Carrier density dependence of the ambipolar diffusion coefficient in GaAs n-i-p structures

We report on investigations of the ambipolar diffusion coefficient in GaAs n-i-p structures in which the electron density in the n channel is varied. The ambipolar diffusion coefficient was determined by time-resolved diffusion experiments of the Shockley–Haynes type. The dependence of the ambipolar diffusion coefficient on the varying carrier density is in excellent agreement with the theory of ambipolar diffusion in n-i-p-i systems. In the investigated sample, the ambipolar diffusion coefficient reaches a maximum value of 16 300 cm2/s. Although the ambipolar diffusion constant declines with decreasing carrier density, it is in a wide range of the carrier density more than two orders of magnitude enhanced compared to bulk materials.