaAlAs.

[0058] In one embodiment, each sublayer is made of one material. In a variation of the embodiment, at least one sublayer is made of multiple materials formed from the same chemical elements, but with different compositions (proportions) of the chemical elements.

[0059] Each sublayer is distinguished from other sublayers in the same stack by at least one characteristic of at least one material of that sublayer, which is referred to as a distinguishing characteristic.

[0060] Preferably, the distinguishing feature is at least one of the doping degree of the material in each sublayer and the composition of the material in the sublayer. The doping degree is defined as the amount of doped impurities (electron donors or electron acceptors) per cubic centimeter of lattice. The doping degree is expressed by volume. The composition is defined as the proportion of chemical elements forming the material.

[0061] In other words, in such an embodiment, for two materials in two different sublayers of the same stack, there are three possible scenarios:

[0062] - The two materials have the same composition but different doping levels;

[0063] - The two materials have the same doping level but different compositions; and

[0064] - The two materials have different levels of doping and different compositions.

[0065] In one embodiment, the stacks forming the modulation layer are identical. Therefore, each stack of the modulation layer is identical to the previous stack, which is a stack on top of the stack in question.

[0066] In a variation of the embodiment, at least one stack body is different from the other stack bodies.

[0067] In a variation of the embodiment, preferably, each stack differs from the previous stack primarily in that the composition of at least one material in each sublayer of the stack varies by a bounded amount compared to the composition of at least one material in the corresponding sublayer of the previous stack (or, at least one material in the two corresponding sublayers of the two stacks has a different composition). In other words, from one stack to another, the number of sublayers, the thickness of the sublayers, the chemical elements of the sublayer materials, and the degree of doping are the same. However, compared to the composition of the corresponding sublayers of the previous stack, the material composition of the sublayers of the stack increases or decreases (by a given value within a bounded variation).

[0068] The term "most" refers to a situation where the change in composition is the only difference, and that difference can be zero, in which case the multiple stacks under consideration are identical.

[0069] The term "corresponding sublayer" refers to a sublayer in another stack that has the same position as a sublayer in the stack under consideration. Thus, for example, the sublayer of the first stack closest to the bottom of the first stack is compared to the sublayer of the second stack closest to the bottom of the second stack, and so on for other sublayers.

[0070] The term "bounded variation" refers to the percentage difference between the material compositions of two sublayers of two stacks under consideration, within a predetermined range. For example, the variation in composition may be between 0% and 2%.

[0071] In this variation, preferably, the change is made gradually along the thickness of the modulation layer, that is, the overall composition increases or decreases with the thickness of the modulation layer.

[0072] For example, as an illustration of this variation, the modulation layer comprises three stacked bodies, each formed by two sublayers. A distinguishing feature is the material composition of the sublayers. The first and second stacked bodies are identical, comprising:

[0073] -10nm thick Al 0.28 Ga 0.72 The first sublayer of As has a doping degree of 5 × 10⁻⁶ Si atoms. 16 cm -3 ;as well as

[0074] -20nm thick Al 0.32 GA 0.68 The second sublayer of As has a doping degree of 5 × 10⁻⁶ Si atoms. 16 cm -3 .

[0075] The third stack includes:

[0076] -10nm thick Al 0.29 Ga 0.71 The first sublayer of As has a doping degree of 5 × 10⁻⁶ Si atoms. 16 cm -3 ,as well as

[0077] -20nm thick Al 0.33 GA 0.67 The second sublayer of As has a doping degree of 5 × 10⁻⁶ Si atoms. 16 cm -3 .

[0078] Therefore, compared with the corresponding sublayers of the first and second stacks, the material composition of the sublayers of the third stack in this example has a change of (0.01).

[0079] The thickness and distinctive features of the sublayer are selected to reduce photon absorption in the corresponding doped region compared to a so-called reference semiconductor laser. This photon absorption is a spurious phenomenon caused by free carriers (holes or electrons) in the doped region absorbing photons from the active region. This phenomenon is also known as "free carrier absorption".

[0080] The reference laser differs from the laser under consideration only in that each modulation layer is replaced by an unmodulated layer. The unmodulated layers have the same thickness as the corresponding modulation layers and have the same characteristics except for the distinguishing feature that the thickness of the unmodulated layers is consistent (within the limitations of the technology used) or gradually varies.

[0081] The term "consistent" means that the values ​​of the distinguishing features are the same across the thickness of the unmodulated layer. Therefore, when the distinguishing feature is the doping level of the sublayer material, the doping level of the unmodulated layer material has the same value across the thickness of the unmodulated layer. When the distinguishing feature is the material composition of the sublayer, the material composition of the unmodulated layer is the same across the thickness of the unmodulated layer.

