Matrix-addressable micropixellated InGaN light-emitting diodes with uniform emission and increased light output

Micropixellated InGaN light-emitting diodes (micro- LEDs) have a wide number of potential applications in areas including microdisplays, fluorescence-based assays and microscopy, and cell micromanipulation. Here, we present fabrication and performance details of matrix-addressable micro-LED devices which show significant improvements over their earlier counterparts. Devices with 64 × 64 micropixel elements, each of them having a 16-μm-diameter emission aperture on a 50-μm pitch, have been fabricated at blue (470 nm), green (510 nm), and UV (370 nm) wavelengths, respectively. Importantly, we have adopted a scheme of running n-metal tracks adjacent to each n-GaN mesa, so that resistance variation between the devices is reduced to below 8%, in contrast to the earlier fivefold resistance variation encountered. We have also made improvements to the spreading-layer formation scheme, resulting in significant increases in output power per element, improved current handling, and reduced turn-on voltages. These devices have been combined with a computerdriven programmable driver interface operating in constantcurrent mode, and representative microdisplay outputs are presented.