title: Direct bandgap narrowing in Ge LED's on Si substrates.
abstract: 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.
authors: Institute for Semiconductor Engineering, University of Stuttgart, 70569 Stuttgart, Germany. oehme@iht.uni-stuttgart.de
authors: Michael
authors: M
authors: Oehme
authors: Martin
authors: M
authors: Gollhofer
authors: Daniel
authors: D
authors: Widmann
authors: Marc
authors: M
authors: Schmid
authors: Mathias
authors: M
authors: Kaschel
authors: Erich
authors: E
authors: Kasper
authors: Jörg
authors: J
authors: Schulze
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D005857:Germanium / Q000737:chemistry*; D008029:Lighting / Q000295:instrumentation*; D008422:Materials Testing; D012666:Semiconductors; D012825:Silicon / Q000737:chemistry*
chemical_list: D005857:Germanium; D012825:Silicon