Effects of contact shape on ballistic phonon transport in semiconductor nanowires

► The effects of five different contact shapes on ballistic phonon transport in semiconductor nanowires are studied. ► The contact shape acts as an 'acoustic impedance adaptor', playing a crucial role on the ballistic phonon transmission and thermal conductance. ► The phonon coupling in the contacts with certain length facilitates ballistic phonon transmission compared to the abrupt interface. ► The more the contact is abrupt, the smaller the thermal conductance is.