Photoluminescence study of II-VI semiconductors by using radioactive As-71dopants

By means of radioactive dopants, photoluminescence signals related to the r espective chemical element are identified. In the present work, the isotope As-71 (t(1/2) = 65.3 h) which decays to Ge-71 (t(1/2) = 11.2 d) and subseq uently to Ga-71 was implanted into CdTe and ZnSe. In CdTe. the (D, A) trans ition related to the Asl, acceptor is identified in agreement with the lite rature. In addition, a new (D, A) transition caused by a shallow Ga accepto r is identified. The corresponding acceptor level having an ionisation ener gy of E-i = 42 meV is still shallower than the effective-mass like state (E -i = 57 meV). It is interpreted in terms of a Ga-71(Te) "antisite" defect i n a Jahn-Teller distorted configuration, Ab initio calculations within the framework of density functional theory confirm the existence of a Jahn-Tell er relaxed stable configuration for Ga-Te. In ZnSe, no clear evidence of a (D, A(As)) transition is found, but like in CdTe, a new shallow acceptor is observed which is supposed to originate from a Ga-71(Se) defect. (C) 2001 Elseiver Science B.V. All rights reserved.