Colloidal quantum dot light emitters and detectors

Abstract

An integrated optoelectronic device (100, 200, 300) comprises a substrate (30) supporting a passive waveguide (31) for confining refractive index in two lateral directions and guiding at least one optical mode in a longitudinal direction. The device further comprises a first charge transport layer (11) for transporting charge carriers of a first conductivity type, a second charge transport layer (12) for transporting charge carriers of a second conductivity type opposite to the first conductivity type, and an active layer (20) comprising a film of particles of solution-processable semiconductor nanocrystals. The active layer is arranged relative to the charge transport layers to form a diode junction. The active layer and the first and second charge transport layers are further formed on the substrate such that they each overlap at least a portion of the waveguide in a cross-section perpendicular to the longitudinal direction. The active layer is evanescently coupled to the waveguide.

Description

Technical Field

[0001] This invention relates to the field of light emitting and light detecting devices, and more particularly to light emitters and light detectors based on photonic integrated circuits made of solution-processable semiconductor materials, such as colloidal quantum dots. Background Technology

[0002] Due to their simplicity and low cost, optoelectronic devices based on solution-processable active materials such as colloidal quantum dots (QDs) have the potential to replace currently prevalent epitaxially grown devices. While the feasibility of using colloidal quantum dot layers as gain materials in electrically pumped laser diodes has long been questioned, recent research has led to the development of specially designed colloidal quantum dots (QDs) that offer a reduced Auger recombination rate, and are therefore promising candidates for realizing the long-sought-after QD laser diodes.

[0003] Lim, J. et al., in their paper "Optical gain in colloidal quantum dots achieved with direct-current electrical pumping," *Nature Materials*, 17, 42–49 (2018), proposed that chemically synthesized semiconductor quantum dots (QDs) can realize solution-processable laser diodes. Continuous gradient QDs were used in electroluminescent devices with a pin architecture to achieve population inversion and optical gain via direct-current pumping. A thin active QD layer was sandwiched between an electron transport layer and a hole transport layer, and specially shaped dielectric LiF spacers were provided as templates for fabricating a tapered hole injection layer. Using this current-focusing architecture, a narrow (70–100 μm wide) contact area with the QD emitting layer was obtained. Gains up to approximately 18 Å / cm² were measured. -2 The current density is achieved without damaging the QD layer or the injection layer.

[0004] The drawback of this method is the lack of an optical cavity suitable for electrically pumped laser emission. Furthermore, additional spacers are required to shape the contact portion of the hole injection layer into a small contact area.

[0005] In Roh, J. et al.'s paper, "Optically pumped colloidal-quantum-dot lasing in LED-like devices with an integrated optical cavity," Nat. Commun., 11, 271 (2020), these specially designed QDs were used to realize multilayer pin structures with dual functionality: serving as light-emitting diodes (LEDs) if an additional p-type contact electrode is provided on top of the pin layer structure; and serving as optically pumped lasers if the p-type contact electrode is removed. They proposed an optical cavity in which a distributed feedback resonator is directly integrated into a bottom low-refractive-index ITO (L-ITO) cathode of a multilayer stack. The optical modes are weakly confined by the ultrathin quantum dot containing the active layer.

[0006] The drawback of this approach is the need for careful design of the refractive index distribution across the device to achieve weak optical confinement of the waveguide modes in the QD medium. A non-standard mixture of ITO and silicon dioxide is necessary to ensure sufficiently stable mode guidance within a very thin active layer (mandatory for electrically pumped laser emission). The maximum current density exhibited in these devices is limited to 0.2 A cm⁻¹. -2 It is too small to reach the laser emission threshold through electrical injection.

[0007] Therefore, there is still a need for high-efficiency optoelectronic devices, especially laser diodes made of solution-processable active materials. Summary of the Invention

[0008] The purpose of embodiments of the present invention is to provide a high-efficiency optoelectronic device structure that supports high injection current density in an active layer comprising a solution-processable semiconductor nanocrystal material and also supports low-loss optical mode guidance.

[0009] Another objective of embodiments of the present invention is to provide optoelectronic device structures that guide and confine optical modes in a robust and reliable manner, regardless of the thickness of the active layer comprising solution-processable semiconductor nanocrystal materials (especially thin-film active layers that are reversible under DC bias current).

[0010] The above objectives are achieved by the method and apparatus according to the present invention.

[0011] This invention relates to an integrated optoelectronic device, comprising: a substrate; a first charge transport layer for transporting carriers of a first conductivity type; a second charge transport layer for transporting carriers of a second conductivity type opposite to the first conductivity type; and an active layer comprising a thin particulate film (e.g., a particulate film of colloidal quantum dots (single-layer, double-layer, multi-layer)) of solution-processable semiconductor nanocrystals. The substrate supports a passive waveguide for guiding light along the longitudinal direction (optical axis) of the device and restricting the refractive index of the guided light to at least one optical mode in each lateral direction of the device. The active layer is arranged relative to the charge transport layer to form a diode junction. The active layer and the first and second charge transport layers are formed on the substrate, and each overlaps at least a portion of the waveguide in a cross-section perpendicular to the propagation direction of at least one optical mode in the waveguide. The active layer is optically coupled to the waveguide. The waveguide is typically a non-planar waveguide, such as a non-planar waveguide, meaning that the lateral refractive index restriction achievable by the waveguide is two-dimensional and allows the optical axis of the waveguide to bend, i.e., the longitudinal direction of the waveguide can vary relative to the substrate supporting the waveguide. In either case, the two lateral directions of the waveguide correspond to the two smaller dimensions of the waveguide, typically having a submicron length scale, while the longitudinal direction of the waveguide corresponds to the optical axis of the waveguide and extends a distance much greater than the two lateral dimensions. In other words, the waveguide achieves refractive index confinement of the at least one optical mode in a first lateral direction parallel to the charge transport layer and the active layer and a second lateral direction perpendicular to the charge transport layer and the active layer, wherein both the first and second lateral directions are perpendicular to the longitudinal direction.

[0012] Compared to conventional III / V semiconductor devices (such as laser diodes, where the lower bandgap material has a higher refractive index to allow optical mode confinement in the active region, and where the bandgap and refractive index are typically tuned by changing the composition), the active layer of solution-processed semiconductor nanocrystal materials is incompatible with these established design principles. The primary reason is that the available current density injected into the active layer is limited for the various organic and inorganic charge transport layers that are widely available, and therefore, reversing the thick active layer of solution-processed semiconductor nanocrystal materials (which would allow for sufficient mode confinement) is impossible. This invention provides solutions to these problems by confining the optical mode refractive index to the waveguide and by overlapping the modes with the active layer.

[0013] In embodiments of the present invention, the average interparticle distance between adjacent particles in the active layer particulate film can be less than 10 nm, for example, less than or equal to 5 nm, thereby achieving a dense assembly (e.g., close packing) of particles in the active layer particulate film. The active layer particulate film is typically discontinuous, i.e., it does not contain a continuous phase matrix material in which semiconductor nanocrystal particles are embedded. Preferably, the nanoparticle surface density relative to the active layer particulate film is greater than 1.0 × 10⁻⁶. 11 cm- 2, for example, greater than 1.0 * 10 12 cm -2 For example, 5.0*10 12 cm -2 Or larger.

[0014] In embodiments of the present invention, the optoelectronic device may be configured to act as a light-emitting device (e.g., a laser diode, LED, or semiconductor optical amplifier), a light-detecting device (e.g., a photodetector), or a dimming device (e.g., an electro-optic modulator).

[0015] In embodiments of the present invention, optoelectronic devices can be provided as photonic integrated circuits (PICs). Therefore, they offer advantages such as miniaturized devices, large-scale production, wafer-level fabrication, and low cost. Solution-processed semiconductor nanocrystal materials are compatible with a variety of passive waveguide platforms. Compared to conventional III / V semiconductor active devices, solution-processed materials for the active layer do not rely on expensive and complex epitaxial growth environments and can be obtained at lower temperatures.

[0016] In embodiments of the present invention, the solution-processable semiconductor nanocrystal material of the active layer includes one or more of the group consisting of colloidal quantum dots, nano-perovskite-based materials, bulk semiconductor crystals, and nanosheets. Semiconductor nanocrystal materials (such as colloidal quantum dots) are attractive due to their large material gain and wavelength tunability.

[0017] In embodiments of the invention, the current path through the first charge transport layer, the active layer, and the second charge transport layer may not extend into the waveguide. This has the advantage of reducing absorption mode loss caused by free carriers. In embodiments of the invention, the active layer can be evanescently optically coupled to the waveguide by mode overlap between at least one guiding mode defined in the waveguide and the active layer. The confinement factor of at least one guided mode in the active layer can be designed according to the waveguide geometry and material, as well as the distance between the active layers. This has the advantage of controlling the saturation power of the optoelectronic device. In embodiments of the invention, the waveguide can be configured to confine and guide the at least one optical mode independently of the active layer. The confinement of the at least one optical mode is controlled by the refractive index of the waveguide. Therefore, variations in the thickness and / or distance of the active layer relative to the waveguide do not result in a loss of optical confinement and waveguide in the device. Typically, the optical waveguide is a non-planar waveguide, such as a ribbed waveguide or a ridge waveguide. Furthermore, optical waveguides supporting only a single guided mode or only a few guided optical modes (e.g., three guided optical modes or fewer) are preferred. In an embodiment of the invention, the contact portion of the active layer in the cross-section may overlap with the waveguide. This is a further advantage because electrical confinement and charge carrier recombination can occur near the location of the peak intensity of at least one guided optical mode, which improves the internal quantum efficiency of the device.

