LED STRUCTURES AND ASSOCIATED METHODS AND DISPLAYS - Patent application

Abstract

The light-emitting diode (LED) structure includes an active region having at least one aluminum-containing quantum well (QW) stack that emits light from the LED structure when activated. The LED structure exhibits a higher modified internal quantum efficiency value than LED structures that do not include aluminum in the QW stack. The LED structure also exhibits a modified peak wavelength that is longer than the unmodified peak wavelength of the unmodified LED structure.

Description

[Technical field]

[0001] Related Applications This application claims priority to U.S. patent application Ser. No. 63 / 019,765, filed May 4, 2020, entitled "Additional Layers Below Quantum Wells in LED Structures for Enhanced Performance and Directionality," and U.S. patent application Ser. No. 63 / 135,288, filed January 8, 2021, entitled "Light Emitting Diodes with Aluminum-Containing Layers Integrated Therein and Associated Methods," both of which are incorporated by reference in their entireties herein. [Background technology]

[0002] background Aspects of the present disclosure relate generally to light emitting devices, such as those used in various types of displays, and more specifically to improved incorporation of active elements into active layers in light emitting devices.

[0003] There is a continuing need to increase the number of emitters (e.g., pixels) in displays to provide better user experiences and enable new applications, but increasing the number of emitters in a display configuration has become a challenge. To achieve even smaller emitters to increase both the number and density of emitters, the possibility of using small light emitting diodes (LEDs), such as micro-LED structures or nano-emitters, is attractive. However, currently available techniques for manufacturing micro-LED structures at high density in large quantities to produce a variety of colors (e.g., red, green, blue) are cumbersome, time consuming, expensive, or result in LED structures with performance limitations.

[0004] Advanced LED structures, such as highly efficient LEDs based on indium gallium nitride (InGaN) quantum well (QW) structures, require the precise formation of layers of various materials designed to work together to produce light emission with desired emission characteristics.

[0005] FIG. 1 illustrates a commonly implemented prior art epitaxial layer LED structure 100. The LED structure 100 includes a semiconductor template 110, also known as a semiconductor substrate, for supporting one or more bulk or prep layers 120. An active multiple quantum well (MQW) region 130 is formed on the bulk or prep layer 120. The bulk or prep layer 120 may be a thick layer of one material or a structure of two or more materials configured to reduce, for example, the effects of lattice mismatch and / or thermal expansion coefficient mismatch and / or defect filtering from the semiconductor template 110 to the active MQW region 130. The material composition of the bulk or prep layer 120 may be tailored to provide increased flexibility in material selection for the active MQW region 130, thereby allowing the formation of an active region with desired light emission characteristics. Finally, one or more p-layers 140 are deposited on the active QWs to form a pn diode that provides electronic connectivity to the LED structure 100. The p-layer 140 includes a p-doped layer and / or a contact layer. The LED structure 100 is then etched or otherwise shaped to form a desired micro-LED form factor for a given application. Summary of the Invention [Problem to be solved by the invention]

[0006] overview Although the prior art LED structure 100 provides a framework for designing micro-LEDs, a variety of material choices, specific epitaxial deposition conditions, and combinations of the two are possible. For example, the inclusion of layers of certain materials within a micro-LED structure is known to provide advantageous optical and electrical properties, such as reducing defects resulting in higher radiative efficiency and reduced emission wavelength shift. However, micro-LEDs with high efficiency and brightness at red wavelengths, particularly indium gallium nitride (InGaN) or indium gallium phosphide (InGaP) based micro-LEDs, have been difficult to manufacture.

[0007] SUMMARY OF THE DISCLOSURE The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all possible aspects, is not intended to identify key or critical elements of all aspects, or delineate the scope of any or all aspects. Its purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description presented later.

[0008] Aspects of the present disclosure provide techniques and structures that improve the performance of light-emitting devices. [Means for solving the problem]

[0009] In a particular embodiment, a light emitting diode (LED) structure includes a bulk or prep layer formed on a semiconductor template and an active region formed on the bulk or prep layer, the active region including a first barrier layer formed on the bulk or prep layer, at least one aluminum-containing active quantum well (QW) stack formed on the first barrier layer, and a second barrier layer formed on the active QW stack, the LED structure further including at least one p-layer formed on the active region, and the active region emits light from the LED structure when the at least one active QW stack is driven by an injection current.

[0010] In another embodiment, a light emitting diode (LED) structure includes a semiconductor template, a first preparation layer formed on the semiconductor template, a second preparation layer formed on the first preparation layer, at least one active quantum well (QW) layer formed on the second preparation layer, and at least one p-layer formed on the active QW layer, wherein the active QW layer emits light from the LED structure when activated.

[0011] In another embodiment, a method forms a light emitting diode (LED) structure on a semiconductor substrate, the method includes depositing at least one prep layer on the semiconductor substrate, forming an active multiple quantum well (MQW) region on the at least one prep layer, and depositing a p-layer on the active MQW region, where forming the active MQW region includes depositing a first barrier material, depositing an active QW material, and depositing a second barrier material, where forming the active MQW region optionally includes depositing a bottom layer between the first barrier material and the active QW material, depositing an intermediate layer between the bottom layer and the active QW material, and depositing a cap layer between the active QW material and the second barrier material, where at least one of depositing the active QW material, depositing the bottom layer, depositing the intermediate layer, and depositing the cap layer includes incorporating aluminum.

[0012] The accompanying drawings illustrate only some implementations and should not be considered as limiting the scope. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 illustrates a commonly implemented prior art micro LED structure. [Diagram 2] FIG. 2 is a top view of a portion of an exemplary LED array having multiple micro LED structures supported by a single substrate for use in a display, according to an embodiment. [Diagram 3] FIG. 2 is a schematic cross-sectional view of an exemplary micro LED structure having first and second preparation layers with improved morphology and distortion characteristics according to an embodiment. [Figure 4] FIG. 2 is a schematic cross-sectional view of an exemplary LED structure having inactive QW layers and AlGaN layers with improved morphology and strain characteristics, according to an embodiment. [Diagram 5]FIG. 2 is a schematic cross-sectional view of an exemplary LED structure with improved directivity, according to an embodiment. [Figure 6] FIG. 2 is a schematic cross-sectional view of an exemplary LED structure with improved performance due to reduced hole leakage, according to an embodiment. [Figure 7] FIG. 1 is a schematic cross-sectional view of an exemplary micro LED structure including aluminum in the active multiple quantum well (MQW) region, according to an embodiment. [Figure 8A] FIG. 2 is a schematic cross-sectional view illustrating an exemplary micro LED structure including an aluminum-containing bottom layer in the active MQW region according to an embodiment. [Figure 8B] FIG. 2 is a schematic cross-sectional view illustrating an exemplary micro LED structure including an aluminum-containing bottom layer in the active MQW region according to an embodiment. [Figure 9] FIG. 2 is a schematic cross-sectional view illustrating an exemplary micro LED structure including an aluminum-containing cap layer disposed above the active QWs in the active MQW region according to an embodiment. [Figure 10] FIG. 2 is a schematic cross-sectional view of an exemplary micro LED structure including aluminum incorporated within at least one active QW layer according to an embodiment. [Figure 11] FIG. 11 is a schematic cross-sectional view of an exemplary micro LED structure similar to that of FIG. 10 and further including an aluminum-containing bottom layer, according to an embodiment. [Figure 12] FIG. 11 is a schematic cross-sectional view of an exemplary micro LED structure similar to that of FIG. 10 and further including an aluminum-containing cap layer, according to an embodiment. [Figure 13] FIG. 13 is a schematic cross-sectional view of an exemplary micro LED structure similar to that of FIG. 12 and further including an aluminum-containing bottom layer, according to an embodiment. [Figure 14] 1 is a flowchart illustrating an exemplary process for fabricating a micro LED structure, according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Detailed Description of the Embodiments The detailed description set forth below in connection with the accompanying drawings or figures is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details to enable a full understanding of various concepts. However, it will be apparent to one of ordinary skill in the art that these concepts may be practiced without these specific details. In some instances, well-known components are shown in block diagram form to avoid obscuring such concepts.