[0082] The term "gradual change" refers to the gradual increase or decrease of the value of the distinctive feature across the thickness of the unmodulated layer.

[0083] In one example, photon absorption in the doped region under consideration is quantified by regressing the external efficiency of lasers of different lengths as a function of cavity length. Such a regression is described, for example, in the book entitled “Diode Lasers and Photonic Integrated Circuits”, Coldren, L. et al., Chap. 2 (1995).

[0084] Preferably, compared to a reference laser, photon absorption in the considered region is reduced by at least 0.1 cm⁻¹. -1 .

[0085] Preferably, the PIN junction 12 is obtained solely through epitaxy from the substrate 14. Epitaxy is understood as a technique for growing crystals on another crystal, each crystal comprising a lattice having the same plurality of symmetry elements as the other crystal. Epitaxial techniques used are selected, for example, from molecular beam epitaxy, liquid phase epitaxy, and organometallic vapor phase epitaxy.

[0086] Therefore, by creating a modulation layer composed of repeating, alternating specific sublayers, rather than a uniform or graded layer, it is possible to modify the absorption of photons by free carriers in the doped region under consideration, thereby reducing internal losses. In other words, the structure of the modulation layer allows for alteration of the electro-optic properties of the conduction band when the modulation layer is in an N-doped region, and alteration of the electro-optic properties of the valence band when the modulation layer is in a P-doped region. This modification is one of the factors that helps suppress the absorption of photons by free carriers in the doped region under consideration.

[0087] In the following sections, advantageous features of the modulation layer structure are presented, where the distinguishing characteristic is the doping degree of the sublayer material. In this case, a doped superlattice structure is produced. Superlattices (SRs) are typically nini-type for N-layers or pipi-type for P-layers.

[0088] Preferably, the doping degree of each sublayer differs from that of other sublayers in the same stack by at least one percent.

[0089] Preferably, the average doping degree of the modulation layer (obtained from the doping degree of the sublayers taking into account their thickness) is less than or equal to the doping degree of the corresponding unmodulated layer (in the reference laser). Therefore, a structure with repeating sublayer stacks can reduce the average doping degree compared to layers with the same doping degree in their thickness.

[0090] Preferably, the doping degree of one of the sublayers in each stack is the residual doping degree of the material used to manufacture that sublayer. The residual doping degree is the doping degree obtained even if no impurities are intentionally added to the material. Therefore, in the case where each stack comprises only two sublayers, the modulation layer consists of alternating doped sublayers and intrinsically doped sublayers that repeat along the thickness of the modulation layer.

[0091] Preferably, the thickness of each sublayer of a stack whose doping degree is greater than that of another sublayer in the same stack is less than the thickness of the other sublayer.

[0092] The following describes specific examples obtained from experimental embodiments.

[0093] In such an example, the structure of the 980nm GaAs laser has been generated according to two variants, namely:

[0094] - A standard laser structure forming a reference laser. This structure is fabricated based on the structural principles described in the article entitled "Reaching 1 watt reliable output power on single-mode 980 nm pump lasers," M. Bettiati et al., Proc. SPIE 7198, High Power Diode Laser Technology and Applications VII, 71981D (February 23, 2009). In this structure, the N-doped region includes:

[0095] • A first non-modulated layer with a 3 μm thick cladding layer is formed, and its (Si atom) doping level is constant at 5 × 10⁻⁶. 16 cm -3 The matrix is ​​AlGaAs material; and

[0096] • A second unmodulated layer is formed, with a core thickness of 900 nm, and its (Si atom) doping level is kept constant at 5 × 10⁻⁶. 16 cm -3 The matrix is ​​AlGaAs material.

[0097] - An equivalent laser structure, the difference being that the first and second unmodulated layers are replaced by first and second modulated layers of the same thickness, respectively, and are formed by multiple identical and stacked sublayer stacks. Each sublayer stack comprises two sublayers. The first sublayer of each stack has a thickness of 10 nm and a constant density of 6 × 10⁻⁶.16 cm -3 The degree of Si atom doping. The second sublayer of each stack has a thickness of 20 nm and is constant at 2.5 × 10⁻⁶. 16 cm -3 The degree of Si atom doping (the degree of residual doping in the material). Therefore, the first modulation layer (cladding) consists of 100 stacks (3 μm thick, each stack 30 nm thick), and the second modulation layer (core) consists of 30 stacks.