[0018] In embodiments of the invention, the first charge transport layer may be an organic semiconductor hole transport layer, while the second charge transport layer may be an inorganic semiconductor electron transport layer. In the cross-section, the first and second charge transport layers, the active layer, and the waveguide may be stacked vertically. This has the advantage that the second charge transport layer can also act as the bottom contact of the diode junction. Therefore, a further bottom contact layer (cathode) is not required, which allows for reduced carrier-induced mode losses. Furthermore, no additional layers, such as adhesive or bonding layers, are required in the vertical stack between the waveguide and the active layer. This has the advantage of reducing mode losses and / or achieving improved mode overlap with the active layer, which reduces the laser threshold current density in laser diodes using optoelectronic devices according to these embodiments.

[0019] In embodiments of the invention, the second charge transport layer may be a semiconductor electron transport layer disposed between the active layer and the waveguide. The semiconductor electron transport layer can be optimized for good electron mobility, good conductivity, and reduced optical loss. This has the advantage that the mode loss of at least one guided mode occurring near the waveguide is further reduced. This can be further improved by providing a thicker first charge transport layer, such that the top contact electrode is further away from the waveguide and the optical modes guided therein.

[0020] In embodiments of the invention, the second charge transport layer may conform to the contour of a waveguide that rises from the surface of the substrate. This has the advantage of carrier recombination or generation occurring near the peak intensity of the waveguide and at least one optical guiding mode. Therefore, the internal quantum efficiency of the device can be improved. Furthermore, in these embodiments, good current focusing is achieved at the active layer, allowing for the injection or extraction of larger current densities into or from the active layer, and further enabling the inversion of the thin-film active layer, including solution-processed semiconductor nanocrystal materials, through DC current bias.

[0021] In embodiments of the invention, the first charge transport layer and the second charge transport layer may be coplanar and arranged to overlap with different portions of the waveguide in the cross-section, such that adjacent edges of the first and second charge transport layers are separated by a gap, and the active layer extends over at least a portion of the first and second charge transport layers and into the gap. The waveguide may be a slotted waveguide, such that the gap extends between two waveguide tracks of the slotted waveguide. An advantage of such an embodiment is that increased mode overlap with the active layer can be obtained, and the electric field associated with the at least one light-guiding mode is relatively uniform within the gap.

[0022] In another aspect, the present invention relates to an integrated light-emitting device comprising an integrated optoelectronic device according to an embodiment of the preceding aspect, particularly an integrated light-emitting diode (LED) or an integrated laser diode (LD). In embodiments of this aspect, an optical waveguide is transiently coupled to a light-emitting layer stack (comprising an active layer and a charge-transport layer) of the integrated light-emitting device, such as the light-emitting layer stack of an LED or LD. This light-emitting layer stack is typically oriented perpendicularly to the substrate carrying the waveguide, i.e., perpendicular to the top surface of the waveguide, and each layer of the light-emitting layer stack is coplanar with the plane containing the waveguide (e.g., a substrate layer).

[0023] In another aspect, the invention may also relate to an integrated photodetector (PD) comprising an integrated optoelectronic device according to an embodiment of the first aspect. The photodetector further includes a first electrode electrically contacted with a first charge transport layer and a second electrode electrically contacted with a second charge transport layer to induce a reverse bias condition across a diode junction, wherein the active layer is adapted to generate carriers with opposite conductivity under the reverse bias condition, and wherein the diode junction is adapted to separate and collect the generated carriers into a corresponding charge transport layer under the reverse bias condition. In an embodiment of this aspect, an optical waveguide is eerily coupled to a light-absorbing layer stack of the integrated PD, which includes an active layer and a charge transport layer. This light-absorbing layer stack is typically oriented perpendicularly to the substrate carrying the waveguide, i.e., perpendicular to the top surface of the waveguide, and the layers of the light-emitting layer stack are coplanar with the plane containing the waveguide (e.g., a substrate layer).

[0024] In another aspect, the present invention relates to a method for decoupling charge current injection and refractive index confinement of a light guiding mode in an active layer of an integrated optoelectronic device. The integrated optoelectronic device includes a first charge transport layer for transporting carriers of a first conductivity type, a second charge transport layer for transporting carriers of a second conductivity type opposite to the first conductivity type, and an active layer comprising a solution-processed semiconductor nanocrystal material. The active layer is arranged relative to the charge transport layer to form a diode junction. The method includes the step of providing a substrate supporting a passive waveguide for refractive index confinement and guidance of light in at least one optical mode while being optically coupled to the active layer. The refractive index confinement is obtained for two lateral directions (e.g., the width and height directions of the waveguide) of an elongated waveguide, while the confined light in the at least one optical mode is guided in a longitudinal direction (corresponding to a preferred extension direction of the waveguide). The method further includes the step of arranging each of the active layer, the first charge transport layer, and the second charge transport layer on the substrate to overlap with at least a portion of the waveguide in a cross-section perpendicular to the longitudinal direction in which the confined light propagates along the waveguide.

[0025] The advantage of these decoupling methods is that low-loss passive waveguides can be combined with high material gain, thin-film active layers without compromising reliable optical guidance within the waveguide. Furthermore, this provides a more flexible design approach, helping to reduce mode overlap or leakage to lossy contact layers. This contrasts with existing laser devices based on solution-processable semiconductor nanomaterials, where combined refractive index confinement and carrier injection are achieved in a single active layer within a stacked device. In these existing devices, there are conflicting requirements regarding the thickness of the active layer. On the one hand, a relatively thin active layer is necessary to achieve efficient carrier injection at rates capable of population inversion and laser emission. On the other hand, a relatively thick active layer is preferred due to better refractive index confinement and mode gain characteristics of the guiding modes (especially those with high optical loss in metallic contact layers and charge transport layers), for example, light is guided more reliably without significant leakage into surrounding layers, thereby increasing the laser emission threshold too much to be achieved by purely electric pumping.

[0026] The final aspect of the invention relates to a method of manufacturing an integrated optoelectronic device according to any embodiment of the embodiments associated with the first aspect. The method includes providing a substrate having a passive waveguide and forming a layer stack by sequentially depositing layers on the substrate in the following order:

[0027] (i) A second charge transport layer for transporting charge carriers of the second conductivity type

[0028] (ii) An active layer comprising a particulate film of semiconductor nanocrystals, wherein the semiconductor nanocrystals are deposited from a solution, and

[0029] (iii) A first charge transport layer for transporting charge carriers of a first conductivity type opposite to the second conductivity type.

[0030] According to the method of the present invention, the waveguide is configured to guide light in the longitudinal direction and limit the refractive index of the guided light in each transverse direction in at least one guiding mode. Furthermore, each of the deposited active layer and the deposited first and second charge transport layers overlaps with at least a portion of the waveguide in a cross-section perpendicular to the longitudinal direction (i.e., the direction of light propagation in the waveguide). The active layer is arranged relative to the two charge transport layers to form a diode junction, and the active layer is evanescently optically coupled to the waveguide.

[0031] According to a preferred embodiment, the deposited first charge transport layer is an organic layer, while the deposited second charge transport layer is an inorganic layer. Depositing the first charge transport layer may include vacuum thermal evaporation or organic vapor deposition, while depositing the second charge transport layer may include thermally controlled atomic layer deposition (ALD), with or without reactive plasma assistance (plasma-assisted ALD). In a particularly preferred embodiment, depositing the second charge transport layer includes depositing a polycrystalline zinc oxide (ZnO) nanolayer using atomic layer deposition at a substrate temperature between 60°C and 300°C, with an optional subsequent annealing step at approximately 400°C. Annealing may be performed in a nitrogen or hydrogen atmosphere. Plasma or radical-assisted atomic layer deposition processes can be used and offer particular advantages such as: reduced processing temperature, greater process flexibility (e.g., selection of precursors and their reactivity), reduced cleanup time, precursor ligand removal, improved film properties, and increased film growth per deposition cycle.

[0032] According to a preferred embodiment, the deposition of an active layer from a solution of semiconductor nanocrystals includes subjecting a dispersion of preformed semiconductor nanocrystals (e.g., pre-synthesized colloidal core-shell quantum dots) to wet processing techniques such as spin coating, dip coating, spray coating, Langmuir-Blodgett or Langmuir Schaeffer deposition or inkjet printing.

[0033] According to some embodiments of the present invention, the second charge transport layer can be directly deposited on the waveguide to obtain an externally coated waveguide. Furthermore, the method may include depositing a cladding material on both sides of the externally coated waveguide, thereby passivating the second charge transport layer and planarizing the deposited cladding material such that the top surface of the deposited cladding material is flush with the top surface of the externally coated waveguide. Additionally, one or more of the following steps may be performed: contacting the first charge transport layer with a first metal electrode, contacting the second charge transport layer with a second metal electrode, and encapsulating the integrated optoelectronic device.

