We have studied the mobility and carrier concentration as a function of temperature between 4 and 300 K in n-type Si–Ge short-period superlattices. In the parallel transport configuration, we have measured a mobility ratio μ77/μ300≫50 in an n-type strained-layer superlattice with a carrier concentration in the mid 1016 cm-3 range. The peak mobility measured was 17 000 cm2/V s-1 at 70 K. Carrier freeze-out effects frustrated transport measurements below 60 K. Above 80 K the mobility is limited by optical phonon scattering with a characteristic phonon energy of 60 meV. These characteristics indicate electron transport via extended states. © 1998 American Institute of Physics.