Open AccessDirect bandgap narrowing in Ge LED’s on Si substrates
Author(s) -
Michael Oehme,
Martin Gollhofer,
Daniel Widmann,
M. Schmid,
Mathias Kaschel,
E. Kasper,
Jörg Schulze
Publication year - 2013
Publication title -
optics express
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.21.002206
Subject(s) - materials science , doping , electroluminescence , band gap , optoelectronics , molecular beam epitaxy , light emitting diode , optics , diode , silicon , epitaxy , layer (electronics) , nanotechnology , physics
In this paper we investigate the influence of n-type doping in Ge light emitting diodes on Si substrates on the room temperature emission spectrum. The layer structures are grown with a special low temperature molecular beam epitaxy process resulting in a slight tensile strain of 0.13%. The Ge LED's show a dominant direct bandgap emission with shrinking bandgap at the Γ point in dependence of n-type doping level. The emission shift (38 meV at 10²⁰cm⁻³) is mainly assigned to bandgap narrowing at high doping. The electroluminescence intensity increases with doping concentrations up to 3x10¹⁹cm⁻³ and decreases sharply at higher doping levels. The integrated direct gap emission intensity increases superlinear with electrical current density. Power exponents vary from about 2 at low doping densities up to 3.6 at 10²⁰cm⁻³ doping density.