The asymmetric intracavity-contacted oxide-aperture vertical-cavity surface-emitting lasers (VCSELs), operating at lambda similar to 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 mu m to 16 mu m and it increased significantly below 8 mu m. 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 mu m and 16 mu m, the VCSELs with SiNx passivation layer, 5 mu m thick extra Au layer, and 100 mu m thick substrate indicate R-th = 3050 K/W and 778 K/W, respectively, leading to an improvement by >30% compared to the fabricated devices. (C) 2009 Elsevier Ltd. All rights reserved.