[0015] In certain applications, micro-LED structures operating at red, green and blue (RGB) wavelengths are combined into low fill factor, low density displays for low cost, low power consumption applications such as smart watches, smartphones and televisions. In such low density displays, micro-LED structures for each color are fabricated separately and then transferred and combined onto a separate display backplane of low fill factor RGB pixels to provide the full color equivalent of existing liquid crystal displays or organic light emitting diode displays, for example, with the advantage of lower power consumption.

[0016] In another application approach, micro-LED structures (e.g., LEDs with a form factor of approximately 10 microns or less) may be used to form dense arrays of light emitters to enable new kinds of display applications, such as compact light field displays for augmented reality (AR) or virtual reality (VR) imaging. One way to achieve such a dense array of micro-LED structures is to monolithically integrate micron-scale light emitters on a single substrate. However, monolithic integration of micro-LED structures emitting at different wavelengths is inherently problematic due to differences in structure and material composition of micro-LED structures intended to emit at different ranges of wavelengths (e.g., red, green and blue), as well as the difficulty of achieving the precision required to transfer separately formed micro-LED structures onto a backplane in a dense configuration. For example, while blue and green micro-LED structures operating at high brightness and efficiency are possible using compatible materials, it has proven difficult to achieve red (or long-wavelength green, amber or red-orange) micro-LED structures with comparable brightness and efficiency. For example, micro-LED structures in the blue and green visible wavelength range have proven to have high efficiency, while micro-LED structures in the red visible wavelength range have been more difficult to fabricate.

[0017] An article entitled "Polar InGaN / GaN quantum wells: Revisiting the impact of carrier localization on the green gap problem" (Jan. 28, 2020, Tanner et al.) describes that InGaN-based red LEDs (e.g., at 620 nm and above) are known to have very low internal quantum efficiency (IQE) (see, e.g., FIG. 1 of Tanner, which shows the IQE to be essentially zero). The embodiments described therein disclose the inclusion of aluminum within various layers of the LED structure, achieving IQE values ​​of 12% or greater at 635 nm wavelength. Exemplary QW structure layer compositions include one or more of GaN, AlGaN, GaN, InxGa1-xN, and AlGaN. The improved LED structure may also include one or more additional intermediate layers including aluminum.

[0018] One aspect of the present embodiment includes the recognition that to meet the needs of a display device, the number and density of light-emitting structures forming a display element (e.g., pixel) should be increased, and therefore the size of the light-emitting structures needs to be reduced while maintaining light-emitting efficiency and quality. Although it is attractive to use small LEDs (e.g., micro LED structures or nano-emitters) to achieve even smaller light-emitting structures, some techniques for manufacturing small LEDs in large quantities and at high density to generate a variety of colors (e.g., red, green, blue) are currently cumbersome, time-consuming, expensive, or result in structures with performance limitations. More advanced display architectures, such as for light field displays, can benefit from the use of small LED structures, but the requirements of such displays make small LEDs difficult to achieve. The present embodiment solves this problem by providing a new technique that allows the monolithic integration of a large number of small light-emitting structures generating a variety of colors on the same substrate (e.g., a single integrated semiconductor device).

[0019] The use of certain semiconductor processing techniques to fabricate the light-emitting structures, such as epitaxial growth and dry etching or selective area growth (SAG), offers a promising approach to monolithically integrate a large number of microLEDs onto a single integrated semiconductor device. The quality of the material grown on the template for fabricating the light-emitting structures has a significant impact on the performance characteristics of the LED.

[0020] To this end, structural configurations are needed that enable the formation of small light-emitting structures with high-quality active (e.g., light-emitting) areas. For example, in QW-based LEDs, the strategic inclusion of additional layers can introduce complexities into the fabrication process, but offers the ability to refine or improve the morphology and / or directionality of the light-emitting structure.

[0021] One approach disclosed herein involves incorporating high bandgap materials or layers into the LED structure. In conventional semiconductor devices, high bandgap layers are typically not included unless they are required for device operation or somehow improve device performance. However, the embodiments described herein provide aluminum-containing layers grown in front of (e.g., below or underneath) the light-emitting multiple quantum well (MQW) active region or incorporated into the MQW active region itself, which improve the quality of the active quantum wells to provide better directionality to the light generated by the active quantum wells. These embodiments provide multiple high brightness micro-LED structures operating over a wavelength range across the electromagnetic spectrum, with dimensions on the order of 10 microns or less, in a monolithic structure that enables a wide range of new applications not previously possible.

[0022] While the following description focuses on improvements to micro LED structures operating in the red wavelength range, it should be noted that the techniques and structures described herein are applicable to other micro LEDs or larger LEDs, and other semiconductor-based light emitters operating at other wavelengths, such as visible (including long-wave green, amber, and red-orange), infrared, or ultraviolet wavelengths. A first example of a red wavelength range is 0.59 μm to 0.76 μm. A second, narrower example of a red wavelength range is 0.61 μm to 0.76 μm.

[0023] FIG. 2 is a top view of a portion of an exemplary LED array 200 having multiple micro LED structures 210, 220, and 230 supported by a single substrate 240, which may be used in a display. The micro LED structures 210, 220, and 230 may emit light at red, green, and blue wavelengths, respectively. Although a portion of the LED array 200 is shown having 16 micro LED structures, the LED array 200 may be a much larger array of micro LED structures 210, 220, and 230 that may be used in a display, for example, where the micro LED structures 210, 220, and 230 may be arranged in pixels (e.g., groups or subarrays of micro LED structures 210, 220, and 230). In such cases, the arrangement of the pixels, their shapes, their numbers, their sizes, and their corresponding wavelength emissions are configurable during manufacturing to tailor the LED array 200 to a particular application. In certain embodiments, the LED array 200 is used in high resolution, high density displays, such as displays used in light field applications. In other embodiments, the LED array 200 may be incorporated into a compact display for augmented reality (AR) or virtual reality (VR) applications.

[0024] In particular, to achieve a high density of light emitters, it is desirable to form the micro LED structures 210, 220 and 230 on the substrate 240 in a monolithically integrated manner using mutually compatible processes. That is, rather than forming each type of micro LED structure on a separate substrate (e.g., one or more red-emitting micro LED structures on a first substrate, one or more green-emitting micro LED structures on a second substrate, and one or more blue-emitting micro LED structures on a third substrate) and then transferring each micro LED structure to a fourth substrate to form a micro LED array for use in a display, an array of all three types of micro LED structures 210, 220 and 230 is formed directly on the substrate 240. In particular, by forming all three types of micro LED structures 210, 220 and 230 as an array directly on the substrate 240 (e.g., a single substrate), a higher density LED array can be formed. In other words, rather than forming the micro LED structures 210, 220 and 230 for each color on a separate wafer and then transferring each LED to a separate substrate to form an LED array for a display, the micro LED structures 210, 220 and 230 are formed directly on the substrate 240, thereby allowing the LED array 200 to achieve higher density.

