Growth engineering of monolithic color tunable light emitting diodes and methods thereof

Abstract

To provide an LED system having color adjustability in response to changes in drive current density.SOLUTION: In one example, the system includes a patterned dielectric layer, a multiple quantum well (MQW) region, an electron blocking layer (EBL), and a p-type GaN layer. The EBL is deposited on the MQW region and is structured such that injection of holes into the MQW region is planar specific. The planar intrinsic hole injection leads to a target color emission associated with the level of band bending. A p-type GaN layer is deposited over the EBL and is doped to be a source of holes. For shorter wavelength emission, the p-GaN is engineered to provide sufficient holes to the underlying layers of the MQW region. This selective hole injection in the direction of the various crystal planes, together with a managed indium concentration in the MQW region and a sufficient supply of holes, enables smooth color tunability.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63 / 682,571, filed August 13, 2024, both of which are incorporated herein by reference for all purposes.

[0002] The present technology relates to the architecture and fabrication of color-tunable LEDs, LED elements, systems, and displays based on such LEDs. [Background technology]

[0003] Light-emitting diode (LED)-based solid-state light sources and displays have been widely developed across many lighting markets. More recently, continued interest in higher-resolution LED displays, particularly those used in wearable and portable consumer products, has led to efforts to increase the total number of pixels and pixel density in displays to enhance resolution and improve LED performance in smaller form factor displays. These advances have been most challenging for microLED displays, with diameters of less than 200 microns for larger format applications such as monitors and televisions, and less than 30 microns for displays in wearable or portable products. More recently, displays for near-eye applications such as virtual reality and augmented reality have benefited from even smaller LEDs, where LED diameters can be in the low single-digit microns.

[0004] In most displays, the base light-emitting unit, called a pixel, requires three LEDs that emit red, green, and blue light, which, when driven in the proper relationship, can produce a range of colors across the visible spectrum. However, there has been a continuous effort to reduce the number of LEDs required to produce full-color emission, as this will improve the ability to produce displays with higher resolution and higher pixel density, particularly in applications where microLED displays are favored.

[0005] Recent efforts have demonstrated some success in enabling individual LED light sources to emit more than one color when driven at various current densities. Such approaches involve physical stacking of light-emitting structures, such as when different multiple quantum well (MQW) regions, each optimized for a different color, are grown sequentially, or when the completed epitaxial layer structures of red-, green-, and blue-emitting LEDs are transferred to a single host wafer. However, stacking approaches suffer from structural inefficiencies, such as light absorption and scattering due to the depth of each color's light-emitting region, as well as insufficient LED spacing and the additional switches (including transistors and wiring) required to power each LED. When more exotic or semiconductor-hostile materials (such as Eu or Au) are used, the stacking approach becomes even more limited, making scaled production of these devices difficult.

[0006] More recently, various approaches have been explored to achieve more than a single color emission from LEDs through crystal growth techniques. Early studies investigated indium content and emission from different crystal facets to achieve different discrete emission wavelengths. However, these multicolor emissions of different discrete colors are achieved through simultaneous additive properties, from longer to shorter wavelengths based on current density, such that mixed emission, for example, includes the generation of white light. These multicolor selective area grown (SAG) LEDs provide additive colors, but have not achieved fully smoothly tunable colors, where a single LED can emit multiple colors across a wide region of the visible spectrum by emitting distinct primary colors at different current densities and corresponding band bending. Such existing research has not suggested a means to control the indium concentration distribution, nor has it suggested a means to affect different crystal facets and vary the current injection, which is critical for achieving smooth and full-spectrum color tunability. Summary of the Invention [Means for solving the problem]

[0007] An exemplary embodiment of the present disclosure provides an LED system having color tunability in response to changes in drive current density, the system comprising one or more pixel elements each including one or more LEDs, the one or more LEDs each including: a first layer; a patterned dielectric layer formed on the first layer, the patterned dielectric layer including openings; and a second layer formed on the first layer to provide a pattern along one surface of the second layer through the openings, the pattern along one surface of the second layer having one or more spacing features to facilitate controlled color emission in the MQW layer of the MQW region, the pattern including one or more protrusions of a shape and size according to the openings; the MQW region formed across one surface of the second layer, each MQW layer being alloyed with a percentage of indium that promotes controlled color emission, the portion of the MQW layer conforming to the sidewall of the protrusion having a lower indium alloy percentage than the other portion of the MQW layer; an electron blocking layer formed over the MQW region and opposite in charge to the second layer, the electron blocking layer being actively doped; and a third layer formed over the electron blocking layer and opposite in charge to the second layer, the third layer being actively doped. The portion of the MQW layer conforming to the sidewall can emit light in the blue wavelength range of 400 nm to 520 nm.

[0008] In one example, each of the one or more LEDs further includes a transition region in each MQW layer between a respective portion of the MQW layer that conforms to the sidewall of the protrusion and a respective other portion of the MQW layer, the transition region having a higher concentration of indium alloy percentage than the other portions of the MQW layer, the indium alloy percentage decreasing with distance from the portion of the MQW layer that conforms to the sidewall of the protrusion.

[0009] In one example, holes are injected at least laterally from the third layer into the transition region.

[0010] In one embodiment, the first layer is actively doped.

[0011] In one example, the second layer includes at least one crystal plane selected from the following five crystal planes: (0001), (11-22), (1-101), (11-20), or (1-100).

[0012] In one example, the electron blocking layer includes AlGaN.

[0013] In one example, the third layer includes p-type GaN.

[0014] In one example, the third layer further comprises at least one characteristic selected from the group consisting of a resistivity of less than 10 ohm·cm, a p-type doping concentration level of 1E16 to 1E21 per cubic centimeter, a thickness of 10 to 500 nm, and combinations thereof.

[0015] In one example, each of the one or more LEDs further includes a p-type InGaN layer formed on the third layer.

[0016] In one example, each of the one or more LEDs further includes a metal layer formed over the third layer.

[0017] Another exemplary embodiment of the present disclosure provides a method for operating an LED system having color tunability in response to changes in drive current density, the method including providing one or more pixel elements each including one or more LEDs, the one or more LEDs each including: a first layer; a patterned dielectric layer formed on the first layer, the patterned dielectric layer including openings; and a second layer formed on the first layer to provide a pattern along one surface of the second layer through the openings, the pattern along the one surface of the second layer having one or more spacing features to promote controlled color emission in the MQW layer of the MQW region, the pattern including one or more protrusions of a shape and size according to the openings; a second layer overlaid on the protrusion, an MQW region formed across one surface of the second layer, each MQW layer alloyed with a percentage of indium that promotes controlled color emission, the portion of the MQW layer conforming to the sidewall of the protrusion having a lower indium alloy percentage than other portions of the MQW layer, an electron blocking layer formed over the MQW region and opposite in charge to the second layer, the electron blocking layer being actively doped, and a third layer formed over the electron blocking layer and opposite in charge to the second layer, the third layer being actively doped. The method further includes applying a current to one of the LEDs such that holes from the third layer are injected into the portion of the MQW layer conforming to the sidewall, such that the portion of the MQW layer conforming to the sidewall emits light in the blue wavelength range of 400 nm to 520 nm.

