The frequency response of an amplitude-modulated GaAs luminescence diode

The frequency response of an amptitude-modulated GaAs luminescence diode has been studied for optical communication application. The modulated light intensity is found to fan off inversely proportional to the modulation frequency over the frequency range ωτ ≳ 1, where τ is the recombinative lifetime. We show that the falloff characteristic is a result of the complex diffusion process of the minority carrier in the presence of an ac perturbation across the junction. A simple relation which can be employed to determine the minority lifetime accurately to within a nanosecond is derived.