Thermal conductivity of isotopically enriched.: 71GaAs crystal

A gallium arsenide bulk crystal highly enriched with gallium isotope Ga-71 to 99.40 at% has been grown using the seedless horizontal Bridgman method. The crystal has a total impurity concentration of about 2 x 10(17) atoms cm(-3) and a high electrical resistivity rho (300 K) similar to 10(3)-10(8) Omega cm. Thermal conductivity measurements have been made from 90 K to 300 K of the enriched (GaAs)-Ga-71 sample and three different (GaAs)-Ga-nat samples with a natural isotope composition of gallium. The (GaAs)-Ga-71 has a higher value of thermal conductivity due to reduced isotope scattering of phonons: the observed isotope effect amounts to 5% at room temperature, increasing to 13% with a temperature decrease down to 100 K.