Abstract
InGaN-based micro-structured light-emitting diodes (µLEDs) play a critical role in the field of full-color display. In this work, selected area growth (SAG) of a micro-pyramid LED array was performed on a 2-inch wafer-scale patterned SiO2 template (periodicity: 4 µm diameter), by which a uniform periodic µLED array was achieved. The single-element pyramid-shaped LED exhibited 6 equivalent semipolar {1-101} planes and a size of about 5 µm, revealing a good crystalline quality with screw and edge dislocation densities of 8.27 × 107 and 4.49 × 108 cm−2. Due to the stress–relaxation out of the SAG, the as-built compressive strain was reduced to 0.59 GPa. The µLED array demonstrated a stable emission, confirmed by a small variation of electroluminescence (EL) peak wavelength over a wide range of current density up to 44.89 A/cm2, as well as tiny fluctuations (within 1.9 nm) in the EL full width at half maximum. The photoluminescence peak wavelength exhibits a good uniformity throughout the whole wafer with a discrete probability of only 0.25%.
Highlights
2-inch wafer-scale patterned SiO2 layer on n-GaN template revealed a pattern consisting of uniformly created periodical holes, in which the hole diameter was 4 μm and the period was 6 μm
The typical morphology of a pyramid μLED array is observed from a 25◦ -tilted scanning electron microscopy (SEM) image in Figure 1c, from which it can be seen that the growth exhibited good uniformity and selectivity, as epitaxy only took place in the pattern openings
All μLED structures showed a smooth-faceted identical image in Figure 1c, from which it can be seen that the growth exhibited good uniformity and selectivity, as epitaxy only took place in the pattern openings
Summary
Over the past few years, nitride-based light-emitting diodes (LEDs) with chip size larger than 200 μm have been proven to be a great success in general lighting, outdoor displaying, display backlighting, and many other applications [1,2,3]. Compared with the traditional cathode ray tube (CRT) and liquid-crystal display (LCD), as well as emerging organic LED technologies, nitride-based μLEDs hold the promise of visually perfect displays with lower power consumption, enhanced speed, higher luminescence, and feasibility of 2D integration [5,6], emerging as great candidates for the generation of display technology in the applications of high-end televisions, mobile phones, wearable display panels, augmented reality, and virtual reality [7,8]. Various types of nitride microstructures have been widely investigated, including waveguides, micro-disks, rings, pyramids, and nanowires [9,10,11,12,13]
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