Comparison of single heterostructure and double heterostructure GaAs-GaAIAs LEDs for optical data links

This paper presents a theoretical and experimental comparison of the performance of single heterostructure (sh) and double heterostructure (dh) GaAs-GaAIAs light-emitting diodes (leds). These leds are designed for optical data links operating at rates up to T3 (45 Mb/a), The sh leds were optimized with respect to active layer carrier concentration and thickness; similar dh led active layer parameters have not yet been optimized. We find experimentally that the dh diodes launch approximately 8 times the sh power into a butt-coupled, 0.36 numerical aperture (na), graded index fiber. Using a diffusion model, we show that the pouter output of the sh led is limited by surface recombination and reduced current crowding. These results demonstrate that dh leds are necessary for applications requiring high launched power.