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

Abstract

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 ( R th) 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 R th decreased from 4612 K/W to 1130 K/W as the oxide aperture diameter ( D a) 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 R th. Furthermore, thick Au layers on contact pads and top DBR in intracavity-contacted VCSEL structures help increase heat removal from the active region. For D a = 8 μm and 16 μm, the VCSELs with SiN x passivation layer, 5 μm thick extra Au layer, and 100 μm thick substrate indicate R th = 3050 K/W and 778 K/W, respectively, leading to an improvement by >30% compared to the fabricated devices.