Patent Publication Number: US-2023154966-A1

Title: Multi-led structures

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     Reference is made to U.S. patent application Ser. No. 16/778,948, filed Jan. 31, 2020, entitled Micro-LED Color Display with Different Current Densities by Bower et al., the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD The present disclosure relates to micro-light-emitting diode structures for transfer printing. 
     BACKGROUND 
     Large-format inorganic light-emitting diode (iLED) displays are used in outdoor and stadium displays. Because the iLEDs are relatively large, for example one square millimeter, they are restricted to relatively low-resolution displays. However, as iLED technology develops, there is increasing interest in applying smaller iLEDs to displays having higher resolution. Full-color displays typically include pixels with three (or more) emitters, usually red, green, and blue emitters, distributed in an array over the display surface. For example, inorganic light-emitting diodes used in flat-panel displays are disclosed in U.S. Pat. No. 9,818,725 entitled Inorganic-Light-Emitter Display with Integrated Black Matrix. 
     Inorganic light-emitting diodes are semiconductor light sources relying on p-n junctions to emit light when a suitable voltage is applied across the light-emitting diode. The color of the light emitted from the iLED corresponds to the energy bandgap of the semiconductor. Thus, different semiconductor materials can emit different colors of light when stimulated with suitably different voltages. Typical materials include InGaN (emitting blue light), AlGaP (emitting green light), and AlGaAs (emitting red light), among many other materials. Blue-light-emitting materials can emit light at voltages ranging from 2.5-3.7 volts, green-light-emitting materials can emit light at voltages ranging from 1.9-4 volts, and red-light-emitting materials can emit light at voltages ranging from 1.6-2 volts, for example as taught in U.S. Pat. No 10,453,826, entitled Voltage-Balanced Serial ILED Pixel and Display. Moreover, the efficiency with which the different materials emit light can depend on the density of the current passing through the materials. 
     In order to provide the different voltages and currents needed by the different light-emitting diodes emitting different colors of light in a full-color pixel, a separate power supply can supply power, ground, and control signals to each color light emitter in each multi-color pixel. By supplying the appropriate voltages and currents to each light emitter, the light emitters efficiently emit light. However, providing three (or more) different power, ground, and control signals to each multi-color pixel requires three times as many power supplies, lines, and connections, reducing the available space in the display and increasing costs. 
     Alternatively, a single power supply can provide power to all three different iLEDs in the full-color pixels. In this case any excess voltage is dropped across other circuit components, increasing heat and reducing overall display system power efficiency. 
     There is a need, therefore, for an improved pixel and LED structure that improves power efficiency and reduces circuitry, wiring, and assembly costs. 
     SUMMARY 
     According to some embodiments of the present disclosure, a multi-LED structure comprises a multi-LED native substrate and a patterned semiconductor layer comprising semiconductor portions disposed on or over the multi-LED native substrate. The multi-LED native substrate can be a single, unitary, and contiguous substrate on which is disposed the semiconductor portions. In some embodiments, the multi-LED native substrate is not divided into separate or distinct portions (e.g., each portion comprising a separate and independent individual semiconductor portion) that can be separately disposed in different locations and is therefore a single, unitary, and contiguous substrate. The semiconductor portions define at least a first LED and a second LED separate from the first LED. The first LED and the second LED each comprise (i) a first layer having a cantilever portion and a base portion, and (ii) a second layer disposed only over the base portion of the first layer and comprising an emission portion. In some embodiments, at least a portion of the first layer is shared between the first LED and the second LED. In some embodiments, at least a portion of the first layer is at least a portion of the multi-LED native substrate. An LED electrode is disposed on at least a portion of the multi-LED native substrate or disposed on at least a portion of a non-semiconductor structure in the semiconductor layer, or both. The LED electrode is also disposed on at least a portion of the first LED and on at least a portion of the second LED so that the LED electrode electrically connects the first LED to the second LED. In some embodiments, the cantilever portion of the first LED extends in a first direction and the base portion of the first LED extends in a second direction different from the first direction. In some embodiments, the cantilever portion of the first LED has a first cantilever length, the cantilever portion of the second LED has a second cantilever length, and an LED emission separation distance between the emission portion of the first LED and the emission portion of the second LED is less than or equal to the first cantilever length and less than or equal to the second cantilever length. In some embodiments, both are true. The first LED and the second LED can be electrically connected in serial or electrically connected in parallel. The multi-LED structure can comprise more than two semiconductor portions and LEDs that are electrically connected in any combination of series and parallel for any combination of LEDs. For example, the semiconductor portions can define at least a third LED separate from the first LED and separate from the second LED. Separate LEDs have independent emission portions that can be spatially separate or electrically separate in the absence of electrodes. Separate LEDs can share at least a portion of a cantilever portion or can have separate cantilever portions. The first LED and the second LED can have any one or combination of substantially the same size, substantially the same area over the multi-LED substrate, and different size or same size light-emitting areas of the first LED and the second LED. 
     The multi-LED structure can comprise a tether or a broken or fractured tether. In embodiments, the first and second LEDs do not comprise a tether or portion of a tether. The multi-LED structure can be transfer printed, for example micro-transfer printed. The multi-LED structure can be a bare die without an enclosing package, e.g., a ceramic or plastic package. 
     According to embodiments of the present disclosure, the multi-LED native substrate has a surface and the first direction of the cantilever portion is orthogonal to the second direction of the base portion and both the first and the second directions are substantially parallel to the surface. According to some embodiments, the cantilever portion extends in a same direction as the base portion. According to some embodiments, the first LED and the second LED extend in substantially a same direction. According to some embodiments, the first LED and the second LED extend in substantially orthogonal directions. 
     According to embodiments of the present disclosure, the multi-LED structure can comprise a first LED contact disposed on the first LED and a second LED contact disposed on the second LED, the first LED contact and the second LED contact separate from the LED electrode and not electrically connected to the LED electrode. The LED contact separation distance between the first and second LED contacts separate from the LED electrode can be greater than a first LED length of the first LED, greater than a second LED length of the second LED, or greater than the larger of the first LED length and the second LED length. A length of an LED can be the longest dimension of the LED parallel to a surface of the multi-LED native substrate. The separate first and second LED contacts can be electrically connected to an external device through wires separate from the LED electrode. For example, the multi-LED structure can be disposed on a target substrate having target substrate wires that are electrically connected to the separate first and second LED contacts, for example using photolithographic methods and materials. 
     According to some embodiments of the present disclosure, the multi-LED native substrate has a center, a first edge, and a second edge different from the first edge. In some embodiments, the first LED contact separate from the LED electrode is disposed closer to the first edge than to the center and the second LED contact separate from the LED electrode is disposed closer to the second edge than to the center. In some embodiments, the multi-LED native substrate has a center, a first corner, and a second corner different from the first corner, and the first LED contact separate from the LED electrode is disposed closer to the first corner than to the center and the second LED contact separate from the LED electrode is disposed closer to the second corner than to the center. 
     According to some embodiments, the multi-LED native substrate is a first multi-LED native substrate and the multi-LED structure comprises a second multi-LED native substrate disposed on the first multi-LED substrate, comprises other LEDs separate and independent of the first and second LEDs disposed on the second multi-LED native substrate, or comprises both. The one or more LEDs (first and second LEDs) disposed on the first multi-LED native substrate and the other LEDs separate and independent of the first and second LEDs disposed on the second multi-LED native substrate comprise a semiconductor material different from a semiconductor material of the semiconductor layer, and can, for example can emit different colors of light than the first and second LEDs can emit. 
     According to some embodiments, one or more other LEDs separate from the first LED and separate from the second LED are disposed on the first multi-LED native substrate. The one or more LEDs (first and second LEDs) disposed on the first multi-LED native substrate and the other LEDs separate and independent of the first and second LEDs disposed on the first multi-LED native substrate comprise a semiconductor material different from a semiconductor material of the semiconductor layer, and can, for example can emit different colors of light than the first and second LEDs can emit. 
     According to some embodiments, the multi-LED native substrate comprises at least a portion of the first layer or the first layer comprises at least a portion of the multi-LED native substrate and the multi-LED native substrate is electrically conductive. 
     According to embodiments of the present disclosure, a multi-LED component structure comprises a component substrate and a first multi-LED structure is disposed on the component substrate. The multi-LED component structure can comprise a second multi-LED structure disposed on the component substrate, can comprise one or more other LEDs disposed on the component substrate, or can comprise both. In some embodiments, the first multi-LED structure and the second multi-LED structure can emit different colors of light. In some embodiments, the first multi-LED structure and the one or more other LEDs emit different colors of light. The first LED and the second LED of the first multi-LED structure can be electrically connected in series and the first LED and second LED of the second multi-LED structure can be electrically connected in parallel. 
     For example, the first multi-LED structure can emit red light and the second multi-LED structure can emit green or blue light. 
     According to some embodiments, the multi-LED structure comprises a third individual and separate LED separate from the first and second LEDs of the multi-LED structure or a third multi-LED structure disposed on the component substrate and the third LED or third multi-LED structure emits a color of light different from a color of light emitted by the first and second LEDs of the first multi-LED structure and different from a color of light emitted by the one or more other LEDs or second multi-LED structure. According to some embodiments, the multi-LED component structure comprises another LED or second multi-LED structure disposed on the component substrate, a third LED or third multi-LED structure disposed on the component substrate, and a fourth LED or fourth multi-LED structure disposed on the component substrate. The one or more other LEDs or second multi-LED structure, the third LED or third multi-LED structure, and the fourth LED or fourth multi-LED structure can be electrically serially connected. According to some embodiments, the second LED or second multi-LED structure emits a second color of light, the third LED or third multi-LED structure emits a third color of light, and the fourth LED or fourth multi-LED structure emits a fourth color of light and the second, third, and fourth colors of light are all different. The second color of light can be red, the third color of light can be green, and the fourth color of light can be blue. 
     According to some embodiments, an LED wafer comprises a wafer comprising sacrificial portions separated by anchor portions and a multi-LED structure is disposed entirely and completely over each sacrificial portion and each multi-LED structure is physically connected to an anchor with a tether. 
     According to some embodiments of the present disclosure, a method of making a multi-LED structure comprises providing a multi-LED native substrate and disposing semiconductor layers on the multi-LED native substrate. The semiconductor layers are patterned to form spatially separated semiconductor portions. The semiconductor portions define at least a first LED and a second LED separate from the first LED. The first LED and the second LED each comprise a first layer having a cantilever portion and a base portion. A patterned second layer is disposed only over the base portion. An LED electrode is disposed on at least a portion of the multi-LED native substrate or on at least a portion of a non-semiconductor structure in the semiconductor layer. The LED electrode is also disposed on at least a portion of the first LED and on at least a portion of the second LED, so that the LED electrode electrically connects the first LED to the second LED. In some embodiments, the cantilever portion of the first LED extends in a first direction and the base portion of the first LED extends in a second direction different from the first direction. In some embodiments, the cantilever portion of the first LED has a first cantilever length, the cantilever portion of the second LED has a second cantilever length, and an LED emission separation distance between the emission portion of the first LED and the emission portion of the second LED is less than or equal to the first cantilever length and less than or equal to the second cantilever length. In some embodiments, both are true. 