[0098] Therefore, this method allows for comparison of structures integrating the alternating sublayer principle with the periodicity of doping levels (also known as digital doping) in N-doped regions, compared to standard structures with known performance. In this method, a key parameter of the power laser, called efficiency, is compared, quantifying the laser emission efficiency of the component. It is commonly referred to as SE (slope efficiency) and is measured in watts per ampere (W / A). The technical expression for this parameter is defined, for example, in the book entitled "Diode Lasers and Photonic Integrated Circuits," Coldren, L. et al., Chap. 2 (1995), namely:

[0099]

[0100] in:

[0101] ·η i Internal quantum efficiency is defined as the fraction of charge carriers injected into the active region;

[0102] ·h is Planck's constant;

[0103] ·v is the frequency of laser emission;

[0104] ·e is the charge of the electron;

[0105] ·α i It is internal loss; and

[0106] ·α m The mirror loss (α) of a multifaceted laser with the same reflectivity R is... m = (1 / L)ln(1 / R)), where L is the length of the laser.

[0107] The expression SE clearly shows the internal loss α i Therefore, it is clear that the internal loss α i The reduction in SE increases efficiency.

[0108] For a laser with a cavity length of 3.9 mm, the efficiency measured under short pulse injection conditions (<1 μs) is 0.460 W / A for the standard structure and 0.494 W / A for the improved structure (sublayer). Since 0.494 / 0.460 = 1.074, the efficiency improvement is approximately 7%. Therefore, the increase in efficiency SE indicates that the sublayer structure reduces internal losses. However, it should be noted that this initial achievement was made with a laser with a cavity length of 3.9 mm. For lasers with longer cavity lengths, the efficiency improvement is expected to be even higher, reasonably reaching a maximum length of 8 mm to 10 mm. For such cavities, the efficiency improvement is estimated to be as high as 10% to 11%. For example, for a laser with a large surface area (100 μm active region width) and a cavity length of 10.2 mm, a gain of 10% to 11% was found, as the SE has increased from 0.36 W / A to 0.40 W / A.

[0109] It should be noted that by changing the layers of the P-doped region, internal losses can be further reduced, thereby further improving the efficiency of the laser.

[0110] In another example, the modulation layer comprises the same stack of the following sublayers, each stack comprising:

[0111] The first sublayer of AlGaAs is 10 nm thick, with a Si atom doping level of 6 × 10⁻⁶. 16 cm -3 ;as well as

[0112] A 25 nm thick AlGaAs second sublayer with a Si atom doping level of 5 × 10⁻⁶. 16 cm -3 .

[0113] In yet another example, the modulation layer comprises the same stack of the following sublayers, each stack comprising:

[0114] The first sublayer of InP is 15 nm thick, and its (Si atom) doping level is 6 × 10⁻⁶. 16 cm -3 ;as well as

[0115] A 30nm thick InP second sublayer with a Si atom doping level of 3×10⁻⁶. 16 cm -3 .

[0116] In yet another example, the modulation layer comprises the same stack of the following sublayers, each stack comprising:

[0117] -10nm thick Al 0.28 Ga 0.72 The first sublayer of As has a doping degree of 5 × 10⁻⁶ Si atoms. 16cm -3 ;as well as

[0118] -20nm thick Al 0.32 GA 0.68 The second sublayer of As has a doping degree of 5 × 10⁻⁶ Si atoms. 16 cm -3 .

[0119] In yet another example, the modulation layer comprises the same stack of the following sublayers, each stack comprising:

[0120] -10nm thick Al 0.28 Ga 0.72 The first sublayer of As has a doping degree of 6 × 10⁻⁶ Si atoms. 16 cm -3 ;as well as

[0121] -20nm thick Al 0.32 GA 0.68 The second sublayer of As has a doping degree of 2.5 × 10⁻⁶ Si atoms. 16 cm -3 .

[0122] In yet another example, the modulation layer comprises the same stack of the following sublayers, each stack comprising:

[0123] -10nm thick Al 0.28 Ga 0.72 The first sublayer of As has a doping degree of 6 × 10⁻⁶ Si atoms. 16 cm -3 ;

[0124] -20nm thick Al 0.32 GA 0.68 The second sublayer of As has a doping degree of 2.5 × 10⁻⁶ Si atoms. 16 cm -3 ;as well as

[0125] -10nm thick Al 0.3 GA 0.7 The third sublayer of As has a doping degree of 4 × 10⁻⁶ Si atoms. 16 cm -3 .

