(Invited) Emission from Strained Germanium Nanocrystals. (5th April 2018)

• Record Type: Journal Article
• Authors: Rowell, Nelson L.; Lockwood, David J.
• Is Part Of: ECS transactions. Volume 85:Number 3(2018)
• Page Start: 41
• Page End: 52
• Publication Date: 2018-04-05
• Subjects: Electrochemistry -- Periodicals; Electrochemistry; Periodicals; Electronic journals; Electronic journal; 541.37
• DOI: 10.1149/08503.0041ecst
• Languages: English
• ISSNs: 1938-5862

Abstract

Abstract : We analyse the intense photoluminescence (PL) observed at energies from 600 to 1500 meV for many molecular beam epitaxy grown Si1-x Gex epitaxial layers. We show that the unexplained broad PL peak is due to self-assembled Ge nanocrystals (NCs) within the SiGe layers. The NCs are assumed lattice matched to the SiGe in the vertical, growth direction. As the Ge-fraction in the SiGe layer increases, the vertical strain in the NCs changes from compressive to tensile at x ~ 0.36, lowering the NC band gap (BG) below that of bulk Ge. We analyse PL results for 64 samples exhibiting this broad PL peak by examining how it follows the strained Ge BG for x from 0.05 to 0.53. The PL is resolvable as two narrower peaks separated by the TO phonon energy for Ge. Strain and confinement shifted NC bound exciton energies calculated numerically agree well with the measured ones.