[0034] The advantages of embodiments of the present invention are that the semiconductor nanocrystals of the active layer particulate film can be obtained from solution, which is more versatile and cheaper than epitaxial growth methods (e.g., molecular beam epitaxy). For example, solution processing of semiconductor nanocrystals allows for monolayer or multilayer deposition, even on irregular or patterned surfaces, and on amorphous surfaces. Furthermore, denser particulate films can be obtained compared to conventional epitaxial growth methods, and no matrix material is required.

[0035] Embodiments of the present invention also offer the advantage of making it easier to fabricate integrated optoelectronic devices without requiring additional intermediate layer bonding steps between two wafers or between a wafer and a die. Therefore, relatively thick intermediate bonding layers (e.g., adhesive layers) relative to the waveguide dimension (especially height) can be avoided, thereby improving mode overlap and evanescent coupling efficiency between the waveguide optical modes and the active layer. In the case of conductive intermediate bonding layers, eliminating the intermediate bonding layer results in lower series resistance along the current path and increases the achievable current density of carriers after injection into the active layer.

[0036] From the perspective of alignment and overall device compactness, the fabrication of bondless integrated optoelectronic devices is also preferred because bonding is not self-aligned and typically requires wide design tolerances. Bonding of patterned mesa typically also results in larger overall devices, thus hindering dense integration of compact optoelectronic devices on a single chip. Furthermore, the materials used for epitaxial growth of the mesa to be bonded generally involve higher costs compared to the solution-processed semiconductor nanocrystals of this invention.

[0037] Specific and preferred aspects of the invention are set forth in the appended independent and dependent claims. Features from the dependent claims may be suitably combined with features of the independent claims and other dependent claims, and not merely as expressly set forth in the claims.

[0038] For the purpose of summarizing the invention and its advantages over the prior art, certain objects and advantages of the invention have been described above. It should be understood, of course, that not all such objects or advantages may be achieved according to any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention can be embodied or practiced in a manner that achieves or optimizes one or more advantages as taught herein, without necessarily achieving other objects or advantages as may be taught or suggested herein.

[0039] The above and other aspects of the invention will be apparent from the embodiments described herein(s), and will be illustrated with reference to the embodiments described herein(s). Attached Figure Description

[0040] The invention will now be further described by way of example with reference to the accompanying drawings, in which:

[0041] Figure 1 This is a cross-sectional view of an integrated optoelectronic device according to a first embodiment of the present invention, including a vertical diode junction and a strip waveguide flush with the substrate.

[0042] Figure 2 This is a cross-sectional view of an integrated optoelectronic device according to a second embodiment of the present invention, including a horizontal diode junction and a slotted waveguide.

[0043] Figure 3 This is a cross-sectional view of an integrated optoelectronic device according to a third embodiment of the present invention, including a horizontal diode junction and a strip waveguide.

[0044] Figure 4 This is a cross-sectional view of an integrated optoelectronic device according to a fourth embodiment of the present invention, including a vertical diode junction and a ridge waveguide rising from the substrate.

[0045] Figure 5 yes Figure 4 Perspective view of the embodiment shown.

[0046] Figures 6 to 11 An example of an optical feedback device that can be used in an integrated optoelectronic device according to an embodiment of the present invention is shown.

[0047] Figure 12 It shows that according to Figure 4 The spatial mode distribution of the fundamental waveguide modes in the cross section of the integrated optoelectronic device in the embodiment.

[0048] Figure 13 This demonstrates how to remove the active layer from Figure 12 The spatial mode distribution of the basic waveguide modes obtained.

[0049] The accompanying drawings are illustrative only and not restrictive. In the drawings, some elements may be enlarged and not drawn to scale for illustrative purposes. Scale and relative scale do not necessarily correspond to an actual simplification of the practice of the invention.

[0050] Any reference numerals in the claims should not be construed as limiting the scope.

[0051] In different accompanying drawings, the same reference numerals refer to the same or similar elements. Detailed Implementation

[0052] The invention will be described with reference to specific embodiments and particular drawings, but the invention is not limited thereto but is defined only by the claims.

[0053] The terms first, second, etc., used in the specification and claims are used to distinguish between similar elements and are not necessarily used to describe a temporal, spatial, hierarchical, or any other order. It will be understood that the terms thus used are interchangeable where appropriate, and that embodiments of the invention described herein can be operated in a different order than those described or illustrated herein.

[0054] Furthermore, directional terms such as top, bottom, front, rear, below, and above in the specification and claims are used for descriptive purposes in relation to the orientation of the figures being described, and not necessarily for describing relative positions. Because components of various embodiments of the invention can be positioned in several different orientations, directional terms are used for illustrative purposes only and are not intended to be limiting unless otherwise stated. Therefore, it should be understood that these terms are interchangeable where appropriate, and that the embodiments of the invention described herein can operate in orientations other than those described or explained herein.

[0055] It should be noted that the term "comprising" as used in the claims should not be construed as limiting oneself to the means listed thereafter; it does not exclude other elements or steps. Therefore, the term should be interpreted as specifying the presence of the features, integers, steps, or components stated as mentioned, but does not exclude the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Thus, the scope of the statement "device comprising means A and B" should not be limited to a device consisting solely of components A and B. It means that for the purposes of this invention, the only relevant components of the device are A and B.

[0056] Throughout this specification, the reference to "an embodiment" or "an embodiment" means that a specific feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the phrase "in an embodiment" or "in an embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment in all instances, but may refer to the same embodiment.

[0057] Similarly, it should be understood that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, drawing, or description for the purpose of simplification and aiding in the understanding of one or more of the various inventive aspects. However, this method of disclosure should not be construed as reflecting an intention to claim more features than are expressly recited in each claim. Rather, as reflected in the appended claims, inventive aspects exist in fewer features than all the features of a single foregoing disclosed embodiment. Therefore, the claims appended to the Detailed Description are thus explicitly incorporated into this Detailed Description, wherein each claim itself represents a separate embodiment of the invention.

[0058] Furthermore, as will be understood by those skilled in the art, although some embodiments described herein include some features included in other embodiments but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments.

[0059] Numerous specific details are set forth in the description provided herein. However, it should be understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description.

[0060] definition

[0061] When referring to solution-processable materials, this means materials obtained from a wet chemical environment (e.g., a solution) using any deposition technique that forms part of the prior art. Known solution deposition techniques include, but are not limited to, spin coating, evaporation, centrifugation, sol-gel processes, inkjet printing, screen printing, spraying, and precipitation. A significant advantage of solution-processable materials compared to epitaxially grown materials is that they can be deposited on amorphous solid interfaces.

[0062] When nanocrystalline materials are mentioned, it refers to materials composed of particles with no more than 100 nanometers in any of the three dimensions. Specifically, quantum dots are particles that are typically no larger than 20 nanometers in each spatial direction. More generally, quantum dots are nanoscale crystals that exhibit quantum confinement effects in all three spatial dimensions of charge carriers of at least one type of conductivity.

[0063] In the context of this invention, when a layer is referred to as overlapping or intersecting with a portion of a waveguide in a given cross section, the projected surface of the layer in a direction perpendicular to the layer includes the projected surface of that portion of the waveguide in the same direction, which also includes the cross section plane.

[0064] In a first aspect, the present invention relates to an integrated optoelectronic device. According to embodiments of the invention, the optoelectronic device structure can be adapted to primarily function as a light-emitting device (e.g., a semiconductor laser diode (LD) or semiconductor light-emitting diode (LED)), an optical amplification device (e.g., a semiconductor optical amplifier (SOA)), a light detection device (e.g., a photodiode or wavelength-resolved photodetector), or a dimming device (e.g., an electro-optic modulator based on an electroabsorption effect (e.g., the quantum-confined Stark effect) or an electrorefractive effect (e.g., the Pockels effect). The optoelectronic device according to embodiments of the invention is an integrated device that can be fabricated as a wafer-level photonic integrated circuit. Therefore, the advantages of embodiments of the invention are that they provide low-cost, mass-producible, and compact optoelectronic devices with different functionalities, including light emission, laser emission, optical amplification, and optical detection. The integrated optoelectronic devices according to various embodiments can be combined on the same integrated photonic chip to provide more versatile circuitry, such as a laser device coupled to a modulator or a photodiode including a preamplifier stage.

[0065] Figure 1 This is a cross-sectional view of an integrated optoelectronic device according to a first embodiment. The optoelectronic device 100 includes a substrate 30 in which an optical waveguide 31 is formed, such that the top surface of the waveguide is flush with the top surface of the substrate. The waveguide is configured to guide at least one optical mode in a direction perpendicular to the cross-section. A vertical layer stack is formed on a region of the substrate containing the waveguide, the region including, in order from top to bottom of the stack, a contact layer forming a first electrode 40, a first charge transport layer 11, an active layer 20 comprising solution-processed semiconductor nanocrystal material, and a second charge transport layer 12. The second charge transport layer 12 and the substrate 30 are arranged adjacent to each other at least at the location where the waveguide 31 is formed in the substrate 30, i.e., the second charge transport layer is in physical contact with the top surface of the waveguide. A second electrode 50 is provided as a pair of electrodes in electrical contact with the second charge transport layer 12.

