ELECTRON-PARAMAGNETIC-RESONANCE OF NI+ IMPURITIES IN AGGASE2

Electron paramagnetic resonance (EPR) has been used to detect Ni+ impu rities substituting for Ag+ ions in a single crystal of AgGaSe2. The o bserved EPR spectrum has axial symmetry about the c axis of the crysta l and is described by g(parallel to) = 2.635 and g(perpendicular to) = 2.241. A partially resolved hyperfine pattern in the c-axis spectrum is consistent with equivalent interactions with four I = 3/2 nuclei (e .g., Ga-69,Ga-71). The concentration of Ni+ ions in the undoped crysta l was approximately 7 x 10(17) cm(-3) These substitutional Ni+ impurit y ions are suggested to be responsible for the polarized 2.2 mu m abso rption band that is presently limiting the use of AgCaSe2 as a 2 mu m pumped optical parametric oscillator with mid-infrared output. (C) 199 6 American Institute of Physics.