Ultrathin InAs and modulated InGaAs layers in GaAs grown by MOVPE studied by photomodulated reflectance spectroscopy

Optical characterisation of MOVPE grown vertically correlated InAs/GaAs quantum dots

“…Although e2h1 transition is forbidden, the built-in electric field in the structure makes it observable in PR measurement. Close agreement between experiment and simulation for the magnitude of GaAs separation layer thickness of 7.5 nm, which was confirmed XRD measurement, indicate on the validity of the model which was used for simulation of multi QWs formed by WLs [10]. It is worth to point out, that the simulation results are very sensitive to WL separation thickness, the In content and the spreading of the In profile in the WL.…”

“…To get exact magnitudes of WL thickness, we compared the measured e1h1 and e1l1 transitions from Fig. 3 with those received on ultrathin InAs quantum wells (QW) grown by the same apparatus [10]. This is shown in Fig.…”

“…clearly shows that increasing of the GIT substantially decreases the apparent WL thickness (from close-to-relaxation limit of 1.4 ML for GIT=7.5 s to 1.05 ML for GIT=30 s) and corresponding strain in the structure. At this point, it is worth to mention, that our MOVPE grown ultrathin (~1 ML) InAs layers are in fact formed by ~2.5 ML thick InGaAs well where the In atom distribution can be assumed to be Gaussian [10]. The results of PL measurement of samples with different number of vertically stacked InAs QD layers are shown in Fig.…”