Berlin 2005 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 17: Poster Ib

HL 17.46: Poster

Freitag, 4. März 2005, 16:30–19:00, Poster TU F

Luminescence of Ge/Si heterostructures with miniband realized by Sb doping — •Vadim Talalaev, George Cirlin, Alexander Tonkikh, Nikolay Zakharov, and Peter Werner — Max-Planck-Institut, Weinberg 2, 06120 Halle (Saale)

The structure and emission properties of Ge/Si quantum dot superlattices (QDSLs) grown by molecular beam epitaxy are studied. In our particular system, an unusual large conduction band offset is formed by Sb doping of the Si spacer layers. Thereby, this heterostructure has a quantum well (QW) system for the electrons. The Arrhenius analysis of photoluminescence spectrum and a strict dependence of the activation energy versus spacer thickness indicate the existence of the electron state in this QWs. Related to this energy level, we measure the electroluminescence with a external efficiency 4E-4 at 1.55 um up to room temperature. We demonstate that such high luminescence efficiency is related to the formation of a conduction miniband due to tunneling of electrons between adjacent QWs and to the transition to quasi-direct excitons in Ge/Si QDSL. Miniband width (15-35 mev) and conduction band offset (110 mev) are calculated assuming different effective masse of electron state density for the Si QWs and Ge barriers as well. The details and limitations of the miniband concept are discussed.