[0066] The vertically stacked layers have a pin diode structure and operate accordingly. Therefore, the integrated optoelectronic device 100 can selectively operate as a light-emitting device (e.g., a laser diode) or a photodetector, depending on the selected bias state of the diode structure included in the optoelectronic device: forward biasing the diode structure results in light emission, while reverse or zero biasing of the diode structure results in light absorption. More specifically, the active layer 20 is arranged between the first charge transport layer 11 and the second charge transport layer 12 such that, under forward bias conditions, majority carriers pumped in and transported by the respective charge transport layers 11, 12 are efficiently injected into the active layer and recombine therein to generate light. Conversely, under reverse or zero bias conditions, light is absorbed in the active layer 20, generating electron-hole pairs, which are subsequently separated into majority carriers in the first and second charge transport layers 11, 12. Those skilled in the art will understand that the layer thickness and specific material selection of the active layer 20 and the two charge transport layers 11, 12 largely depend on the intended use of the optoelectronic device. Selecting materials and optimizing layer thicknesses based on device function is routine work for those skilled in the art, such as in the implementation of light-emitting or light-amplifying devices (LDs, LEDs, SOAs), photodetectors, or dimmers. Since the presence of the waveguide precludes the possibility of forming direct back-side contact with the vertical layer stack, it is preferable to make lateral contact with the vertical layer stack via a laterally offset electrode pair 50. This has the advantages that all electrical contacts are located on the same device side, and the second electrode 50 can be formed close to the diode structure of the vertical stack, reducing resistive heat loss. In this embodiment, lateral charge transport towards the vertical layer stack is also achieved by the second charge transport layer 12. Therefore, no additional contact layer is required to electrically contact the bottom side of the vertical layer stack. By limiting the lateral extent of the vertical layer stack, high current density can be obtained in the active layer, which is a prerequisite for achieving population inversion and laser emission in semiconductor laser diodes including optoelectronic devices according to this embodiment. Furthermore, laterally offsetting the pair of conductive electrodes 50 reduces the contribution of optical losses caused by free carriers in waveguide 31. Although vertical layers are stacked... Figure 1 The image is shown centered relative to waveguide 31, but it can also be positioned asymmetrically relative to the waveguide. The optoelectronic device 100 is therefore robust to misalignments during the manufacturing process (e.g., misalignment during photolithography). As an alternative to forming the first electrode 40 of the flat-top electrode layer, the first electrode 40 can also be patterned, for example, to form the shape of two parallel coplanar electrodes. Despite the additional patterning step, this electrode configuration has the advantage of further reducing metal-induced propagation losses of the light-guiding modes in the waveguide.

[0067] Now for reference Figure 2A cross-sectional view of an integrated optoelectronic device 200 according to a second embodiment of the present invention is shown. In this embodiment, the waveguide is arranged as a slotted waveguide consisting of two waveguide tracks 31a and 31b separated by a gap 21. A first charge transport layer 11 is formed adjoiningly on the substrate surface only on one side of the waveguide (e.g., at the location of the first waveguide track 31b), and a second charge transport layer 12 is formed adjoiningly on the substrate surface only on the other side of the waveguide (e.g., at the location of the second waveguide track 31b). Both the first charge transport layer 11 and the second charge transport layer 12 extend into the gap 21 but do not contact each other, such that the sidewall of each of the two waveguide tracks 31a and 31b facing the gap is covered by the corresponding one of the first charge transport layer and the second charge transport layer. The remaining gap portion not filled by the charge transport layer contains the active layer 20. A first electrode 40 and a second electrode 50 are disposed at a location away from the waveguide and are in electrical contact with the first charge transport layer 11 and the second charge transport layer 12, respectively. Figure 2 As shown, the active layer 20 may have a gap-filling portion included in the gap 21 and an expansion portion not included in the gap 21. The expansion portion and the gap-filling portion of the active layer 20 together have a T-shaped appearance in a cross-sectional view. An advantage of this embodiment is that the active layer has a gap-filling portion extending into the gap between the slotted waveguides, which amplifies the mode overlap with the active layer. Furthermore, for example, the electric field of the fundamental mode supported by the slotted waveguide is relatively uniform in the gap region compared to the strongly diminished evanescent tail above the ridge waveguide. The expansion portion may cover the two charge transport layers 11, 12, for example, covering a lateral extent corresponding to the lateral dimensions of waveguides 31a-b. The thickness (e.g., height) of the overgrown expansion portion can be controlled. This has the advantage that contact portions of the active layer can also exist outside the gap, thereby moderately increasing unity gain or unity absorption coefficient without simultaneously increasing the width of the active layer within the gap, i.e., without significantly altering the current density supported by the diode structure in the gap region. Furthermore, in this embodiment, the two charge transport layers 11, 12 and the active layer 20 sandwiched therebetween form a horizontal pin diode junction, such as a diode junction having a junction plane oriented perpendicular to the substrate, illustrating that the layer stacking is not limited to a vertical stacking configuration. Good electrical confinement of the concentrated charge carriers is automatically achieved by means of a gap, which can be shallow relative to the longitudinal extent of the optoelectronic device. Therefore, high current density can be obtained in the narrow gap-filled portion of the active layer, which is a prerequisite for achieving population inversion and laser emission in a semiconductor laser diode including the optoelectronic device according to this embodiment.

[0068] Figure 3 This is a cross-sectional view of the integrated optoelectronic device 300 according to the third embodiment of the present invention, which is similar to... Figure 2In the second embodiment, waveguide 31 is configured as a strip waveguide. Therefore, gap 21 is not naturally provided by the waveguide structure itself. For this embodiment, gap 21 is defined as a partition space (e.g., an elongated hole, a slit) extending between the first and second charge transport layers 11, 12, each charge transport layer being formed adjoiningly on the substrate surface only on one side of waveguide 31. Gap 21 is filled with an active layer 20 extending over a portion of the first and second charge transport layers 11, 12 on each side of gap 21, for example, over a portion of the first charge transport layer 11 and the second charge transport layer 12 covering waveguide 31. Therefore, active layer 20 may have a gap-filling portion included in gap 21 and an expansion portion not included in gap 21. The expansion portion and gap-filling portion of active layer 20 together have a T-shaped appearance in cross-sectional views. Preferably, the gap 21 is centered relative to the waveguide 31 to symmetrically couple light from the waveguide 31 into the active layer 20, or vice versa, for example, from the active layer 20 into the waveguide 31.

[0069] Figure 4 A cross-sectional view of an integrated optoelectronic device 400 according to a fourth embodiment of the present invention is shown. It is related to... Figure 1The first embodiment differs in that the waveguide 31 is formed on the surface of the substrate 30. The top surface of the waveguide protrudes from the substrate surface. Therefore, the top surface of the waveguide is not at the same height as the substrate surface. Consistent with the contour of the waveguide 31, the second charge transport layer 12 covers the top and sides of the waveguide 31 with a substantially constant layer thickness, for example, the second charge transport layer 12 conformally covers the waveguide 31 at the position where the waveguide 31 rises from the substrate surface. A covering material 32 can be disposed on both sides of the waveguide 31 and flush with its coated top surface. The covering material 32 can serve as an additional support member relative to a vertical layer stack disposed on top of the coated waveguide rising from the substrate. Another advantage of this embodiment is that the covering layer 32 serves as a passivation layer for the second charge transport layer 12. Holes can be provided in the covering layer 32 at the location where the second electrode 50 electrically contacts the second charge transport layer 12, or the covering layer 32 can have a limited lateral range to achieve electrical contact between the second electrode 50 and the second charge transport layer 12. This embodiment is particularly suitable for achieving good current focusing and high current density in the active layer 20 because the contact portion between the active layer 20 and the second charge transport layer 12 is limited by the lateral dimension (width) of the waveguide 31. Another advantage is that the waveguide 31 is adjacent to the current injection and recombination region of the active layer, thereby allowing light generated or absorbed in the active layer to be efficiently coupled into or out of the waveguide, respectively. As an alternative to forming a flat-top electrode layer, the first electrode 40 can also be patterned, for example, to form the shape of two parallel coplanar electrodes. Despite the additional patterning step, this electrode configuration has the advantage of further reducing the metal-induced propagation loss of the light-guiding mode in the waveguide.

[0070] Figure 5 yes Figure 4 A perspective view of the integrated optoelectronic device 400. Waveguide 31 is configured as a straight waveguide, but may also have a different shape and / or a shape that varies in the longitudinal direction (e.g., the direction of light propagation in the waveguide). For example, the waveguide may be curved, S-shaped, or otherwise bent along the direction of light propagation in the waveguide. Electrodes 40, 50 may extend longitudinally to allow all of them to be stacked along the vertical layers to deliver or extract current.