[0018] In one example, each of the one or more LEDs further includes a transition region in each MQW layer between a respective portion of the MQW layer that conforms to the sidewall of the protrusion and a respective other portion of the MQW layer, the transition region having a higher concentration of indium alloy percentage than the other portions of the MQW layer, the indium alloy percentage decreasing with distance from the portion of the MQW layer that conforms to the sidewall of the protrusion.

[0019] In one example, the method further includes applying another current to one of the LEDs such that holes are injected at least laterally from the third layer into the transition region such that the transition region emits light in a red wavelength range of 580 nm to 700 nm, the other current being lower than the current applied to emit blue wavelengths.

[0020] In one example, the method further includes applying an additional current to one of the LEDs such that holes are injected from the third layer at least perpendicularly into the portion of the MQW layer away from the transition region and into the portion of the MQW layer that conforms to the sidewall of the protrusion, such that the portion of the MQW layer away from the transition region emits light in a green wavelength range of 520 nm to 580 nm, the additional current being lower than the current applied to emit blue wavelengths and higher than another current applied to emit red wavelengths.

[0021] In one embodiment, the first layer is actively doped.

[0022] In one example, the second layer includes at least one crystal plane selected from the following five crystal planes: (0001), (11-22), (1-101), (11-20), or (1-100).

[0023] In one example, the electron blocking layer includes AlGaN.

[0024] In one example, the third layer includes p-type GaN.

[0025] In one example, the third layer further comprises at least one characteristic selected from the group consisting of a resistivity less than 10 ohm-cm, a p-type doping concentration level of 1E16 to 1E21 per cubic centimeter, a thickness of 10 to 500 nm, and combinations thereof, such that upon application of a current, holes can be injected from the third layer into the portion of the MQW layer that conforms to the sidewall of the protrusion to achieve light emission in the blue wavelength range of 400 nm to 520 nm.

[0026] In one example, each of the one or more LEDs further includes a p-type InGaN layer formed on the third layer.

[0027] In one example, each of the one or more LEDs further includes a metal layer formed over the third layer.

[0028] Another exemplary embodiment of the present disclosure provides an LED system having color tunability in response to changes in drive current density, the system including: a current driver configured to drive changes in current density; and one or more pixel elements coupled to the current driver, each pixel element including one or more LEDs, each of the one or more LEDs comprising: a first layer; a patterned dielectric layer formed on the first layer, the patterned dielectric layer including openings; and a second layer formed on the first layer to provide a pattern along one surface of the second layer through the openings, the pattern along the one surface of the second layer having one or more spacing features to facilitate controlled color emission in the MQW layer of the MQW region, and one or more shapes according to the openings. The device includes a second layer including protrusions of a certain shape and size, the second layer being actively doped; MQW regions formed across one surface of the second layer, each MQW layer being alloyed with a percentage of indium that promotes controlled color emission, the portion of the MQW layer conforming to a sidewall of the protrusion having a lower indium alloy percentage than the remaining portion of the MQW layer; an electron blocking layer formed over the MQW region and opposite in charge to the second layer, the electron blocking layer being actively doped; and a third layer formed over the electron blocking layer and opposite in charge to the second layer, the third layer being actively doped. The portion of the MQW layer conforming to the sidewall can emit light in the blue wavelength range of 400 nm to 520 nm.

