Analysis of dislocation-related and point-defects in III-As layers by extensive DLTS study

Silicon photonics is a technology that aims at improving state-of-the-art optical communication systems through high performance lasers, which currently rely mostly on III-As materials grown on silicon-on-insulator platforms and, in the future, on InAs quantum dots (QDs). In this work, we present an extensive investigation on the properties of defects in III-As layers as a function of the presence/absence of QDs layers and of dislocation density. By using deep level transient spectroscopy (DLTS), we analyzed two kinds of devices: GaAs diodes grown on Si (high dislocation density) and GaAs diodes grown on GaAs (low dislocation density) with QDs embedded.Our study showed that the device grown on Si exhibits four distinct traps (3 electron and 1 hole trap), whereas the sample grown on GaAs contains only one hole trap, which is in common among the two devices. These defects are placed in proximity of the semiconductor midgap, therefore they can act as efficient non-radiative recombination centers (NNRCs). The analysis of the capture kinetics showed that two of the traps are associated to point defects and that the remaining two seem to be related to point defects arranged along a dislocation.According our investigation, embedding QDs into the pin structure does not lead to the generation of additional defects, since the only measurable trap in the device with QDs is common to both samples. Finally, a tentative association of the detected traps with previous reports revealed that the dominant traps may be associated with native III-As defects or oxygen-related complexes.