An oscillatory absorption spectrum which could not be detected in thin samp
les was observed for FIR magneto-optical absorption measurements in bulk n-
InP at 4.2 K. It was found that the peak positions of the oscillation did n
ot correspond to a series of direct transitions from the Is ground state of
donors into the Landau levels, and these peak positions considerably chang
ed with the donor concentration. We have concluded that those oscillations
are associated with a series of transitions from the Is ground state into d
onor bands formed by the excited states and their accompanying the Landau l
evels. (C) 2001 Elsevier Science B.V. All rights reserved.