Ferromagnetic (Ga,Mn)As Layers and ... - OPUS Würzburg

64 5. Local Anisotropy Control by Strain Engineering
1M
100k
GaAs
10k
Intensity [a.u.]
1k
100
10
(In,Ga)As
(Ga,Mn)As
1
0.1
0.01
-2000 -1500
-1000
-500
0
500 1000
Omega [rel. sec.]
Figure 5.2: HRXRD ω-2Θ-scan (blue line) of the (004) reflection of the unpatterned, asgrown
wafer from which samples B and C were processed. The red line is a simulation of
the scan with the sample parameters given in table 5.1. The substrate peak is located at
ω = 32.086 ◦ .
5.1.1 HRXRD Measurements
Parent Layer ω-2Θ-Scans
The parent layers were investigated with high resolution X-ray diffraction measurements
of the (004) reflection to guarantee high layer quality and fully pseudomorphic
layers. Fig. 5.2 shows an ω-2Θ-scan of an unpatterned piece of the parent layer for
samples B and C. The good agreement between the scan and the simulation of a completely
pseudomorphic structure with parameters as given for the samples in Table 5.1
proofs high layer quality and confirms that no significant relaxation has taken place
during growth. Similar measurements have been performed for all samples discussed
in this chapter.
HRXRD RSM, Relaxation Triangles
To quantify the strain relaxation after pattering the layer into the stripe structure, two
different XRD techniques were used. We will first focus on the HRXRD RSM method
as introduced in Section 3.5.2. The crucial difference to the situation discussed in
Section 3.5.2, in which we showed measurements on a biaxially relaxed layer, is that
stripe samples are subject to uniaxial and therefore anisotropic lattice relaxation in
the plane of the sample.
To discuss how we model this uniaxial relaxation, i.e. how we construct the re-