[0025] However, it is well documented in the existing literature that it is very difficult to form micro-LED structures using processes and materials compatible with efficient emission over the required wavelength range to produce full color displays (e.g., red-green-blue (RGB) displays). While highly efficient large-scale (e.g., hundreds of microns in dimensions) nitride-based blue LEDs, such as LEDs based on indium gallium nitride (InGaN) QWs, and highly efficient large-scale phosphide-based red LEDs, such as LEDs based on aluminum gallium indium phosphide (AlGaInP), are readily available, a "green gap" has been recognized for decades due to the lack of green LEDs that operate at similarly high efficiency. The conventional approach to forming each type of LED for each emission range (e.g., red, blue, green) uses its own optimized process and then transfers the resulting LED structures onto separate display substrates to form an LED array. This approach has constraints related to the minimum size of the LEDs required to enable the transfer of the independently formed micro-LED structures to separate display substrates, and the alignment fidelity required for precise alignment of the micro-LED structures to form a high density micro-LED array. One aspect of the present embodiment involves the recognition that it is very difficult to form an array of micro LED structures (e.g., red, green and blue emitting micro LED structures) on a single substrate to provide a full color image with similar brightness and efficiency levels.

[0026] The present embodiment solves this problem by using a micro LED structure design and fabrication process to control the inclusion of active elements in the quantum well (QW) to achieve high efficiency micro LED structures at longer wavelengths while using materials and fabrication processes compatible with monolithic integration of multiple colors of micro LED structures. More specifically, the present embodiment discloses a device structure and fabrication process that allows for the realization of a monolithically integrated array of micro LED structures emitting at various colors by allowing for the formation of high efficiency micro LED structures at longer wavelengths (e.g., red) using materials compatible with the fabrication of high efficiency micro LED structures at shorter wavelengths (e.g., blue and green). However, it is emphasized that the techniques disclosed herein are applicable to epitaxially formed LEDs of all sizes and configurations, including, for example, red-only micro LED structures.

[0027] As mentioned above, separately fabricated high efficiency large scale nitride based blue LEDs and phosphide based red LEDs are known. In forming light emitting nitride based QW structures for long wavelength LEDs (e.g. red), it is difficult to increase the percentage composition of the required active material (e.g. indium (In)) in the QWs to achieve long wavelength emission while maintaining layer uniformity and controlling defects. In particular, it is difficult to obtain the desired high percentage of In with good uniformity in the QWs, especially under high reactant vapor pressures. As the percentage of Indium decreases, the emission wavelength from the QW structure becomes shorter than the nominal design of the LED. Furthermore, defects such as In clustering, phase separation and pitting are commonly found in the QW structures. There is limited tuning available via growth condition parameters (e.g. temperature, time, vapor pressure) before improvements in In composition while maintaining suitable material quality reach the limits of conventional gallium nitride (GaN) / InGaN / GaN QW materials and growth techniques.

[0028] It has been found that the inclusion of a thin layer of aluminum (Al) as a bottom layer prior to the deposition of the active InGaN QW layer in the MQW structure provides improved blue LED performance due to an increase in the hole concentration in the QW resulting from additional polarization charge at the aluminum gallium nitride (AlGaN) / InGaN interface and possibly some reduction in point defects. Such a technique has been used to produce blue LEDs on silicon substrates using a stack of a 1 nm layer of AlGaN, a 3.5 nm thick InGaN QW layer, followed by a 5 nm layer of GaN as a barrier layer ("High-efficiency blue LEDs with thin AlGaN interlayers in InGaN / GaN MQWs grown on Si (111) substrates," S. Kimura et al., Proc. of SPIE, Vol. 9748, 97481U). The inclusion of a material such as Al as a bottom layer appears to promote carrier distribution and possibly reduction in defects in the active region.

[0029] However, conventional wisdom would dictate that while the inclusion of Al in InGaN QWs may be feasible for blue LEDs, it is not feasible for red LEDs. In particular, since Al is a wide bandgap material compared to In, the inclusion of Al in the QW structure would widen the overall bandgap of the QWs, which would tend to result in a blue shift in the emitter wavelength (i.e., toward shorter wavelengths). This blue shift can be easily compensated for in blue LEDs, but since the usual goal for red LEDs is to achieve emission at longer wavelengths, the inclusion of Al in the QW structure of a red LED would seem counterproductive.

[0030] Previously, in an attempt to extend the emission wavelength of nitride-based blue LEDs to green and even reddish-orange wavelengths, a thin layer of AlGaN (e.g., 1-2 nm thick layer) was used to cap the QW structure. For example, a 1 nm thick AlGaN layer was deposited directly on each 3 nm thick InGaN QW layer as a cap layer and then capped by a 10 nm thick InGaN barrier layer in an MQW structure to achieve green-yellow, yellow and amber wavelength emission with external quantum efficiency (EQE) values ​​in the range of 11% to 20% (Hashimoto, "Addressing the green gap with a novel active region," www.compoundsemiconductor.net, March 2014, p. 44). The Hashimoto paper speculates that the AlGaN cap layer acts to shift the electron wavefunction toward the interior of the wells, thereby increasing electron-hole overlap and radiative recombination, and creating a barrier to electron overflow from each well while restoring surface smoothness after the InGaN wells. As yet another example, the same technique, including a 1 nm thick layer of AlGaN as a cap layer for each QW layer (i.e., a 3 nm thick active layer of indium gallium nitride (InGaN) grown at 755°C, followed by a 1 nm layer of AlGaN grown at 755°C, capped by a 10 nm layer of InGaN grown at 855°C as a barrier layer), was found to produce LEDs operating at a wavelength of 629 nm, at the short-wavelength end of the red wavelength range, albeit with a low EQE value of 2.9% (JI Fan et al., "Development of InGaN-based red LED grown on (0001) polar surface," Applied Physics Express 7, 071003 (2014)). However, the AlGaN cap layer does not appear to prevent In-containing defects within the QW structure itself, which are a common cause of the shift in red LED emission toward shorter wavelengths and low EQE values.Indeed, Fan et al. specifically note that the red shift in emission wavelength disappears as the injection current used to drive the resulting LED is increased. Furthermore, in all of the experimental results reported above, each of the LED devices is a large area device having dimensions on the order of several hundred microns on each side.

[0031] Contrary to this conventional wisdom, an unexpected result, described in more detail below, has been found that the inclusion of Al uniformly within the MQW structure or at one or more locations within the MQW structure does in fact result in improved red LED performance, including highly efficient production of long wavelength emission. In particular, the appropriate incorporation of aluminum in the bottom layer, the appropriate incorporation of aluminum in the cap layer, and even the appropriate incorporation of aluminum within the active quantum well itself, and combinations thereof, unexpectedly resulted in improved red LED performance at high efficiency in the red range of the visible spectrum (e.g., greater than 625 nm), even in microLED devices having dimensions as small as one micron on a side.

