In this article, we investigate the influence of electrostatic discharge (ESD) stress voltage on the device performance of 850 nm vertical-cavity surface-emitting lasers (VCSELs). The ESD effect induces dark-region defects, which act as nonradiative recombination centers in the active layer and increase the leakage current and degrade the light output power. Without ESD stress voltage, the VCSELs exhibit multiple transverse mode. However, the devices exhibit a weak but single fundamental mode with smaller beam divergence by increasing the stress voltage up to 2.6 kv. In addition, the VCSELs have serious degradation in light output. power and a lifetime of less than 5 h at stress voltage beyond the ESD threshold voltage of 1.2 kV (C) 2004 American Vacuum Society.