Patent Sample 3 – Electrical Engineering – Provisional Patent Application

Arrays of Light Emitting Devices

(Publication No.: US 2011/0084292)

RELATED APPLICATIONS
[001] This application claims priority to U.S. Provisional Application No. 61/247,862, filed Oct. 1, 2009, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD
[002] The invention relates to light-emitting devices, and related components, processes, systems and methods.

BACKGROUND
[003] A light emitting diode (LED) often can provide light in a more efficient manner than an incandescent light source and/or a fluorescent light source. The relatively high power efficiency associated with LEDs has created an interest in using LEDs to displace conventional light sources in a variety of lighting applications. For example, in some instances LEDs are being used as traffic lights and to illuminate cell phone keypads and displays.

[004] Typically, an LED is formed of multiple layers, with at least some of the layers being formed of different materials. In general, the materials and thicknesses selected for the layers determine the wavelength(s) of light emitted by the LED. In addition, the chemical composition of the layers can be selected to try to isolate injected electrical charge carriers into regions (commonly referred to as quantum wells) for relatively efficient conversion to optical power. Generally, the layers on one side of the junction where a quantum well is grown are doped with donor atoms that result in high electron concentration (such layers are commonly referred to as n-type layers), and the layers on the opposite side are doped with acceptor atoms that result in a relatively high hole concentration (such layers are commonly referred to as p-type layers).

[005] A common approach to preparing an LED is as follows. The layers of material are prepared in the form of a wafer. Typically, the layers are formed using an epitaxial deposition technique, such as metal-organic chemical vapor deposition (MOCVD), with the  initially deposited layer being formed on a growth substrate. The layers are then exposed to various etching and metallization  techniques to form contacts for electrical current injection, and the wafer is subsequently sectioned into individual LED chips.  Usually, the LED chips are packaged.

[006] During use, electrical energy is usually injected into an LED and then converted into electromagnetic radiation (light), some of which is extracted from the LED.

[007] Conventional systems can be configured such that the array of light emitting devices comprises light emitting devices having equal emitting areas and often the same aspect ratio of the surface of the light emitting devices. For example, an array of four light emitting devices wherein each light emitting device has a 12 mm.sup.2 emitting area and a 3.times.4 aspect ratio of the surface of the light emitting device. Such systems may have non-optimum emission efficiency, especially when light emission having a particular color is produced by selecting each light emitting device with a particular color point, or chromaticity, and maximizing light output in the same time.

[008] FIGS. 3, 3A, and 3B show exemplary light emitting device (LED) die orientations for multi-chip arrays employed in the prior art. FIG. 3 shows an array 100 of light emitting devices that includes two LEDs 102 and 104 arranged in a single row. The emitting area of LED 102 is equal to emitting area of LED 104. FIG. 3A shows an array 110 of light emitting devices that includes four LEDs 112, 114, 116, and 118 arranged in a 2.times.2 matrix (i.e., arranged in two rows and two columns). The array is configured such that each LED in the array has an equal to each other emitting areas (the emitting area of LED 112 is equal to emitting area of LED 114, LED 116, and LED 118). FIG. 3B shows an array 120 of light emitting devices that includes twelve LEDs 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133 arranged in a 3.times.4 matrix (i.e., arranged in three rows and four columns). The array is configured such that each LED in the array has an equal to each other emitting areas (the emitting area of LED 122 is equal to emitting area of LED 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, and 133).

SUMMARY

[009] The invention relates to arrays of light-emitting devices, and related components, systems and methods.

[010] In one embodiment, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices being configured such that at least one of the light emitting devices in the array has an emitting area different than an emitting area of the other light emitting devices in the array.

[011] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices has all the light emitting devices with different than each other emitting areas.

[012] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises two light emitting devices with unequal emitting areas. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof.

[013] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises three light emitting devices. The array could be formed of Red, Green, Blue, White, UV LED or combinations thereof. The array of light emitting devices is configured such that two light emitting devices have equal emitting areas and the other light emitting device has an emitting area different than that of said two light emitting devices. The three light emitting devices could be disposed randomly, or in a matrix having two rows and two columns, or in a rectangular matrix having one row and three columns.

[014] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises three light emitting devices. The array of light emitting devices is configured such that the three light emitting devices of said array have emitting areas different from each other. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The three light emitting devices could be disposed randomly, or in a matrix having two rows and two columns, or in a rectangular matrix having one row and three columns.

[015] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises four light emitting devices. The array of light emitting devices is configured such that three light emitting devices have equal emitting areas, and the other light emitting device has emitting area different from those of said three light emitting devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The four light emitting devices could be disposed randomly, or in a matrix having two rows and two columns, or in a rectangular matrix having one row and four columns.