[0032] FIG. 3 is a schematic cross-sectional view illustrating one exemplary micro LED structure 300 having first and second preparation layers 320 and 330 with improved morphology and strain characteristics. The LED structure 300 is formed on a surface of a semiconductor template 310 (e.g., a support layer). The LED structure 300 includes a first preparation layer 320 (preparation layer 1) formed, grown (e.g., epitaxially grown) or deposited on the semiconductor template 310, a second preparation layer 330 (preparation layer 2) formed, grown or deposited on the first preparation layer 320, an active QW region 340 formed, grown or deposited on the second preparation layer 330, and a p-layer 350 including a contact layer (e.g., a p-doped layer) formed, grown or deposited on the active QW region 340. In some implementations, techniques such as epitaxial growth and dry etching or selective area growth may be used to define the location, shape and size of the LED structure 300 on the semiconductor template 310.

[0033] The first preparation layer 320 and the second preparation layer 330 are configured to prepare a surface that is used to form the active QW region 340 with the proper morphology and strain so that the active QW region 340 has enhanced material properties and light emitting performance. To this end, the first preparation layer 320, the second preparation layer 330, or both, include a high band gap material, such as an aluminum-containing layer. The aluminum-containing layer includes, for example, an AlInGaN alloy having a composition of Al in the range of 5% to 100%. The first and Each of the second preparation layers 320 and 330 may have a thickness in the range of 0.3 nanometers to 250 nanometers.

[0034] The active QW region 340 is configured to emit light during operation of the LED structure 300 . In one example, the first preparation layer 320 is an aluminum-containing layer and includes a superlattice. The superlattice may be formed, for example, by alternating layers of AlInGaN and AlGaN. As an example, the superlattice may be formed by alternating layers of AlInGaN and AlGaN having different Al and In compositions. In another example, the first preparation layer 320 are bulk layers. The bulk layers may be aluminum-containing layers. Unlike the active QW region 340, the first and second preparation layers 320 and 330, respectively, are not configured to emit light at the same visible wavelengths as the active QW region 340. For example, if the active QW region 340 is intended to emit light at red wavelengths, the superlattices included in the first or second preparation layers may be associated with wavelengths in the green, blue or ultraviolet wavelengths so as not to interfere with the intended function of the active QW region 340.

[0035] As an example, as described above, the second preparation layer 330 may be an aluminum-containing layer. In an example, the second preparation layer 330 may include a superlattice, bulk layer, one or more QW structures that are not configured to emit light at the same wavelength as the active QW region 340 during operation of the LED structure 300. Furthermore, in cases where the second preparation layer 330 includes a single quantum well or multiple quantum wells, the second preparation layer 330 may further include a high band gap intermediate layer, such as an AlGaN layer, formed under or over the single quantum well or multiple quantum wells. The inclusion of the first and second preparation layers 320 and 330, respectively, such as incorporating a high band gap material, such as an Al-containing layer, enhances the light emission properties of the active QW region 340. For example, the light emission performance, such as emission wavelength specification, narrow peaking of the emission wavelength, and the emission intensity of the active QWs may be improved by providing beneficial effects, such as, but not limited to, improved resistance to high temperature processing, trapping of mobile impurities, improved strain characteristics, and optimized stoichiometry of the active QW region 340.

[0036] 4 is a schematic cross-sectional view of an exemplary LED structure 400 with improved morphology and strain characteristics. The LED structure 400 is similar to the LED structure 300 of FIG. 3 and is formed on a surface of a semiconductor template 310, which may be a GaN template or support layer. The LED structure 400 includes an inactive QW layer 410, an AlGaN layer 420, an active QW region 340, and a p-layer 350. layer 41 0 and Although only one combination with an AlGaN layer 420 is shown, the LED structure 400 may include multiple or repeated combinations of inactive QW layers 410 and AlGaN layers 420. The inactive QW layers 410 may be associated with wavelengths shorter than the emission wavelength of the active QW region 340. For example, if the active QW region 340 is configured to produce red wavelength emission, the inactive QW layers 410 may be associated with wavelengths in the green, blue or ultraviolet wavelengths. The AlGaN layers 420 may be made of various alloys including AlGaN, such as AlInGaN alloys having a composition of 5% to 100% Al with respect to In.

[0037] 3, LED structure 400 includes at least one QW in an inactive QW layer 410, with an AlGaN layer 420 formed on the at least one QW. For example, inactive QW layer 410, which may include a single or multiple inactive QWs, corresponds to first prepared layer 320, and AlGaN layer 420 corresponds to second prepared layer 330. Although FIG. 4 shows only one pair of inactive QW layer 410 and AlGaN layer 420, LED structure 400 may include multiple layered pairs of inactive QW layer 410 and AlGaN layer 420 without departing from its scope.

[0038] FIG. 5 is a schematic cross-sectional view of an exemplary LED structure 500 with improved directivity. The LED structure 500 is similar to the LED structure 300 of FIG. 3 and is formed on a surface of a semiconductor template 310. The LED structure 500 includes a first preparation layer 320, a reflective layer 510, an active QW region 340, and a p-layer 350. The reflective layer 510 may be an AlInN / GaN bottom mirror or an AlInGaN / InGaN bottom mirror and may be formed before the active QW region 340. In another example, the reflective layer 510 may include AlInGaN / AlInGaN with different Al and In compositions. Thus, the reflective layer 510 may include at least one aluminum-containing layer forming a reflective stack. When the reflective layer 510 is an AlInN / GaN bottom mirror, the AlInN layer has an Al to In ratio of approximately 82% that can be lattice matched to GaN, thus avoiding strain-related problems in the subsequent active layers while maintaining a high refractive index contrast of 7%, comparable to the AlGaN / GaN system, which has an Al to In ratio of about 50%.

[0039] Additionally, the reflective layer 510 may be or may be configured to function as a distributed Bragg reflector (DBR) that allows the radiation pattern produced by the active QW region 340 to be tailored to a particular application, thereby improving the directionality of the light emission from the active QWs 340. For example, if the reflective layer 510 is or is configured to operate as a DBR, the LED structure 500 may be configured to operate as a resonant cavity LED or a vertical cavity surface emitting laser (VCSEL). That is, the p-layer 350 and the reflective layer 510 form a resonant cavity that includes the active QWs 340, such that the LED structure 500 may operate as a resonant cavity LED or a VCSEL, depending on the thickness of the active QWs 340 relative to the intended emission wavelength of light from the active QWs 340.

[0040] Each of the above LED structures 300, 400 and 500 can be fabricated by techniques such as epitaxial growth and dry etching or selective area growth to have diameter or feature sizes up to 1 micron suitable for high density applications. In certain embodiments, the diameter size is greater than 1 micron, such as 1 micron to 10 microns.

[0041] The use of aluminum-containing layers has other advantages in addition to the morphology, distortion and directionality advantages offered by the LED structures 300, 400 and 500 in connection with the fabrication of small LEDs and the monolithic integration of such small LEDs. These aluminum-containing layers can act as getters to trap impurities and thus reduce impurities in the active region (e.g., active QW region 340) by localizing them in the passive regions of the LED structure. Furthermore, trapped or localized impurities can be prevented from migrating even under high temperature applications in subsequent process operations. In the example of FIG. 4, the AlGaN layer 420 grown on the inactive QW layer 410 can be used for impurity (e.g., oxygen) gettering to reduce impurity (e.g., oxygen) incorporation into the active QW region 340. In the example of FIG. 5, the AlInN layer used to form the reflective layer 510 can also function as an oxygen gettering layer.