     Methods of the present disclosure comprise providing an LED source wafer comprising sacrificial portions separated by anchor portions. A multi-LED structure is disposed entirely and completely over each sacrificial portion and each multi-LED structure is physically connected to an anchor with a tether. The sacrificial portions are etched to suspend each multi-LED structure over a corresponding sacrificial portion. A stamp and a target substrate are provided, and each multi-LED structure is micro-transfer printed from the multi-LED native substrate to the target substrate with the stamp. 
     According to an embodiment of the present disclosure, a multi-LED structure comprises an electrically conductive semiconductor layer comprising a cantilever portion and two or more spatially separated base portions, a separate emissive portion comprising a light-emissive semiconductor portion disposed on each base portion, and an LED contact pad disposed on each emissive portion. Each emissive portion emits light when electrical power is provided to the cantilever portion and the LED contact pad. 
     According to some embodiments of the present disclosure, a multi-LED component structure comprises a component substrate, a first multi-LED native substrate disposed on the component substrate, the first multi-LED native substrate having a first LED and a separate second LED disposed thereon, wherein the first LED and the second LED are native to the first multi-LED native substrate and electrically connected, and a second multi-LED native substrate having a third LED and a separate fourth LED disposed thereon, the third LED and the fourth LED are native to the second multi-LED native substrate and electrically connected, wherein the first LED, the second LED, the third LED, and the fourth LED are electrically connected to a common electrical connection. At least one of (i) the first LED and the second LED can be electrically connected in series and the third LED and the fourth LED can be electrically connected in parallel and (ii) the first LED and the second LED can emit a first color of light and the third LED and the fourth LED can emit a second color of light. The second multi-LED native substrate can be disposed on the first multi-LED native substrate. 
     According to some embodiments of the present disclosure, a multi-LED component structure further comprises a fifth LED non-native to the component substrate, the first multi-LED native substrate and the second multi-LED native substrate, wherein the fifth LED emits a different color of light from the first LED, the second LED, the third LED, and the fourth LED. 
     Embodiments of the present disclosure provide a display, lamps, pixels, or light emitters having improved optical characteristics and power efficiency and fewer separate components, control circuits, and electrical connections that can be constructed in fewer manufacturing steps. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, aspects, features, and advantages of the present disclosure will become more apparent and better understood by referring to the following description taken in conjunction with the accompanying drawings, in which: 
         FIG.  1 A  is a schematic cross section of a multi-LED structure taken across cross section line A of the schematic plan view of  FIG.  1 B  illustrating embodiments of the present disclosure; 
         FIG.  1 C  is a schematic cross section of a multi-LED structure wherein a semiconductor layer and a multi-LED native substrate comprise a same material according to illustrative embodiments of the present disclosure; 
         FIG.  1 D  is a schematic cross section of a multi-LED structure wherein a first layer is common to multiple LEDs according to illustrative embodiments of the present disclosure; 
         FIG.  1 E  is a schematic cross section of a multi-LED structure wherein a first layer and a multi-LED native substrate are a common layer according to illustrative embodiments of the present disclosure; 
         FIG.  2 A  is a schematic perspective of an LED indicating cross-section line A of the cross section of  FIG.  2 D ,  FIG.  2 B  is a schematic perspective indicating layers of the 
       LED, and  FIG.  2 C  is an exploded schematic perspective of the LED according to illustrative embodiments of the present disclosure; 
         FIG.  3 A  is a schematic perspective of an LED indicating cross-section line A also corresponding to the cross section of  FIG.  2 D ,  FIG.  3 B  is a schematic perspective indicating layers of the LED, and  FIG.  3 C  is an exploded schematic perspective of the LED according to illustrative embodiments of the present disclosure; 
         FIG.  4 A  is a schematic perspective of an LED,  FIG.  4 B  is a schematic perspective indicating layers of the LED, and  FIG.  4 C  is an exploded schematic perspective of the LED according to illustrative embodiments of the present disclosure; 
         FIGS.  5 - 23    are schematic plan views illustrating electrical connections within multi-LED structures according to illustrative embodiments of the present disclosure; 
         FIG.  24 A  is a schematic cross section of a multi-LED structure on a native source wafer and  FIGS.  24 B and  24 C  are schematic cross sections of a multi-LED structure on a native source wafer with a handle substrate according to illustrative embodiments of the present disclosure; 
         FIG.  25    is a schematic perspective of a component comprising multi-LED structures and LEDs illustrating embodiments of the present disclosure; 
         FIG.  26    is a graph illustrating inorganic LED light output efficiency with respect to current density useful in understanding embodiments of the present disclosure; 
         FIG.  27    is a schematic plan view and pixel detail of a display comprising multi-LED structures and LEDs illustrating embodiments of the present disclosure; 
         FIGS.  28 - 30    are schematic display pixel details comprising multi-LED structures and LEDs illustrating embodiments of the present disclosure; 
         FIG.  31    is a schematic diagram of an active-matrix display comprising multi-LED structures illustrating embodiments of the present disclosure; 
         FIG.  32    is a schematic perspective of an active-matrix display according to illustrative embodiments of the present disclosure; 
         FIG.  33    is a schematic plan view illustrating reverse-bias electrical connections within multi-LED structures according to embodiments of the present disclosure; 
         FIG.  34    is a schematic perspective of an individual LED disposed on a multi-LED native substrate of a multi-LED structure according to illustrative embodiments of the present disclosure; 
         FIG.  35    is a schematic perspective of a multi-LED structure and individual LEDs disposed on a multi-LED native substrate of another multi-LED structure according to illustrative embodiments of the present disclosure; and 
         FIGS.  36  and  37    are flow charts according to illustrative embodiments of the present disclosure. 
     
    
    
     Features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The figures are not drawn to scale since the variation in size of various elements in the Figures is too great to permit depiction to scale. 
     DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS 
     Embodiments of the present disclosure provide electrically connected iLEDs formed at the same time with common materials in a single process, e.g., a photolithographic process. The iLEDs can have one or more of a reduced area and structure size, improved manufacturing efficiency, improved operating efficiency, and simplified power and control circuitry when incorporated in a display or in other multi-color light output devices such as lamps, or as individual structures in an optical indicator. In some embodiments, a power supply for differently colored light emitters in an illumination device or display pixel can comprise a single current supply and a single voltage supply rather than multiple current and voltage supplies. 
     According to some embodiments of the present disclosure and as illustrated in the cross section of  FIG.  1 A  taken along cross section line A of the corresponding plan view of  FIG.  1 B  and  FIG.  1 C , a multi-LED structure  99  comprises a multi-LED native substrate  10  and a patterned semiconductor layer  30  comprising spatially separated semiconductor portions  30 P (e.g., first semiconductor portion  30 A and second semiconductor portion  30 B) disposed on or over multi-LED native substrate  10 . A multi-LED native substrate  10  can be a single, unitary, and contiguous substrate. Semiconductor layer  30  is formed (e.g., photolithographically patterned) on multi-LED native substrate  10  making first semiconductor portion  30 A and second semiconductor portion  30 B native to multi-LED native substrate. First semiconductor portion  30 A and second semiconductor portion  30 B, both native to multi-LED native substrate  10 , can be defined in common steps using common materials and tools. In some embodiments, multi-LED native substrate  10  is not divided into separate or distinct portions (e.g., each portion comprising a separate semiconductor portion such as first semiconductor portion  30 A or second semiconductor portion  30 B) that can be separately disposed in different locations, and is therefore a single, unitary, and contiguous substrate. Multi-LED native substrate  10  can comprise any suitable material on which semiconductor layer  30  can be formed and can include a seed layer. In some embodiments, semiconductor layer  30  comprises a seed layer. For example, multi-LED native substrate  10  can comprise a sapphire, silicon, silicon carbide, or compound semiconductor wafer, such as those found in the integrated circuit, flat-panel display, or opto-electronic arts. Multi-LED native substrate  10  can comprise an undoped semiconductor, for example undoped silicon, or an ion-doped semiconductor that is resistive to the flow of electrical current, e.g., as shown in  FIG.  1 C  with semiconductor structures shown with common shading. First and second semiconductor portions  30 A,  30 B (and any other semiconductor portions  30 P) are collectively referred to as semiconductor portions  30 P. 
     Semiconductor layer  30  and semiconductor portions  30 P can be constructed by depositing epitaxial layers of semiconductor materials, for example doped or undoped semiconductor materials such as Si or compound semiconductor materials such as GaN, GaAs, In x Ga 1-x N, Al x Ga 1-x P, and Al x Ga 1-x As, or other semiconductor or compound semiconductor materials and alloys, for example with p or n doping, and, in some embodiments, then pattern-wise etched to form separate semiconductor portions  30 P. Semiconductor layer  30  can comprise mono-crystalline semiconductor materials and can be deposited, together with any suitable dopants, for example by sputtering, evaporative, or vapor deposition methods and processed using photolithographic methods and materials, for example using patterned photoresist masking and etching techniques. Semiconductor layer  30  can include sublayers (e.g., first layer  31  and second layer  32 ) and first and second layers  31 ,  32  can be patterned and can also include sub-layers, for example with different material compositions or doping or both. 
     Semiconductor portions  30 P (e.g., first semiconductor portion  30 A and second semiconductor portion  30 B) can define at least a first LED  20 A and a second LED  20 B spatially separate from first LED  20 A on multi-LED native substrate  10 . First and second LEDs  20 A and  20 B are referred to collectively as LEDs  20 . First LED  20 A and second LED  20 B can each comprise (i) a first layer  31  having a cantilever portion  34  and a base portion  36 , and (ii) a second layer  32  disposed only over base portion  36  of first layer  31  comprising an emission portion  33  that emits light and is a light-emitting portion. Spatially separate LEDs  20  have separate emission portions  33  (and base portions  36 ) and can be independently operable with suitable electrical connections. First and second layers  31 ,  32  can be semiconductor layers with or without doping or sub-layers. First layer  31  can be separate for both first and second LEDs  20 A,  20 B or, in some embodiments, first layer  31  is common (for example at least partially common) to both first and second LEDs  20 A,  20 B, e.g., as shown in  FIG.  1 D and  1 E . First layer  31  can be common, for example at least partially common, with multi-LED native substrate  10 , e.g., as shown in  FIG.  1 E . 
