K. Takahei et al., ATOMIC CONFIGURATIONS OF ER CENTERS IN GAAS-ER,O AND ALGAAS-ER,O STUDIED BY SITE-SELECTIVE LUMINESCENCE SPECTROSCOPY, Journal of applied physics, 82(8), 1997, pp. 3997-4005
Er-doped GaAs codoped with oxygen was studied by site-selective measur
ements of photoluminescence spectra and photoluminescence-excitation s
pectra directly exciting the 4f-shell electrons of one kind of Er cent
er at a time. Within one sample, more than 10 kinds of distinctly diff
erent Er centers, showing different Er-related spectra, were observed,
although its host-excited photoluminescence spectrum is dominated by
the luminescence from one kind of Er center. The atomic configuration
of that center has been identified as an Er atom located at the Ga sub
lattice with two adjacent oxygen atoms (Er-2O center). Seven kinds of
Er centers in GaAs:Er, O and two kinds of Er centers in AlGaAs:Er, O w
ere studied in detail. The numbers of lines and the magnitudes of ener
gy separations among the lines in each spectrum indicate that the Er a
toms of all nine kinds of centers are coupled with oxygen atoms and ha
ve noncubic symmetry. The nine Er centers were grouped into several cl
asses according to similarities in their spectra which should reflect
symmetries of the Er centers. The atomic configurations of two classes
of Er centers are discussed in detail. The Er centers of both classes
have a nearest-neighbor site atomic configuration similar to that of
the Er-2O center with a symmetry close to rhombic C-2 upsilon, but Er
centers in the two classes have different types of deviation from C-2
upsilon due to the difference in the second-nearest-neighbor atomic co
nfigurations of the Er Atoms. We also discuss a large difference in th
e efficiency of the Er-related luminescence under host photoexcitation
caused by the difference in the second-nearest-neighbor atomic config
urations. (C) 1997 American Institute of Physics.