Thermal-conductivity measurements of GaAs/AlAs superlattices using a picosecond optical pump-and-probe technique

We present measurements of the lattice thermal conductivity K-perpendicular to, normal to the interfaces of (GaAs)(n)/(AlAs)(n) superlattices with n b etween 1 and 40 monolayers. The conductivity was measured by an optical pum p-and-probe technique in the temperature range of 100 to 375 K. In the expe riment, an Al film is deposited onto a superlattice sample, and the rate at which this film cools by conduction into the superlattice is determined. W e find a general decrease in K, with a reduction of the superlattice period . At 300 K, K, of the (GaAs)(40)/(AlAs)(40) superlattice is approximately t hree times less than kappa of bulk GaAs, and kappa(perpendicular to) of the (GaAs)(1)/(AlAs)(1) superlattice is an order of magnitude less than kappa of bulk GaAs. We discuss the decrease in kappa(perpendicular to) compared t o the bulk constituents in terms of extrinsic and intrinsic scattering mech anisms. [S0163-1829(99)05611-8].