Structural and Luminescence Properties of Ordered Ge Islands on Patterned Substrates

Abstract

Ge quantum dots promise to become building blocks for future electronic and optoelectronic devices with enhanced functionality. Most of the proposed technological applications require ordered ensembles of dots identical in size and shape. Meeting these requirements remains a formidable challenge for all the techniques used to fabricate dots. The growth of a single layer of quantum dots via self-assembly, a process of particular interest as the quantum dots essentially fabricate themselves, typically produces island ensembles that are disordered and show significant fluctuation in island size.

Several techniques have attracted interest as promising in achieving control over the lateral distribution of Ge islands, such as growth on miscut substrates which induces alignment along steps [1–3], or growth on relaxed templates with dislocation networks [4,5]. Long-range ordered nucleation was achieved by growth on a template with a strain-field modulation made by a Si/SiGe superlattice [6]. Islands are also expected to undergo ordering along the soft crystallographic directions <100> in the diamond structure [7].

One of the most studied and effective approaches in achieving lateral ordering of the quantum dots is growth of Ge islands on Si mesas made by selective epitaxial growth. The ordering along mesa edges will be discussed in several chapters of this book.