Wafer-bonded 850-nm vertical-cavity surface-emitting lasers on Si substrate with metal mirror

An 850-nm vertical-cavity surface-emitting laser (VCSEL) with a Au/AuBe/TaN/Ta/Si mirror substrate has been realized by low-temperature wafer bonding. It is found that the mirror substrate can be used as the bottom reflector to enhance the reflectivity of a bottom distributed Bragg reflector. The metal mirrors also served as the adhesive layers and ohmic contact layers to bond the Si substrate and the VCSEL epilayers. When the mirror-substrate-bonded VCSELs are excited by continuous-wave current at room temperature, they exhibit lower threshold current density and differential resistance (22 A/cm², 35 Ω) as compared with the original VCSELs on GaAs substrates (77 A/cm², 60 Ω). This feature is attributed to the finding that the Si substrate provides a good heat sink.