Thermal conductivity of isotopically enriched71GaAs crystal

A gallium arsenide bulk crystal highly enriched with gallium isotope 71 Ga to 99.40 at% has been grown using the seedless horizontal Bridgman method. The crystal has a total impurity concentration of about 2 × 10 17 atoms cm −3 and a high electrical resistivity ρ(300 K) ∼ 10 3 –10 8 Ω cm. Thermal conductivity measurements have been made from 90 K to 300 K of the enriched 71 GaAs sample and three different nat GaAs samples with a natural isotope composition of gallium. The 71 GaAs 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.