[0029] These and other aspects of the present disclosure are described in the following detailed description and accompanying drawings. Other aspects and features of the embodiments will become apparent to those skilled in the art upon review of the following description of certain exemplary embodiments in conjunction with the drawings. While features of the present disclosure may be described with reference to particular embodiments and figures, all embodiments of the present disclosure may include one or more of the features described herein. Furthermore, while one or more embodiments may be described as having certain advantageous features, one or more of such features may be used with various embodiments described herein. Similarly, while exemplary embodiments may be described below as device, system, or method embodiments, it should be understood that such exemplary embodiments may be implemented in various devices, systems, and methods of the present disclosure. The present invention provides, for example, the following. (Item 1) 1. An LED system having color tunability in response to changes in drive current density, the system comprising: one or more pixel elements each including one or more LEDs, each of said one or more LEDs: a first layer; a patterned dielectric layer formed on the first layer, the patterned dielectric layer including an opening; and a second layer formed on the first layer through the opening to provide a pattern along one surface of the second layer, the pattern along the one surface of the second layer including one or more shaped protrusions having one or more spacing features to promote controlled color emission in an MQW layer of an MQW region, the second layer being actively doped; the MQW region formed across said one surface of said second layer, each of said MQW layers being alloyed with a percentage of indium that promotes said controlled color emission, and a portion of said MQW layer conforming to a sidewall of said protrusion having a lower indium alloy percentage than other portions of said MQW layer; an electron blocking layer formed on the MQW region and having a charge opposite to that of the second layer, the electron blocking layer being actively doped; a third layer formed on the electron blocking layer and having an opposite charge to the second layer, the third layer being actively doped; The portion of the MQW layer that conforms to the sidewall of the protrusion is capable of emitting light in the blue wavelength range of 400 nm to 520 nm. (Item 2) Each of the one or more LEDs comprises: The system of claim 1, further comprising a transition region in each MQW layer between each of the portions of the MQW layer that conform to the sidewall of the protrusion and each of the other portions of the MQW layer, the transition region having a higher concentration of the indium alloy percentage than the other portions of the MQW layer, the indium alloy percentage decreasing with distance from the portion of the MQW layer that conforms to the sidewall of the protrusion. (Item 3) 3. The system of claim 1, wherein holes are injected at least laterally from the third layer into the transition region. (Item 4) 10. The system of claim 1, wherein the first layer is actively doped. (Item 5) 2. The system of claim 1, wherein the second layer includes at least one crystal plane selected from the five crystal planes (0001), (11-22), (1-101), (11-20), or (1-100). (Item 6) Item 11. The system of any one of the preceding items, wherein the electron blocking layer comprises AlGaN. (Item 7) 2. The system of claim 1, wherein the third layer comprises p-type GaN. (Item 8) 10. The system of claim 1, wherein the third layer further comprises at least one characteristic selected from the group consisting of a resistivity of less than 10 ohm-cm, a p-type doping concentration level of 1E16 to 1E21 per cubic centimeter, a thickness of 10 to 500 nm, and combinations thereof. (Item 9) Item 10. The system of any one of the preceding items, wherein each of the one or more LEDs further includes a p-type InGaN layer formed on the third layer. (Item 10) Item 10. The system of any one of the preceding items, wherein each of the one or more LEDs further includes a metal layer formed on the third layer. (Item 11) 1. A method of operating an LED system having color tunability in response to changes in drive current density, the method comprising: providing one or more pixel elements each including one or more LEDs, each of said one or more LEDs comprising: a first layer; a patterned dielectric layer formed on the first layer, the patterned dielectric layer including an opening; and a second layer formed on the first layer through the opening to provide a pattern along one surface of the second layer, the pattern along the one surface of the second layer including one or more shaped protrusions having one or more spacing features to promote controlled color emission in an MQW layer of an MQW region, the second layer being actively doped; the MQW region formed across said one surface of said second layer, each of said MQW layers being alloyed with a percentage of indium that promotes said controlled color emission, and a portion of said MQW layer conforming to a sidewall of said protrusion having a lower indium alloy percentage than other portions of said MQW layer; an electron blocking layer formed on the MQW region and having a charge opposite to that of the second layer, the electron blocking layer being actively doped; a third layer formed on the electron blocking layer and having an opposite charge to the second layer, the third layer being actively doped; applying a current to one of the LEDs such that holes from the third layer are injected into the portion of the MQW layer conforming to the sidewall of the protrusion, such that the portion of the MQW layer conforming to the sidewall of the protrusion emits light in the blue wavelength range of 400 nm to 520 nm; A method comprising: (Item 12) Each of the one or more LEDs comprises: 10. The method of claim 9, further comprising a transition region in each MQW layer between each of the portions of the MQW layer that conform to the sidewall of the protrusion and each of the other portions of the MQW layer, the transition region having a higher concentration of the indium alloy percentage than the other portions of the MQW layer, the indium alloy percentage decreasing with distance from the portion of the MQW layer that conforms to the sidewall of the protrusion. (Item 13) 10. The method of claim 9, further comprising applying another current to one of the LEDs such that holes are injected at least laterally from the third layer into the transition region such that the transition region emits light in a red wavelength range of 580 nm to 700 nm, the other current being lower than the current applied to emit the blue wavelength. (Item 14) 10. The method of claim 9, further comprising applying an additional current to one of the LEDs such that holes are injected from the third layer at least perpendicularly into a portion of the MQW layer away from the transition region and into a portion of the MQW layer conforming to the sidewall of the protrusion, such that a portion of the MQW layer away from the transition region emits light in a green wavelength range of 520 nm to 580 nm, the additional current being lower than the current applied to emit the blue wavelength and higher than the other current applied to emit the red wavelength. (Item 15) Item 10. The method of any one of the preceding items, wherein the first layer is actively doped. (Item 16) Item 10. The method of any one of the preceding items, wherein the second layer comprises at least one crystal plane selected from five crystal planes: (0001), (11-22), (1-101), (11-20), or (1-100). (Item 17) Item 10. The method of any one of the preceding items, wherein the electron blocking layer comprises AlGaN. (Item 18) Item 10. The method of any one of the preceding items, wherein the third layer comprises p-type GaN. (Item 19) Item 10. The method of any one of the preceding items, wherein the third layer further comprises at least one characteristic selected from the group consisting of a resistivity of less than 10 ohm-cm, a p-type doping concentration level of 1E16 to 1E21 per cubic centimeter, a thickness of 10 to 500 nm, and combinations thereof, such that upon application of the current, the holes are injected from the third layer into the portion of the MQW layer that conforms to the sidewall of the protrusion to achieve the emission in the blue wavelength range of 400 nm to 520 nm. (Item 20) Item 10. The method of any one of the preceding items, wherein each of the one or more LEDs further includes a p-type InGaN layer formed on the third layer. (Item 21) Item 10. The method of any one of the preceding items, wherein each of the one or more LEDs further comprises a metal layer formed on the third layer. (Item 22) 1. An LED system having color tunability in response to changes in drive current density, the system comprising: a current driver configured to drive a change in current density; one or more pixel elements coupled to the current driver, each pixel element including one or more LEDs, each of the one or more LEDs: a first layer; a patterned dielectric layer formed on the first layer, the patterned dielectric layer including an opening; and a second layer formed on the first layer through the opening to provide a pattern along one surface of the second layer, the pattern along the one surface of the second layer including one or more shaped protrusions having one or more spacing features to promote controlled color emission in an MQW layer of an MQW region, the second layer being actively doped; the MQW region formed across said one surface of said second layer, each of said MQW layers being alloyed with a percentage of indium that promotes said controlled color emission, and a portion of said MQW layer conforming to a sidewall of said protrusion having a lower indium alloy percentage than other portions of said MQW layer; an electron blocking layer formed on the MQW region and having a charge opposite to that of the second layer, the electron blocking layer being actively doped; a third layer formed on the electron blocking layer and having an opposite charge to the second layer, the third layer being actively doped; The portion of the MQW layer that conforms to the sidewall of the protrusion is capable of emitting light in the blue wavelength range of 400 nm to 520 nm. (Summary) An LED system with color tunability in response to changes in drive current density is disclosed. In one example, the system includes a patterned dielectric layer, a multiple quantum well (MQW) region, an electron blocking layer (EBL), and a p-type GaN layer. The EBL is deposited on the MQW region and structured so that hole injection into the MQW region is planar-specific. Planar-specific hole injection leads to a target color emission associated with the level of band bending. A p-type GaN layer is deposited on top of the EBL and doped to be a hole source. For shorter wavelength emission, the p-GaN is engineered to provide sufficient hole supply to the underlying layers of the MQW region. This selective hole injection in the direction of various crystal planes, along with the controlled indium concentration and sufficient hole supply in the MQW region, enables smooth color tunability. [Brief explanation of the drawings]

[0030] The foregoing summary and the following detailed description can be better understood when read in conjunction with the accompanying drawings. For purposes of illustration only, specific embodiments are shown in the drawings. It should be understood, however, that the inventive concepts disclosed herein are not limited to the precise arrangements and instrumentalities shown in the drawings. The detailed description will refer to the following drawings, in which like numerals refer to like items where present, and in which:

[0031] [Figure 1A] 1 shows a cross section of an exemplary color-tunable single LED including a single selectively grown structure.

[0032] [Figure 1B] 1 shows a cross-sectional side view of an exemplary color-tunable LED including multiple selectively grown structures.

[0033] [Figure 2] 1A-1C show plan views of different optimized exemplary patterns of dielectric on a surface before selective area growth.

[0034] [Figure 3A]FIG. 2 shows a cross-sectional side view of an exemplary color-tunable single LED including a single structure selectively grown using a patterned dielectric (see, e.g., FIG. 2) and having anode and cathode contacts.

[0035] [Figure 3B] FIG. 2 shows a cross-sectional side view of an exemplary color-tunable LED including multiple structures selectively grown in succession using a patterned dielectric (see, e.g., FIG. 2) and having anode and cathode contacts. DETAILED DESCRIPTION OF THE INVENTION

[0036] As shown in FIGS. 1A-3B, example color-tunable LED technology offers several advantages, including providing a completely smooth, color-tunable LED system that can be effectively utilized in several different applications, such as displays (including VR or AR glasses / visors / headsets, etc.), commercial lighting, communications, etc.

