TEMPERATURE-DEPENDENCE OF MOBILITY IN N-TYPE SHORT-PERIOD SI-GE SUPERLATTICES

We have studied the mobility and carrier concentration as a function o f temperature between 4 and 300 K in n-type Si-Ge short-period superla ttices. In the parallel transport configuration, we have measured a mo bility ratio mu(77)/mu(300)>50 in an n-type strained-layer superlattic e with a carrier concentration in the mid 10(16) cm(-3) range. The pea k mobility measured was 17 000 cm(2)/V s(-1) at 70 K. Carrier freeze-o ut effects frustrated transport measurements below 60 K. Above 80 K th e mobility is limited by optical phonon scattering with a characterist ic phonon energy of 60 meV. These characteristics indicate electron tr ansport via extended states. (C) 1998 American Institute of Physics.