Abstract: An array of highly efficient micro-LEDs where each micro-LED is an integrated diode structure in a mesa, in which the mesa shape and the light-emitting region are chosen for optimum efficiency. A single one of the micro-LEDs includes, on a substrate and a semiconductor layer, a mesa, a light emitting layer, and an electrical contact. The micro-LEDs in this device have a very high EE because of their shape. Light is generated within the mesa, which is shaped to enhance the escape probability of the light. Very high EEs are achieved, particularly with a near parabolic mesa that has a high aspect ratio. The top of the mesa is truncated above the light-emitted layer (LEL), providing a flat surface for the electronic contact on the top of the semiconductor mesa. It has been found that the efficiency is high, provided the top contact has a good reflectivity value. Also, it has been found that efficiency is particularly high if the contact occupies an area of less than 16% of the truncated top mesa surface area.

Abstract: An initial epitaxial layer of GaN is grown on a sapphire substrate. The epitaxial layer is then etched in a reactive ion etch (RIE) chamber. This etching acts preferentially at defects, causing them to become enlarged cavities. The cavities are too large in proportion to the crystal lattice to act as defects in the usual sense, and so a further GaN epitaxial layer fills into the cavities. Thus, propagation of defects is avoided.