Visible-light-emitting diodes based on microcavity concepts

Abstract

State of the art resonant microcavity light emitting diodes (RC-LEDs) for the red wavelength range are presented in the paper. Our red-emitting RC-LEDs were mainly intended for low- cost short-haul communication systems on polymethyl methacrylate plastic optical fiber (POF) but the devices provide viable alternatives for conventional LEDs or for VCSELs in applications where moderate spectral purity, moderate bandwidth and low-cost are required. The paper discusses the design concepts, fabrication issues and performance characteristics of monolithic RC-LEDs' emission is centered in the 650 - 655 nm range, which corresponds to the PMMA POF transmission window, and has a spectral linewidth below 15 nm. The RC-LEDs with 500 micrometer diameter windows launch 15 mW of light power. Smaller 40 micrometer devices are very fast exhibiting f<SUB>-3dB</SUB> up to 350 MHz at reasonable power levels. The 84 micrometer devices achieve a record external quantum efficiency of 9.5% and a back-to-back error- free data transmission rate beyond 622 Mbit/s. Alignment tests with 1 mm POF fibers, without lenses, showed that +/- 0.5 mm misalignment might be tolerated in x-y-z directions without significant reduction in coupling efficiency. The devices appear to be very robust, neither sudden unexpected failure nor gradual power degradation has been observed during more than 93000 device hours on accelerated aging tests.