Thermodynamics of excitons in semiconductors

MAR 01, 1982

Groups of photoexcited electrons and holes in silicon and germanium, observed through spectroscopy and imaging techniques, show thermodynamic behavior much like that of atomic and molecular gases and liquids.

DOI: 10.1063/1.2914968

James P. Wolfe

During the few microseconds between its laser‐induced creation in a pure semiconductor crystal and its destruction by recombination, a bound electron–hole pair, or exciton, is very active. Like the negative and positive charge carriers from which it forms, the exciton exhibits great mobility, whether it is coaxed by an applied force or simply moves under its own thermal energy. And like an atom in free space, it is bound by Coulomb forces, has discrete energy levels and may combine with other excitons into molecules or even condense into a liquid‐like state. In a semiconductor crystal such as silicon, all of this occurs at temperatures below about 30 K, for these weakly bound neutral particles ionize easily into electrons and holes at higher temperatures. The study of these particles and their products has occupied many physicists over the last couple of decades, and the investigations continue to uncover interesting new phenomena.

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More about the authors

James P. Wolfe, University of Illinois, Urbana–Champaign.