     Referring to  FIG.  1 C , in some embodiments, multi-LED native substrate  10  and first layer  31  are the same, or at least partially the same, layer, and cantilever portion  34  is a raised portion of multi-LED native substrate  10  that extends beyond emission portion  33 . First layer  31  comprising cantilever portion  34  and base portion  36  is an electrically conductive layer and does not emit light. First layer  31  conducts electrical current to second layer  32  which emits light from emissive portion  33  in response to the electrical current. LED contact pads  26 , for example comprising a photolithographically patterned evaporatively deposited metal such as aluminum, a transparent conductive oxide, or a doped semiconductor, can be disposed on emission portion  33  and cantilever portion  34  of first and second LEDs  20 A,  20 B to provide electrical contacts to first and second LEDs  20 A,  20 B. Electrical power (e.g., electrical current at a suitable voltage) can be provided to first and second LEDs  20 A,  20 B so that first and second LEDs  20 A,  20 B emit light. LEDs  20  can be horizontal LEDs  20  and can be either top-emitting LEDs  20  that emit light away from multi-LED native substrate  10  or bottom-emitting LEDs  20  that emit light through multi-LED native substrate  10 . 
     Multi-LED native substrate  10  can be electrically conductive and electrically connect first and second semiconductor portions  30 A,  30 B, for example such that sufficient electrical current can flow to provide a desired amount of light output from emission portions  33 . In some embodiments, for example as shown in  FIG.  1 D , first layer  31  can be at least partially common to both first and second LEDs  20 A,  20 . In some such embodiments, cantilever portions  34  can be at least partially common to both first and second LEDs  20 A,  20  but base portions  36  and emission portions  33  are separate. In some embodiments, for example as shown in  FIG.  1 E , multi-LED native substrate  10  is at least a portion of first layer  30  or is first layer  30  or first layer  30  comprises at least a portion of multi-LED native substrate  10 . In the illustrative embodiment of  FIG.  1 E , first and second LEDs  20 A,  20 B can have a common first layer  31 . In some such configurations, first LED  20 A separate from second LED  20 B means that emission portions  33  of each of first LED  20 A and second LED  20 B are spatially separate, separately controllable, and with a common electrical connection through first layer  31 . 
     As shown in  FIG.  1 E , a multi-LED structure  99  comprises an electrically conductive semiconductor layer (first layer  31 , multi-LED native substrate  10 ) comprising a cantilever portion  34  and two or more spatially separated base portions  36 . A separate emissive portion  33  comprises a light-emissive semiconductor portion disposed on each base portion  36 . An LED contact pad  26  is disposed on each emissive portion  33 . Each emissive portion  33  emits light when electrical power is provided to cantilever portion  34  and LED contact pad  26 . In some embodiments, LED electrode  38  electrically connects each LED contact pad  26  so that emissive portions  33  are electrically connected in parallel. 
     Patterned dielectric layers  24  or dielectric structures (e.g., comprising silicon dioxide or silicon nitride deposited by sputtering or vapor deposition and photolithographically patterned) can electrically insulate and environmentally protect portions of first and second LEDs  20 A,  20 B. First and second LED electrodes  28 A,  28 B, for example comprising reflective patterned metal traces such as aluminum for a bottom-emitter LED  20  or transparent conductive oxides for a top-emitter LED  20  (collectively LED electrodes  28 ), can be pattern-wise disposed by sputtering or vapor deposition over patterned dielectric layers  24  in electrical contact with LED contact pads  26  to conduct electrical current to first and second LEDs  20 A,  20 B through LED contact pads  26 .  FIGS.  1 A and  1 B  illustrate two semiconductor portions  30 P (defining first and second LEDs  20 A and  20 B) but embodiments of the present disclosure are not limited to only two semiconductor portions  30 P and LEDs  20 . In some embodiments of the present disclosure and as illustrated further below, semiconductor layer  30  can comprise three, four, five, six, seven, eight, nine, ten, or more semiconductor portions  30 P defining corresponding LEDs  20 . Different LEDs  20  can have different sizes or shapes and, optionally, be electrically connected with different sizes, shapes, or arrangements of contact pads  26 . 
     According to some embodiments of the present disclosure, multi-LED structures  99  have at least one of a width and a length that is no greater than 500 microns (e.g., no greater than 200 microns, no greater than 100 microns, no greater than 50 microns, no greater than 25 microns, no greater than 15 microns, no greater than 12 microns, no greater than 8 microns, or no greater than 5 microns). Different multi-LED structures  99  can have different sizes. Multi-LED structures  99  provide an advantage according to embodiments of the present disclosure since they are sufficiently small and can be disposed spatially close together so that different multi-LED structures  99  in a pixel  60  and sub-pixel cannot be readily distinguished by the human visual system in a display or lamp at a desired viewing distance, improving color mixing of light emitted by a pixel  60  and sub-pixel and providing apparent improvements in resolution and a reduction of pixelization. Multi-LED structures  99  can also assemble multiple LEDs  20  in fewer manufacturing steps and can require fewer LED packages. Multi-LED structures  99  can be unpackaged (e.g., bare) die. 
     The perspectives of  FIGS.  2 A- 2 C  and the corresponding cross section of  FIG.  2 D  illustrate the detailed structure of an individual LED  20  (e.g., first LED  20 A or second LED  20 B). As shown, LED  20  comprises a semiconductor layer  30  comprising first layer  31  and second layer  32 . Semiconductor layer  30  can comprise a seed layer on which epitaxial semiconductor material is disposed, e.g., by vapor deposition. First layer  31  has a cantilever portion  34  and an adjacent base portion  36 . Patterned second layer  32  has an emission portion  33  disposed on base portion  36  of first layer  31 . First layer  31  is electrically conductive and second layer  32  is both conductive and light-emissive. LED contact pads  26  are disposed on each of cantilever portion  34  and emission portion  33 .  FIG.  2 D  shows a conduction zone  39  of first layer  31  that conducts electrical current to a recombination zone  38  of emission portion  33  of second layer  32 . Electrons and holes conducted by LED contact pads  26  through conduction zone  39  of conductive first layer  31  and through emission portion  33  combine in recombination zone  38  to emit light having a frequency and color corresponding to a bandgap of the semiconductor material comprising recombination zone  38  and emission portion  33 . 
       FIGS.  1 A- 1 C  illustrate LED structure tethers  25  related to micro-transfer printing multi-LED structures  99 , as discussed further below, for example comprising a portion of multi-LED native substrate  10 , a dielectric material such as silicon dioxide or silicon nitride, or an organic material such as a photolithographically deposited and patterned photoresist.  FIGS.  2 A- 2 D  illustrate similarly constructed LED tethers  22 . However, LED tethers  22  are found on individual LEDs  20 , not in multi-LED structures  99  as discussed further below and are distinct structures from LED structure tethers  25 . LEDs  20  with LED tethers  22  can be individually micro-transfer printed, unlike first and second LEDs  20 A,  20 B. LEDs  20  (e.g., first LED  20 A and second LED  20 B) included in multi-LED structures  99  do not include individual LED tethers  22 , since first LED  20 A and second LED  20 B are constructed together in a common process on multi-LED native substrate  10 , that is are native to multi-LED native substrate  10 . Multi-LED native substrate  10  can have an LED structure tether  25  that enables the entire multi-LED native substrate  10  together with first LED  20 A and second LED  20 B to be micro-transfer printed from a source wafer as a complete unit. (LED tether  22  of  FIG.  2 D  is shown for illustration and is not properly part of cross section line A of  FIG.  2 A .) Printed LEDs  20  that include LED tethers  22  can be used in combination with a multi-LED structure  99 , for example that includes an LED structure tether  25 , as discussed further below. 
     As shown in  FIGS.  1 A and  1 B , first LED electrode  28 A is disposed on at least a portion of multi-LED native substrate  10  or disposed on a non-semiconductor structure in semiconductor layer  30  (e.g., a portion of patterned dielectric layer  24 ) and is disposed on at least a portion of first LED  20 A and on at least a portion of second LED  20 B to electrically connect first LED  20 A to second LED  20 B on multi-LED native substrate  10 . As shown in  FIG.  1 A , first LED electrode  28 A is disposed on patterned dielectric layer  24  in semiconductor layer  30  and second LED electrode  28 B is disposed directly on multi-LED native substrate  10  and patterned dielectric layer  24  in semiconductor layer  30 . Electrodes  28  can comprise a metal such as aluminum or a transparent conductive oxide and can be made using relatively fine high-resolution lithography methods and materials practiced in the photolithographic arts. First and second LED electrodes  28 A and  28 B can conduct electrical current to external electrical contacts to provide electrical power to multi-LED structure  99 . According to some embodiments of the present disclosure, external electrical connections to LED electrodes  28  or LED contact pads  26  are constructed using relative coarse, low-resolution, and less expensive methods and materials, for example found in the printed circuit board arts, thereby reducing the costs of using multi-LED structures  99  (as compared to using high-resolution photolithographic processing for all connections). 
     In some embodiments of the present disclosure and as illustrated in  FIGS.  1 A and  1 B , cantilever portion  34  of first LED  20 A has a first cantilever length L 1 , cantilever portion  34  of second LED  20 B has a second cantilever length L 2 , and an LED emission separation distance LS between emission portion  33  of first LED  20 A and emission portion  33  of second LED  20 B is less than or equal to one or more of first cantilever length L 1  and second cantilever length L 2 . According to some embodiments, an LED emission separation distance LS between emission portions  33  of two LEDs  20  is the smallest distance between emission portions  33  of first and second LEDs  20 A,  20 B parallel to a surface of multi-LED native substrate  10 . According to some embodiments, first LED  20 A and second LED  20 B can extend in substantially a same direction, for example in substantially parallel directions, but are not collinear (a center line of first and second LEDs  20 A,  20 B are not in a common line). In some embodiments, first LED  20 A and second LED  20 B extend in substantially a same direction and are collinear having collinear center lines (e.g., within manufacturing tolerances). An LED  20  extending in a direction can refer to the direction of a longest dimension of the LED  20  parallel to multi-LED native substrate  10 , as shown with cross section line A of  FIG.  2 A . In some embodiments, a cantilever portion  34  extending in a direction refers to the direction of a longest dimension of cantilever portion  34  parallel to multi-LED native substrate  10 , as shown with cross section line A of  FIG.  4 A . In some embodiments, a cantilever portion  34  extending in a direction refers to the direction of a cantilever portion midline from an LED contact pad  26  disposed on cantilever portion  34  towards base portion  36  parallel to multi-LED native substrate  10 , as shown with cross section line A of  FIG.  3 A . In some embodiments, a base portion  36  or emission portion  33  extending in a direction refers to the direction of a longest dimension of base portion  36  or emission portion  33  parallel to multi-LED native substrate  10 , as shown with cross section line B of  FIG.  3 A . In some embodiments, a base portion  36  or emission portion  33  extending in a direction refers to the direction of a base portion midline (centerline) from an LED contact pad  26  disposed on emission portion  33  towards cantilever portion  34  parallel to multi-LED native substrate  10 , as shown with cross section line B of  FIG.  4 A . According to some embodiments, first LED  20 A and second LED  20 B can extend in different directions, for example in substantially orthogonal directions. Similarly, according to some embodiments, cantilever portion  34  and emission portion  33  (and base portion  36 ) can extend in different directions, for example in substantially orthogonal directions. Substantially can mean within the tolerances of a design or manufacturing process or within 10 degrees, for example with reference to parallel structures or elements. 