[0126] Therefore, by periodically repeating and alternating sublayers with different characteristics (doping degree and / or composition), the described laser structure can reduce internal losses caused by photon absorption by free carriers in the doped regions of the PIN junction, thereby improving the efficiency and reliability of the laser. Furthermore, in addition to the purely optical efficiency of the laser, significantly reducing internal losses can also increase the overall conversion efficiency of the component, denoted as normalized P.opt The ratio of the total optical power emitted by the laser to the total electrical power injected into the laser, and equal to the product I×V (the product of the current injected into the laser and the voltage required for the injection current).

[0127] Those skilled in the art will understand that if the above embodiments are technically compatible, they can be combined to form new embodiments. The invention described herein is not limited to the specifically described embodiments, and any other equivalent embodiments should be assimilated with this disclosure. More specifically, although this disclosure is described in the context of semiconductor lasers, it applies to all semiconductor optoelectronic devices, particularly photodetectors or photovoltaic cells. In this case, the term "laser" in the specification should be replaced with the term "semiconductor optoelectronic device."

[0128] Furthermore, it should be noted that by altering the electro-optic properties of the conduction band and / or valence band, the oscillation intensity of spurious intraband transitions can be redistributed (at the onset of free carrier absorption of photons) between different polarizations of photons circulating in the laser cavity of the optoelectronic device, and in particular, most (or even all) of the oscillation intensity of the intraband transitions can be transferred to polarizations orthogonal to the laser emission polarization. In this way, laser emission can be almost completely decoupled from the transitions responsible for free carrier absorption.

[0129] More specifically, it should be noted that when the modulation layer is in an N-doped or P-doped region, but not both simultaneously, the modulation layer does not have a favorable effect on the reduction of photon absorption by free carriers in the conduction band of the modulation layer in the N-doped region or in the valence band of the modulation layer in the P-doped region. On the other hand, in both cases, the electro-optic properties of the conduction and valence bands are generally altered by the modulation layer, especially because the material has quasi-two-dimensional properties.

[0130] Furthermore, the electro-optic properties of the conduction and valence bands can be altered by generating quasi-2D modulation layers (doped superlattices and / or composite superlattices), which are essentially two-dimensional and produce discrete subbands in both the conduction and valence bands. Moreover, in the modulation layer, the selection rules and distribution of the oscillation intensities of intraband transitions with different polarizations are advantageously different from those of isotropic three-dimensional materials without this specific structure (the fact that the material is isotropic implies that the oscillation intensities are the same in all three directions).

[0131] It should also be noted that, in addition to the thickness and distinguishing features of the sublayers, the thickness of each sublayer stack is preferably selected to reduce the absorption of photons by free carriers in the corresponding doped regions relative to the reference electronics.

[0132] Preferably, the thickness of each sublayer stack is greater than or equal to 5 nm, and more preferably greater than or equal to 10 nm.

[0133] It should also be noted that each modulation layer is different from a short-period superlattice (SPSL).

[0134] In certain embodiments (supplements or variations), it should be noted that each sublayer of each stack does not contain any gallium nitride (GaN).

[0135] In certain embodiments (supplements or variations), it should be noted that the modulation layer is at least one layer of the core of the corresponding doped region.

[0136] Those skilled in the art will understand that the described optoelectronic devices are particularly suitable for III-V semiconductors with so-called "diamond" crystal structures or zincblende structures.

[0137] Furthermore, in alternative embodiments, the modulation layer described above is also applicable to semiconductor optoelectronic devices comprising a junction formed by a stack of layers defining an N-doped region, an intermediate region (between the N-doped and P-doped regions), and a P-doped region along the stacking direction. In this case, the modulation layer is a layer belonging to the intermediate region, for example, more precisely, to the active region (the region where charge carrier recombination occurs). More specifically, the modulation layer is, for example, a layer of the active (isotropic) region of a dual heterostructure (DH) laser with sufficient thickness for integrating multiple modulation cycles of distinguishing features. The thickness considered is, for example, greater than or equal to 100 nm.

[0138] Therefore, in this alternative embodiment, all the features of the above embodiments described in the specification are applicable, the only difference being that the junction is not necessarily a PIN junction and the intermediate region is not necessarily intrinsic, and that the modulation layer is integrated into the intermediate region. It should be noted that in the foregoing embodiments, the intrinsic region corresponds to the intermediate region.

[0139] More specifically, in this alternative embodiment, when the distinguishing feature is the composition of the material, the intermediate region can be the intrinsic region. On the other hand, when the distinguishing feature is the degree of doping, the intermediate region differs from the intrinsic region (because the same region is doped via a modulation layer). When the intermediate region is doped, the doping is N-doping and / or P-doping.

