Design and implementation of metallization structures for epi-down bonded high power semiconductor lasers

High power semiconductor lasers have found increasing applications in industrial, military, commercial and consumer products. The thermal management of high power lasers is critical since the junction temperature rise resulting from large heat fluxes strongly affects the device characteristics, such as wavelength, kink power, threshold current and efficiency, and reliability. The epitaxial-side metallization structure of epi-down bonded lasers has significant impact on the thermal performance and reliability of the high power semiconductor lasers. In this paper, the influence of the epitaxial-side metal (p-metal) on the thermal behavior of a GaAs-based high power single-mode laser, mounted epi-side down, is studied using finite element analysis. Metallization structures having different diffusion barriers for eutectic AuSn solder are designed and implemented, and the metallurgical stability of the four metal systems, Ti/Pt/thick Au (2-3 μm thick), Ti/Pt/thick Au/Ti/Pt/Au, Ti/Pt/thick Au/Ti/Ni/Au, and Ti/Pt/thick Au/Ti/Cr/Au, are reported.