Understanding recombination-enhanced dislocation motion for reliable III-V on Si lasers

Dislocations are an important class of defects in semiconductors that are key to the epitaxial integration of heterostructures of dissimilar materials in consideration for new types of electronic and photonic circuits. Fundamentally, dislocations in semiconductors affect both mechanical and electronic properties and this leads to well-known coupled phenomena: equilibrium processes such as electronic doping impacting mechanical properties and out-of-equilibrium processes such as non-radiative minority carrier recombination enhancing dislocation motion under otherwise brittle conditions. The latter has been implicated in the accelerated degradation of GaAs-based lasers on Si, where even record low dislocation densities through substrate engineering fail in yielding commercially viable devices for the burgeoning field of silicon photonics as the dislocations increase in length over time during device operation.

In this work, we use new microscopy tools to describe the salient features and driving forces behind recombination-enhanced dislocation glide and climb in GaAs on Si lasers, with an emphasis on InAs quantum dot devices. Our recent experiments harness the mechanical properties of indium to counter III-V and Si thermal expansion mismatch strain and pin the dislocations against glide, yielding record-lifetime lasers on silicon that are now comparable to devices on native substrates. Although the driving force behind dislocation climb remains under investigation, we describe the nature of interaction of point defects with dislocations and the benefits of quantum dots in mediating this. An updated understanding of recombination-enhanced dislocation glide and climb may eventually result in viable integrated lasers in a range of materials systems.