[0037] Previous selective area growth efforts to generate multiple color emissions from a single LED have shown that certain architectures produce at most a few discrete, limited wavelength emission bands that vary over a narrow range based on drive intensity. These can be viewed as "polychromatic" emission, i.e., multiple emissions of constrained bandwidth that combine to produce an overall color that is an additive combination of these emission bands. These have not suggested or achieved continuously variable, or "tunable," spectral emission across the entire visible spectrum to enable full color production from a single LED, as achieved in the present disclosure.

[0038] Compared to conventional, multicolor emission from light emitting diodes (LEDs), novel color tunability is achieved from the LED architecture according to the present invention, which produces tunable colors such that a selected range of unique colors spanning from red to blue are emitted by varying the drive current density and / or pulse width modulation to produce colors across the entire visible light spectrum.

[0039] The LEDs of the present disclosure can include a substrate (i.e., a dielectric) onto which one or more GaN layers are first deposited to create an n-type region. This initial n-type region / layer(s) can be an undoped buffer layer or a doped n-type layer. A patterned dielectric layer is deposited on the last-deposited doped n-type layer, but in one embodiment, it can be deposited directly on a GaN-growth-compatible substrate, such as sapphire. Once deposited, the dielectric layer masks the underlying doped n-type layer or GaN-growth-compatible surface from the growth of any additional n-type layers. The engineered n-type layer / protrusion is grown vertically on the previously deposited doped n-type layer or growth-compatible surface in the dielectric-free region, creating an architectural feature that, after processing, results in a laterally varying indium concentration across each layer of the MQW region. This is necessary to enable color-tunable emission from each such MQW region layer. Examples of such engineered n-type layers / protrusions, described more fully below, include specific growth features such as engineered adjacent sidewall planarities, selected growth-related attributes (such as temperature, pressure, and precursor flow rates), and specific shapes and / or spacings of LED elements.

[0040] The MQW region is deposited on an adjacent underlying engineered n-type layer. As explained more fully below, each layer within the MQW region can be optimized to emit a desired range of tunable colors. Each quantum well (QW) deposited on the flat c-plane surface along the center of each engineered n-type protrusion functions as a center point for light emission and corresponding indium concentration. The indium concentration varies based on the structure's topography combined with the open space around the structure's edges. QW growth proceeds simultaneously along each facet of the engineered n-type surface. QW regions grown on the sidewall surfaces incorporate a lower concentration of indium, resulting in shorter wavelength emission. Meanwhile, QW regions grown on the c-plane near the sidewalls experience reduced stress due to the nearby free surface, resulting in a higher indium concentration compared to the same QW regions located toward the center of the engineered n-type protrusion. Editing the QW region grown at the center of the designed n-type protrusion to a specified nominal indium concentration modifies the indium content along the sidewalls and the indium content on the c-plane near the sidewalls, thereby adjusting the total range of light emission possible from a single QW. For example, increasing the indium concentration in a QW located at the center of the designed n-type protrusion will correspondingly increase the indium concentration along the sidewalls and the indium concentration on the c-plane near the sidewall edges, and vice versa. In this manner of modifying the nominal indium concentration of the QWs, each QW within the MQW region can be individually tuned to further enhance the total emission color range of the LED.

[0041] An electron blocking layer (EBL) is deposited over the MQW region and structured so that hole injection into the MQW region is plane-specific. As explained in more detail below, plane-specific hole injection leads to targeted color emission associated with the level of band bending. This selective hole injection in various crystal plane directions, together with controlled indium concentration, enables full color tunability.

[0042] A p-type GaN layer is deposited on the EBL and doped to provide a source of holes with a p-type doping concentration of 1E16 to 1E21 per cubic centimeter. For shorter wavelength emission, the p-GaN is designed to provide sufficient holes to the underlying layers of the MQW region. Below, additional details are provided regarding the relationship between the engineered n-type protrusion, MQW region, and p-GaN layer, which form the active device layers of the color-tunable LED.

[0043] The spacing of these structures within the n-type region grown on the dielectric layer, as described below, as well as their designed architecture, including shape and size, contribute to the efficiency and spectral characteristics of the resulting light emission. The resulting structure spacing and shape design provides a tool for tailoring the light emission level of each color. In one embodiment, a single LED pixel can be optionally constructed from multiple SAG LED structures to tailor the spectral characteristics and efficiency of a more complex pixel. Examples include partially fused structures that can enhance the green and shorter wavelength ranges, or smaller, more widely spaced structures that can enhance the longer wavelength ranges. As an example, connecting multiple such structures (i.e., LEDs producing red) in series is particularly useful for generating an overall increase in red emission intensity compared to green and blue emission.

[0044] Using these novel structures and layers, full color tunability can be achieved, such that the sidewall planarity and structural spacing of the n-type GaN region / layer of interest grown on the substrate / dielectric layer can be further used to laterally tune the indium concentration in the engineered n-GaN region / layer / protrusion to affect color tuning and the resulting light emission. Each quantum well can also be optimized for vertical tunability based on the design and function of the EBL. One light-emitting characteristic that can benefit from such vertical optimization is enhanced green emission.

[0045] Referring to FIG. 1A, an exemplary selectively grown LED structure 100a is formed. First, a first layer of c-plane (0001) n-type GaN1 may be grown, including one or more intentionally or unintentionally doped regions. The first layer of n-type GaN1 may or may not be grown on a host substrate (not shown), such as Si, SiC, AlN, or Al2O3, for example, or on a buffer region on the original GaN substrate. Intentional doping concentrations, if used, may be between 1E16 and 1E21 per cubic centimeter.

[0046] A dielectric layer 2 is formed on the first n-GaN layer 1 and may be, for example, SiO 2 , Si 3 N 4 , or SiON. This dielectric layer 2 is then patterned and selectively etched to expose portions of the first n-GaN layer 1, or in other embodiments, the underlying substrate (in this scenario, the n-GaN layer 1 itself may be replaced with a substrate comprising another material, eliminating the need for an additional underlying substrate), making the exposed areas available for further growth or formation of n-GaN material (i.e., an extended n-GaN layer 1a). The thickness of the dielectric layer 2 may be between 1 nm and 1 μm. Alternatively, to avoid the need for selective etching, the dielectric layer 2 may be selectively deposited in a desired pattern to create exposed areas of the underlying n-GaN layer 1 or GaN support surface (i.e., substrate) in a desired pattern for growth (or additional growth) of n-GaN material in areas not occupied by the dielectric layer. A surface treatment on the exposed n-GaN layer 1 (or substrate) may be performed to remove any surface damage and contamination associated with the deposition of the dielectric layer 2.

