Identification of dislocation-related and point-defects in III-As layers for silicon photonics applications

Abstract

The aim of this paper is to identify, analyze and compare the defects present in III-As, as a function of dislocation density, and as a function of the presence/absence of quantum dots (QDs). Such materials are of fundamental importance for the development of lasers and photodiodes for silicon photonics. The study is based on an extensive deep-level transient spectroscopy investigation, carried out on GaAs pin diodes grown on Si and on GaAs (that differ in the dislocation density), with and without embedded QDs. The original results described in this paper demonstrate that: (a) we were able to identify four different defects within the device grown on Si (three electron and one hole traps) and one defect (hole trap) in the device on GaAs, common to both samples; (b) all the majority carrier traps identified are located near midgap, i.e. are efficient non-radiative recombination centers; (c) such defects are absent (or non-detectable) in the sample grown on GaAs substrate, having a very low dislocation density; (d) the presence of QDs does not result in additional defects within the semiconductor material; (e) the analysis of the capture kinetics revealed that two of the identified traps are related to point defects, whereas the other two traps can be associated with point defects located near a dislocation; (f) a comparison with previous reports indicate that the detected traps are related to native III-As defects, or to oxygen-related complexes.

Addressing the Optical Degradation of 1.3 μm Quantum Dot Lasers through Subthreshold Characterization

“…This reduction can be ascribed to the increase in carrier losses within the DWELL, which is mainly driven by the increase of defects close to the InGaAs well, ,,, which are responsible of enhancing the carrier losses affecting the QD reservoir (Figure ). According to previous investigations, the origin of the defects contributing to the increase in SRH recombination could be related to point defects participating to the recombination enhanced growth of pre-existent misfit dislocations, , such as As Ga or V As , , or, in general, to the extended defects themselves.…”

Gradual degradation in InAs quantum dot lasers on Si and GaAs

“…Recent collaborations have demonstrated, via DLTS measurements, that QD lasers on silicon and GaAs share a common hole trap associated with a native point defect species or an oxygen complex. 32 Extending this experiment to test devices before and after aging can reveal whether this trap state multiplies over time and is the likely source of gradual degradation. Additional experiments link the rate of degradation to a diffusion limited process and find the dopant beryllium to be a likely candidate.…”

Degradation mechanisms of laser diodes for silicon photonics applications

“…10 An extensive analysis of the defects correlated to the presence of dislocations in samples with and without quantum dots grown on native (GaAs) and foreign (Si) substrate is present in the literature. 11 The authors report three electron traps and one hole trap in the samples grown on Si, whereas only the hole trap is present in the samples grown on GaAs. Two of the traps can be ascribed to point defects, and the remaining two to point defects in proximity of a dislocation.…”