[0071] Figure 12 It shows Figure 4 and Figure 5 The light intensity distribution (mode profile) of the basic guided transverse electrical (TE) mode of waveguide 31 in the embodiment. This will be related to... Figure 13The optical mode distributions of the same waveguide and nearly identical vertical layer stacks are compared, with only the active layer omitted. This comparison shows that the optical mode distribution associated with the waveguide remains essentially unchanged without the active layer, compared to the case including the active layer. In other words, the general shape and optical properties (e.g., 1 / e spatial range and confinement factor) of the waveguide and its associated optical modes are not significantly affected by the presence of the active layer. Figure 13 The overlap between the basic waveguide mode and the active layer in the model achieves a certain degree of evanescent wave coupling. For example, the overlap of modes can be between 0.1% and 10% of the effective mode area.

[0072] The substrate can be an insulating or semi-insulating substrate, such as a silicon substrate, which includes a buried oxide layer between bulk silicon and a material layer for the formation and functionality of photonic integrated circuits, such as a silicon nitride layer (visible and infrared light) or a silicon layer (infrared light).

[0073] The first charge transport layer 11 can be a hole transport layer and is preferably implemented as an organic hole transport layer, but an inorganic hole transport layer can also be used. Typical materials for the first charge transport layer may include semiconductor OLED materials, such as organic molecular semiconductors with a large HUMO-LUMO bandgap, such as triphenylamine, such as N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPD), tetraphenylnaphthalene (Rubrene), or carbazole derivatives, such as tris(4-carbazoyl-9-ylphenyl)amine (TCTA). Furthermore, the first charge transport layer can be multilayered, including a transport layer (e.g., a hole transport layer) and an injection layer (e.g., a hole injection layer) and / or a layer for band alignment or charge generation. The multilayer first charge transport layer may also include at least one electron blocking layer. The thickness of the first charge transport layer 11 may vary from tens of nanometers to hundreds of nanometers, for example, up to 2 μm. Non-limiting examples of the first charge transport layer include a three-layer charge transport layer consisting of a charge generation layer (e.g., 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HATCN) layer), a hole transport layer (e.g., an NPD layer), and a hole injection layer (e.g., a TCTA layer).

[0074] The second charge transport layer 12 can be an electron transport layer. It can be a thin layer of organic or inorganic semiconductor material, such as a thin layer of polycrystalline zinc oxide or zinc oxide nanocrystals. However, conductive polymers or electron-deficient molecular semiconductors can also be used. If, in some embodiments of the invention, the first charge transport layer 11 is arranged closer to the optical waveguide 31, this layer is preferably formed of a semiconductor material combining good carrier mobility (e.g., low resistance) and low optical attenuation. This has the advantage of reducing laser threshold current and power consumption. Embodiments of the invention are not limited to a hole-oriented first charge transport layer and an electron-oriented second charge transport layer. For example, the first charge transport layer can be an electron transport layer, while the second charge transport layer can be a hole transport layer.

[0075] Although in the foregoing embodiments the second charge transport layer has been described as being arranged adjoiningly to the substrate at least where the waveguide is formed in the substrate, i.e., the second charge transport layer is in physical contact with the top surface of the waveguide, this is not a limiting feature of the invention. In alternative embodiments, a low-refractive-index intermediate layer having a lower refractive index than the waveguide can be inserted between the waveguide and the second charge transport layer, thereby avoiding direct physical contact. The intermediate layer can be used in embodiments where it is advantageous, for example, to have a seed layer to initiate uniform growth of the second charge transport layer during device fabrication. Preferably, such an intermediate layer remains thin to maintain good pattern overlap with the active layer. Furthermore, in embodiments of the invention, the waveguide can extend longitudinally beyond the active device region including the active layer. This can be advantageous because it allows the shadow mask of the organic hole transport layer 11 and the p-metal contact electrode 40, which has a very rough coverage accuracy, to evaporate.

[0076] Semiconductor nanomaterials comprising an active layer 20 are disposed between a first charge transport layer 11 and a second charge transport layer 12 to form a diode junction, for example, a planar pin junction parallel to the substrate 30. When the diode junction is forward biased (e.g., under a forward bias condition), the transported majority carriers (e.g., holes and electrons) are injected from each side into the active layer 20 and subsequently recombine to generate electroluminescence. If the diode junction is negatively biased (e.g., under a reverse bias condition) or remains unbiased (e.g., under a zero bias condition), the majority carriers originating from the active layer 20 (e.g., generated by light absorption and electron-hole pairs) are separated into the respective charge transport layers under the influence of the built-in electric field present on the diode junction. The semiconductor nanocrystal material may include colloidal quantum dots, sheet-like nanoparticles, nanorods, nanosheets, or perovskite structure materials, such as calcium lead halide perovskite nanocrystals, which may be filled into single-layer, bilayer, or multilayer thin films. Colloidal QDs can be core-shell type, with engineered core and shell diameters, for example, based on material gain and gain threshold, as described in Bisschop, S. et al., “The impact of Core / Shell Sizes on the Optical Gain Characteristics of CdSe / CdS Quantum Dots,” ACS Nano 12(9), 9011-9021(2018). Another type of colloidal QD that can be used in embodiments of the present invention is a sequentially hierarchical core-shell QD as described in the references of Lim et al. Semiconductor nanocrystal materials (such as colloidal QDs) can be filled into the thin film active layer with a fill factor of up to 50%, or even higher if the organic ligands on the QD shell are at least partially removed. The gaps in the thin film active layer not filled by semiconductor nanocrystal materials (such as colloidal QDs) typically include organic ligands and air. However, in certain embodiments, colloidal QDs can also be embedded in an inorganic or polymer matrix. The optical properties of active layers containing solution-processed semiconductor nanocrystals are well described using the effective dielectric method, which illustrates their subwavelength inhomogeneities. As a result, the effective refractive index of active layers containing solution-processed semiconductor nanocrystals is relatively low compared to dense bulk materials used for integrated waveguides (e.g., silicon nitride), which is why robust refractive index confinement in such thin-film active layers is a challenging task. Conversely, thicker active layers containing solution-processed semiconductor nanocrystals are generally not reversible by DC bias current and cannot be used as electrically pumped gain media.

[0077] In another aspect, the present invention relates to an integrated light-emitting device comprising or based on an integrated optoelectronic device according to embodiments of the foregoing aspects. The light-emitting device may be a light-emitting diode (LED). Unlike laser diodes, LEDs emit incoherent and broad-spectral light beams. The output spectrum of the LED is determined by the electroluminescence spectrum of the semiconductor nanocrystal material of the active layer. A portion of the spontaneously emitted photons is coupled into a waveguide (e.g., a multimode waveguide) of the optoelectronic device to obtain better photon collection efficiency. For use as an LED, high light extraction efficiency from the waveguide is desirable to achieve a good brightness level. This can be achieved by further providing an anti-reflective coating on both end faces of the waveguide, or by providing a highly reflective element (e.g., a broadband mirror or reflective coating) at one end of the waveguide and an anti-reflective coating at the other end. The light-emitting device may also be a superluminescent light-emitting diode (SLED) if the spontaneous emission of the active layer is coupled into the waveguide and subsequently amplified by the active layer before emission from the device. Furthermore, the light-emitting device based on the integrated optoelectronic device according to a particular embodiment may be configured as a white LED. For this purpose, multiple active device regions can be provided along the same passive waveguide and coupled to the same passive waveguide. Each active device region is arranged according to the embodiments of the optoelectronic device described above, and each active device region includes an active layer comprising different solution-processed semiconductor nanocrystal materials (e.g., QDs of different diameters emitted at different wavelengths).

[0078] The integrated light-emitting device can also be a semiconductor laser diode. To enable laser emission, the optoelectronic device according to embodiments of the invention further includes an optical feedback device, such as a reflector, arranged relative to the active layer to form a high-quality optical cavity including the active layer as a gain medium. The optical feedback device ensures a large number of cavity round trips of the intracavity light generated and repeatedly amplified by stimulated emission, ultimately resulting in highly coherent radiation with high spectral intensity output from the laser diode. In its simplest form, the optical feedback device can be implemented by dicing the waveguide endface. While the achievable quality of an optical cavity formed by dicing a waveguide is limited, this can be sufficient in some applications. Various other optical feedback devices can be used to conceive high-quality optical cavities, as shown in the references. Figure 6-11Further description. Typically, an optical feedback device includes a highly reflective first component located on one side of the optical cavity and a slightly less reflective second component located on the other side (i.e., the side from which light couples out of the cavity). These figures are intended to illustrate the different optical feedback devices and the associated optical cavities thus derived. Therefore, not all elements of the optoelectronic device are shown in these figures, but only the active layer 20 serving as the gain medium for the laser diode (LD), the waveguide 31 as part of the optical cavity, and the feedback device optically coupled to the waveguide for transforming the cavity into a high-quality optical cavity (e.g., an optical cavity with good fineness F>>1 and / or a good quality factor (Q-factor) (e.g., Q>>1, such as Q>1000). Phase shifters (e.g., heaters, spatial mode filters, and / or converters) may be provided along the waveguide 31 to tune, select, and stabilize the output wavelength and / or spatial mode distribution of the LD. To achieve mode-locking of the mode-locked laser diode, a saturable absorber may be provided along the waveguide 31. This saturable absorber may include, but is not limited to, the same solution-processed semiconductor nanocrystal material as the active layer of the optoelectronic device.

