Thermal analysis of asymmetric intracavity-contacted oxide-aperture VCSELs for efficient heat dissipation

The asymmetric intracavity-contacted oxide-aperture vertical-cavity surface-emitting lasers (VCSELs), operating at λ ∼ 980 nm, with different oxide aperture diameters were fabricated and their thermal analysis was theoretically performed using a three-dimensional cylindrical heat dissipation model. The heat flux, temperature profile, and thermal resistance (Rth) of the devices were investigated by incorporating heat source values, obtained from experimentally measured results, into the thermal simulation. For the fabricated VCSELs with benzocyclobutene passivation layer, the Rth decreased from 4612 K/W to 1130 K/W as the oxide aperture diameter (Da) increased from 8 μm to 16 μm and it increased significantly below 8 μm. The use of the thin substrate and the passivation layer with a high conductivity enhances the heat dissipation, allowing for a low Rth. Furthermore, thick Au layers on contact pads and top DBR in intracavity-contacted VCSEL structures help increase heat removal from the active region. For Da = 8 μm and 16 μm, the VCSELs with SiNx passivation layer, 5 μm thick extra Au layer, and 100 μm thick substrate indicate Rth = 3050 K/W and 778 K/W, respectively, leading to an improvement by >30% compared to the fabricated devices.