     As shown in  FIGS.  3 A- 4 C , in some embodiments of the present disclosure cantilever portion  34  of first LED  20 A extends in a first direction D 1  and base portion  36  of first LED  20 A extends in a second direction D 2  different from first direction D 1 . In some embodiments of the present disclosure, cantilever portion  34  of second LED  20 B extends in a first direction D 1  and base portion  36  of second LED  20 B extends in a second direction D 2  different from first direction D 1 . Referring to the perspectives of  FIGS.  3 A- 3 C , emission portion  33  of second layer  32  of semiconductor layer  30  is disposed on base portion  36  of first layer  31  of semiconductor layer  30 . Emission portion  33  extends as far as possible in second direction D 2  over base portion  36  of first layer  31 . Referring to the perspectives of  FIGS.  4 A- 4 C , emission portion  33  of second layer  32  of semiconductor layer  30  is likewise disposed on base portion  36  of first layer  31  of semiconductor layer  30  but extends only as far as cantilever portion  34  in second direction D 2  over first layer  31 . LEDs  20  can incorporate either or both of the structures of  FIGS.  3 A- 3 C  and  FIGS.  4 A- 4 C  according to various embodiments of the present disclosure. 
     In some embodiments of the present disclosure, and as illustrated in  FIGS.  3 A and  4 C , cantilever portion  34  of first LED  20 A extends in a first direction D 1  and base portion  36  of first LED  20 A extends in a second direction D 2  different from first direction D 1 . Similarly, in some embodiments, cantilever portion  34  of second LED  20 B extends in a first direction D 1  and base portion  36  of second LED  20 B extends in a second direction D 2  different from first direction D 1 . Cantilever and base portions  34 ,  36  that extend in different directions can enable LEDs  20  disposed in close proximity with reduced area over multi-LED native substrate  10 . In some embodiments, cantilever portion  34  extends in a different direction from base portion  36  and an LED emission separation distance LS between emission portions  33  of first and second LEDs  20 A and  20 B can be less than one or more of first cantilever length L 1  and second cantilever length L 2 . According to some embodiments, first and second directions D 1  and D 2  can be orthogonal, as shown in  FIGS.  3 A- 4 C , and parallel to a surface of multi-LED native substrate  10 . 
     By disposing emission portions  33  of first LED  20 A and second LED  20 B in close proximity, emission portions  33  can appear as a single emitting area to a viewer of multi-LED structures  99  of the present disclosure at a desired viewing distance, thereby reducing the apparent pixelization of multi-LED structures  99 , for example used in displays or for lighting. Such small LED emission separation distances LS in multi-LED structures  99  can also improve color mixing for applications in which a multi-color emitter or white light is desired. Furthermore, such close-proximity emission portion  33  arrangements for multiple LEDs  20  can enable small light-emitting structures useful in display and illumination, improving the resolution of the displays and lamps, and can facilitate high-density micro-transfer printing with fewer print steps from a multi-LED structure  99  native source wafer  40  since two (or more) LEDs  20  can be transferred in a single step, rather than requiring two (or more) transfer steps, one for each LED  20 . 
     According to some embodiments of the present disclosure, first LED  20 A and second LED  20 B of multi-LED structure  99  can be substantially (e.g., within 5%) the same size, can cover substantially (e.g., within 5%) a same-size area over multi-LED native substrate  10 , can have substantially (e.g., within 5%) the same light-emitting area of emission portion  33 , or any combination of these. In some embodiments, first LED  20 A and second LED  20 B of multi-LED structure  99  can be different sizes, can cover different-size areas over multi-LED native substrate  10 , can have different light-emitting areas of emission portion  33 , or any combination of these. Size can be defined by any combination of length, width, or height over multi-LED native substrate  10  and area can be defined by any combination of length or width over multi-LED native substrate  10 . 
     LEDs  20  of multi-LED structure  99  of the present disclosure can be electrically connected in serial or in parallel, or in a combination of serial and parallel connections. Referring to the plan view and electrical schematic of  FIG.  5   , first LED  20 A is electrically connected in parallel with second LED  20 B. LED contact pad  26  of cantilever portion  34  of first LED  20 A is electrically connected to LED contact pad  26  of cantilever portion  34  of second LED  20 B with first LED electrode  28 A and LED contact pad  26  of emission portion  33  of first LED  20 A is electrically connected to LED contact pad  26  of emission portion  33  of second LED  20 B with second LED electrode  28 B. Both first and second LED electrodes  28 A and  28 B are partially disposed on a portion of multi-LED native substrate  10  or non-semiconductor structure (e.g., patterned dielectric layer  24  as shown in  FIG.  1 A ) between first and second LEDs  20 A,  20 B. First and second electrodes  28 A and  28 B can be contacted by external power sources, for example through electrodes connected to first and second electrodes  28 A,  28 B. Emission portions  33  of first and second LEDs  20 A,  20 B are separated by an LED emission separation distance LS less than a cantilever length L. A third LED  20 , or more LEDs  20 , can be similarly arranged on multi-LED native substrate  10  on a side of second LED  20 B opposite first LED  20 A and electrically connected in parallel with first and second LEDs  20 A,  20 B using first and second electrodes  28 A,  28 B. LED structure tether  25  can be physically connected to LED substrate  10  to enable, or as a consequence of, micro-transfer printing multi-LED structure  99 . 
       FIGS.  1 D and  1 E  illustrate embodiments in which first and second LEDs  20 A,  20 B are electrically connected in parallel. In some such configurations, a separate electrode to electrically connect cantilever portions  34  is not necessary, since first and second LEDs  20 A,  20 B share at least a portion of common first layer  31  that provides a common electrical connection to emission portions  33  of first and second LEDs  20 A,  20 B. Thus, the physical structure illustrated in  FIGS.  1 D,  1 E  can provide the electrical connections illustrated in  FIG.  5   . 
     Referring to the plan view and electrical schematic of  FIG.  6   , first LED  20 A is electrically connected in serial with second LED  20 B. LED contact pad  26  of cantilever portion  34  of first LED  20 A is electrically connected to LED contact pad  26  of emission portion  33  of second LED  20 B with LED electrode  28 . LED contact pad  26  of cantilever portion  34  of second LED  20 B and LED contact pad  26  of emission portion  33  of first LED  20 A can be contacted by external power sources, for example through electrodes connected to them. LED electrode  28  is partially disposed on a portion of multi-LED native substrate  10  or a non-semiconductor structure in semiconductor layer  30  between first and second LEDs  20 A,  20 B. Emission portions  33  of first and second LEDs  20 A,  20 B are separated by an LED emission separation distance LS less than a cantilever length L. A third LED  20 , or more LEDs  20 , can be similarly arranged on multi-LED native substrate  10  in alternating orientations on a side of second LED  20 B opposite first LED  20 A and electrically connected in serial with first and second LEDs  20 A,  20 B using additional LED electrodes  28 . 
       FIGS.  7 A- 7 C  illustrate other spatial arrangements of first LED  20 A with respect to second LED  20 B on multi-LED native substrate  10 . In these arrangements, LED contact pads  26  that are not contacted by LED electrode  28  are farther apart so that they can be connected with coarser, lower-resolution electrodes than LED electrode  28 , reducing the cost of using multi-LED structures  99  in electronic or electro-optical systems. For example, multi-LED structures  99  can be constructed using high-resolution photolithographic methods and materials found in the integrated circuit or display arts and can be applied or used in lower-cost electronic or optical systems such as printed circuit boards constructed using lower cost methods and materials, for example found in the printed circuit art. 
     For example, and as shown in  FIG.  7 A , multi-LED structures  99  can comprise a first LED contact pad  26 A disposed on first LED  20 A and a second LED contact pad  26 B disposed on second LED  20 B. First LED contact pad  26 A and second LED contact pad  26 B are separate from LED electrode  28 , that is LED electrode  28  is not electrically connected to first and second LED contact pads  26 A,  26 B and is therefore an open LED contact pad  26 . An LED contact separation distance CS is the distance between the centers of LED contact pads  26  in a direction parallel to a surface of multi-LED native substrate  10  and an LED length E is the longest dimension of LED  20  parallel to a surface of multi-LED native substrate  10 . According to some embodiments of the present disclosure, LED contact separation distance CS between first LED contact pad  26 A and second LED contact pad  26 B is greater than (i) a first LED length E 1  of first LED  20 A, (ii) a second LED length E 2  of second LED  20 B, or (iii) the larger of first LED length E 1  and second LED length E 2 . Because LED contact separation distance CS is greater than a length of an LED  20  or LED separation length LS, a lower-resolution and less-expensive process can be used to construct electrical connections (wires or traces) to LED contact pads  26  (e.g., first and second LED contact pads  26 A,  26 B). 
     According to some embodiments of the present disclosure, and as illustrated in  FIG.  7 B , multi-LED native substrate  10  has an LED center C, a first LED substrate edge  12 A, and a second LED substrate edge  12 B different from first LED substrate edge  12 A. First LED contact pad  26 A is disposed a first distance Y 1  closer to first LED substrate edge  12 A than to center C a second distance Y 2 . Second LED contact pad  26 B is disposed a first distance Y 1  closer to second LED substrate edge  12 B than to center C a second distance Y 2 . First LED substrate edge  12 A and second LED substrate edge  12 B can be on opposite edges of multi-LED native substrate  10 , where multi-LED native substrate  10  has a quadrilateral surface, for example a rectangle. 
     According to some embodiments of the present disclosure and as shown in  FIG.  7 C , multi-LED native substrate  10  has an LED center C, a first LED substrate corner  14 A and a second LED substrate corner  14 B different from first LED substrate corner  14 A. First LED contact pad  26 A is disposed closer to first LED substrate corner  14 A a first distance X 1  than to center C a second distance X 2  and second LED contact pad  26 B is disposed closer to second LED substrate corner  14 B a first distance X 1  than to center C a second distance X 2 . First LED substrate corner  14 A and second LED substrate corner  14 B can be on opposite corners of multi-LED native substrate  10 , where multi-LED native substrate  10  is a quadrilateral, for example a rectangle. Because LED contact pads  26  are disposed closer to first or second LED substrate edges  12 A,  12 B or first or second LED substrate corners  14 A,  14 B than to LED centers C of multi-LED native substrate  10 , a lower-resolution and less expensive process can be used to construct electrical connections (wires or traces) to LED contact pads  26 . 
       FIG.  7 D  shows an illustrative multi-LED structure  99  arrangement having four LEDs  20  electrically connected in parallel (omitting a portion of second LED electrode  28 B). Any of LED  20  arrangements of  FIGS.  5 - 7 C  or those of  FIGS.  8 - 23    can be extended to more than two LEDs  20  and can be electrically connected in series, in parallel, or in combinations of series and parallel, as discussed with respect to  FIGS.  27 - 30   . 
