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Theoretical study of the group IV antisite acceptor defects



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APPLIED PHYSICS LETTERS VOLUME 85 NUMBER 19 8 NOVEMBER 2004 Theoretical study of the group IV antisite acceptor defects in CdGeAs2 Miguel A Blanco a Aurora Costales a and Victor Lua a Departamento de Qu mica F sica y Anal tica Facultad de Qu mica Universidad de Oviedo 33006 Oviedo Spain Ravindra Pandeyb Department of Physics Michigan Technological University Houghton Michigan 49931 Received 7 July 2004 accepted 14 September 2004 Native and impurity antisite point defects in CdGeAs2 are studied here using an embedded quantum cluster model based on density functional theory The calculated geometric relaxations and spin densities of the antisite defects considered here show a clear and distinct difference in the nature of native i e GeAs and impurity i e CAs and SiAs antisite defects in CdGeAs2 For the native antisite acceptor the hole appears to be delocalized in contrast to impurity antisites where the hole is mainly localized at the acceptor site 2004 American Institute of Physics DOI 10 1063 1 1818731 Cadmium germanium arsenide CdGeAs2 is an ideal candidate material for nonlinear optical NLO applications since it has the highest NLO coefficient 236 pm V known for a phase matchable compound semiconductor 1 2 Recent successes3 in the horizontal gradient freeze growth technique made it possible to grow large single crystals of CdGeAs2 which led to renewed efforts to utilize this material for optoelectronic devices However a discrete absorption band near 5 5 m is found to hinder the performance of devices This absorption band is attributed to acceptor levels in CdGeAs2 4 7 A recent experimental study8 further confirms the association of a paramagnetic state of the acceptor level to the absorption band at 5 5 m The most likely candidate for the acceptor level was suggested to be the Ge on As antisite i e GeAs defect though a small possibility was allowed for impurities such as C or Si antisites In this work our aim is to obtain local electronic and structural properties



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