[0047] Next, selective area growth (SAG) is performed to vertically grow (add) n-type GaN to form or extend the n-GaN layer 1 in areas free of the patterned dielectric material, thereby forming extended / grown / protruding n-GaN layers 1a. Such growth areas (i.e., extended n-GaN layers 1a) result from the chemical inertness of the dielectric layer 2. The growth conditions during this extended SAG, such as temperature, gas ratio, pressure, and gas flow, combined with the pattern design and orientation, define the resulting structure(s) (i.e., extended n-GaN layer / region(s) 1a). However, the resulting structure may include at least one of the five available crystallographic planes: (0001), (11-22), (1-101), (11-20), or (1-100). As a result of SAG, n-type GaN 1 is formed / extended vertically through the opening in the dielectric layer 2 from the n-type GaN previously deposited on the substrate or n-GaN layer 1. Depending on the growth conditions, the lateral growth of the extended n-GaN layer 1a overlying the top of the dielectric layer 2 varies. The overlapping growth of the extended n-GaN layer 1a over the dielectric layer 2 is necessary to form the sidewalls of the extended n-GaN layer 1a (i.e., a half or full V-groove shape). The final structure of the extended n-GaN layer 1a affects the subsequent growth of the LED and the resulting color tunability. For example, an extended n-GaN layer 1a with a (1-101) plane promotes longer wavelength emission compared to an extended n-GaN layer 1a with sidewalls in the (1-100) or (11-20) planes, which promote shorter wavelength emission.

[0048] The MQW regions 3a-3c are grown on the extended n-GaN layer 1a, created by SAG. The MQW regions 3a-3c comprise parallel, thin (e.g., 0.5-10 nm) InGaN layers, each followed by a low-indium-content InGaN barrier, GaN layer, or AlGaN layer, each 0.5-30 nm thick. Similarly, MQW growth occurs only along the GaN facets and not on the dielectric layer 2. A moderate indium concentration, e.g., between 5% and 35%, is selected for growth. For example, a moderate indium concentration results in green emission within the planar MQW region 3a, away from any topography. Further optimization can be employed to ensure that each individual quantum well has a unique indium content for the purposes of enhancing emission color and / or improving material quality. Simultaneous growth of the MQW regions 3c along the sidewalls of the extended n-GaN layer 1, such as on the (1-101) plane, leads to reduced indium incorporation. The resulting indium-deficient incorporation of the sidewall-conformed MQW region 3c can be, for example, 0-25%. By way of example, the indium-deficient MQW region 3c exhibits blue light emission. The sidewall-conformed MQW region 3c has a lower indium content than the c-plane-conformed MQW region 3a due to indium migration and surface differences between these planes. A transitional indium-rich MQW region 3b (referred to herein as the "transition region") is formed between the portion of the c-plane-conformed MQW region 3a away from any sidewalls and the sidewall-conformed MQW region 3c. The indium-rich MQW transition region 3b can have an indium content between 20-100% due to, for example, indium migration from the sidewalls and reduced compressive stress caused by free surfaces during growth. The indium content of the transition region 3b decreases toward the expected indium content of the planar MQW region 3a as it moves away from the presence of the sidewalls. For example, the indium-rich MQW region 3b emits red light.The proposed structure effectively modifies the indium distribution laterally to form regions of low indium content (MQW region 3c), medium indium content (MQW region 3a), and high indium content (MQW region 3b) to emit light across the entire visible color spectrum.

[0049] To advantageously guide charge carriers, an EBL4 containing AlGaN (e.g., p-doped AlGaN) is utilized. The aluminum content may be, for example, between 1 and 100%, the thickness of the AlGaN layer may be, for example, between 0.5 and 300 nm, and the p-doping concentration may be, for example, between 1E16 and 1E20 per cubic centimeter. In some advantageous embodiments, the EBL may be, for example, 16 nm thick and have an aluminum concentration of, for example, 5%. Similarly, EBL4 is grown simultaneously on the MQW regions 3a-3c rather than on the dielectric layer 2. AlGaN has a smaller lattice constant than GaN, which leads to polarization forces at the AlGaN interfaces in proportion to the aluminum content. The polarization forces induce band bending in the EBL4, increasing the barrier height for hole injection in the direction perpendicular to the c-plane. However, for EBL4 formed on the sidewalls, the barrier height for holes is reduced, or perhaps not increased at all, due to the formation of semipolar or nonpolar planes, respectively. Beneficially, the reduced hole barrier height along the sidewalls of the EBL 4 is utilized to provide crystal orientation specific hole injection. The distribution of indium in the EBL 4 and MQW regions 3a-3c can enable fully color tunable light emission.

[0050] At low currents and corresponding low levels of band bending, holes can initially be injected only laterally from the EBL 4 overlying the sidewalls, filling the indium-rich MQW transition region 3b and producing longer wavelength emission, such as red light. As the current density and corresponding band bending increase, vertical injection from the conventional c-plane EBL 4 into the MQW region 3a instead dominates, producing intermediate wavelength emission, such as green light. As the current density and corresponding band bending increase further, the MQW region 3c fills with carriers along the band bending from the MQW region 3a, and together they produce shorter wavelength emission, such as blue light.

[0051] In other words, as the applied voltage and respective current increase, different paths exist for current to flow. More fully explained, the third doped region is important because holes from this layer are injected into MQW regions 3b and / or 3c. Of particular importance, this occurs at low voltages and currents, where holes are laterally injected from p-GaN layer 5 (as explained more fully below) and fill indium-rich transition region 3b, an MQW near the sidewall but still parallel to the top surface. As the voltage increases and the current correspondingly rises, the initial energy barrier from EBL 4 decreases, resulting in vertical injection dominating, and holes instead more readily filling region 3a. Region 3a contains less indium compared to region 3b, which leads to shorter wavelength emission, such as green light rather than red light. Subsequently, as the voltage is further increased and the current rises further, holes are again injected laterally, this time into the MQW conforming to sidewall 3c. These MQWs (region 3c) have less indium than region 3a, leading to emission of even shorter, bluer wavelengths. Combined with this, the MQWs in region 3a also start to emit blue light instead of green.

[0052] Note that the EBL4 provides a small barrier to holes, which causes this initial lateral injection at low voltages and currents. As the voltage increases, the barrier to holes from the EBL4 is effectively eliminated. Thus, essentially, the EBL has no effect on lateral injection, once 3c plays a role.

