Improvement in heat dissipation by transfer of IV-VI epilayers from silicon to copper

A successful metallization (Au-InSn alloy) bonding and substrate removal procedure is described for improving epilayer heat dissipation. Two IV-VI semiconductor multiple quantum well (MQW) structures grown on silicon host substrates by molecular beam epitaxy with a CaF₂ (or CaF₂-BaF₂) buffer layer were bonded epilayer down to the tips of a copper bar assembly and then the Si substrates were removed by dissolving the CaF₂ (or CaF₂-BaF₂) buffer layer in water. The bonded IV-VI epilayers were cleaved by separation of the copper bars. Photoluminescence (PL) data before and after transfer showed that an increase in diode laser pumping caused a smaller blue shift in the PL energies for the structures bonded to copper when compared to the as-grown samples. Calculations revealed that epilayers transferred to copper were at least 20°C cooler than the same epilayers on silicon when illuminated with a continuous wave (λ=911 nm) laser at a power density of about 25 W/cm².