Influence of Isolation Etching Depth on RC Characteristic of GaN-based Micro-LED Chip

The fabrication of the isolation trough is an effective way to realize independence of the array chip unit. In this paper, four kinds of isolation depth and six different chip sizes were fabricated on GaN-based LED arrays using inductively coupled plasma dry etching(ICP) with high etching ratio hybrid-mask SiO2 and photoresist. The effect of different etching sizes and depths on the electrical performance of LED array chip was characterized by electroluminescence(EL) and capacitance tester. The experimental results show that the smaller chip has a higher endured current density and smaller capacitance. With the increase of the etching depth, both the resistance and capacitance decrease, which reduces the RC time constant. The RC bandwidth of the samples with 120 μm Mesa increases from 155 MHz to 176 MHz when the etch depth is from Mesa etch only to completely etch to the sapphire substrate. Reducing the chip size and completely etching to the sapphire substrate can effectively reduce the chip RC time constant. These efforts will facilitate the future design and manufacture of GaN-based LEDs to improve the modulation bandwidth of high-frequency visible light communications. © 2018, Science Press. All right reserved.