[0042] FIG. 6 is a schematic cross-sectional view of an exemplary LED structure 600 that improves performance by reducing hole leakage. The LED structure 600 is similar to the LED structure 300 of FIG. 3 and is formed on a surface of a semiconductor template 310. The LED structure 600 includes a first prepared layer 320, a hole blocking layer 610, an active QW region 340, and a p-layer 350. The hole blocking layer 610 prevents holes from overflowing from the semiconductor template 310 and the first prepared layer 320 into the active QW region 340, and from the active QW region 340 into the first prepared layer 320 and the semiconductor template 310. In certain embodiments, the hole blocking layer 610 may include n-AlGaN. In other embodiments, the hole blocking layer 610 is a superlattice of AlGaN / GaN or InAlN / GaN layers that improves the light emission efficiency of the active QW region 340. However, the hole blocking layer 610 may use other suitable materials, including n-AlGaN, n-doped AlGaN / GaN superlattices, and n-doped InAlN / GaN superlattices.

[0043] 7 is a schematic cross-sectional view of an exemplary micro LED structure 700 having aluminum introduced into an active MQW region 730. The micro LED structure 700 includes a semiconductor template 710, also known as a semiconductor substrate, for supporting one or more bulk or prep layers 720, an active MQW region 730, and at least one p-layer 740. The active MQW region 730 may be formed on the bulk or prep layer 720 and includes at least one active QW stack 732 containing aluminum having an adjacent barrier layer 734 (e.g., a GaN or InGaN barrier layer). Each active QW stack 732 may include a single layer of an aluminum-containing material or may include two or more layers of different materials, such that at least one of the layers contains aluminum. Although the example of FIG. 7 shows an active MQW region 730 having four active QW stacks 732 each with an adjacent barrier layer 734, fewer or more active QW stacks 732 and corresponding barrier layers 734 may be included depending on the desired light emitting performance of the micro LED structure 700.

[0044] As discussed above, the inclusion of Al, a material with a wider band gap compared to In, would appear to be advantageous in shortening the wavelength of emission from the resulting micro-LED structure. However, counterintuitively, the proper inclusion of Al results in a micro-LED structure with higher efficiency and photoluminescence performance compared to a micro-LED structure without the inclusion of Al. More specifically, the inclusion of Al, as discussed above, shifts the wavelength emitted from the micro-LED structure toward shorter wavelengths (e.g., blue-shift) when the current density across the LED structure is increased, necessitating adjustments throughout the micro-LED structure to compensate for this blue-shift. Various methods of incorporating Al into the active QW stack 732, such as specific layers within and around the active QW region, have been disclosed and are described in further detail below.

[0045] 8A and 8B are schematic cross-sectional views illustrating exemplary micro LED structures 800A and 800B including aluminum-containing bottom layers in the active MQW regions 830A and 830B, respectively. The micro LED structures 800A and 800B are similar to the micro LED structure of FIG. 7. The active MQW regions 830A and 830B are formed on a bulk or prep layer 720. FIG. 8A illustrates the active MQW region 830A of the micro LED structure 800A including a stack of four active QW layers 832, collectively referred to as a QW stack. Each QW layer 832 is deposited on a respective AlGa(In)N bottom layer 836 (hereafter Al bottom layer 836) to form a pair of layers separated by a barrier layer 734. The Al bottom layer 836 may be a few atomic layers to a few nanometers in thickness. Beyond such a thickness, the Al bottom layer 836 may cause an undesirable blue shift in the micro LED structure due to an increase in the band gap. The active QW layer 832 may be made of InGaN. The Al bottom layer 836 is an aluminum-containing alloy, such as one of AlGaN, AlInN, and InAlGaN, that is compatible with the fabrication process of a nitride-based micro LED structure, such as the micro LED structure 800A. The Al bottom layer 836 may be referred to as an intermediate layer.

[0046] The inclusion of an AlGaN bottom layer under the active QW layer in a QW-based LED structure has been demonstrated at blue wavelengths and is conceptually reasonable since the blue shift in emission wavelength due to the introduction of Al corresponds to a blue LED. However, the further inclusion of an Al bottom layer 836 would further widen the effective bandgap of the active MQW region 830A, but the inclusion of Al in the Al bottom layer 836 would improve the quality and uniformity of the high In content material in the active QW layer 832. The inclusion of an AlGaN or AlInN bottom layer would modify the crystal plane morphology on which the active QW layer is grown, reducing defects and improving the stability of the material during high temperature processing such as during the growth of the barrier layer 734. Thus, any blue shift due to the effectively wider bandgap of the active MQW region 830A would be overcome by the improved growth mode and reduced defects in the active QW layer 832. As a result, unexpectedly, the micro LED structure 800A provides superior efficiency and longer wavelength emission compared to micro LED structures that do not have the combination of features shown in FIG. 8A. For example, the micro LED structure 800A has been shown to exhibit similar peak IQE values ​​with a blue shift of up to 10 nm in wavelength as the applied current density increases compared to the prior art LED structure 100 having an otherwise similar material structure.

[0047] FIG. 8B illustrates a micro LED structure 800B similar to that of FIG. 8A, but including an intermediate layer 838 between the Al bottom layer 836 and the active QW layers 832 of the active MQW region 830B. The intermediate layer 838 may be made of conventional barrier layer materials such as GaN, or other materials such as AlGaN, InGaN, and AlInGaN materials of various compositions compatible with the fabrication of nitride-based micro LEDs. The combination of the Al bottom layer 836 and the intermediate layer 838 further improves the adhesion and uniformity of the active QW layers 832, reduces defects at the interface and within the active QW layers 832, and improves the retention of In within each active QW layer 832. As a result, the emission of the micro LED structure 800B is shifted toward red wavelengths, and the quantum efficiency performance of the micro LED structure 800B is improved compared to a micro LED structure that does not include the Al bottom layer 836.

[0048] 9 is a schematic cross-sectional view of an exemplary micro LED structure 900 similar to the micro LED structure 700 of FIG. 7 and further including an aluminum-containing cap layer 932 (hereinafter referred to as Al cap layer 932) disposed above the active QW layer 832 in an active MQW region 930 formed on a bulk or prep layer 720. For example, an AlGaN layer having a thickness of approximately 1 nanometer or less may be used as the cap layer 932. The Al cap layer 932 may be referred to as another intermediate layer. Although the inclusion of the Al cap layer 932 would likely widen the effective bandgap of the active MQW region 930, the Al cap layer 932 provides a number of advantages since, like the Al bottom layer 836 of micro-LED structures 800A and 800B, the Al cap layer 932 serves to balance strain between the active QW layer 832 and the barrier layer 734, allowing for matching pre- and post-growth morphology of the active QW layer 832, retaining In within the active QW layer 832, and / or providing band alignment that contributes to long wavelength emission while minimizing blue shift. Thus, the active QW layer 832 exhibits better In retention and uniformity, resulting in superior efficiency and long wavelength emission compared to micro-LEDs that do not have the combination of features shown in FIG. 9.

[0049] The Al cap layer 932 can act as a barrier to migration of hydrogen-containing point defects from the p-layer and any electron blocking layers that may be incorporated into the overall structure, but the Al cap layer 932 does not necessarily help prevent defects in the active QW layer 832 itself, so additional measures may be necessary, such as the inclusion of an Al bottom layer 836 as shown in Figures 8A and 8B.

