Efficient flip-chip InGaN micro-pixellated light-emitting diode arrays: promising candidates for micro-displays and colour conversion

Flip-chip InGaN micro-pixellated LED arrays with high pixel density and improved device performance are presented. The devices, with 64 × 64 elements, each of which have a 20 µm emission aperture on a 50 µm pitch, are fabricated with a matrix-addressable scheme at blue (470 nm) and UV (370 nm) wavelengths, respectively. These devices are then flip-chip bonded onto silicon mounts. Good emission uniformity across the LED array is demonstrated, which can be attributed to the introduced n-metal tracks adjacent to each n-GaN mesa and the p-contact lines running across parallel columns. More importantly, with a flip-chip configuration, the optical power output and the current-handling capability of these new devices are substantially enhanced, due to the improved heat dissipation capability and the increased light extraction efficiency. For instance, each pixel in the flip-chip blue (respectively UV) LED arrays can provide a maximum power density 43 W cm−2 (respectively 6.5 W cm−2) at an extremely high current density up to 4000 A cm−2 before breakdown. These flip-chip devices are then combined with a computer-programmable driver circuit interface to produce high-quality micro-scale displays. Other promising applications of these LEDs, such as colour conversion with quantum dots, are also demonstrated.