Electric-Field-Induced Impact Ionization of Excitons
in GaN and GaN/AlGaN Quantum Wells

D. K. Nelson*, M. A. Yacobson*, V. D. Kagan*, B. Gil**, N. Grandjean***,
B. Beaumont***, J. Massies***, and P. Gibart***

* Ioffe Physicotechnical Institute, Russian Academy of Sciences,
Politekhnicheskaya ul. 26, St. Petersburg, 194021 Russia

** CNRS-GES, Université de Montpellier II, Montpellier Cedex 5, 34095 France

*** CNRS-CRHEA, Sophia-Antipolis, Valbonne, 06560 France

Received April 27, 2001

Abstract—Impact ionization of exciton states in epitaxial GaN films and GaN/AlGaN quantum-well structures
was studied. The study was done using an optical method based on the observation of exciton photolumines-
cence quenching under application of an electric field. It was established that electron scattering on impurities
dominates over that from acoustic phonons in electron relaxation in energy and momentum. The mean free path
of the hot electrons was estimated. The hot-electron mean free path in GaN/AlGaN quantum wells was found
to be an order of magnitude larger than that in epitaxial GaN films, which is due to the electron scattering prob-
ability being lower in the two-dimensional case. © 2001 MAIK “Nauka/Interperiodica”.

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