Formation of subcritical thickness InAs nanostructures on InGaAs cross-hatch patterns by in situ annealing

Abstract

This thesis presents the formation of subcritical thickness InAs nanostructures on In0.2Ga0.8­As cross-hatch patterns (CHPs) with GaAs (001) substrate by in situ annealing in molecular beam epitaxy (MBE). The subcritical formation of InAs is characterized by atomic force microscopy (AFM) for surface morphology and topology. The real time observation showed no sign of quantum dots (QDs) formation during the subcritical thickness. Subcritical thickness InAs nanostructures on In0.2Ga0.8As CHPs show interesting nanostructures which formed into atomic wires along [1-10] direction. If varies the thickness of InAs layer from 1.4, 1.5, and 1.6 monolayer (ML), the distance between atomic wires become closer to each other, resulting in higher density of wires. However, the height of the wires is considered to be the same at 0.3 nm, which is equivalent to 1 ML of InAs layer. Moreover, the CHPs also affect the formation of subcritical thickness InAs on both [110] and [1-10] directions as well. The results indicate that subcritical thickness InAs tends to elongate along [1-10] direction, and confined on the [110] direction. For the photoluminescence (PL) spectrum displays the highest PL peak at 1.45 eV, corresponding to the InAs wetting layer indicating a high structural quality which may be suitable for optical applications.