[0050] FIG. 10 is a schematic cross-sectional view illustrating one exemplary micro LED structure 1000 including aluminum in at least one active QW layer 1032 of an active MQW region 1030 formed on a bulk or prep layer 720. The active MQW region 1030 is shown having four active QW layers 1032, also collectively referred to as a QW stack, but may include more or fewer active QW layers 1032 without departing from the scope. In certain embodiments, an Al-containing gas is introduced at a specific concentration during deposition of the active QW layers 1032 to incorporate Al into the alloy composition of the active QW layers 1032, for example at a concentration of 0.01-5%. In certain embodiments, this process is performed for all active QW layers 1032 in the active MQW region 1030 to include Al. In other embodiments, a similar process is used to vary the amount of Al included in each active QW layer 1032 of the active MQW region 1030. For example, the inclusion of Al in a particular QW layer may be in the form of a pseudoalloy, digital alloy, or short period superlattice.Within the active MQW region 1030, active QW layers 1032 are separated by barrier layers 734 of a suitable material such as GaN.

[0051] The inclusion of Al in the active QW layer 1032 improves the uniformity of In distribution and prevents desorption of In from the active QW layer 1032 during subsequent high temperature processing, such as during the growth of the barrier layer 734, which typically requires temperatures about 100° C. higher than during the deposition of the active QW layer 1032. The inclusion of Al is believed to modify the polarization-induced electric field by compensating for QW strain. In other words, the inclusion of Al during the deposition of the active QW layer 1032 is believed to improve In confinement and In retention, reduce defects associated with high In content InGaN materials, and / or improve the stability of InGaN in the active QW layer 1032, thus overcoming possible negative effects of including a wider band gap material such as Al. Furthermore, Al can be used in the active MQW region 1030 as a dopant for various wavelengths of light emitting structures, including conventional LEDs (having dimensions of approximately 100 microns or more) as well as micro-LED structures configured to operate at infrared, visible, and ultraviolet wavelengths. Al is advantageous because it is a standard precursor that is readily available in systems commonly used to produce QW structures, such as metalorganic chemical vapor deposition (MOCVD) systems.

[0052] Since the incorporation of Al into the active QW layers 1032 varies depending on the growth conditions (e.g., temperature, pressure, time) of the active QW material, the Al content in the active QW layers 1032 can be tailored to provide desired properties of the active QW layers 1032. Although the active MQW region 1030 is shown as having four active QW layers 1032, more or fewer active QW layers 1032 and corresponding barrier layers 734 may be included to achieve the desired emission and operating characteristics of the micro LED structure 1000.

[0053] FIG. 11 is a schematic cross-sectional view of an exemplary micro LED structure 1100 similar to the micro LED structure 1000 of FIG. 10, but further including an aluminum-containing bottom layer, such as the Al bottom layer 836 of the micro LED structures 800A and 800B of FIGS. 8A and 8B. An active MQW region 1130 is formed on the bulk or prep layer 720, and includes a combination of the Al bottom layer 836 and the active QW layer 1032, both having an Al content. The Al bottom layer 836 is believed to promote uniformity of deposition and adhesion of the active QW layer 1032 therein, and the inclusion of Al in the active QW layer 1032 promotes retention of In in the QWs, thereby improving the quantum efficiency at red wavelengths compared to the quantum efficiency at red wavelengths of the micro LED structure not including the features of FIG. 11. In certain embodiments, an intermediate layer 838 (shown in FIG. 8B) may be included between the Al bottom layer 836 and the active QW layer 1032.

[0054] Figure 12 is a schematic cross-sectional view of an exemplary micro LED structure 1200 similar to the micro LED structure 1000 of Figure 10, but further including the Al cap layer 932 of the micro LED structure 900 (Figure 9). The active MQW region 1230 of the micro LED structure 1200 is formed on the bulk or prep layer 720 and includes an Al cap layer 932 with an active QW layer 1032 also including Al. The combination of the active QW layer 1032 on top of the Al cap layer 932 promotes retention of In in the active QW layer 1032, thereby improving the quantum efficiency at red wavelengths compared to the quantum efficiency at red wavelengths of a micro LED structure without the active MQW region 1230.

[0055] Figure 13 is a schematic cross-sectional view of an exemplary micro LED structure 1300 similar to the micro LED structure 1200 of Figure 12, but further including the Al bottom layer 836 of Figure 8B. The micro LED structure 1300 has an active MQW region 1330 formed on a bulk or prep layer 720, the active MQW region 1330 including an Al bottom layer 836 and an Al cap layer 932 for each active QW layer 1032, and further including a barrier layer 734 adjacent the Al bottom layer 836 and the Al cap layer 932. Optionally, as shown in Figure 13, an intermediate layer 838 may be disposed between the Al bottom layer 836 and the active QW layer 1032, where the Al bottom layer 836 is, for example, AlGa(In)N. The inclusion of Al in the active MQW region 1330 improves the uniformity of In distribution within each active QW layer 1032, promotes retention of In within the active MQW region 1330, and reduces desorption of In from the active QW layers 1032 during growth of the barrier layer 734. Thus, the micro LED structure 1300 combines the beneficial effects of the micro LED structures shown in Figures 8B, 9 and 10.

[0056] FIG. 14 is a flow chart illustrating one exemplary process 1400 for fabricating a micro LED structure. The process 1400 may be performed, for example, in an MOCVD system or other system suitable for fabricating micro LEDs. In block 1410 of the process 1400, one or more bulk or prep layers are deposited on a substrate. In one example of block 1410, the first and second preparation layers 320, 330 are deposited on the semiconductor template 310. In another example of block 1410, a bulk or prep layer 720 is deposited on the semiconductor template 710. Block 1412 is optional. If included, in block 1412, the process 1400 deposits one or more barrier materials. In one example of block 1412, a barrier layer 734 is deposited on the bulk or prep layer 720. It should be noted that in certain embodiments, a first barrier material may be incorporated into one or more bulk or prep layers 720 deposited in block 1410 rather than separately depositing a barrier material in block 1412.

[0057] Block 1420 is a decision. If the decision at block 1420 is to add a bottom layer having Al, then the process 1400 proceeds to block 1422, otherwise the process 1400 proceeds to block 1424. At block 1422, the process 1400 deposits an Al-containing bottom layer. In one example of block 1422, an Al bottom layer 836 is deposited on the previously deposited layer.

[0058] Block 1424 is a decision. If the decision at block 1424 is to add an intermediate layer, then the process 1400 proceeds to block 1426, otherwise, the process 1400 proceeds to block 1430. At block 1426, the process 1400 deposits the intermediate layer within the previously deposited layers. In one example of block 1426, the intermediate layer 838 is deposited on the Al bottom layer 836.

[0059] Block 1430 is a decision. If the decision in block 1430 is to include Al in the active QW layer, then the process 1400 proceeds to block 1432, otherwise the process 1400 proceeds to block 1440. In block 1432, the process 1400 deposits an active QW material incorporating Al. In one example of block 1432, Al is added when the active QW layer 1032 is deposited on the barrier layer 734. In another example of block 1432, Al is added when the active QW layer 1032 is deposited on the Al bottom layer 836. In another example of block 1432, Al is added when the active QW layer 1032 is deposited on the intermediate layer 838. The process 1400 then proceeds to block 1450. In block 1440, the process 1400 deposits an active QW material without adding Al. In one example of block 1440, the active QW region 340 is deposited on the second preparation layer 330. In another example of block 1440, the active QW layer 832 is deposited on the Al bottom layer 836. In another example of block 1440, the active QW layer 832 is deposited on the intermediate layer 838. In another example of block 1440, the active QW layer 832 is deposited on the barrier layer 734.

