Abstract

Fully processed wafers of III -V semiconductor lasers have a potential value of tens of thousands of pounds; yield and reliability issues can therefore be very expensive. The most challenging problems occur when defects or processing issues which are introduced during fabrication are latent in the device; performance is good upon initial test, but the devices degrade during burn in or an accelerated life test trial. This talk describes the type of failure analysis study which is needed to solve these issues, using examples from work done at Bookham Technology, Caswell. Specimen preparation is challenging, requiring analysis of specific sites on individual devices, and usually several types of analysis are used, including electroluminescence, SEM , FIB and TEM - often on the same device. Results of an accelerated life test study of InAs/GaAs quantum dot lasers are also presented. These indicate that quantum dot material is inherently resistant to defect propagation – much more so than devices which use quantum wells.