     First and second LEDs  20 A,  20 B arranged as illustrated in  FIGS.  7 A- 7 C  can be electrically connected serially or in parallel as shown in  FIGS.  5  and  6   . In some embodiments, the portions connected by LED electrode  28  are the same portion of first LED  20 A and second LED  20 B, for example both cantilever portions  34  or both emission portions  33 . In that case, first and second LEDs  20 A,  20 B are electrically connected in parallel and are separated by LED emission separation distance LS smaller than cantilever length L as shown in  FIG.  5   . In some embodiments, the portion of first LED  20 A connected by LED electrode  28  is different from the portion of second LED  20 B connected by LED electrode  28 . For example, if cantilever portion  34  of first LED  20 A is connected by LED electrode  28  to emission portion  33  of second LED  20 B (or vice versa), first and second LEDs  20 A,  20 B are electrically connected in serial and are separated by LED emission separation distance LS smaller than cantilever length L as shown in  FIG.  6   . Regardless of LED  20  arrangement, emission portions  33  are closer together than would be the case for LEDs  20  separately constructed and disposed on separate substrates, especially for packaged LEDs, improving the appearance of the light emitted by LEDs  20  and improving manufacturing efficiency by reducing the number of micro-transfer steps necessary to construct a multi-LED pixel or lamp (illuminator). 
     The embodiments of the present disclosure illustrated in  FIGS.  5 - 7 D  have emission portions  33  separated by an LED emission separation distance LS that is less than a cantilever length L of cantilever portion  34  and have base portions  36  and cantilever portions  34  that extend in the same direction and have a common midline. The embodiments illustrated in  FIGS.  8 - 23    have base portions  36  and emission portions  33  that extend in a direction different from the direction of cantilever portions  34 , forming an L shape where the different directions are orthogonal, for example. In  FIGS.  5 - 23   , emission portions  33  overlap base portions  36  and can be labeled as such, as in  FIGS.  5 - 6   . For clarity, base portions  36  in  FIGS.  8 - 23    are not labeled. LED  20  structures of  FIGS.  3 A- 3 C  are used in  FIGS.  8 - 21    but the structures of  FIGS.  4 A- 4 C  could equally be used, or a combination thereof. L-shaped LEDs  20  as in  FIGS.  8 - 21    can also be combined with straight LEDs  20  as in  FIGS.  5 - 7 D . 
     As shown in  FIGS.  8  and  11   , an L-shaped first LED  20 A and an L-shaped second LED  20 B are disposed on multi-LED native substrate  10  and electrically connected in parallel. LED contact pad  26  of first emission portion  33 A of first LED  20 A is electrically connected to LED contact pad  26  of second emission portion  33 B of second LED  20 B with first LED electrode  28 A and LED contact pad  26  of first cantilever portion  34 A of first LED  20 A is electrically connected to LED contact pad  26  of second cantilever portion  34 B of second LED  20 B with second LED electrode  28 B. As shown in  FIGS.  9  and  10   , an L-shaped first LED  20 A and an L-shaped second LED  20 B are disposed on multi-LED native substrate  10  and electrically connected in series. LED contact pad  26  of first emission portion  33 A of first LED  20 A is electrically connected to LED contact pad  26  of second cantilever portion  34 B of second LED  20 B with LED electrode  28 . In the embodiments of  FIGS.  9  and  11   , first and second LED lengths E 1 , E 2  are less than LED contact separation distance CS (as shown in  FIG.  7 A , not indicated in  FIGS.  9  and  11   ) providing well-separated open LED contact pads  26  enabling lower-resolution electrical connections to open LED contact pads  26 . The embodiments of  FIGS.  8 - 11    comprise first or second LEDs  20 A,  20 B that are mirror reflections and rotations of each other and provide a compact arrangement of L-shaped first and second LEDs  20 A and  20 B in a multi-LED structure  99 . 
       FIGS.  12 - 15    illustrate reflected and rotated arrangements of LEDs  20  with greater LED contact pad  26  separation different from the arrangements of  FIGS.  8 - 11   . Each of the embodiments of  FIGS.  12 - 15    comprise L-shaped first and second LEDs  20 A,  20 B electrically connected with LED electrode  28  that are rotated mirror images of each other. The embodiments of  FIGS.  12  and  15    are electrically connected in serial, since first emission portion  33 A of first LED  20 A is electrically connected to second cantilever portion  34 B of second LED  20 B, as in  FIG.  12   , and second emission portion  33 B of second LED  20 B is electrically connected to first cantilever portion  34 A of first LED  20 A, as in  FIG.  15   . The embodiments of  FIGS.  13  and  14    are electrically connected in parallel, since first emission portion  33 A of first LED  20 A is electrically connected to second emission portion  33 B of second LED  20 B, as in  FIG.  13   , and first cantilever portion  34 A of first LED  20 A is electrically connected to second cantilever portion  34 B of second LED  20 B, as in  FIG.  14   . All of the embodiments of  FIGS.  12 - 15    provide well-separated open LED contact pads  26  enabling low-resolution connections to open LED contact pads  26  (as illustrated in  FIG.  7 A ). 
       FIGS.  16 - 19    illustrate longer and narrower horizontal (or vertical) arrangements of LEDs  20  different from the arrangements of  FIGS.  8 - 15   . Each of the embodiments of  FIGS.  16 - 19    comprise L-shaped first and second LEDs  20 A,  20 B electrically connected with LED electrode  28  that are rotated mirror images of each other. The embodiments of  FIGS.  16  and  17    are electrically connected in parallel, since first emission portions  33 A of first LED  20 A are electrically connected to second emission portions  33 B of second LED  20 B. The embodiments of  FIGS.  18  and  19    are electrically connected in serial, since first emission portions  33 A of first LED  20 A are electrically connected to second cantilever portions  34 B of second LED  20 B. The embodiments of  FIGS.  17  and  19    provide well-separated open LED contact pads  26  enabling low-resolution connections to open LED contact pads  26  (e.g., as illustrated in  FIG.  7 A ). 
       FIGS.  20 - 23    illustrate longer and narrower horizontal (or vertical) mirror arrangements of LEDs  20  different from the arrangements of  FIGS.  8 - 19   . Each of the embodiments of  FIGS.  20 - 23    comprise L-shaped first and second LEDs  20 A,  20 B electrically connected with LED electrode  28  that are rotated mirror images of each other. The embodiments of  FIGS.  20  and  23    are electrically connected in serial, since first emission portion  33 A of first LED  20 A is electrically connected to second cantilever portion  34 B of second LED  20 B, as in  FIG.  20   , and second emission portion  33 B of second LED  20 B is electrically connected to first cantilever portion  34 A of first LED  20 A, as in  FIG.  23   . The embodiments of  FIGS.  21  and  22    are electrically connected in parallel, since first emission portion  33 A of first LED  20 A is electrically connected to second emission portion  33 B of second LED  20 B, as in  FIG.  21   , and first cantilever portion  34 A of first LED  20 A is electrically connected to second cantilever portion  34 B of second LED  20 B, as in  FIG.  22   . All of the embodiments of  FIGS.  20 - 23    provide well-separated open LED contact pads  26  enabling low-resolution connections to open LED contact pads  26  (as illustrated in  FIG.  7 A ). 
     Any mirror reflection, rotation, or mirror reflection and rotation about any axis, for example by 90, 180, or 270 degrees, of one or more of LEDs  20  in any illustrated configuration of the present disclosure are contemplated as embodiments of the present disclosure. 
     Any of the parallel-connected embodiments of  FIGS.  5 - 23    can be constructed and electrically connected using the configuration of  FIGS.  1 D or  1 E . In some such embodiments, open LED contact pads  26  can be disposed anywhere suitable on multi-LED native substrate  10  separate from base portions  36  (and therefore emission portions  33 ) and can be separated as described to provide electrical contacts that can be connected using lower-resolution, coarse electrical connections (wires). 
     Multi-LED structures  99  of the present disclosure can be constructed on a native source wafer  40 , for example a semiconductor or compound semiconductor wafer. As illustrated in  FIG.  24 A , a native source wafer  40  comprises a sacrificial layer  42  having sacrificial portions  44  separated by anchors  46 . A multi-LED native substrate  10  is disposed directly over each sacrificial portion  44  and epitaxial layers  48  disposed on sacrificial portion  44  with or without seed layers. Sacrificial portions  44  can be, for example, anisotropically etchable portions of sacrificial layer  42  or patterned layers of material that are differentially etchable from multi-LED native substrate  10 , such as oxide or nitride layers. Sacrificial portions  44  and anchor  46  of sacrificial layer  42  can include a same material (e.g., anisotropically etchable material) and be defined, at least in part, by their relative accessibility to an etchant applied to native source wafer  40 . For example, in some embodiments, and as illustrated in  FIG.  24 A , an etchant can access sacrificial portions  44  through entry paths adjacent to multi-LED structures  99  such that sacrificial portions  44  are etched before the etchant reaches anchors  46 . Epitaxial layers  48  (semiconductor layer  30 ) can comprise one or more layers of semiconductor material, for example compound semiconductor materials such as GaN, GaAs, or InP with or without dopants and are patterned using photolithographic methods and materials (e.g., by masked etching with patterned photoresist) to form separate semiconductor portions  30 P. Any desired LED contact pads  26  are patterned, for example by depositing metal such as aluminum or a transparent conductive oxide such as indium tin oxide (e.g., by evaporation or sputtering) and patterning (e.g., by using mask-exposure photoresist followed by etching) over semiconductor portions  30 P. Patterned dielectric layers  24  can be deposited and patterned (e.g., photolithographically patterned silicon dioxide or silicon nitride) to insulate parts of semiconductor portions  30 P. LED electrode(s)  28  are patterned, for example similarly to LED contact pads  26 , over multi-LED native substrate  10 , patterned dielectric layers  24 , and semiconductor portions  30 P to form electrically connected LEDs  20 . Sacrificial portions  44  can be etched to release multi-LED structure  99  from native source wafer  40  so that multi-LED structure  99  is only attached to anchor  46  by LED structure tether  25 . Multi-LED structure  99  can then be transfer printed, for example micro-transfer printed. 
