Contact : Antoine.letoublon@insa-rennes.fr
Required skills: basic knowledge of crystallography and X-ray characterization, ability in
programming language.
Sujet/Subject :
Modelisation of antiphase domains in GaP/Si nanolayers
and X-ray diffraction
Our laboratory is highly skilled in molecular beam epitaxy (MBE) growth of InAs
QDs on InP, for laser devices with potential applications telecommunication (emission at
1.55m). In order to extend these applications to laser emission on Si for very large
scale integration, GaP (III-V) growth on silicon is studied. Several types of defects are
observed on such layer and are detrimental for applications. Amongst them APB and thus
anti-phase domains (APD) are difficult to avoid since they are due to the intrinsic nature of
the interface. The fig. 1a presents a typical APD above a single monolayer (ML) Si step
(indeed 1 GaP ML corresponds to 2 Si ML). As shown on figure 1b, a broad peak is observed
in X-ray diffraction around the (002) “antiphase” reflection. This feature can be interpreted in
term of distribution of APD included in a coherent GaP matrix.
The aim of this training period is to modelize the atomic positions in the vicinity of an
APD, taking into account two things :
i) the lattice mismatch of GaP/Si and the strain of positions induced by Si steps
ii) the strain induced by the presence of different atomic bounds at the APB and at
GaP/Si interface. Depending on traing period duration and affinity, the candidate could
participate to experimental X-ray acquisitions.
This model will be used to simulate the X-ray diffraction diagrams in interaction with
experimental ones. This will increase the characterization power of X-ray diffraction and will
have a large impact in the success of a ANR project : GaPhoSiX.
a)
b)
Fig. 1 a : Scheme of APD on Si monostep b :X-ray rocking curves around (004) and (002) of
GaP.