Correlation of InGaAs/GaAs quantum dot and wetting layer formation

The formation and correlation of the wetting layer (WL) and quantum dots (QD) is investigated for the Stranski-Krastanow growth of InGaAs on GaAs in metalorganic chemical vapour deposition. For nominally 1.8 nm In0.4Ga0.6 As deposition QDs coexist with a complex structured WL. Temperature dependent photoluminescence (PL) and PL excitation (PLE) results show the WL thickness to vary locally between 5 and 9 monolayers, with thermal activation being necessary for carrier transfer from the thicker WL regions into the QDs. We find an (anti) correlation between QD size and WL thickness from which the most efficient capture into the QDs results, i.e. larger QDs capture preferentially from thinner WL regions. The existence of WL growth islands which did not transform into QDs and the anti-correlation of QD size and WL thickness hint at an incomplete InGaAs QD formation for the investigated deposition despite a growth interruption of three minutes after deposition of the InGaAs layer.