[0060] Block 1450 is a decision. If a decision is made in block 1450 to include an Al cap layer, then the process 1400 proceeds to block 1452; otherwise, the process 1400 proceeds to block 1470. In block 1452, the process 1400 deposits an Al cap layer. In one example of block 1452, an Al cap layer 932 is deposited on the active QW layer 832. 1452 In another example, an Al cap layer 932 is deposited on the active QW layer 1032 .

[0061] Block 1470 is a decision. If it is determined in block 1470 that an additional QW layer is to be deposited, then process 1400 proceeds to block 1412; otherwise, process 1400 proceeds to block 1480. Thus, blocks 1412-1470 are repeated for each additional QW layer that is added.

[0062] In block 1480, the process 1400 deposits a barrier material. In one example of block 1480, the barrier layer 734 is deposited on the active QW stack 732. In another example of block 1480, the barrier layer 734 is deposited on the active QW layer 832. In another example of block 1480, the barrier layer 734 is deposited on the Al cap layer 932. In block 1482, the process 1400 deposits one or more p-layers. In one example of block 1482, one or more p-layers 350 are deposited on the active QW region 340. In another example of block 1482, the p-layer 740 is deposited on the barrier layer 734. The process 1400 may then end.

[0063] The present disclosure describes various embodiments that use techniques and structures to improve performance at red wavelengths emitted from a micro-LED structure. While the above description has focused on micro-LED structures emitting at red wavelengths, the techniques and structures of the described embodiments may also be used to tailor the performance of LEDs operating at other wavelength ranges, including shorter visible and infrared wavelengths. Additionally, while the disclosed embodiments primarily show nitride-based micro-LED structures, similar material and layering structure modifications for bandgap and defect engineering are applicable to other light emitting structures, such as phosphide-based LED structures. Additionally, while the disclosed embodiments relate to the inclusion of Al, a standard precursor readily available in MOCVD systems commonly used to produce QW structures, the inclusion of other materials within the MQW region of the micro-LED structure may also be contemplated to further engineer the desired emission from the micro-LED structure. Additionally, additional intermediate layers may be included between the active QW layer 832 and the Al cap layer 932 in FIG. 9 and / or between the active QW layer 1032 and the Al cap layer 932 in FIG. 12 and FIG. 13.

[0064] The LED structure may include an active region having at least one quantum well, the active region configured to provide light emission associated with the LED structure. An amount of aluminum is incorporated within the at least one quantum well. The active region of the LED structure may further include at least one aluminum-containing layer incorporating an amount of aluminum greater than the amount of aluminum incorporated within the at least one quantum well. The amount of aluminum incorporated within the at least one quantum well is between 0.01 and 5% of the at least one quantum well. The LED structure exhibits a modified internal quantum efficiency value that is greater than an unmodified internal quantum efficiency value exhibited by an unmodified LED structure that does not have the amount of aluminum incorporated within the at least one quantum well. The LED structure operates at a modified peak wavelength that is greater than an unmodified peak wavelength of an unmodified LED structure that does not have the amount of aluminum incorporated within the at least one quantum well. The LED structure has a diameter of less than 10 microns.

[0065] The LED structure includes an active region configured to provide light emission associated with the LED structure, the active region including a barrier layer and an active QW layer, the active QW layer being substantially composed of a primary active QW material, the active QW layer further including an amount of a secondary material incorporated within the active QW layer, the secondary material exhibiting a wider band gap than the primary active QW material. The active region may further include at least one intermediate layer incorporating an amount of the secondary material greater than the amount of the secondary material incorporated within the active quantum well layer. The at least one intermediate layer is disposed between the barrier layer and the active quantum well layer. The at least one intermediate layer may be a bottom layer. The at least one intermediate layer may be a cap layer. The secondary material is aluminum. The LED structure exhibits a modified internal quantum efficiency value that is greater than an unmodified internal quantum efficiency value exhibited by an unmodified LED structure not having an amount of the secondary material dispersed throughout the at least one quantum well. The LED structure operates at a modified peak wavelength that is greater than an unmodified peak wavelength of an unmodified LED structure not having an amount of the secondary material dispersed throughout the at least one quantum well. The diameter of the LED structure is less than 10 microns.

[0066] The method forms a light emitting diode (LED) structure including at least one quantum well region including a barrier layer and an active quantum well layer. In forming the at least one quantum well region, a primary active quantum well material is deposited along with a quantity of a secondary material exhibiting a wider bandgap than the primary active quantum well material. The amount of secondary material is 0.01-5% of the primary active quantum well material. Depositing the primary active quantum well material along with the quantity of secondary material includes forming a pseudoalloy of the primary active material and the secondary material.

[0067] Combination of features The following embodiments, and any combination of such embodiments that are mutually compatible, are specifically contemplated.

[0068] (A) A light emitting diode (LED) structure includes a bulk or prep layer formed on a semiconductor template, an active region formed on the bulk or prep layer, and at least one p-layer formed on the active region. The active region includes a first barrier layer formed on the bulk or prep layer, at least one aluminum-containing active quantum well (QW) stack formed on the first barrier layer, and a second barrier layer formed on the active QW stack. When the at least one active QW stack is driven by an injection current, the active region emits light from the LED structure.

[0069] (B) In the LED structure depicted as (A), the active region is configured to emit light at red wavelengths from the LED structure.

[0070] (C) In either of the LED structures depicted as (A) and (B), the at least one active QW stack comprises (a) an aluminum-containing bottom layer formed on the first barrier layer, and (b) an active QW layer formed on the aluminum-containing bottom layer.

[0071] (D) In ​​any of the LED structures depicted as (A)-(C), the aluminum-containing bottom layer comprises an alloy selected from the group consisting of AlGa(In)N, AlGaN, AlInN, and InAlGaN.

[0072] (E) In any of the LED structures depicted as (A)-(D), the at least one active QW stack further comprises (c) an aluminum-containing cap layer formed on the active QW layer.

[0073] (F) In any of the LED structures depicted as (A)-(E), the aluminum-containing cap layer comprises a 1 nm thick AlGaN material.

[0074] (G) In any of the LED structures represented as (A)-(F), the at least one active QW stack comprises: (a) an aluminum-containing bottom layer formed on the first barrier layer; (b) an intermediate layer formed on the aluminum-containing bottom layer; and (c) an active QW layer formed on the intermediate layer.

[0075] (H) In any of the LED structures represented as (A) to (G), the intermediate layer comprises a material selected from the group consisting of GaN, AlGaN, InGaN, and AlInGaN.

[0076] (I) In any of the LED structures represented as (A)-(H), the at least one active QW stack comprises an aluminum-containing QW layer formed on the first barrier layer.

[0077] (J) In any of the LED structures designated as (A)-(I), the aluminum-containing QW layer comprises one of a pseudoalloy, a digital alloy, and a short period superlattice.