[0053] Above the MQW regions 3a-3c, a p-type GaN layer 5 is grown conformally on the EBL 4, with substantial (or unintentional) growth not occurring on the dielectric layer 2. The p-type GaN layer 5 may include multiple doped layers with an alloy of indium and aluminum to influence the lateral hole concentration and for purposes such as improving contact resistance and current flow direction. Importantly, the p-GaN layer 5 functions as a hole source and has a p-type doping concentration of 1E16-1E21 per cubic centimeter. In practical devices using the LED structural layers described herein, the hole concentration is more limited than the electron concentration due to the high ionization energy of many conventional p-type dopants in the GaN material system. For shorter wavelength emission, it is important to have the p-GaN layer 5 designed to provide sufficient holes to the lower MQW region 3c. A sufficient hole supply here means that the transport of holes and corresponding current to different crystal planes, such as the sidewall length, is not limited by the resistivity of the p-GaN layer 5. To achieve a sufficient supply of holes, the resistivity of the p-GaN layer 5 can be designed to be less than 10 ohm-cm. If this is not readily achievable, or to further reduce the overall resistance, the structure can further include an upper, low-resistivity (less than 3 ohm-cm) current spreading layer, such as a heavily doped p-InGaN layer (not shown), on top of the p-GaN layer 5. In other words, the resistance of the p-GaN layer 5 can often be too high (greater than 10 ohm-cm), resulting in few holes being able to migrate downward to fill the MQW region 3c. Therefore, the design of the LED structure is designed so that it is not limited by the resistance of the p-GaN layer 5. This can include having sufficient doping and thickness of the p-GaN layer 5, or using a low-resistivity current spreading layer, such as a metal layer uniformly present on top of the p-InGaN or p-GaN layer 5. To minimize the increase in resistivity due to factors such as scattering, the thickness of the p-GaN layer 5 may be increased (e.g., between 10 and 500 nm), the doping of the p-GaN layer 5 may be increased to provide more holes, and the use of an external top metal (see p-type contact 7 in Figure 3B) may be employed to spread the current.The outer top metal may be on top of the p-InGaN layer (if employed) or directly on top of the p-GaN layer 5 .

[0054] As an example, a p-type GaN layer 5 between 50 and 300 nm thick with a doping level of at least 1E19 per cubic centimeter and a resistivity of less than 9 ohm-cm can be employed, along with an additional top layer of p-InGaN with 3-10% indium and a doping level of at least 1E20 per cubic centimeter. Note that the thickness of the p-GaN layer 5 corresponds to the thickness perpendicular to the c-plane; the resulting thickness along the semipolar or nonpolar sidewalls will be greater due to the enhanced growth rate from the doping. The combination of the extended n-GaN layer 1a, MQW regions 3a-3c, EBL 4, and p-GaN layer 5 forms the active device layers of a single, fully color-tunable LED.

[0055] As another example, to achieve sufficient hole supply if no additional top layer of p-InGaN is employed, a p-type GaN layer 5 between 100 nm and 300 nm thick may have a doping level of at least 1.5E19 per cubic centimeter and a resistivity of less than 8 ohm·cm.

[0056] Referring to FIG. 1B, multiple selectively grown protrusions / structures are utilized together to form a single, full-color tunable LED 100b. In some embodiments, a single, full-color tunable LED may include fused protrusions, initially independently selectively grown, for optimized color emission. These selectively grown protrusions follow the same types of growth techniques and practices as the separate structures of FIG. 1A, with slight differences due to the patterning of the dielectric layer 2. Designing the dielectric layer 2 with closely spaced openings may result in partial or complete fusion of the selectively grown protrusions. Partial fusion can be advantageously applied in select embodiments to reduce the amount of long-wavelength emission. The reduction in longer-wavelength emission is due to less indium incorporation in the MQW transition region 3b around the partial fusion due to less compressive strain relaxation and the shorter length of the MQW region 3c on the sidewalls, reducing indium diffusion. In such a structure, the EBL 4 and p-GaN layer 5 also partially fuse and share conductivity. The p-GaN layer 5 may also partially or completely planarize the area between the structures.

[0057] Designing the dielectric layer 2 to have a smaller opening in such an LED structure has the opposite effect to a partially fused structure. Due to the small device area, e.g., less than 30 μm, the majority of the device exhibits compressive strain relaxation in the MQW regions 3a-3b. Furthermore, if the structure were spaced further apart on one or more sides, more indium could be incorporated as it diffuses out of the dielectric layer 2. The resulting selectively grown structure would have a shifted overall spectrum, resulting in longer wavelength emission, particularly from the MQW regions 3a-3b.

[0058] The use of multiple selectively grown structures in color-tunable LEDs can be a useful technique for providing additional control over the emission spectrum at various current densities. In certain embodiments, it is desirable to use spacing between multiple selectively grown structures to enhance long wavelength emission at the expense of mid- and short wavelength emission.

[0059] Referring to FIG. 2, forming the initial pattern of the dielectric layer 2 is a critical step for tailoring the device outcome because it translates into the pitch and size of the resulting LED structures. By way of example, isolated feature designs 6a-6d, each comprising a circle, triangle, hexagon, or square, can be formed. Isolated feature designs 6a-6d have the effect of increasing indium diffusion and incorporation into the structure compared to denser designs, as indium on the dielectric layer 2 diffuses and becomes incorporated into these structures. The term "isolated" is defined herein as having a spacing greater than two times the feature width of the device, but may also be utilized with other structures to form arrays. The openings in the isolated feature designs can have sizes ranging from 100 nm to 500 μm, for example.

[0060] Having multiple openings 6e patterned in the dielectric layer 2 close to one another can be utilized for the growth of ordered, high-density arrays. The term "close" is defined herein as a spacing less than twice the feature width. Each of the multiple openings 6e in the dielectric layer 2 may be, for example, 100 nm to 500 μm. When multiple selectively grown structures together form a complete LED, openings 6(f) of different shapes can be fabricated. To modify the light emission pattern, openings 6f of the same shape but different sizes, or different shapes and sizes, can be fabricated to form these multiple selectively grown LEDs. The spacing design of these differently sized and / or shaped openings 6f can be oriented into a 2D array, or individual openings can be advantageously grouped, with the grouping conforming to the overall 2D array. Compared to isolated features, closely spaced features compete for available indium, leading to a shorter wavelength range.

[0061] Instead of shapes, line openings 6g may be patterned through the dielectric layer 2, resulting in one or more lines that can later comprise a full-color tunable LED. After selective area growth of the completed LED structure, vertical etching can be performed to transform the grown lines into discrete LED rectangles or other suitable shapes. The etching to form the line openings 6g may be as small as 100 nm and as large as 500 μm, with spacings between 100 nm and 500 μm, or as small as 1 μm or as long as 1 cm. The spacing of the line openings 6g, similar to FIG. 1B, will have a significant effect on the growth of the resulting selectively grown structure, with closely spaced lines resulting in shorter wavelengths and small and / or separated lines resulting in longer wavelengths. The orientation of the line openings 6g during growth can affect the resulting sidewalls and the amount of lateral growth. Line openings oriented parallel to the <10·0> direction may favor low lateral growth, while line openings oriented parallel to the <21·0> direction favor higher lateral growth due to different sidewall crystal formation.

