Size-dependent bandwidth of semipolar (1122) light-emitting-diodes

The limited modulation bandwidth of commercial light-emitting diodes (LEDs) is one of the critical bottlenecks for visible light communications. Possible approaches to increase the bandwidth include the use of micron sized LEDs, which can withstand higher current densities, as well as the use of LED structures that are grown on different crystal planes to the conventional polar c-plane. We compare c-plane InGaN/GaN LEDs with semipolar ( $11\overline {2}2$ ) LEDs containing a 4- and 8-nm single quantum well. The modulation bandwidth of semipolar LEDs with active areas varying from $200\times 200$ to $30\times 30\,\,\mu \text{m}^{2}$ is shown to be governed by both current density and size. A small signal bandwidth of over 800 MHz for a relatively low applied current density of 385 A/cm2 is reported for $30\times 30 \,\,\mu \text{m}^{2}$ LEDs with 8-nm thick quantum well. An optical link using an easy non-return-to-zero ON–OFF keying modulation scheme with a data rate of 1.5 Gb/s is demonstrated.