TRANSPORT OF NONEQUILIBRIUM CARRIERS IN VARIABLE-GAP STRUCTURES ALLOWING FOR THE DEPENDENCE OF THE MOBILITY ON THE SOLID-SOLUTION COMPOSITION

An analysis is made of the dependence of the effective transport length L+ of nonequilibrium carriers on the band-gap gradient \del E(g)\. It is assumed that the mobility mu varies exponentially with the composition x of a solid solution. An analytic dependence is proposed and it is shown that it describes well the distribution of nonequilibrium carriers found by solving the diffusion-drift problem. It is demonstrated that the diffusion-drift lengths can be introduced if the mobility depends on the composition mu(x). A nonmonotonic dependence L+(\del E(g)\) is predicted and it leads to restrictions on the maximum values of the effective transport lengths for variable-gap structures. Estimates are obtained of the influence of the composition dependence of the nonequilibrium lifetime on L+(\del E(g)\).