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Abstract:
There are three exciton branches in wurzite-GaN: A, B and C.
Here, time-resolved photoluminescence and magneto-optic
spectroscopy of the B-exciton are presented, both free (FXB)
and bound to donor ((DXB)-X-0) in homoepitaxial GaN. The free
B-exciton has an energy of about 3.483 eV and a very short
lifetime of about 20 ps. The B-exciton bound to donor ((DXB)-X-
0) has an energy of 3.475 eV and a lifetime longer than the
free excitons but shorter than the lifetime of the A-exciton
bound to donor. It is shown that a simple model based on an
invariant expression describes properly the behavior of (DXA)-
X-0 and (DXB)-X-0 in a magnetic field. Results of resonance
excitation experiments suggest that in many cases the process
of binding a free exciton to a donor conserves the exciton type
and that the relaxation of B- to A-exciton takes place later.
Moreover, thermal excitation of (DXA)-X-0 to (DXB)-X-0 has been
observed.