[0062] FIG. 3A shows an example in which metallization forms electrical contacts for an individual selectively grown color-tunable LED 300a. For contacts to the n-type GaN layer 1, openings can be made in the dielectric layer 2 followed by selective or patterned deposition of a low work function metal or formation of a tunneling contact. As an example, Ti-Al-Ni-Au can be used, followed by annealing to provide a low-resistance n-GaN layer contact 8. Next, for the p-GaN layer 5, the p-type contact 7 can be directly formed by selective or patterned deposition of a high work function metal or formation of a tunneling contact, such as, but not limited to, Ni-Au (or a combination of Ni-Au with an indium tin oxide layer or mixture), followed by annealing. The p-type contact 7 can be selectively formed only on the c-plane surface, or it can extend to all of the surface of the p-GaN layer 5, including the sidewalls. Advantageously, coating the sidewalls with p-type contact 7 can aid in current spreading within p-GaN layer 5 and, specifically, hole injection into MQW region 3c for shorter wavelength light emission. P-type contact 7 may be fully or partially transparent in region (e.g., using indium tin oxide) for improved light emission.

[0063] 3B shows an example in which multiple selectively grown structures are utilized together to form a single, full-color, tunable LED 300b, whether by forming separate features 6e and 6f or by forming lines 6g in the dielectric layer 2 prior to growth. As noted above, for the n-GaN layer 1 contact 8, an opening can be created in the dielectric layer 2, followed by selective or patterned deposition of a low work function metal or a tunneling contact. As an example, Ti-Al-Ni-Au can be utilized, followed by annealing to provide a low-resistance n-GaN layer 1 contact 8. For the n-GaN layer 1 contact 8, a contact as small as a single contact can be shared among multiple selectively grown structures if the n-GaN layer 1 is sufficiently doped and the structures are in close proximity. Next, as described above, for the p-GaN layer 5, a p-type contact 7 may be formed directly by selective or patterned deposition of a high work function metal or a tunneling contact, such as, but not limited to, Ni-Au (or a combination of Ni-Au and an indium tin oxide layer or mixture), followed by annealing. The p-type contact 7 is shared between multiple selectively grown structures on the surface of the p-GaN layer 5, including the sidewalls, and any dielectric layers 2 between them. If not all structures are partially or completely fused, sharing the p-type contact 7 between the structures is necessary, with the added benefit of enhancing current spreading in the p-GaN layer 5 for shorter wavelengths and aiding hole injection into the MQW region 3c. The p-type contact 7 may be fully or partially transparent in the region (e.g., using indium tin oxide) for improved light emission.

[0064] For both the LED structures of Figures 3A and 3B, it is often desirable to integrate the final full-color-tunable LED structure into a completed display system, and there are several ways this can be achieved. By way of example, one such technique is to invert the entire color-tunable LED structure and bond it to a pre-fabricated control wafer to integrate the transistor with the display. Another exemplary technique is through monolithic integration by pairing the control transistor above or below the n-type GaN layer 1. Active, passive, or custom current driver matrix array configurations can be created to control the full-color-tunable LEDs with drive methods such as pulse-width modulation or steady-state current supply. In either case, additional metallization, etching, dielectric deposition, and other such corresponding processes may be performed.

[0065] Active, passive, or custom current drivers can have matrix array configurations that can be implemented in a variety of different ways. The current driver can include a driver circuit, which can be fabricated on a silicon wafer using standard CMOS process technology. The fabricated silicon wafer containing the driver circuit can be bonded to the entire color-tunable LED wafer or individual arrays. Bonding approaches can include metal eutectic bonding, laser lift-off, indium-based dots, interposers, and other techniques. Alternatively, monolithic approaches can be used for the driver circuit, such as those disclosed in U.S. Patent No. 11,011,571 issued to Hartensveld et al., which integrate the driver circuit directly from the same GaN-based material. Using GaN-based materials for both the color-tunable LEDs and the driver circuit can significantly reduce or completely eliminate the need for external silicon wafers or dies.

[0066] Whether a single structure or multiple selectively grown structures are used, the resulting device's emission color changes based on current density, starting with long wavelengths and progressing to shorter wavelengths. The resulting turn-on voltage for these full-color tunable LEDs can also be lower than conventional c-plane LEDs due to the lateral injection of carriers in the technology presented herein. Strategically, the structure is designed so that red emission occurs at low current densities, green emission at medium current densities, and blue emission at high current densities. As an example, a separated 35 μm 2 For color-tunable LEDs, the current density is approximately 6×10 for red and blue, respectively. -4 ~Approx. 8×10 -3 mA / μm 2 The range can be as follows:

[0067] As mentioned above, at low current densities, longer wavelengths are emitted from the indium-rich MQW transition region 3b due to the lateral injection of holes due to the barrier reduction engineered through the EBL 4. With increasing current density and corresponding band bending, vertical injection from the c-plane becomes dominant, leading to green emission from the MQW region 3a away from either sidewall. As the current density and band bending increase further, the MQW region 3c conforming to the sidewalls fills, causing band bending in the MQW region on the c-plane of region 3a, resulting in blue light.

[0068] Increasing current density presents a problem in that current is generally proportional to light output. This means that red light is dimmer than green and much dimmer than blue. To balance the colors, the duty cycle of each color is controlled so that blue is on for only a small portion of a period, green is on a little longer, and red is on all the time. This allows all colors to be referenced to the lowest current density red light. However, mismatches between emitted colors can be partially mitigated through the techniques presented herein. To achieve mixed-color emission, such as white or purple, field-sequential color modulation is utilized, in which colors are appropriately weighted and swapped between two or more emission wavelengths to produce the desired output. For example, the operating points of yellow and blue can be rapidly swapped with each other when appropriately weighted to create the perception of white light. Utilizing these concepts, fully color-tunable LED technology becomes possible.

[0069] Thus, as shown and described as examples herein, the present technology provides monolithic multicolor LEDs for use in displays (including VR or AR glasses / visors / headsets, etc.), commercial lighting, communications, etc. Monolithic integration of color-tunable LEDs without the need for color converters reduces complexity, provides better performance, and lowers cost in many applications. Monolithic is defined for some examples herein as the same InGaN / GaN, III-N material system used within the same wafer. In monolithic devices, LEDs and transistors may also be fabricated on a single wafer. Examples of the claimed technology can provide monolithic color-tunable LEDs without Eu doping, growth of separate MQW regions, or excessive increase in planar indium percentage.

[0070] Although embodiments are described above with reference to a fully color-tunable LED system, the LED system described in any of the above embodiments may alternatively be a partially color-tunable LED system. Such alternatives are considered to be within the spirit and scope of the present invention and may therefore take advantage of the configurations and embodiments described above.

[0071] Having thus described the basic concepts of the present technology, it will be apparent to those skilled in the art that the above detailed disclosure is intended to be given by way of example only, and not by way of limitation. Although not expressly stated herein, it will be apparent to those skilled in the art that various changes, improvements, and modifications are conceivable and intended. These changes, improvements, and modifications are intended to be suggested by this specification and are within the spirit and scope of the present technology. Furthermore, the described order of process elements or sequences, or the use of numbers, letters, or other designations, are therefore not intended to limit the scope of the present invention.