[016] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises four light emitting devices. The array of light emitting devices is configured such that the two light emitting devices in the array have equal emitting areas and the other two light emitting devices have equal emitting areas; the emitting area of the two devices is being different than the emitting area of the other two devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The four light emitting devices could be disposed randomly, or in a matrix having two rows and two columns, or in a rectangular matrix having one row and four columns.

[017] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises four light emitting devices. The array of light emitting devices is configured such that two light emitting devices have equal emitting areas and the other two light emitting devices have different than each other and different than emitting areas of the other two light emitting devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The four light emitting devices could be disposed randomly, or in a matrix having two rows and two columns, or in a rectangular matrix having one row and four columns.

[018] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises four light emitting devices. The array of light emitting devices is configured such that the four light emitting devices of said array have emitting areas different from each other. The array could be  formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The four light emitting devices could be  disposed randomly, or in a matrix having two rows and two columns, or in a rectangular matrix having one row and four columns.

[019] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises five light emitting devices. The array of light emitting devices is configured such that the four light emitting devices in the array have equal emitting areas and the other light emitting device has an emitting area different than that of said four light emitting devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The five light emitting devices could be disposed randomly, or in a matrix having two rows and three columns, or in a rectangular matrix having one row and five columns.

[020] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises five light emitting devices. The array of light emitting devices is configured such that three light emitting devices have equal emitting areas and the other two light emitting devices have equal emitting areas; the emitting area of said three devices is being different than the emitting area of the other two devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The five light emitting devices could be disposed randomly, or in a matrix having two rows and three columns, or in a rectangular matrix having one row and five columns.

[021] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises five light emitting devices. The array of light emitting devices is configured such that three light emitting devices have equal emitting areas and the other two light emitting devices have different than each other and different than emitting areas of the other three light emitting devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The five light emitting devices could be disposed randomly, or in a matrix having two rows and three columns, or in a rectangular matrix having one row and five columns.

[022] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises five light emitting devices. The array of light emitting devices is configured such that two light emitting devices have equal emitting areas and the other three light emitting devices have different than each other and different than emitting areas of the other two light emitting devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or ombinations thereof. The five light emitting devices could be disposed randomly, or in a matrix having two rows and three columns, or in a rectangular matrix having one row and five columns.

[023] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises five light emitting devices. The array of light emitting devices is configured such that two light emitting devices have equal emitting areas and other two light emitting devices have equal emitting areas; the emitting area of the first two devices is being different than the emitting area of the other said two devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The five light emitting devices could be disposed randomly, or in a matrix having two rows and three columns, or in a rectangular matrix having one row and five columns.

[024] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises five light emitting devices. The array of light emitting devices is configured such that the five light emitting devices of said array have emitting areas different from each other. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The five light emitting devices could be disposed randomly, or in a matrix having two rows and three columns, or in a rectangular matrix having one row and five columns.

[025] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises six light emitting devices. The array of light emitting devices is configured such that the five light emitting devices in said array have equal emitting areas and the other light emitting device has an emitting area different than that of said five light emitting devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The six light emitting devices could be disposed randomly, or in a rectangular matrix having two rows and three columns, or in a rectangular matrix having one row and six columns.

[026] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises six light emitting devices. The array of light emitting devices is configured such that four light emitting devices have equal emitting areas and the other two light emitting devices have equal emitting areas; the emitting area of the said four devices is being different than the emitting area of the other two devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The six light emitting devices could be disposed randomly, or in a rectangular matrix having two rows and three columns, or in a rectangular matrix having one row and six columns.

[027] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises six light emitting devices. The array of light emitting devices is configured such that four light emitting devices have equal emitting areas and the other two light emitting devices have different than each other and different than emitting areas of the other four light emitting devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or ombinations thereof. The six light emitting devices could be disposed randomly, or in a rectangular matrix having two rows and three columns, or in a rectangular matrix having one row and six columns.

[028] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises six light emitting devices. The array of light emitting devices is configured such that two light emitting devices have equal emitting areas and the other four light emitting devices have different than each other and different than emitting areas of the other two light emitting devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The six light emitting devices could be disposed randomly, or in a rectangular matrix having two rows and three columns, or in a rectangular matrix having one row and six columns.

[029] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises six light emitting devices. The array of light emitting devices is configured such that three light emitting devices have equal emitting areas and the other three light emitting devices have equal emitting areas; the emitting area of the said three devices is being different than the emitting area of the other three devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The six light emitting devices could be disposed randomly, or in a rectangular matrix having two rows and three columns, or in a rectangular matrix having one row and six columns.