       FIG.  24 A  illustrates a multi-LED structure  99  that is micro-transfer printable directly from native source wafer  40  to a target substrate  70 , shown in  FIG.  25   . In some embodiments, for example as illustrated in  FIG.  24 B  and further described in U.S. Pat. No. 10,224,231, multi-LED native substrate  10  does not include sacrificial layer  42  and sacrificial portions  44  as in  FIG.  24 A . Instead, patterned sacrificial portions  44  are deposited and patterned over multi-LED structure  99  and adhered with an adhesive layer  45  to a handle substrate  41  (handle wafer), native source wafer  40  is removed (e.g., by grinding or laser liftoff), and patterned sacrificial portions  44  etched away to release micro-transfer printable multi-LED structure  99  from handle substrate  41  and adhesive layer  45  so that multi-LED structure  99  is only attached to anchor  46  by LED structure tether  25 . Inverted multi-LED structure  99  can then be micro-transfer printed to a desired target substrate  70 , as shown in  FIG.  25   . Similarly, any individual LEDs  20  can be disposed on target substrate  70  by micro-transfer printing in an inverted state. Micro-transfer printed LEDs  20  can comprise fractured or separate tethers  22  and multi-LED structures  99  can comprise fractured or separated LED structure tethers  25  as a consequence of the micro-transfer printing process. Although not illustrated in  FIG.  25   , a controller (e.g., a pixel controller  66  as discussed with reference to  FIGS.  27 - 30    below) can be disposed by micro-transfer printing onto target substrate  70  to control LEDs  20  and multi-LED structures  99  on target substrate  70  or onto multi-LED native substrate  10  to control LEDs  20  of multi-LED structures  99 . 
     According to some embodiments of the present disclosure and as illustrated in  FIG.  24 C , multi-LED native substrate  10  is provided as a mesa  10 M on native source substrate  40  and semiconductor layer  30  is disposed on mesa  10 M. When native source substrate  40  is removed (step  230 ), mesa  10 M (multi-LED native substrate  10 ) remains in place as a portion of multi-LED structure  99 . For example, native source substrate  40  and multi-LED native substrate  10  (and mesa  10 M) can be sapphire. 
     Some embodiments of the present disclosure comprise both multi-LED structures  99  of  FIGS.  1 A- 2 C  and multi-LED structures  99  of  FIGS.  3 A- 4 C , for example disposed on a component, pixel, display, or illumination target substrate  70 . Each multi-LED structure  99  can emit light of a specific color, for example, red, green, or blue, since LEDs  20  in each multi-LED structure  99  can be formed in a common process with common materials, for example a common epitaxial material such as compound semiconductor materials, like GaN, GaAs, or other LED materials, with suitable doping, and therefore emit the same color of light. A multi-color light-emitting device such as a pixel  60  or white-light lamp (illuminator) can comprise a multi-LED structure  99  with one or more separate, individual LEDs  20  or multiple different multi-LED structures  99  and, optionally, one or more separate, individual LEDs  20  that emit different colors of light. For example, and as shown in  FIG.  25   , first and second multi-LED structures  99 A and  99 B are disposed on target substrate  70 . Target substrate  70  can be any one or more of a component substrate, pixel substrate, display substrate, or lamp (illuminator) substrate. First multi-LED structure  99 A can emit a first color of light, for example red, and multi-LED structure  99 B can emit a second color of light different from the first color of light, for example green. Either or both of first and second multi-LED structures  99 A and  99 B can comprise first and second LEDs  20 A,  20 B that are electrically serially connected or electrically connected in parallel. In some embodiments, LEDs  20  of first multi-LED structure  99 A are connected in series and LEDs  20  of second multi-LED structure  99 B are electrically connected in parallel. For example, red-light-emitting red LEDs  20 R of a red multi-LED structure  99 R can be electrically connected in series and green-light-emitting green LEDs  20 G of a green multi-LED structure  99 G can be electrically connected in parallel. A pixel  60  (for example used in a display or lamp) can comprise multi-LED structures  99  and individual LEDs  20 , for example a blue-light-emitting blue LED  20 B. In some embodiments, a pixel  60  comprises a series-connected set of different light-emitters that emit different colors of light, for example a red-light emitter, a green-light emitter, and a blue-light emitter controlled by a single control signal. Any one or more of the series-connected set of red-light emitter, green-light emitter, or blue-light emitter can be individual LEDs  20  or multi-LED structures  99 . The series-connected set of light-emitters can be separately controlled from the colored-light emitters and together emit white light, and the white-point color of pixel  60  can be adjusted by controlling the luminance of the red, green, or blue light-emitters (e.g., LEDs  20  or multi-LED structures  99 ) with respect to the white color of light emitted by the series-connected set of light emitters. 
     Thus, embodiments of the present disclosure provide multi-LED structures  99  that, used individually, enable light-emitting products that are smaller in area, are more highly integrated, and are more efficiently incorporated in products by using micro-transfer printing. Moreover, devices using groups of multi-LED structures  99  and LEDs  20  that emit different colors of light can also have improved electrical power efficiency. Such devices can be, for example, displays or lamps (illuminators). 
     According to embodiments of the present disclosure, by providing series-connected multiple differently colored LEDs  20  that emit different colors of light controlled by a common control signal (e.g., to emit white light), a higher voltage can be applied to LEDs  20 , improving power distribution and operating voltage to pixels  60  and reducing system power losses. For example, a series-connected set of light emitters with a red-light-emitting red LED  20 R, a green-light-emitting green LED  20 G, and a blue-light-emitting blue LED  20 B can be operated at 8 volts, as can a series-connected four-LED multi-LED structure  99  of red-light-emitting red LEDs  20 R (or two series-connected red-light-emitting multi-LED structures  99  comprising two red LEDS  20 R), a series-connected two-LED (or three-LED) multi-LED structure  99  of green-light-emitting green LEDs  20 G, and a series-connected three-LED multi-LED structure  99  of blue-light-emitting blue LEDs  20 B. 
     Referring to  FIG.  26   , according to some embodiments of the present disclosure, LEDs  20  that each emit a different color of light, for example red LED  20 R that emits red light, green LED  20 G that emits green light, and blue LED  20 B that emits blue light, have different light-output efficiencies with respect to current density for the respective LEDs  20 . According to some embodiments, different LEDs  20  can also have different preferred driving voltages, for example a forward voltage across the diode. As shown in  FIG.  26   , blue LED  20 B has a blue efficiency vs. current density  71 , green LED  20 G has a green efficiency vs. current density  72 , and red LED  20 R has a red efficiency vs. current density  73  illustrated by the labeled lines of the graph. Blue efficiency vs. current density  71  has a blue efficiency maximum  71 M, green efficiency vs. current density  72  has a green efficiency maximum  72 M, and red efficiency vs. current density  73  has an approximate red efficiency maximum  73 M (that can be at a greater current density than is shown in  FIG.  26   , given the limited data set acquired and plotted in  FIG.  26   ). 
     As shown in  FIG.  26   , green LED  20 G has green efficiency maximum  72 M at a lower current density than blue efficiency maximum  71 M. Both blue and green efficiency maximums  71 M and  72 M are at a lower current density than red efficiency maximum  73 M. Green efficiency maximum  72 M is at a current or current density that is approximately one half of blue efficiency maximum  71 M. Therefore, if current is supplied to both a single blue LED  20 B and a multi-LED structure  99  comprising two green LEDs  20 G electrically connected in parallel (e.g., as shown in  FIGS.  1 A,  1 B,  5 ,  8 ,  11    and others) at blue efficiency maximum  71 M, the electrical current that passes through each green LED  20 G will be one half the electrical current that passes through blue LED  20 B and the current density passing through green LED  20 G will likewise be one half that of the current density passing through blue LED  20 B. In this configuration, both blue LED  20 B and green LED  20 G can operate at approximately maximum efficiency while using the same current supplied by a common current supply, improving their efficiency in a display or lamp  80  (as discussed further below with respect to  FIGS.  27 - 30   ). (Both current and current density are referenced since, if LEDs  20  are the same size, current and current density are directly related.) 
     As shown in  FIG.  26   , red LED  20 R is less efficient than blue or green LEDs  20 B,  20 G at a given current density. Moreover, according to some embodiments, red LEDs  20 R can operate at a lower voltage than blue or green LEDs  20 B,  20 G. For example, blue-light-emitting compound semiconductor materials can emit light at voltages ranging from 2.5-3.7 volts, green-light-emitting compound semiconductor materials can emit light at voltages ranging from 1.9-4 volts, and red-light-emitting compound semiconductor materials can emit light at voltages ranging from 1.6-2 volts. Thus, blue and green LEDs  20 B,  20 G can operate effectively at a common voltage (e.g., 3.6 volts) but red LEDs  20 R can require a different voltage. Providing such different voltages can require additional control or power circuitry in a display or lamp  80 . Therefore, according to embodiments of the present disclosure, red LEDs  20 R are provided in a series connected red multi-LED structure  99 R used in a display, lamp, or indicator so that the driving voltage of red multi-LED structure  99 R is greater than that of a single red LED  20 R therein. Consequently, each red LED  20 R in a red multi-LED structure  99 R can be operated more efficiently by providing a more optimized driving voltage even while red multi-LED structure  99 R itself is driven at the same voltage as parallel connected green and blue LEDs  20 G,  20 B. 
     According to some embodiments of the present disclosure and as illustrated in  FIG.  27   , a display or lamp controller  50  or pixel controller  66  supplies pixels  60  and red, green, and blue LEDs  20 R,  20 G,  20 B with a common voltage. For example, if two red LEDs  20 R are connected in series at a given voltage, each of red LEDs  20 R can be driven at one half the given voltage. For example, if 3.6 volts is provided to blue, green, and red 
     LEDs  20 B,  20 G,  20 R, blue and green LEDs  20 B,  20 G can be driven at 3.6 volts and two red LEDs  20 R are each driven at 1.8 volts because they are electrically connected in series. Furthermore, if two sets of LEDs  20  as described are electrically connected in series, doubling the driving voltage to 7.2-8 volts, the driving voltage can be approximately equal to the voltage used to drive series-connected red, green, and blue LEDs  20 R,  20 G,  20 B. Green LEDs  20 G can be connected in parallel as part of a green multi-LED structure  99 G and red LEDs  20 R can be connected in series as part of a red multi-LED structure  99 R. Therefore, according to embodiments of the present disclosure, providing a higher voltage color light-emitting system (e.g., a display or lamp  80 ) and using series- and parallel-connected multi-LED structures  99  and LEDs  20  increases system power efficiency and also increases LED  20  light-emitting efficiency by optimizing LED driving voltage and current density, and therefore external quantum efficiency. 
     A matrix-addressed display  80  (or lamp  80 ) with pixels  60  using multi-LED structures  99  is illustrated in  FIGS.  27 - 30   . As shown in these Figures, pixels  60  are arranged in a pixel array  68  on a display or lamp substrate  82  or any other desired substrate. Embodiments of the present disclosure are not limited to display or lamp applications. Each pixel  60  comprises a pixel controller  66  driven by a power/voltage signal  54 , ground  56 , and control signals  52  (e.g., a row control signal and a column control signal). As shown in  FIG.  27   , each pixel  60  comprises a blue sub-pixel  63  comprising a blue LED  20 B, a green sub-pixel  62  comprising a green multi-LED structure  99 G having green LEDs  20 G electrically connected in parallel, and a red sub-pixel  61  comprising a red multi-LED structure  99 R having red LEDs  20 R electrically connected in series. Red, green, and blue sub-pixels  61 ,  62 ,  63  can be driven at a common voltage and with more efficient current density and quantum efficiency. 