[0079] exist Figure 6 In this embodiment, the semiconductor LD 600 includes a ring waveguide 31, such as a micro-ring resonator waveguide, which serves as the optical cavity of the LD and also provides optical feedback relative to the active layer 20. A coupling segment 601 (e.g., a directional coupler) is provided along the ring waveguide 31 to couple light from the optical cavity to the output waveguide 602 of the LD. The output waveguide 602 may have an anti-reflective coating on its end faces to prevent residual reflections from re-entering the optical cavity.

[0080] Figure 7 yes Figure 6 A variation of the illustrated embodiment, where the LD 700 includes a non-circular, bent waveguide 31, for example, not implemented as a ring resonator waveguide, and therefore cannot provide optical feedback on its own. For this embodiment, an additional ring resonator 702, such as a micro-ring resonator, is provided. It achieves optical feedback by receiving light from a first end of the waveguide 31 via a first coupling segment 701a and by feeding the light back to a second end of the waveguide 31 via a second coupling segment 702b. The advantage of the additional ring resonator 702 is that it can be used as a wavelength filter incorporated into the optical cavity; for example, it can be used as a wavelength selection device to select the laser wavelength from multiple longitudinal cavity modes.

[0081] Figure 8An LD 800 configured as a distributed feedback laser (DFB) is shown. Distributed reflectors (e.g., a pair of Bragg reflectors 801a-b) are arranged within or near the gain region of the LD 800, such as within or near the active layer 20. The distributed reflectors can be implemented as diffraction waveguide gratings or cladding ripples, modulated doping concentrations, or others. The pair of Bragg reflectors 801a, 801b may include phase shift segments, such as π / 2 or quarter-Bragg wavelength shift segments. The distributed reflectors act as wavelength-selective filters, maximizing optical feedback at a predetermined wavelength of laser emission while suppressing optical feedback at other wavelengths (e.g., competing longitudinal cavity modes). Conversely, Figure 9 The LD 900 is configured as a distributed Bragg reflector laser (DBR), wherein the distributed reflectors (e.g., a pair of Bragg reflectors 901a-b) are arranged outside the gain region of the LD900, for example, outside the active layer 20. As a result, the DBR configuration is unaffected by changes in current density or gain.

[0082] Figure 10 The LD 1000 is shown, wherein waveguide 31 is terminated on one side by a waveguide loop mirror 1003 and on the other side by a reflector arrangement comprising a micro-ring resonator 1002, two access waveguides leading to the micro-ring resonator 1002, and a coupling element 1001. The two access waveguides are coupled to the micro-ring resonator 1002 via their respective coupling segments and correspond to the two outgoing branches of the coupling element 1001 (e.g., a pair of two-way directional couplers or a multimode interferometer).

[0083] Figure 11 The LD 1100 shown includes a ring waveguide 31 as an optical cavity. (And...) Figure 6 Compared to the LD 600, the active layer 20 of this LD 1100 completely overlaps with the waveguide 31. The output waveguide 602 is evanescently coupled to the optical cavity waveguide 31, for example, through a coupling segment 601, and may be provided with anti-reflection devices to suppress external feedback from re-entering the optical cavity. Alternatively, the output waveguide 602 can be used as an external cavity to provide feedback to the ring cavity. In this case, the output waveguide 602 may include its own reflector.

[0084] In the integrated light-emitting device according to an embodiment of the present invention, a plurality of gain segments may be arranged along waveguide 31, each gain segment having the cross-section described above for embodiments of the present invention. The solution-processed semiconductor nanocrystal material in the active layer of each of the plurality of segments may be selected such that its corresponding electroluminescence spectrum partially overlaps with the electroluminescence spectrum of another segment. This may be used to extend the tunable operating wavelength of the light-emitting device (e.g., a laser diode), or may be used to achieve independent gain or absorption modulation in the same optical cavity.

[0085] If the electrical bias is below the laser emission threshold, either a light-emitting diode configuration or a laser diode configuration can be used as a traveling-wave SOA or a Fabry Perot SOA, respectively. The waveguide can be tilted relative to the cut end face to further reduce the effects of multiple reflections, for example, as a supplement to an anti-reflective coating provided on the waveguide end face.

[0086] In another aspect, the present invention relates to an integrated photodetector. The photodetector includes or uses any integrated optoelectronic device associated with the embodiments of the first aspect. The thickness and material selection of the individual layers of the optoelectronic device are preferably optimized for the target absorption wavelength region and detector responsivity under reverse bias conditions. It is possible to have a multi-segment photodetector, wherein each segment includes a reverse-biased optoelectronic device according to embodiments of the present invention. Each segment can be designed, for example, to absorb light of different wavelengths or bands by adapting the quantum dot diameter or composition in the active layer of each segment. Such a multi-segment photodetector can be used for spectroscopic applications.

[0087] To operate the integrated optoelectronic device according to the foregoing embodiments as a light-emitting device, electrodes 40, 50 are connected to a power supply that applies a forward bias across the diode junction. Consequently, majority carriers of opposite charge polarities are injected into the active layer 20 through the respective charge transport layers 11, 12 and recombine in the semiconductor nanocrystal material (e.g., solution-processed quantum dots) to generate light. The power supply may be a constant current source for controlling the current density injected into the active layer 20 and thus controlling the output light intensity of the device. Current amplitude modulation may be provided during operation of the optoelectronic device, for example, for gain modulation in a semiconductor laser diode. The optoelectronic device may be mounted on a heat dissipation structure (e.g., a heat sink) to avoid large temperature rises in the device (which typically accompany thermal drift in device performance). A temperature controller, including a control unit and a thermoelectric cooling unit, may be provided to ensure stable temperature conditions when using the device.

[0088] To operate the integrated optoelectronic device according to the foregoing embodiments as a photodetector, electrodes 40 and 50 are connected to a power supply that applies a reverse bias across the diode junction. Thus, majority carriers of opposite charge polarities are collected from the active layer 20 by the corresponding charge transport layers 11 and 12, where they are generated as photogenerated electron-hole pairs and subsequently extracted from the device at electrodes 40 and 50 in the form of a photocurrent. The photocurrent can then be processed (e.g., amplified and / or quantized) in the electrical domain.

[0089] The integrated optoelectronic device according to embodiments of the present invention can be further packaged according to techniques known in the art, such as mounting the optoelectronic device on a device carrier and connecting its wires in a sealed, externally accessible package, such as a butterfly package with pin connectors.

[0090] Example

[0091] Exemplary integrated optoelectronic devices have Figure 4 The cross-section of the illustrated embodiment is shown. A silicon nitride strip waveguide 31 (e.g., 300 nm high and 1000 nm wide) protrudes from a silicon-on-insulator substrate 30 and can be fabricated using standard SOI technology for PICs. Silicon nitride-based dielectric waveguides typically have very low optical propagation losses, such as as low as 1 dB / m, and are transparent to light in the visible and infrared spectra. Although waveguide 31 is configured as a multimode waveguide in this example—it guides another higher-order TE1 mode in addition to the basic TE0 mode—where efficiency and excess loss coupled to the active layer are balanced, other embodiments of the invention may include single-mode waveguides, particularly in embodiments intended for implantation into laser diodes, although a wider multimode waveguide may also be advantageous for delivering increased output power in high-power laser diodes. The second charge layer 12 corresponds to a thin layer of continuous semiconductive zinc oxide and is an inorganic electron transport layer. This natural n-type zinc oxide thin layer (e.g., 10 nm thick) is disposed on top of waveguide 31 and conformally covers its contour. A pair of Ti / Au / Ti (20nm / 100nm / 20nm) metal n-contacts are formed on a zinc oxide layer and constitute the second electrode 50. Silicon oxide is used as a side cladding material 32 to externally coat the waveguide. The top surface of the side cladding 32 is flush with the top surface of the externally coated waveguide (e.g., the top surface of the second charge transport layer 12 covering the waveguide 31), providing a flat interface for uniform deposition of the active layer 20. In this example, the active layer 20 comprises a 20nm thick film of solution-processed, randomly oriented quantum dots (e.g., spherical colloidal CdSe / CdS core-shell quantum dots or non-spherical nanocrystals with isotropic dipole orientation). Suitable values ​​for the core and shell diameters can be 3.5nm and 7.5nm, respectively, to obtain high intrinsic material gain (e.g., up to 2800 cm⁻¹). -1 and a reasonably low injection current density threshold (e.g., j) at the active layer for net stimulated emission. th (≈60 A cm⁻²). Ultimately, the first charge transport layer 11 is realized as a 600 nm thick organic hole transport layer, on which a 300 nm thick aluminum p-contact is formed as the first electrode 40. More specifically, the first charge transport layer 11 includes a 70 nm TCTA (hole injection layer), a 500 nm NPD (hole transport layer), and a 30 nm HTA-CN (hole band alignment layer).

