Light emitting diodes with improved light extraction efficiency

#1. Field of the Invention

#The present invention relates generally to light emitting devices and more particularly to light emitting diodes with enhanced light extraction efficiency.

#2. Description of the Related Art

#FIG. 1A is a schematic diagram of an optical element and a light emitting diode to be bonded to each other in accordance with an embodiment of the present invention.

#FIG. 1B is a schematic diagram of an optical element bonded with a bonding layer to a light emitting diode in accordance with an embodiment of the present invention.

#FIG. 1C is a schematic diagram of an optical element bonded to a light emitting diode in accordance with another embodiment of the present invention.

#FIG. 1A depicts a transparent optical element 2 and a light emitting diode (LED) die 4 to be bonded to each other in accordance with an embodiment of the present invention. In FIG. 1B, in accordance with one embodiment of the present invention, transparent optical element, 2 is bonded to LED die 4 with a transparent bonding layer 6.

#The term “transparent” is used herein to indicate that an optical element so described, such as a “transparent optical element,” a “transparent bonding layer,” a “transparent substrate,” or a “transparent superstrate” transmits light at the emission wavelengths of the LED with less than about 50%, preferably less than about 10%, single pass loss due to absorption or scattering. The emission wavelengths of the LED may lie in the infrared, visible, or ultraviolet regions of the electromagnetic spectrum. One of ordinary skill in the art will recognize that the conditions “less than 50% single pass loss” and “less than 10% single pass loss” may be met by various combinations of transmission path length and absorption constant. As used herein, “optical concentrator” includes but is not limited to total internal reflectors, and includes optical elements having a wall coated with a reflective metal or a dielectric material to reflect or redirect incident light.

#LED die 4 illustrated in FIGS. 1A and 1B includes a first semiconductor layer 8 of n-type conductivity (n-layer) and a second semiconductor layer 10 of p-type conductivity (p-layer). Semiconductor layers 8 and 10 are electrically coupled to active region 12. Active region 12 is, for example, a p-n diode junction associated with the interface of layers 8 and 10. Alternatively, active region 12 includes one or more semiconductor layers that are doped n-type or p-type or are undoped. N-contact 14 and p-contact 16 are electrically coupled to semiconductor layers 8 and 10, respectively. Active region 12 emits light upon application of a suitable voltage across contacts 14 and 16. In alternative implementations, the conductivity types of layers 8 and 9, together with contacts 14 and 16, are reversed. That is, layer 8 is a p-type layer, contact 14 is a p-contact, layer 10 is an n-type layer, and contact 16 is an n-contact.