Self-assembling SiGe and SiGeC nanostructures for light emitters and tunneling diodes

We report structural and photoluminescence (PL) investigations of self-asse mbling typically 100 nm lateral size Ge islands and 10 nm size C-induced Ge quantum dots in Si. The different recombination pathways are discussed for single and stacked dot layers. The aim is to evaluate different ways of us ing self-assembling quantum structures for Si-based emitters in the wave le ngth range of 1.3 to 1.55 mu m The pre-growth of a small fraction of a mono layer C on Si(100) introduces nucleation centers for the subsequent formati on of Ge islands which results in the formation of a high density of extrem ely small 10 nm size quantum dots. PL-studies indicate a spatially indirect radiative recombination mechanism with the no-phonon line strongly dominat ing. For larger stacked Ge islands with 13 nm thin Si spacer layers, we obs erve a significantly enhanced Ge dot-related PL signal up to room temperatu re at 1.55 mu m wave length. This is attributed to a spatially indirect tra nsition between heavy holes confined within the compressively strained Ga: dots and two-fold degenerated Delta state electrons in the tensile strained Si spacer layers between the stacked Ge dots. In the second part we presen t the preparation and I-V characteristics of Si/SiGe/ Si p(+)/i/n(+) Esaki diodes. The incorporation of a maximum amount of Ge within the i-zone incre ases the interband tunneling probability and thus, gives rise to an increas ed peak current density of about 3 kA/cm(2) and a peak to valley current ra tio of 4.2 at room temperature. The further increase of Ge content by incor poration of self assembling Ge islands within the intrinsic cone of the dio de is discussed. (C) 2000 Elsevier Science S.A. All rights reserved.