We have studied the mobility and carrier concentration as a function of temperature between 4 and 300 K inn-type Si–Ge short-period superlattices. In the parallel transport configuration, we have measured a mobility ratio&mgr;77/&mgr;300>50in ann-type strained-layer superlattice with a carrier concentration in the mid1016 cm−3range. The peak mobility measured was 17 000cm2/V s−1at 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.