[0092] Finite element method (FEM) and finite-difference time-domain (FDTD) simulations were performed to optimize the waveguide geometry (e.g., width and height) and the individual layer thicknesses of the vertical layer stack, with the aim of achieving good LED characteristics. The simulations were performed at a wavelength of 650 nm, assumed to be the peak wavelength of the electroluminescence spectrum. These simulations were based on the refractive indices of charge transport layers 11 and 12 and silicon nitride waveguide 31 obtained from elliptic polarization techniques. It was found that, in the presence of the first electrode 40, the metal-induced propagation loss experienced by the fundamental waveguide mode (and all higher-order modes) decays exponentially with increasing layer thickness of the first charge transport layer. For example, for a 500 nm thick first charge transport layer, a metal-induced propagation loss of 4 dB / cm was found through simulation and verified by cut-back measurement, while for the 600 nm thick second charge transport layer in this example, a metal-induced propagation loss of 2 dB / cm was estimated. The imaginary part of the complex refractive index of the zinc oxide layer was determined by cut-back measurement to be k = 2.5 × 10⁻⁶. -4 Additional propagation loss occurs because the evanescent tails of the guiding modes confined in the waveguide inevitably overlap with the lossy zinc oxide layer. The silicon nitride waveguide dimensions are part of the simulation results and constitute a trade-off between the overall propagation loss on the one hand and the good spontaneous dipole emission coupling efficiency from the quantum dot of the active layer 20 to the waveguide 31 on the other hand. Based on the simulation results, the former is estimated to be 12 dB / cm for the mode overlap with the active layer of approximately 3.6%, and the latter is estimated to be 0.5% to 1.0% (integrated over the waveguide width). The material gain required to overcome propagation is approximately 880 cm⁻¹. -1 Furthermore, it is within the feasible range of gain-optimized core-shell quantum dots. Moreover, it has been found that if only coupling efficiency is considered for optimization, the optimal waveguide height for a single-mode waveguide will be in the range of 100 nm to 150 nm.

[0093] The fabrication method of the integrated optoelectronic device of this example is briefly described below. Starting with a bare silicon sample having a 1.0 μm thick thermal oxide layer, a 300 nm thick silicon nitride layer is deposited by plasma-enhanced chemical vapor deposition. Waveguides are defined by patterning the silicon nitride layer using electron beam lithography and reactive ion etching. Alternatively, a photonic integrated circuit with a pre-fabricated waveguide can be provided, such as cast patterned silicon nitride on an insulator (e.g., a silicon oxide insulating layer on a silicon substrate).

[0094] Next, a 10 nm thin zinc oxide (ZnO) layer (polycrystalline, continuous) was deposited via atomic layer deposition (ALD) to conformally cover the waveguide. The ZnO deposition was approximately 5*10 nm. -6The reaction is carried out at a base pressure of millibars and a temperature between 60°C and 300°C, preferably at about 150°C, and may be assisted by a reactive plasma (e.g., oxygen and / or ozone-rich plasma). The gas flow pressure of the precursor (e.g., diethylzinc zinc) and reactant material (e.g., distilled water vapor) has been adjusted to 5 x 10⁻⁶ mbars using a needle valve. -3 Millibars. Alternative deposition techniques for the second charge transport layer (e.g., a ZnO layer) include sol-gel deposition or sputtering deposition. Alternatively, a thin layer of ZnO nanocrystals can be deposited, for example, by spin coating. Subsequently, prior to an optional annealing step (e.g., annealing at a maximum temperature of 400°C in a N2 and H2 atmosphere), a passivation and etch-stop layer comprising 15 nm thick alumina is applied via ALD (e.g., using trimethylaluminum as a precursor and distilled water vapor as a reactant). The result is a high-performance zinc oxide layer with good resistance and optical loss, e.g., a sheet resistance of (1.2 ± 0.1) kΩ / sq and a free carrier absorption loss of approximately 10 dB / cm. The passivation layer is locally removed using diluted KOH to allow the formation of metal contacts for the second electrode on each side of the waveguide (e.g., 20 nm Ti / 100 nm Au / 20 nm Ti); photolithography and lift-off processes can optionally be performed on this step. In a further step, the zinc oxide layer outside the device is removed by wet etching in diluted HCl, followed by chemical vapor deposition of a silicon oxide layer. The silicon oxide layer is then reopened (e.g., by electron beam lithography, reactive ion etching, and KOH wet etching to remove the etch stop layer) to expose the zinc oxide layer in the region where the waveguide is located and where subsequent layers to be formed in a vertical layer stack will reside. Thus, a 20 nm thick active layer is deposited onto the exposed portion of the zinc oxide layer by stripping a CdSe / CdS quantum dot layer (e.g., oleate-capped) spin-coated from toluene. In a shadow mask evaporation step, three organic layers (TCTA, NPD, HAT-CN) constituting the first charge transport layer are obtained under continuous rotation of the sample holder. Alternatively, organic charge transport layers can be deposited using organic vapor deposition with an inert carrier gas. Finally, a 300 nm thick aluminum layer is deposited from the vapor phase to form the first electrode.

[0095] Multiple prototype integrated optoelectronic devices were fabricated and tested in the manner described above. Each device included a 2 mm long active device region and an approximately 1 cm long waveguide. The highest optical output power was observed in the first device, with a measured amplitude of 47 A / cm at a forward bias voltage of 100 V. -2 The current density. For the second device, fabricated on the same chip as the first device, a current density as high as 100 A cm⁻¹ was achieved at a forward bias voltage of 120 V. -2The current density is too high; even higher voltages lead to device failure. The measured turn-on voltage at which the fabricated optoelectronic device produces observable optical output is approximately 3V. However, these measurements are limited by the noise floor of the optical power meter used during testing, and true electrical turn-on is expected at a forward bias voltage of approximately 2V. The emission peak of the obtained electroluminescence spectrum is located at 642nm. At 47A cm⁻¹ -2 In the fundamental waveguide mode of the first device under test pumped at current density, a spectral integrated optical output power of approximately 2.0 nW was obtained. This corresponds to 1.5 W cm⁻¹. -2 The optical power density is high. By simultaneously defining two single-mode waveguide sections (e.g., 450 nm wide, each 0.4 mm long) with the multimode waveguide 31, higher-order modes can be efficiently filtered out, allowing them to be directly connected to the multimode waveguide at either end. Based on the measured device output power, the maximum internal quantum efficiency is estimated to be approximately 11%.

[0096] Another optoelectronic device prototype (0.5 mm long) was fabricated in the manner described above, and its photodetector performance was tested. Although these prototypes were developed for LED applications, they function as photodetectors under reverse bias conditions. For the photodetector characteristics of the exemplary optoelectronic device, light from an external LED (λ = 635 nm) was coupled into waveguide 31. A reverse bias voltage of -7 V was measured to be 1.5 μA / cm. 2 The dark current was measured, and a suboptimal quantum efficiency of approximately 6% was extracted from the measurement data. The detector quantum efficiency can be further improved by optimizing band alignment and device fabrication.

[0097] In another aspect, the present invention relates to a method for decoupling the width of an active layer from an optically confined waveguide mode in an integrated optoelectronic device (e.g., an integrated light-emitting device or a photodetector). The integrated optoelectronic device includes a substrate, a first charge transport layer formed on the substrate for transporting carriers of a first conductivity type, a second charge transport layer for transporting carriers of a second conductivity type opposite to the first conductivity type, and an active layer comprising a solution-processed semiconductor nanocrystal material. The active layer is arranged relative to the first and second charge transport layers to form a diode junction that can operate under forward bias or under zero bias or reverse bias. Under forward bias, the active layer is configured to generate light upon recombination of carriers of opposite conductivity types injected into the active layer by the respective charge transport layers. Under zero bias or reverse bias, the active layer is configured to generate carriers of opposite conductivity types upon absorption of light incident on the diode junction, and the diode structure is further configured to separate the generated carriers to the first and second charge transport layers according to their conductivity types. The first and second charge transport layers are typically provided as n-type or p-type semiconductor layers. This decoupling method includes providing a passive waveguide on a substrate such that, in a cross-section perpendicular to the longitudinal direction of the optoelectronic device (e.g., the direction of light propagation in the waveguide), each of the first and second charge transport layers and the active layer overlaps with a portion of the waveguide. Thus, the waveguide is provided separately from the active layer. The waveguide is configured to confine and guide at least one optical waveguide mode, wherein the confinement is relative to the direction of the cross-section. Furthermore, the position of the waveguide relative to the active layer is adapted for evanescent coupling of light between them. For example, evanescent coupling occurs between the active layer and the waveguide if at least one light-guiding mode supported by the waveguide extends into and partially overlaps the active layer. The waveguide may extend from the substrate surface into the substrate or may protrude from the substrate surface. The waveguide may support single-mode or multi-mode in the cross-section. The method may also include the step of providing a current path to and through a diode junction formed by the first and second charge transport layers and the active layer, which does not pass through the waveguide. This can be achieved by arranging the waveguide relative to the diode junction such that the waveguide does not form part of the diode junction.

[0098] Although the invention has been described and illustrated in detail in the accompanying drawings and the foregoing description, such description and illustration are to be considered illustrative or exemplary, and not restrictive. The foregoing description details certain embodiments of the invention. However, it will be appreciated that the invention can be practiced in many ways, however detailed the foregoing description may appear in the text. The invention is not limited to the disclosed embodiments.

