VANADIUM CENTERS IN ZNTE CRYSTALS .2. ELECTRON-PARAMAGNETIC-RESONANCE

Four V-related electron-paramagnetic-resonance (EPR) spectra are obser ved in Bridgman-grown ZnTe doped with vanadium. Two of them are attrib uted to the charge states V-Zn(3+)(A(+)) and V-Zn(2+)(A(0)) of the iso lated V impurity. For the ionized donor, V-Zn(3+)(A(+)), the spectrum reveals the typical behavior of the expected (3)A(2)(F) ground state i n tetrahedral symmetry. The incorporation on a cation lattice site cou ld be proved by the resolved superhyperfine interaction with four Te i ons. The second spectrum showing triclinic symmetry and S=3/2 is inter preted as the neutral donor state V-Zn(2+)(A(0)). The origin of the tr iclinic distortion of the cubic (T-d) crystal field could be a static Jahn-Teller effect. The two additionally observed EPR spectra are attr ibuted to nearest-neighbor V-related defect pairs. The spectrum of the first one, V-Zn(2+)-Y-Te, shows trigonal symmetry and can be explaine d by the S=3/2 manifold of an orbital singlet ground state. An associa ted defect ''Y-Te'' is responsible for the trigonal distortion of the tetrahedral crystal field of V-Zn(2+). The spectrum of the second pair defect also shows trigonal symmetry and can be described by S=1/2. Th e ground-state manifold implies a V-Zn(3+)-X(Te) pair as the most prob able origin of this spectrum. The S=1/2 ground state is produced by a dominating isotropic exchange interaction coupling the S=1 ground-stat e manifold of V(Zn)3+ to an assumed S=1/2 ground state of (''X(Te)'') in antiferromagnetic orientation. The nature of the associated defects ''Y-Te'' and ''X(Te)'' remains unknown for both pairs since no hyperf ine structure has been observed, but most probably acceptorlike defect s are involved.