     As shown in  FIG.  28   , blue sub-pixel  63  can comprise one blue LED  20 B, green sub-pixel  62  can comprise three green LEDs  20 G electrically connected in parallel in one green multi-LED structure  99 G, and red sub-pixel  61  can comprise three red LEDs  20 R electrically connected in series in one red multi-LED structure  99 R. Such arrangements of LEDs  20  and multi-LED structures  99  can improve system power efficiency. 
     As illustrated in the embodiment of  FIG.  29   , blue sub-pixel  63  can comprise two blue-light-emitting blue LEDs  20 B in a blue multi-LED structure  99 B. Green sub-pixel  62  can comprise four green LEDs  20 G in one or two green multi-LED structures  99 G that emit green light. For example, four green LEDs  20 G can be electrically connected in series and parallel in one green multi-LED structure  99 G as shown, two series-connected green multi-LED structures  99 G each comprising two green LEDs  20 G connected in parallel, or two parallel-connected green multi-LED structures  99 G each comprising two green LEDs  20 G connected in series. Red sub-pixel  61  can comprise four red LEDs  20 R electrically connected in series that emit red light in one red multi-LED structure  99 R or two series-connected red multi-LED structures  99 R each comprising two red LEDs  20 R electrically connected in series. 
     As illustrated in the embodiment of  FIG.  30   , red, green, and blue sub-pixels  61 ,  62 ,  63  can be connected as illustrated in  FIG.  29   . In addition, a white-light emitting white sub-pixel  64  comprises a series-connected combination of red, green, and blue LEDs  20 R,  20 G,  20 B that together emit white light. Red, green, blue, and white sub-pixels  61 ,  62 ,  63 ,  64  can be driven at a common voltage greater than the driving voltage of at least one and, in some embodiments any, single LED  20  and each of the color sub-pixels are controlled with approximately their best light-emitting efficiency. Such an arrangement, as in  FIG.  29   , can use double the driving voltage and consequently reduce power losses in a display or lamp  80  system. 
     As shown in  FIG.  31   , a display or lamp  80  according to embodiments of the present disclosure can comprise a pixel array  68  of pixels  60  disposed on a display or lamp substrate  82  and controlled by controller  50  with power and ground signals  54 ,  56  and control signals  52 . Each pixel  60  comprises red, green, and blue sub-pixels  61 ,  62 ,  63  (and optionally white sub-pixel  64 , not shown) disposed on a target (pixel) substrate  70  and comprises one or more multi-LED structures  99  and, optionally, LEDs  20 , for example as illustrated in any of  FIGS.  25  and  27 - 30   .  FIG.  32    is a schematic structural perspective of the structure of  FIG.  31    with the addition of a pixel controller  66  and without the electrical connections indicated in  FIG.  31   . In some embodiments, pixel  60  is an active-matrix pixel with a pixel controller  66 . In some embodiments, pixel  60  is a passive-matrix pixel and does not include a pixel controller  66  (not shown). 
     In some embodiments of the present disclosure and as illustrated in  FIG.  33   , multi-LED structures  99  comprise at least one LED  20  biased in a forward direction and one LED  20  biased in an opposite direction. As shown in  FIG.  33   , first LED  20 A is biased in one direction, indicated by the ‘+’ symbol on emission portion  33  and ‘−’ symbol on cantilever portion  34  and second LED  20 B is biased in an opposite direction, indicated by the ‘+’ symbol on cantilever portion  34  and ‘−’ symbol on emission portion  33 . Thus, if multi-LED structure  99  is driven by an alternating current, multi-LED structure  99  can emit light in both positive and negative cycles, alternately from first LED  20 A and second LED  20 B. 
     As shown in  FIG.  34   , additional non-native LEDs  20  can be disposed on multi-LED native substrate  10  of multi-LED structure  99 , for example by micro-transfer printing the additional LEDs  20  onto multi-LED native substrate  10 . The additional LED  20  and native first and second LEDs  20 A,  20 B of multi-LED structure  99  can be electrically connected in a common step with common materials. 
     Furthermore, according to some embodiments, a multi-LED structure  99  can comprise additional multi-LED structures  99  disposed on multi-LED native substrate  10 , as shown in  FIG.  35    with first multi-LED structure  99 A comprising first multi-LED native substrate  10 A and second multi-LED structure  99 B comprising second multi-LED native substrate  10 B, disposed on first multi-LED native substrate  10 A, together with additional LEDs  20 . LEDs  20  of multi-LED structure  99  and any LEDs  20  disposed directly on multi-LED native substrate  10  can comprise a semiconductor material different from the semiconductor material of semiconductor layer  30 , for example so that the different LEDs  20  can emit different colors of light and form a display pixel  60  or lamp light-emitter. Thus, all of LEDs  20  of an entire pixel  60  or multi-color emitter (e.g., as shown in  FIGS.  27 - 30   ), possibly including additional multi-LED structures  99  can be disposed on a multi-LED native substrate  10  and can be a micro-transfer printable structure. For example,  FIG.  35    illustrates a series-connected red-light-emitting red multi-LED structure  99 R (e.g., as shown in  FIGS.  6 ,  9   ) with a green-light-emitting green multi-LED structure  99 G (e.g., as shown in  FIGS.  5 ,  8   ) disposed on first multi-LED native substrate  10 A of red multi-LED structure  99 R together with a blue-light-emitting blue LED  20 B (electrically connected as shown in  FIG.  27   ) and a series-connected white-light sub-pixel  64  comprising a red LED  20 R, a green LED  20 G, and a blue LED  20 B (electrically connected as shown in  FIG.  30   ) to construct a pixel  60 . In an active-matrix embodiment, pixel controller  66  can also be micro-transfer printed to first multi-LED native substrate  10 A (not shown). 
     According to embodiments of the present disclosure and as illustrated in  FIG.  36   , a method of making a multi-LED structure  99  comprises providing a native source wafer  40  with sacrificial portions  44  in step  100 , disposing a single, unitary, and contiguous multi-LED native substrate  10  in step  110  with or without a seed layer directly on or over sacrificial portions  44 , disposing semiconductor layers  30  on multi-LED native substrate  10  in step  120 , and patterning semiconductor layers  30  in step  130  to form spatially separated semiconductor portions  30 P, semiconductor portions  30 P defining at least a first LED  20 A and a second LED  20 B separate from first LED  20 A. First LED  20 A and second LED  20 B each comprise (i) a first layer  31  having a cantilever portion  34  and a base portion  36 , and (ii) a second layer  32  disposed only over base portion  36  of first layer  31  forming emission portion  33 . In some embodiments, cantilever portion  34  of first LED  20 A extends in a first direction D 1  and base portion  36  of first LED  20 A extends in a second direction D 2  different from first direction D 1 . In some embodiments, cantilever portion  34  of first LED  20 A has a first cantilever length L 1 , cantilever portion  34  of second LED  20 B has a second cantilever length L 2 , and an LED emission separation distance LS between a light-emitting area of first LED  20 A emission portion  33  and a light-emitting area of second LED  20 B emission portion  33  is less than or equal to first cantilever length L 1  or less than or equal to second cantilever length L 2 , and in some embodiments, both are true. 
     In step  140 , an LED electrode  28  is disposed on at least a portion of multi-LED native substrate  10  or a non-semiconductor structure in semiconductor first layer  31  (e.g., a patterned dielectric layer  24 , and disposed on at least a portion of first LED  20 A and on at least a portion of second LED  20 B so that LED electrode  28  electrically connects first LED  20 A to second LED  20 B. 
     According to some embodiments, sacrificial portions  44  are etched to release multi-LED structures  99  from native source wafer  40  in step  150 , a stamp is provided in step  160 , a target substrate  70  is provided in step  170 , and multi-LED structures  99  are micro-transfer printed from native source wafer  40  to target substrate  70  with the stamp in step  180 . This process corresponds to the native source wafer structure of  FIG.  24 A . In the illustrative method of  FIG.  36   , multi-LED structures  99  can be disposed by a stamp on display or lamp substrate  82  with first layer  31  between second layer  32  and display or lamp substrate  82  (or target substrate  70 ) so that first layer  31  is on or adjacent to display or lamp substrate  82 . If an inverted printed multi-LED structures  99  with second layer  32  between first layer  31  and display or lamp substrate  82  is desired, a second stamp can remove multi-LED structures  99  from the stamp that retrieved multi-LED structures  99  from native source wafer  40  and then print them to display or lamp substrate  82 . 
     According to embodiments of the present disclosure and as illustrated in  FIG.  37   , a method of making a multi-LED structure  99  comprises providing a native source wafer  40  in step  100 A, disposing single, unitary, and contiguous multi-LED native substrate  10  in step  110  with or without a seed layer, disposing semiconductor layers  30  on multi-LED native substrate  10  in step  120 , and patterning semiconductor layers  30  in step  130  to form spatially separated semiconductor portions  30 P, the semiconductor portions  30 P defining at least a first LED  20 A and a second LED  20 B separate from first LED  20 A. First LED  20 A and second LED  20 B each comprise (i) a first layer  31  having a cantilever portion  34  and a base portion  36 , and (ii) a second layer  32  disposed only over base portion  36  of first layer  31  forming emission portion  33 . In some embodiments, cantilever portion  34  of first LED  20 A extends in a first direction D 1  and base portion  36  of first LED  20 A extends in a second direction D 2  different from first direction D 1 . In some embodiments, cantilever portion  34  of first LED  20 A has a first cantilever length L 1 , cantilever portion  34  of second LED  20 B has a second cantilever length L 2 , and an LED emission separation distance LS between a light-emitting area of first LED  20 A emission portion  33  and a light-emitting area of second LED  20 B emission portion  33  is less than or equal to first cantilever length L 1  or less than or equal to second cantilever length L 2 , and in some embodiments, both are true. 
     In step  140 , an LED electrode  28  is disposed on at least a portion of single, unitary, and contiguous multi-LED native substrate  10  or non-semiconductor structure in semiconductor layer  30  and disposed on at least a portion of first LED  20 A and on at least a portion of second LED  20 B, LED electrode  28  electrically connecting first LED  20 A to second LED  20 B. 
     In step  200 , sacrificial portions  44  (release layers) are disposed and patterned over LED  20 , a handle substrate  41  is provided in step  210 , and in step  220  handle substrate  41  is adhered to sacrificial portions  44  with adhesive layer  45 . In step  230 , native source wafer  40  is removed, e.g., by grinding or laser lift-off, leaving multi-LED structure  99  adhered with adhesive layer  45  to handle substrate  41 . 