[030] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises six light emitting devices. The array of light emitting devices is configured such that three light emitting devices have equal emitting areas and the other three light emitting devices have different than each other and different than emitting areas of the other three light emitting devices. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The six light emitting devices could be disposed randomly, or in a rectangular matrix having two rows and three columns, or in a rectangular matrix having one row and six columns.

[031] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises six light emitting devices. The array of light emitting devices is configured such that two light emitting devices have equal emitting areas and other two light emitting devices have equal emitting areas and the other two light emitting devices have equal emitting areas; the emitting area of each pair of light emitting devices is being different than each other. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The six light emitting devices could be disposed randomly, or in a rectangular matrix having two rows and three columns, or in a rectangular matrix having one row and six columns.

[032] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises six light emitting devices. The array of light emitting devices is configured such that two light emitting devices have equal emitting areas (area 1), and another two light emitting devices have equal emitting areas (area 2), but the other two light emitting devices have unequal emitting areas (area 3 and area 4); emitting area 1, 2, 3, and 4 are being unequal to each other. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The six light emitting devices could be disposed randomly, or in a rectangular matrix having two rows and three columns, or in a rectangular matrix having one row and six columns.

[033] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises six light emitting devices. The array of light emitting devices is configured such that three light emitting devices have equal emitting areas (area 1), another two light emitting devices have equal emitting areas (area 2), and the other light emitting device have emitting area (area 3) different than that of each pair; emitting area 1, 2, and 3 are being unequal to each other. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The six light emitting devices could be disposed randomly, or in a rectangular matrix having two rows and three columns, or in a rectangular matrix having one row and six columns.

[034] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices comprises six light emitting devices. The array of light emitting devices is configured such that the six light emitting devices of said array have emitting areas different from each other. The array could be formed of Red, Green, Blue, White, UV light emitting device, or combinations thereof. The six light emitting devices could be disposed randomly, or in a rectangular matrix having two rows and three columns, or in a rectangular matrix having one row and six columns.

[035] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices can comprise one or more of the following: a Red LED, Green LED, Blue LED, and White LED. In some cases, the array is configured such that the ratio of the mitting area of the Red LED to the emitting area of the Green LED is in the range from 0.7 to 1.3. In some cases, the array is configured such that the ratio of the emitting area of the Blue LED to the emitting area of the Red LED is in the range from 0.15 to 0.75. In some cases, the array is configured such that the ratio of the emitting area of the Blue LED to the emitting area of the Green LED is in the range from 0.15 to 0.75. In some cases, the array is
configured such that the ratio of the emitting area of the Blue LED to the emitting area of the White LED is in the range from 0.3 to 0.9. In some cases, the array is configured such that the ratio of the emitting area of the White LED to the emitting area of the Red LED is in the range from 0.45 to 1.05. In some cases, the array is configured such that the ratio of the emitting area of the White LED to the emitting area of the Green LED is in the range from 0.45 to 1.05. It should be understood that an array may include one or any combination of the above-noted ratios of emitting areas including all of the above-noted ratios.

[036] In another embodiment of the present invention, a system includes a substrate and an array of light emitting devices supported by the substrate. The array of light emitting devices consists of a Red LED having an emitting area equal to about 12 mm.sup.2, a Green LED having an emitting area equal to about 12 mm.sup.2, a Blue LED having an mitting area equal to about 5.4 mm.sup.2, and a White LED having an emitting area equal to about 9 mm.sup.2.

[037] Some embodiments could further comprise a package containing the substrate and the array of light emitting devices. The package could have a layer configured so that at least about 75% of the light that emerges from the light emitting devices and impinges on the layer passes through the layer, wherein the layer is disposed such that a distance between a surface of the array of light emitting devices and a surface of the layer nearest to the surface of the array of light emitting devices is from about five microns to about 400 microns.

[038] In some embodiments, the array of light emitting devices is configured such that for any given pair of LEDs having unequal emitting areas, the ratio of emitting area of a smaller LED to the emitting area of a larger LED is in the range from 0.07 to 0.96.

[039] In some embodiments, the array of light emitting devices can consist of 2*N light emitting devices where N is a positive integer and the 2*N light emitting devices disposed in a rectangular matrix having N rows and two columns.

[040] In some embodiments, the array of light emitting devices being positioned such that a ratio of a sum of a total area of all of the light emitting devices in the array of light emitting devices to the area defined by the outer perimeter is at least about 0.75.

[041] In some embodiments, the array of light emitting devices being positioned such that the spacing between the nearest edges of neighboring light emitting devices in the array is no more than 200 microns.

