Color tunable inverted pyramid micro-LEDs based on nano-patterned sapphire substrates

Color-tunable micro-scale light-emitting diodes (Micro-LEDs) can achieve full-color display in a simple and low-cost way. In this paper, we demonstrate growth of three-dimensional (3D) inverted pyramid GaN on nano-patterned sapphire substrates (NPSS). By using the sputtered AlN nucleation layer, the uniformity of the inverted pyramid has been improved to a large extent. Then, Micro-LEDs are epitaxially grown based on these inverted pyramids and fabricated to 20-100 µm devices. As the current increases from 1 to 100 A/cm