[0140] This alternative embodiment is also compatible with integrating other modulation layers into the N-doped and / or P-doped regions.

Claims

1. A semiconductor optoelectronic device (10) comprising a junction (12) capable of emitting or absorbing light, said junction (12) being formed of a stack of layers defining an N-doped region, an intermediate region (I), and a P-doped region along a stacking direction (Z). At least one modulation layer of the N-doped region and / or the P-doped region and / or the intermediate region (I) is formed by stacking multiple sublayers together along the stacking direction (Z). Each of the said sublayer stacks comprises at least two sublayers, wherein, Each sublayer has a thickness along the stacking direction (Z) and is made of at least one material. Each sublayer is distinguished from other sublayers in the same stack by at least one characteristic of that sublayer's at least one material, said at least one characteristic being called a distinguishing feature. Each stack of modulation layers is identical to the previous stack, or differs from the previous stack at most in a bounded variation in the composition of at least one material in the two corresponding sublayers of the two stacks; the thickness and distinguishing features of the sublayers are selected to reduce the absorption of photons by free carriers in the corresponding regions by changing the electro-optic properties of the conduction band and / or valence band, the only difference from the reference semiconductor optoelectronic device being that each modulation layer is replaced by a non-modulation layer, which has the same thickness as the modulation layer and the same characteristics except for the at least one distinguishing feature, which is consistent or gradually varies in thickness across the non-modulation layer.

2. The device (10) according to claim 1, wherein, The modulation layer is a layer of the N-doped region or the P-doped region, the junction (12) is a PIN junction, and the intermediate region (I) is an intrinsic region.

3. The device (10) according to claim 1 or 2, wherein, The modulation layer is a layer of either the N-doped region or the P-doped region, each of the N-doped region and the P-doped region comprising a core and a cladding layer. The optical index of the core is greater than that of the cladding, and the modulation layer is a core or cladding layer of the corresponding doped region.

4. The device (10) according to claim 3, wherein, Each of the core and cladding of the doped region includes a modulation layer.

5. The device (10) according to claim 1 or 2, wherein, The at least one distinguishing feature is the degree of doping of the at least one material in the sublayer.

6. The device (10) according to claim 5, wherein, The doping level of each sublayer differs from that of other sublayers in the same stack by at least one percent.

7. The device (10) according to claim 5, wherein, The average doping degree of the modulation layer is less than or equal to the doping degree of the corresponding non-modulation layer.

8. The device (10) according to claim 5, wherein, The doping level of one of the sublayers of each stack is the residual doping level of at least one material used to make that sublayer.

9. The device (10) according to claim 5, wherein, The thickness of each sublayer of the stack is less than the thickness of the other sublayer, where the doping level is greater than that of the other sublayer.

10. The device (10) according to claim 1 or 2, wherein, The at least one distinguishing feature is the composition of the at least one material of the sublayer.

11. The device (10) according to claim 1 or 2, wherein, The at least one material in each sublayer comprises chemical elements from columns III and V, or columns II and VI, or columns IV of the periodic table.

12. The device (10) according to claim 1 or 2, wherein, The thickness of each sublayer stack is between 1 nanometer and 100 nanometers.

13. The device (10) according to claim 1 or 2, wherein, The thickness of each sublayer stack is greater than or equal to 5 nanometers.

14. The device (10) according to claim 1 or 2, wherein, The thickness of each sublayer stack is greater than or equal to 10 nanometers.

15. The device (10) according to claim 1 or 2, wherein, The thickness of each sublayer stack is selected to reduce the absorption of photons by free carriers in the corresponding region compared to a reference electronic device.

16. The device (10) according to claim 1 or 2, wherein, By changing the electro-optic properties of the conduction band and / or the valence band, the oscillation intensity of the spurious band transition can be redistributed between different polarizations of photons circulating in the optoelectronic device (10) at the onset of free carrier absorption of photons.

17. The device (10) according to claim 16, wherein, By altering the electro-optic properties of the conduction band and / or the valence band, the oscillation intensity of spurious in-band transitions can be redistributed to a polarization orthogonal to the polarization of the laser emission.

18. The device (10) according to claim 1 or 2, wherein, The alteration of the electro-optic properties of the conduction band and the valence band occurs by forming a substantially two-dimensional modulation layer that produces discrete subbands in the conduction band and the valence band.

19. The device (10) according to claim 1 or 2, wherein, Each sublayer of each stack does not contain any gallium nitride.

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