These are often used as light sources for optical sensors in invisible infrared LEDs. They provide large emitted light output. The emitted light wavelength is generally 940 nm in the case of GaAs, 880 nm in the case of GaAlAs, and 830 nm in the case of GaAlAs. GaAlAs is a fast response type and it is optimum for use in communications. Packages include the can type and the resin mold type