Reliability and failure mechanisms of oxide VCSELs in non-hermetic enviroments

High speed fiber optic transceiver modules using parallel optics require that oxide-confined vertical-cavity surface-emitting lasers (VCSELs) be moisture resistant in non-hermetic environments. Conventional storage 85/85 (85°C and 85% relative humidity) testing without a bias does not adequately characterize oxide VCSEL’s moisture resistance. Oxide VCSELs do not fail or degrade significantly under such conditions. With a bias, however, we have found that moisture can cause failure modes not seen in dry reliability testing. Without proper device design and fabrication, these failure modes lead to high failure rates in oxide VCSELs. In this paper, we first discuss the failure mechanisms we have identified, including dense dislocation network growth, semiconductor cracking and aperture surface degradation, all in high humidity and high temperature under operating conditions. We then report the results of environmental reliability tests on Agilent’s oxide VCSELs developed for the parallel optics modules. The results from a large number of wafers produced over an extended period of time have shown consistent, robust environmental reliability.