Claims

1. An integrated optoelectronic device (100, 200, 300), comprising: base plate (30), A passive waveguide (31) supported by the substrate (30) includes a core region having a higher refractive index than the surrounding cladding and is configured to guide light in the longitudinal direction and limit the light in the transverse direction by limiting the refractive index within the core region. The first charge transport layer (11) is used to transport charge carriers of the first conductivity type. The second charge transport layer (12) is used to transport charge carriers of a second conductivity type opposite to the first conductivity type. An active layer (20) comprising a particulate film of solution-processable semiconductor nanocrystals, the active layer being arranged relative to the charge transport layer to form a diode junction. The active layer, the first charge transport layer, and the second charge transport layer are formed on the substrate, and each overlaps with at least a portion of the waveguide in a cross-section perpendicular to the longitudinal direction. The waveguide is configured such that it defines an optical mode independently of the active layer, and The active layer is positioned relative to the waveguide such that the evanescent portion of the optical mode extends from the waveguide into the active layer.

2. The integrated optoelectronic device according to claim 1, characterized in that, The active layer granular membrane is densely packed with individual particles, thereby the average interparticle distance between adjacent particles of the active layer granular membrane is less than 5 nanometers.

3. The integrated optoelectronic device according to claim 1 or 2, characterized in that, The current path through the first charge transport layer, the active layer, and the second charge transport layer does not extend into the waveguide.

4. The integrated optoelectronic device according to claim 1, characterized in that, The second charge transport layer (12) is in direct physical contact with the waveguide (31).

5. The integrated optoelectronic device according to claim 1, characterized in that, The waveguide is configured to confine and guide light in the at least one light guiding mode independently of the active layer.

6. The integrated optoelectronic device according to claim 1, characterized in that, In the cross section, the electrical contact portion of the active layer overlaps with the waveguide.

7. The integrated optoelectronic device according to claim 1, characterized in that, The first charge transport layer (11) is an organic semiconductor hole transport layer, while the second charge transport layer (12) is an inorganic semiconductor electron transport layer.

8. The integrated optoelectronic device according to claim 1, characterized in that, The first charge transport layer (11), the second charge transport layer (12), the active layer (20), and the waveguide (31) are stacked vertically in the cross section.

9. The integrated optoelectronic device according to claim 8, characterized in that, The second charge transport layer (12) is a semiconductor electronic transport layer disposed between the active layer (20) and the waveguide (31).

10. The integrated optoelectronic device according to claim 1, characterized in that, The second charge transport layer (12) conforms to the contour of the waveguide (31), thereby providing a conformally coated waveguide.

11. The integrated optoelectronic device according to claim 10, characterized in that, It also includes a covering material (32), which is disposed on both sides of the conformally coated waveguide and flush with its top surface.

12. The integrated optoelectronic device according to claim 1, characterized in that, The first charge transport layer (11) and the second charge transport layer (12) are coplanar and are arranged to overlap with different portions of the waveguide in the cross section. Adjacent edges of the first charge transport layer and the second charge transport layer are separated by a gap (21), and the active layer (20) extends over at least a portion of the first charge transport layer and the second charge transport layer and enters the gap (21).

13. The integrated optoelectronic device according to claim 12, characterized in that, The waveguide rises from the surface of the substrate and is configured as a slotted waveguide, the slotted waveguide including two waveguide tracks separated by a slot, the first charge transport layer and the second charge transport layer extending into the slot.

14. The integrated optoelectronic device according to claim 1, characterized in that, The particles of the active layer particulate film include one or more of the following: colloidal quantum dots, nano-perovskite-based materials, bulk semiconductor nanocrystals, and nanosheets.

15. An integrated light-emitting diode comprising an integrated optoelectronic device according to claim 1, the diode further comprising a first electrode (40) and a second electrode (50), the first electrode (40) being electrically contacted with a first charge transport layer (11), the second electrode (50) being electrically contacted with a second charge transport layer (12) for inducing a forward bias condition on the diode junction, wherein the active layer is adapted to generate light when carriers of opposite conductivity types injected into the active layer through a respective charge transport layer recombine under the forward bias condition.

16. An integrated laser diode comprising the integrated optoelectronic device according to claim 1, wherein the laser diode further comprises: A first electrode (40) electrically contacts the first charge transport layer (11) and a second electrode (50) electrically contacts the second charge transport layer (12) to induce a forward bias condition across the diode junction, wherein the active layer is adapted to generate light when carriers of opposite conductivity types injected into the active layer through the respective charge transport layer recombine under the forward bias condition. An optical feedback device is optically coupled to the waveguide to form an optical cavity.

17. The integrated laser diode according to claim 16, characterized in that, The optical feedback device includes a pair of distributed Bragg reflectors disposed at corresponding portions of the waveguide overlapping the active layer, or a pair of reflectors disposed at opposite ends of the waveguide, at least one of the pair of reflectors comprising one of the following: a Bragg diffraction grating, a waveguide loop mirror, a waveguide end-face coating, and a waveguide ring resonator.

18. The integrated light-emitting diode or integrated laser diode according to any one of claims 15 to 17, characterized in that, The diode is arranged to emit light horizontally in a plane parallel to the substrate (30), or to emit light at an angle relative to the substrate (30) in an active region of the substrate that is not covered by the active layer and the first charge transport layer and the second charge transport layer.

19. A method for decoupling charge current injection and refractive index confinement of a light guiding mode in an active layer of an integrated optoelectronic device (100, 200, 300), the integrated optoelectronic device comprising a first charge transport layer (11) for transporting carriers of a first conductivity type, a second charge transport layer (12) for transporting carriers of a second conductivity type opposite to the first conductivity type, and an active layer (20) comprising a solution-processed semiconductor nanocrystal material, the active layer being arranged relative to the charge transport layer to form a diode junction, the method comprising: A substrate (30) is provided, which supports a passive waveguide (31) including a core region having a higher refractive index than the surrounding cladding and being configured to guide light in the longitudinal direction and to confine the light in the transverse direction by means of a refractive index limit within the core region. Each of the active layer, the first charge transport layer, and the second charge transport layer is arranged on the substrate to overlap with at least a portion of the waveguide in a cross-section perpendicular to the longitudinal direction. The waveguide is configured such that it defines the light guiding mode independently of the active layer, and that a fleeting portion of the light guiding mode extends into the active layer.

20. A method for manufacturing an integrated optoelectronic device according to any one of claims 1 to 14, the method comprising the following steps: A passive waveguide (31) is provided to the substrate (30), the waveguide (31) including a core region having a higher refractive index than the surrounding cladding and configured to guide light in the longitudinal direction and to confine the light in the transverse direction by means of a refractive index limit within the core region, and A layer stack is formed by sequentially depositing layers on the substrate (30) in the following order: The second charge transport layer (12) is used to transport charge carriers of the first conductivity type. The active layer (20) comprises a particulate film of semiconductor nanocrystals, wherein the semiconductor nanocrystals are deposited from a solution, and The first charge transport layer (11) is used to transport charge carriers of the first conductivity type, which is opposite to the second conductivity type. Each of the deposited active layer (20) and the deposited first and second charge transport layers (11, 12) overlaps with at least a portion of the waveguide in a cross section perpendicular to the longitudinal direction. The active layer (20) is arranged relative to the charge transport layers (11, 12) to form a diode junction. The active layer (20) is evanescently optically coupled to the waveguide (31) such that the evanescent portion of the light-guiding mode extends from the waveguide into the active layer, and The waveguide is configured such that it defines the light guiding mode independently of the active layer.

21. The method according to claim 20, characterized in that, The first charge transport layer (11) deposited is an organic layer, while the second charge transport layer (12) deposited is an inorganic layer.

22. The method according to claim 21, characterized in that, Depositing the first charge transport layer (11) includes vacuum thermal evaporation or organic vapor deposition, and / or depositing the second charge transport layer (12) includes thermally controlled atomic layer deposition.

23. The method according to claim 21, characterized in that, Depositing the second charge transport layer (12) includes depositing a polycrystalline zinc oxide (ZnO) nanolayer using atomic layer deposition at a substrate temperature between 60°C and 300°C, and optionally annealing at 400°C.

24. The method of claim 20, wherein the semiconductor nanocrystals deposited from the solution of the active layer (20) comprise wet processing techniques, such as spin coating, dip coating, spray coating, Langmuir-Blodgett or Langmuir Schaeffer deposition, or inkjet printing, on a dispersion of pre-made semiconductor nanocrystals as starting material.

25. The method according to claim 20, characterized in that, The second charge transport layer (12) is directly deposited on the waveguide (31) to obtain an externally coated waveguide, the method further comprising: - A cladding material (32) is deposited on both sides of the externally coated waveguide (31), thereby passivating the second charge transport layer (12), and The deposited cladding material (32) is planarized so that the top surface of the deposited cladding material is flush with the top surface of the externally coated waveguide.

26. The method as described in claim 20, characterized in that, Also includes: Make the first charge transport layer (11) contact the first metal electrode. Make the second charge transport layer (12) contact the second metal electrode. The integrated optoelectronic device can be optionally packaged.

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