Lateral and cross-well transport of highly and moderately excited carriers in Si1−xGex/Si superlattices

Abstract

Picosecond transient reflectometry and dynamic grating techniques have been applied to investigate the perpendicular and parallel transport of optically excited carriers in strained-layer Si0.83Ge0.17/Si superlattices. We present results of the carrier ambipolar diffusivity and effective lifetime measurements in the layered structure and substrate within the 1017–1020 cm−3 density range. The combined experimental data are discussed in terms of parallel and perpendicular diffusion of carriers, interface recombination, and lattice heating. The estimated lateral and cross-well diffusion constants are 10 and 0.16 cm2/s at room temperature, respectively.