[042] In some embodiments, the light emitting devices that have equal emitting areas can also have different aspect ratio of the surface of light emitting devices.

[043] In some embodiments, at least one of the light emitting devices in the array of light emitting devices can include a multi-layer stack of materials that includes a first layer supported by the light generating region. A surface of the first layer can be configured so that light generated by the light generating region can emerge from the light emitting device via a surface of the first layer. The surface of the first layer can have a dielectric function that varies spatially according to a pattern. The pattern can have an ideal lattice constant and a detuning parameter with a value greater than zero. The surface of the first layer can have a dielectric function that varies spatially according to a non-periodic pattern. The surface of the first layer can have a dielectric function that varies spatially according to a quasicrystalline pattern. The surface of the first layer can have a dielectric function that varies spatially according to a complex periodic pattern. The surface of the first layer can have a dielectric function that varies spatially according to a periodic pattern.

[044] The light emitting device can have an edge that is at least about one millimeter long. The light emitting device can have an edge that is at least about 1.5 millimeters.

[045] The layer can include at least one optical component. The optical component can include a photonic lattice, a color filter, a polarization selective layer, a wavelength conversion layer, and/or an anti-reflective coating.

[046] The package can also include a heat sink layer. The package can be mounted on a heat sink device. The package can be mounted on a heat sink device. The package can include a package substrate. The package substrate can be formed of Al, N, Cu, C, Au or combinations thereof. The package can be mounted on a thermoelectric cooler. The light emitting device can be a light emitting diode. The light emitting diode can be a photonic lattice light emitting diode. The light emitting device can be a surface emitting laser. The light emitting device can be a light emitting diode, a laser, an optical amplifier, and/or combinations thereof. The light emitting device can be an OLED, a flat surface-emitting LED, a HBLED, and/or combinations thereof. The system can also include a cooling system configured so that, during use, the cooling system regulates a temperature of the light emitting diode.

[047] The array of light emitting devices can include a plurality of light emitting devices connected electrically in series. The array of light emitting devices can include a plurality of light emitting devices connected electrically in parallel.

[048] Features and advantages of the invention are in the description, drawings and claims.

[0049] In some embodiments, a method of optimizing an LED system for minimum total die area and device junction temperature while maximizing luminous flux is disclosed. The method comprises the following steps: selecting the white point for which the system is to be optimized, selecting a color bin for the White LED, computing what Red, Green, Blue and White lumens are required to achieve the target optimized white point, establishing minimum flux thresholds for each of the primaries to further constrain the solution space, determining dependence of luminous flux on current density for each LED, determining dependence of die temperature on electrical power for each LED, and performing the optimization for chromaticity by optimizing die area and die junction temperature for each LED while maximizing luminous flux and minimizing the total die area of the system.

[050] The preceding summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the attached drawings. For the purpose of illustration the invention, presently preferred embodiments are shown in the drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.

DESCRIPTION OF DRAWINGS

[051] FIG. 1 is a schematic representation of a light-emitting system.

[052] FIG. 2 is a cross-sectional view of a packaged light emitting device.

[053] FIG. 3 is a top view of an array of light emitting devices.

[054] FIG. 3A is a top view of an array of light emitting devices.

[055] FIG. 3B is a top view of an array of light emitting devices.

[056] FIG. 4 is a top view of an array of light emitting devices.

[057] FIG. 5 is a top view of an array of light emitting devices.

[058] FIG. 5A is a top view of an array of light emitting devices.

[059] FIG. 6 is a top view of an array of light emitting devices.

[060] FIG. 6A is a top view of an array of light emitting devices.

[061] FIG. 7 is a top view of an array of light emitting devices.

[062] FIG. 7A is a top view of an array of light emitting devices.

[063] FIG. 8 is a top view of an array of light emitting devices.

[064] FIG. 8A is a top view of an array of light emitting devices.

[065] FIG. 9 is a top view of an array of light emitting devices.

[066] FIG. 9A is a top view of an array of light emitting devices.

[067] FIG. 10 is a top view of an array of light emitting devices.

[068] FIG. 10A is a top view of an array of light emitting devices.

[069] FIG. 10B is a top view of an array of light emitting devices.

[070] FIG. 11 is a cross-sectional view of a packaged light emitting device.

[071] FIG. 12 is a top view of an array of light emitting devices forming a closely packed configuration.

[072] FIG. 13 is a block diagram corresponding to the method of system optimization.

DETAILED DESCRIPTION

[073] FIG. 1 is a schematic representation of a light-emitting system 50 that has an array 60 of LEDs 100 ncorporated therein. Array 60 is configured so that, during use, light that emerges from LEDs 100 emerges from system 50.

