Equivalence of donor and acceptor fits of temperature dependent Hall carrier density and Hall mobility data: Case of ZnO
Résumé
In this work, statistical formulations of the temperature dependence of ionized and neutral impurity
concentrations in a semiconductor, needed in the charge balance equation and for carrier scattering
calculations, have been developed. These formulations have been used in order to elucidate a
confusing situation, appearing when compensating acceptor (donor) levels are located sufficiently
close to the conduction (valence) band to be thermally ionized and thereby to emit (capture) an
electron to (from) the conduction (valence) band. In this work, the temperature dependent Hall carrier
density and Hall mobility data adjustments are performed in an attempt to distinguish the presence of
a deep acceptor or a deep donor level, coexisting with a shallower donor level and located near the
conduction band. Unfortunately, the present statistical developments, applied to an n-type
hydrothermal ZnO sample, lead in both cases to consistent descriptions of experimental Hall carrier
density and mobility data and thus do not allow to determine the nature, donor or acceptor, of the deep
level. This demonstration shows that the emission of an electron in the conduction band, generally
assigned to a (0/+1) donor transition from a donor level cannot be applied systematically and could
also be attributed to a (-1/0) donor transition from an acceptor level. More generally, this result can
be extended for any semiconductor and also for deep donor levels located close to the valence band
(acceptor transition)