Claims

1. 1. An LED system having color tunability in response to changes in drive current density, the system comprising: one or more pixel elements each including one or more LEDs, each of said one or more LEDs comprising: a first layer; and a patterned dielectric layer formed on the first layer, the patterned dielectric layer including an opening; and a second layer formed on the first layer through the opening to provide a pattern along one surface of the second layer, the pattern along the one surface of the second layer including one or more shaped protrusions having one or more spacing features to promote controlled color emission in an MQW layer of an MQW region, the second layer being actively doped; the MQW region formed across the one surface of the second layer, each of the MQW layers being alloyed with a percentage of indium that promotes the controlled color emission, the portion of the MQW layer conforming to a sidewall of the protrusion having a lower indium alloy percentage than other portions of the MQW layer; an electron blocking layer formed on the MQW region and having a charge opposite to that of the second layer, the electron blocking layer being actively doped; a third layer formed on the electron blocking layer and having a charge opposite to that of the second layer, the third layer being actively doped; The portion of the MQW layer conforming to the sidewall of the protrusion is capable of emitting light in the blue wavelength range of 400 nm to 520 nm.

2. Each of the one or more LEDs comprises:

2. The system of claim 1, further comprising a transition region in each MQW layer between each of the portions of the MQW layer that conform to the sidewall of the protrusion and each of the other portions of the MQW layer, the transition region having a higher concentration of the indium alloy percentage than the other portions of the MQW layer, the indium alloy percentage decreasing with distance from the portion of the MQW layer that conforms to the sidewall of the protrusion.

3. The system of claim 2 , wherein holes are injected at least laterally from the third layer into the transition region.

4. The system of claim 1 , wherein the first layer is actively doped.

5. 10. The system of claim 1, wherein the second layer includes at least one crystal plane selected from five crystal planes: (0001), (11-22), (1-101), (11-20), or (1-100).

6. The system of claim 1 , wherein the electron blocking layer comprises AlGaN.

7. The system of claim 1 , wherein the third layer comprises p-type GaN.

8. 8. The system of claim 7, wherein the third layer further comprises at least one characteristic selected from the group consisting of a resistivity less than 10 ohm-cm, a p-type doping concentration level of 1E16 to 1E21 per cubic centimeter, a thickness of 10 to 500 nm, and combinations thereof.

9. The system of claim 1 , wherein the one or more LEDs each further include a p-type InGaN layer formed on the third layer.

10. The system of claim 1 , wherein the one or more LEDs each further include a metal layer formed over the third layer.

11. 1. A method of operating an LED system having color tunability in response to changes in drive current density, the method comprising: providing one or more pixel elements each including one or more LEDs, each of said one or more LEDs comprising: a first layer; and a patterned dielectric layer formed on the first layer, the patterned dielectric layer including an opening; and a second layer formed on the first layer through the opening to provide a pattern along one surface of the second layer, the pattern along the one surface of the second layer including one or more shaped protrusions having one or more spacing features to promote controlled color emission in an MQW layer of an MQW region, the second layer being actively doped; the MQW region formed across the one surface of the second layer, each of the MQW layers being alloyed with a percentage of indium that promotes the controlled color emission, the portion of the MQW layer conforming to a sidewall of the protrusion having a lower indium alloy percentage than other portions of the MQW layer; an electron blocking layer formed on the MQW region and having a charge opposite to that of the second layer, the electron blocking layer being actively doped; a third layer formed on the electron blocking layer and having a charge opposite to that of the second layer, the third layer being actively doped; applying a current to one of the LEDs such that holes from the third layer are injected into the portion of the MQW layer conforming to the sidewall of the protrusion, such that the portion of the MQW layer conforming to the sidewall of the protrusion emits light in the blue wavelength range of 400 nm to 520 nm; A method comprising:

12. Each of the one or more LEDs comprises:

12. The method of claim 11, further comprising a transition region in each MQW layer between each of the portions of the MQW layer that conform to the sidewall of the protrusion and each of the other portions of the MQW layer, the transition region having a higher concentration of the indium alloy percentage than the other portions of the MQW layer, the indium alloy percentage decreasing with distance from the portion of the MQW layer that conforms to the sidewall of the protrusion.

13. 13. The method of claim 12, further comprising applying another current to one of the LEDs such that holes are injected at least laterally from the third layer into the transition region such that the transition region emits in a red wavelength range of 580 nm to 700 nm, the another current being lower than the current applied to emit the blue wavelengths.

14. 14. The method of claim 13, further comprising applying an additional current to one of the LEDs such that holes are injected from the third layer at least vertically into a portion of the MQW layer away from the transition region and into a portion of the MQW layer conforming to the sidewall of the protrusion, such that a portion of the MQW layer away from the transition region emits light in a green wavelength range of 520 nm to 580 nm, the additional current being lower than the current applied to emit the blue wavelength and higher than the other current applied to emit the red wavelength.

15. The method of claim 11 , wherein the first layer is actively doped.

16. 12. The method of claim 11, wherein the second layer comprises at least one crystallographic plane selected from the five crystallographic planes: (0001), (11-22), (1-101), (11-20), or (1-100).

17. The method of claim 11 , wherein the electron blocking layer comprises AlGaN.

18. The method of claim 11 , wherein the third layer comprises p-type GaN.

19. 19. The method of claim 18, wherein the third layer further comprises at least one characteristic selected from the group consisting of a resistivity less than 10 ohm-cm, a p-type doping concentration level of 1E16 to 1E21 per cubic centimeter, a thickness of 10 to 500 nm, and combinations thereof, such that upon application of the current, the holes can be injected from the third layer into the portion of the MQW layer that conforms to the sidewall of the protrusion to achieve the emission in the blue wavelength range of 400 nm to 520 nm.

20. The method of claim 11 , wherein each of the one or more LEDs further comprises a p-type InGaN layer formed on the third layer.

21. The method of claim 11 , wherein each of the one or more LEDs further comprises a metal layer formed over the third layer.

22. 1. An LED system having color tunability in response to changes in drive current density, the system comprising: a current driver configured to drive a change in current density; one or more pixel elements coupled to the current driver, each pixel element including one or more LEDs, each of the one or more LEDs: a first layer; and a patterned dielectric layer formed on the first layer, the patterned dielectric layer including an opening; and a second layer formed on the first layer through the opening to provide a pattern along one surface of the second layer, the pattern along the one surface of the second layer including one or more shaped protrusions having one or more spacing features to promote controlled color emission in an MQW layer of an MQW region, the second layer being actively doped; the MQW region formed across the one surface of the second layer, each of the MQW layers being alloyed with a percentage of indium that promotes the controlled color emission, the portion of the MQW layer conforming to a sidewall of the protrusion having a lower indium alloy percentage than other portions of the MQW layer; an electron blocking layer formed on the MQW region and having a charge opposite to that of the second layer, the electron blocking layer being actively doped; a third layer formed on the electron blocking layer and having a charge opposite to that of the second layer, the third layer being actively doped; The portion of the MQW layer conforming to the sidewall of the protrusion is capable of emitting light in the blue wavelength range of 400 nm to 520 nm.

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