Latent Electro-Static Damage in Vertical Cavity Surface Emitting Semiconductor Laser Arrays

We describe a novel type of failure mechanism for arrays of vertical cavity surface emitting lasers, such as those used in parallel optical interconnects for clustered computer systems. Conventional failure mechanisms related to electrostatic discharge (ESD) during laser manufacturing will cause multiple lasers in an array to fail at once, shortly after the ESD event. We have found that in some cases, latent ESD damage can occur; the ESD site serves as a nucleation point for dark line defects, which migrate under applied voltage. In this manner, individual elements in the laser array can fail randomly, without affecting adjacent lasers in the same array; furthermore, these failures can occur after 30-40 days of continuous operation. We report empirical data on the failure analysis used to identify this effect, including images of the latent damaged lasers, and recommend procedures for avoiding this damage during manufacturing.