AlGaInP-based resonant-cavity light-emitting diodes (RCLEDs) with high power and high speed have been fabricated. In this study, the RCLEDs were designed with different light-output aperture sizes 84, 60, and 40 µm, for different applications on plastic optical fibers. Small-signal modulation bandwidths as high as 310 MHz at a forward current of 20 mA and an output power as high as 1.5 mW can be achieved for devices with 40 µm apertures. The devices with 84 µm apertures had an output power of more than 3.5 mW at a driving current of 20 mA and a maximum efficiency of over 12% with an epoxy-encapsulated package. The devices with 40 µm apertures satisfied with the IEEE 1394b s400 standard. Furthermore, the devices showed stable coupling efficiency for various currents and output powers at different ambience temperatures. In addition, the lifetime of devices is over 1300 h, and the power decay is less than 0.5 dB at 85 °C for a 40 mA driving current.