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 between 1 and 40 monolayers. The conductivity was measured by an optical pump-and-probe technique in the temperature range of 100 to 375 K. In the experiment, an Al film is deposited onto a superlattice sample, and the rate at which this film cools by conduction into the superlattice is determined. We 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 three 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 to the bulk constituents in terms of extrinsic and intrinsic scattering mechanisms. [S0163-1829(99)05611-8].