Influence of annealing conditions on the structural and photoluminescence properties of Ge quantum dot lattices in a continuous Ge + Al2 O3 film

Abstract

We investigate the structural and photoluminescence (PL) properties of regularly ordered lattices of Ge quantum dots (QDs) formed by self-assembly in a thick film of Ge + Al2O3 mixture. The effects of annealing at different temperatures and different annealing environments (vacuum and air) are studied. We show that the regular ordering of QDs remains unchanged for annealing up to 800 °C in vacuum, while it is preserved up to 700 °C when annealing is performed in air. The inner/crystalline structure of Ge QDs and their shape depend on the annealing conditions. The crystalline grains of γ-Al2O3 form in the initially amorphous Al2O3 matrix after annealing at 800 °C. The PL spectra are found to consist of two main contributions, one from the matrix and the other from Ge QDs. Both contributions depend strongly on the annealing conditions. The annealing treatment of Ge quantum dot lattices formed by self-assembly in alumina matrix influence significantly the internal structure and photoluminescence properties of the films.