[074] Examples of light-emitting systems include projectors (e.g., rear projection projectors, front projection projectors), portable electronic devices (e.g., cell phones, personal digital assistants, laptop computers), computer monitors, large area signage (e.g., highway signage), vehicle interior lighting (e.g. dashboard lighting), vehicle exterior lighting (e.g., vehicle headlights, including color changeable headlights), general lighting (e.g., office overhead lighting), high brightness lighting (e.g., streetlights), camera flashes, medical devices (e.g., endoscopes), telecommunications (e.g., plastic fibers for short range data transfer), security sensing (e.g. biometrics), integrated optoelectronics (e.g., intrachip and interchip optical interconnects and optical clocking), military field communications (e.g., point to point communications), biosensing (e.g., photo-detection of organic or inorganic substances), photodynamic therapy (e.g., skin treatment), night vision goggles, solar powered transit lighting, emergency lighting, airport runway lighting, airline lighting, surgical goggles, wearable light sources (e.g., lifevests). An example of a rear projection projector is a rear projector television. An example of a front projection projector is a projector for displaying on a surface, such as a screen or a wall. In some embodiments, a laptop computer can include a front projection projector.

[075] FIG. 2 shows a side view of an LED 100 in the form of a packaged die. LED 100 includes a multi-layer stack 122 disposed on a submount 120. Multi-layer stack 122 includes a 320 nm thick silicon doped (n-doped) GaN layer 134 having a pattern of openings 150 in its upper surface 110. Multi-layer stack 122 also includes a bonding layer 124, a 100 nm thick silver layer 126, a 40 nm thick magnesium doped (p-doped) GaN layer 128, a 120 nm thick light-generating region 130 formed of multiple InGaN/GaN quantum wells, and a AlGaN layer 132. An n-side contact pad 136 is disposed on layer 134. Packaged LED 100 also includes a package substrate 151 and metalized portions 152 and 138 supported by substrate 151. Metallized portion 152 is electrically connected to n-side contact 136 using a connector 156, for example, a wire bond. Metallized portion 138 is in electrical contact with conductive submount 120 and forms an electrical current path to p-doped layer 128. A frame 142 is supported by substrate 151. Frame 142 supports a transparent cover 140. Typically, transparent cover 140 is formed of a material that transmits at least about 60% (e.g., at least about 70%, at least about 80%, at least about 90%, at least about 95%) of the light that emerges form LED 100 and impinges on transparent cover 140.

[076] Light is generated by LED 100 as follows. P-side contact 138 is held at a positive potential relative to n-side contact 136, which causes electrical current to be injected into LED 100. As the electrical current passes through light-generating region 130, electrons from n-doped layer 134 combine in region 130 with holes from p-doped layer 128, which causes region 130 to generate light. Light-generating region 130 contains a multitude of point dipole radiation sources that emit light (e.g., isotropically) within region 130 with a spectrum of wavelengths characteristic of the material form which light-generating region 130 is formed. For InGaN/GaN quantum wells, the spectrum of wavelengths of light generated by region 130 can have a peak wavelength of about 445 nanometers (nm) and a full width at half maximum (FWHM) of about 30 nm.

[077] It is to be noted that the charge carriers in p-doped layer 126 have relatively low mobility compared to the charge carriers in the n-doped semiconductor layer 134. As a result, placing silver layer 126 (which is conductive) along the surface of p-doped layer 128 can enhance the uniformity of charge injection from contact 138 into p-doped layer 128 and light-generating region 130. This can also reduce the electrical resistance of device 100 and/or increase the injection efficiency of device 100. Because of the relatively high charge carrier mobility of the n-doped layer 134, electrons can spread relatively quickly from n-side contact pad 136 throughout layer 134, so that the current density within light-generating region 130 is substantially uniform across region 130. It is also to be noted that silver layer 126 has relatively high thermal conductivity, allowing layer 126 to act as a heat sink for LED 100 (to transfer heat vertically form multi-layer stack 122 to submount 120).

[078] At least some of the light that is generated by region 130 is directed toward silver layer 126. This light can be reflected by layer 126 and emerge from LED 100 via surface 110, or can be reflected by layer 126 and then absorbed within the semiconductor material in LED 100 via surface 110, or can be reflected by layer 126 and then absorbed within the semiconductor material in LED 100 to produce an electron-hole pair that can combine in region 130, causing region 130 to generate light. Similarly, at least some of the light that is generated by region 130 is directed toward pad 136. The underside of pad 136 is formed of a material (e.g., a Ti/Al/Ni/Au