     According to some embodiments, sacrificial portions  44  are etched to release multi-LED structures  99  from native source wafer  40  in step  150 A, a stamp is provided in step  160 , a target substrate  70  is provided in step  170 , and multi-LED structures  99  are micro-transfer printed from native source wafer  40  to target substrate  70  with the stamp in step  180 . This process corresponds to the native source wafer structure of  FIG.  24 B . In the illustrative method of  FIG.  37   , multi-LED structures  99  can be disposed by a stamp on display or lamp substrate  82  (target substrate  70 ) in an inverted arrangement with second layer  32  between first layer  31  and display or lamp substrate  82  so that second layer  32  is on or adjacent to display or lamp substrate  82 . If a non-inverted printed multi-LED structures  99  with first layer  31  between second layer  32  and display or lamp substrate  82  is desired, a second stamp can remove multi-LED structures  99  from the stamp that retrieved multi-LED structures  99  from native source wafer  40  and then print them to display or lamp substrate  82 . 
     The arrangements of LEDs  20  and multi-LED structures  99  in  FIGS.  27 - 30    can improve system power efficiency by using a common (and optionally greater) voltage for the sub-pixels and electrically connecting LEDs  20  and multi-LED structures  99  to match current densities and quantum efficiencies of sub-pixels to LED  20  characteristics for approximately best efficiencies. For example, in embodiments comprising LEDs  20  having the characteristics illustrated in  FIG.  26   , a driving voltage can be approximately 8 volts or in a range of 7 to 9 volts while operating individual LEDs  20  at approximately their most efficient current density and voltage. 
     In some embodiments of the present disclosure, LEDs  20  are inorganic light-emitting diodes. As used herein, two LEDs  20  that are serially connected are two LEDs  20  that are electrically connected in serial, so that the first terminal of an LED  20  is electrically connected to the second terminal of another LED  20 . The remaining two terminals are electrically connected to common voltage signal  54  or common ground signal  56  and a control signal  52 , for example provided by controller  50  or pixel controller  66 . The first terminals of two LEDs  20  that are electrically connected in parallel are connected together and the second terminals of the two parallel-connected LEDs  20  are likewise connected together. The first and second terminals are electrically connected to common voltage signal  54  or common ground signal  56  and a control signal  52 , for example provided by pixel controller  66 . Both LEDs  20  can be biased in the same forward direction. 
     According to embodiments of the present disclosure, display or lamp substrate  82  is a substrate having substantially parallel and opposing sides, on one of which target substrates  70  are disposed for example by surface mount techniques. In some embodiments, LEDs  20  and multi-LED structures  99  are disposed directly on display or lamp substrate  82 , for example by micro-transfer printing. Display or lamp substrate  82  can be a glass, polymer, ceramic, or metal substrate having at least one side suitable for constructing electrical conductors. Display or lamp substrate  82  or target substrate  70  can have a thickness from 5 microns to 20 mm (e.g., 5 to 10 microns, 10 to 50 microns, 50 to 100 microns, 100 to 200 microns, 200 to 500 microns, 500 microns to 0.5 mm, 0.5 to 1 mm, 1 mm to 5 mm, 5 mm to 10 mm, or 10 mm to 20 mm) and can be, but is not necessarily, transparent (e.g., at least 50%, at least 70%, at least 80%, or at least 90% transparent to visible light). 
     Common power and ground signals  54 ,  56  can be made using photolithographic, printed circuit board, inkjet, or display techniques and materials, for example using copper, aluminum, or silver materials to form patterned electrical conductors that conduct electrical control  52  and power signals  54  to pixels  60  to enable pixels  60  to display information or emit light, for example for an image, illuminator (lamp), or indicator. The electrical conductors can be electrically conductive metal wires formed, or disposed on, display or lamp substrate  82  using, for example, photolithographic methods, tools, and materials. Similarly, electrodes can be made using photolithographic methods, tools, and materials. 
     Target substrate  70  can also be glass or plastic or can be a semiconductor, such as silicon. Target substrate  70  can be transparent or opaque and, if transparent, light emitted from LEDs  20  can be transmitted through target substrate  70 , depending on the orientation of LEDs  20  (e.g., top-emitting or bottom-emitting). 
     Native source wafers  40  can be compound semiconductor or silicon wafers and patterned sacrificial layer  42 , LED structure tethers  25 , and LEDs  20  can be made using photolithographic methods and materials found in the integrated circuit industries. For example, a source wafer can be GaN, InGaN, or GaAs. Inorganic light-emitting diodes  20  can be made in a semiconductor material, such as a compound semiconductor (e.g., GaN or GaAs, with or without doping). The semiconductor material can be crystalline. Any one or each of LEDs  20  can have at least one of a width from 2 to 50 μm (e.g., 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm), a length from 2 to 50 μm (e.g., 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm), and a height from 2 to 50 μm (e.g., 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm). 
     In some embodiments, in operation, power  54 , ground  56 , and control signals  52  (e.g., row signals and column signals) are applied to electrical conductors on display or lamp substrate  82 . The electrical conductors on display or lamp substrate  82  are in electrical contact with multi-LED structure  99  and any other LEDs  20  and supply electrical power at a desired voltage to common power signal  54 , supply an electrical ground to common ground signal  56 , and supply control signals  52  to multi-LED structures  99  and LEDs  20 . The ground  56 , voltage  54 , and control signals  52  are electrically conducted through LED electrodes  28  and electrodes formed on target substrate  70  an any display or lamp substrate  82  to LEDs  20 , any pixel controller  66 , and any display or lamp controller  50  to control LEDs  20  and multi-LED structures  99  to emit light. 
     Methods of forming useful micro-transfer printable structures are described, for example, in the U.S. Pat. 8,889,485. For a discussion of micro-transfer printing techniques see, U.S. Pat. Nos. 8,722,458, 7,622,367 and 8,506,867, the disclosures of which are hereby incorporated by reference in their entirety. Micro-transfer printing using compound micro-assembly structures and methods can also be used with the present disclosure, for example, as described in U.S. patent application Ser. No. 14/822,868, filed Aug. 10, 2015, entitled Compound Micro-Assembly Strategies and Devices, the disclosure of which is hereby incorporated by reference in its entirety. In some embodiments, pixel  60  is a compound micro-assembled device. 
     Micro-transfer printable elements can be constructed using foundry fabrication processes used in the art. Layers of materials can be used, including materials such as metals, oxides, nitrides and other materials used in the integrated-circuit art. Multi-LED structures  99  can have different sizes, for example, of no more than 1000 square microns, 10,000 square microns, 100,000 square microns, or 1 square mm, or larger, and can have variable aspect ratios, for example at least 1:1, 2:1, 5:1, or 10:1. Multi-LED structures  99  and multi-LED native substrate  10  can be rectangular or can have other shapes. 
     Native source wafers  40  and multi-LED structures  99 , micro-transfer printing stamps, target substrates  70 , and display or lamp substrates  82  can be made separately and at different times or in different temporal orders or locations and provided in various process states. 
     As is understood by those skilled in the art, the terms “over” and “under” are relative terms and can be interchanged in reference to different orientations of the layers, elements, and substrates included in the present disclosure. For example, a first layer on a second layer, in some implementations means a first layer directly on and in contact with a second layer. In other implementations a first layer on a second layer includes a first layer and a second layer with another layer therebetween. 
     Having described certain implementations of embodiments, it will now become apparent to one of skill in the art that other implementations incorporating the concepts of the disclosure may be used. Therefore, the disclosure should not be limited to certain implementations, but rather should be limited only by the spirit and scope of the following claims. 
     Throughout the description, where apparatus and systems are described as having, including, or comprising specific components, or where processes and methods are described as having, including, or comprising specific steps, it is contemplated that, additionally, there are apparatus, and systems of the disclosed technology that consist essentially of, or consist of, the recited components, and that there are processes and methods according to the disclosed technology that consist essentially of, or consist of, the recited processing steps. 
     It should be understood that the order of steps or order for performing certain action is immaterial so long as the disclosed technology remains operable. Moreover, two or more steps or actions in some circumstances can be conducted simultaneously. The disclosure has been described in detail with particular reference to certain embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the claimed invention. 
     PARTS LIST 
     A cross section line 
     B cross section line 
     C LED center 
     CS LED contact separation distance 
     D 1  first direction 
     D 2  second direction 
     E LED length 
     E 1  first LED length 
     E 2  second LED length 
     L cantilever length 
     L 1  first cantilever length 
     L 2  second cantilever length 
     LS LED emission separation distance 
     X 1 , Y 1  first distance 
     X 2 , Y 2  second distance 
       10  multi-LED native substrate 
       10 A first multi-LED native substrate 
       10 B second multi-LED native substrate 
       10 M multi-LED native substrate mesa 
       12 A first LED substrate edge 
       12 B second LED substrate edge 
       14 A first LED substrate corner 
       14 B second LED substrate corner 
       20  LED 
       20 A first LED 
       20 B second LED/blue LED 
       20 R red LED 
       20 G green LED 
       22  LED tether 
       24  patterned dielectric layer 
       25  LED structure tether 
       26  LED contact pad 
       26 A first LED contact pad 
       26 B second LED contact pad 
       28  LED electrode 
       28 A first LED electrode 
       28 B second LED electrode 
       30  semiconductor layer 
       30 A first semiconductor portion 
       30 B second semiconductor portion 
       30 P semiconductor portion 
       31  first layer 
       32  second layer 
       33  emission portion 
       33 A first emission portion 
       33 B second emission portion 
       34  cantilever portion 
       34 A first cantilever portion 
       34 B second cantilever portion 
       36  base portion 
       38  recombination zone 
       39  conduction zone 
       40  native source wafer 
       41  handle wafer 
       42  patterned sacrificial layer 
       44  sacrificial portion 
       45  adhesive layer 
       46  anchor 
       48  epitaxial layers 
       50  display controller/lamp controller 
       52  control signal 
       54  power/voltage signal 
       56  ground 
       60  pixel 
       61  red sub-pixel 
       62  green sub-pixel 
       63  blue sub-pixel 
       64  white sub-pixel 
       66  pixel controller 
       68  pixel array 
       70  target substrate 
       71  blue efficiency vs. current density 
       71 M blue efficiency maximum 
       72  green efficiency vs. current density 
       72 M green efficiency maximum 
       73  red efficiency vs. current density 
       73 M red efficiency maximum 
       80  display/lamp 
       82  display substrate/lamp substrate 
       99  multi-LED structure 
       99 A first multi-LED structure 
       99 B second multi-LED structure/blue multi-LED structure 
       99 G green multi-LED structure 
       99 R red multi-LED structure 
       100  provide native source wafer with sacrificial portions step 
       100 A provide native source wafer with sacrificial portions step 
       110  dispose multi-LED native substrate step 
       120  dispose semiconductor layer over sacrificial portions step 
       130  pattern semiconductor layer step 
       140  dispose electrode step 
       150  etch sacrificial portions step 
       150 A etch sacrificial portions step 
       160  provide stamp step 
       170  provide target substrate step 
       180  micro-transfer print multi-LED structure step 
       200  form sacrificial portions step 
       210  provide handle substrate step 
       220  adhere handle substrate step 
       230  remove native source wafer step