Growth and characterization of GaSb and InSb quantum dots on cross-hatch patterns

Abstract

This thesis is dedicated to study guiding effect of strain from cross-hatch pattern (CHP) to GaSb quantum dot (QD) and InSb QD nucleation. A 6-nm GaAs spacer on 30-nm In0.17Ga0.83As CHP on GaAs (001) substrate, fabricated by molecular beam epitaxy (MBE), is used as the CHP guiding template. Two different growth techniques-Conventional and Migration Enhance Epitaxy (MEE)-are performed for the antimonide QDs growth. The morphology of self-aligned GaSb and InSb QDs on CHP are characterized by atomic force microscopy (AFM). The GaSb QDs grown by MEE shows the obvious nucleation on the CHP ridges compares to the QDs grown by MBE, which QDs distribute all over the areas. The average height of GaSb QDs, formed on the CHP ridges, grown by MEE is almost doubled that of GaSb QDs grown by MBE. Moreover, a simple descriptive model is proposed to demonstrate the GaSb QD formation mechanism on CHP ridges. In contrast, the compressive strain from CHP does not affect the nucleation of InSb QDs on the ridges because the InSb QDs prefer to nucleate on the flat areas where the tensile strain exists. The photoluminescence (PL) spectra from side-emission of GaSb QDs grown by MEE shows the energy peaks at ~0.73-0.75 eV and ~1.14 eV. These two peaks correspond to carrier transitions between GaSb QDs and InGaAs and GaAs, respectively.