[0078] (K) In any of the LED structures represented as (A) through (J), the at least one active QW stack comprises: (a) an aluminum-containing bottom layer formed on the first barrier layer; and (b) an aluminum-containing active QW layer formed on the aluminum-containing bottom layer.

[0079] (L) In any of the LED structures represented as (A)-(K), the at least one active QW stack comprises (a) an aluminum-containing active QW layer formed on the first barrier layer, and (b) an aluminum-containing cap layer formed on the active QW layer.

[0080] (M) In any of the LED structures represented as (A)-(L), the at least one active QW stack comprises: (a) an aluminum-containing bottom layer formed on the first barrier layer; (b) an aluminum-containing active QW layer formed on the aluminum-containing bottom layer; and (c) an aluminum-containing cap layer formed on the aluminum-containing active QW layer.

[0081] (N) In any of the LED structures represented as (A) to (M), a plurality of micro LED structures are arranged as an array including a blue micro LED structure emitting light at a blue wavelength, a green micro LED structure emitting light at a green wavelength, and a red micro LED structure emitting light at a red wavelength. semiconductor It is monolithically formed on the template.

[0082] (O) A light emitting diode (LED) structure comprises a semiconductor template, a first preparatory layer formed on the semiconductor template, a second preparatory layer formed on the first preparatory layer, at least one active quantum well (QW) layer formed on the second preparatory layer, and at least one p-layer formed on the active QW layer, wherein the active QW layer generates light from the LED structure when activated.

[0083] In the LED structure designated as (P)(O), the first preparatory layer comprises non-active QWs and the second preparatory layer comprises an aluminum-containing bottom layer.

[0084] In any of the LED structures designated as (Q), (O) or (P), the second preparation layer comprises a reflective layer.

[0085] In any of the LED structures designated as (R), (O) through (Q), the second preparation layer comprises a hole blocking layer.

[0086] (S) A method forms a light emitting diode (LED) structure on a semiconductor substrate. The method comprises depositing at least one prep layer on the semiconductor substrate, forming an active multiple quantum well (MQW) region on the at least one prep layer, and depositing a p-layer on the active MQW region. Forming the active MQW region includes depositing a first barrier material, depositing an active QW material, and depositing a second barrier material. Forming the active MQW region optionally includes depositing a bottom layer between the first barrier material and the active QW material, depositing an intermediate layer between the bottom layer and the active QW material, and depositing a cap layer between the active QW material and the second barrier material. At least one of depositing the active QW material, depositing the bottom layer, depositing the intermediate layer, and depositing the cap layer includes incorporating aluminum.

[0087] Thus, although the present disclosure has been provided according to the implementations shown, those skilled in the art will readily recognize that there may be modifications to these embodiments, and that such modifications would fall within the scope of the present disclosure. Thus, many modifications may be made by those skilled in the art without departing from the scope of the appended claims. Modifications may be made in the above method and system without departing from its scope. Thus, it should be noted that the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all the general and specific features described herein, and all descriptions of the scope of the present method and system that may be said to fall therebetween as a matter of language.

Claims

1. 1. A light emitting diode (LED) structure comprising: a bulk or prep layer formed on a semiconductor template; an active region formed on the bulk or prep layer, the active region comprising: a first barrier layer formed on the bulk or prep layer; at least one nitride-based aluminum-containing active quantum well (QW) layer formed on the first barrier layer; a second barrier layer formed on the at least one nitride-based aluminum-containing active QW layer, the LED structure further comprising: at least one p-layer formed on the active region; The LED structure, wherein the at least one nitride-based aluminum-containing active QW layer emits light at red wavelengths when the at least one nitride-based aluminum-containing active QW layer is driven by an injection current.

2. 2. The LED structure of claim 1 , wherein the active region further comprises an aluminum-containing bottom layer formed on the first barrier layer, and the at least one nitride-based aluminum-containing active QW layer is formed on the aluminum-containing bottom layer.

3. 3. The LED structure of claim 2 wherein the aluminum-containing bottom layer comprises a material selected from the group consisting of AlGa(In)N, AlGaN, AlInN, and InAlGaN.

4. 4. The LED structure of claim 1, wherein the active region further comprises an aluminum-containing cap layer formed on the at least one nitride-based aluminum-containing active QW layer.

5. 5. The LED structure of claim 4 wherein the aluminum-containing cap layer comprises an AlGaN material.

6. An LED structure as described in any one of claims 1 to 5, wherein the at least one nitride-based aluminum-containing active QW layer comprises one of a pseudo alloy, a digital alloy, and a short period superlattice.

7. 1. A light emitting diode (LED) structure comprising: a bulk or prep layer formed on a semiconductor template; an active region formed on the bulk or prep layer, the active region comprising: a first barrier layer formed on the bulk or prep layer; at least one aluminum-containing active quantum well (QW) stack formed on the first barrier layer; a second barrier layer formed on the at least one aluminum-containing active QW stack, the LED structure further comprising: at least one p-layer formed on the active region; the at least one aluminum-containing active QW stack includes: (a) an aluminum-containing bottom layer formed on the first barrier layer; (b) an intermediate layer formed on the aluminum-containing bottom layer; and (c) an active QW layer formed on the intermediate layer; When the at least one aluminum-containing active QW stack is driven by an injection current, the active region emits light from the LED structure.

8. 8. The LED structure of claim 7, wherein the intermediate layer comprises a material selected from the group consisting of GaN, AlGaN, InGaN, and AlInGaN.

9. 9. The LED structure of claim 7 or claim 8, wherein the active QW layer is at least one aluminum-containing active QW layer.

10. 10. The LED structure of claim 9, wherein the at least one aluminum-containing active QW layer comprises one of a pseudoalloy, a digital alloy, and a short period superlattice.

11. a plurality of micro LED structures monolithically formed as an array on a semiconductor template; the plurality of micro LED structures including blue micro LED structures configured to emit light at blue wavelengths, green micro LED structures configured to emit light at green wavelengths, and red micro LED structures configured to emit light at red wavelengths; A display, wherein the red micro LED structure comprises an LED structure according to any one of claims 1 to 10.

12. 1. A light emitting diode (LED) structure comprising: A semiconductor template; a first preparation layer formed on the semiconductor template; a second preparation layer formed on the first preparation layer; at least one active quantum well (QW) layer formed on the second preparation layer; at least one p-layer formed on the at least one active QW layer; the first preparation layer includes non-active QWs; the second preparation layer comprises an aluminum-containing bottom layer; The at least one active QW layer, when activated, emits light from the LED structure.

13. 13. The LED structure of claim 12, wherein the second preparation layer comprises a reflective layer.

14. 14. The LED structure of claim 12 or claim 13, wherein the second preparation layer comprises a hole blocking layer.

15. 1. A method for forming a light emitting diode (LED) structure on a semiconductor substrate, comprising: depositing at least one prep layer over the semiconductor substrate; forming an active multiple quantum well (MQW) region on the at least one prep layer; depositing a p-layer on the active MQW region; forming the active MQW region depositing a first barrier material; depositing an active QW material; depositing a second barrier material; forming the active MQW region depositing a bottom layer between the first barrier material and the active QW material; depositing an intermediate layer between the bottom layer and the active QW material; depositing a cap layer between the active QW material and the second barrier material; The method, wherein at least one of depositing the active QW material, depositing the bottom layer, depositing the intermediate layer, and depositing the cap layer includes incorporating aluminum.

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