Contrasting character of Cr and Mn solitary dopants in CdTe

Solitary dopants or single impurities embedded in semiconductor matrix having unique magnetic and optical properties are emerging as a promising platform to realize novel quantum devices. The realization of such devices however requires an atomic level control over the growth of such quantum defects to establish reproducible and scalable defect creation strategies. Among the solitary dopants, transition metal doped in semiconductor quantum dots are particularly interesting due to the ease of optical spin addressability. In this article we have investigated the challenges associated with embedding magnetic impurities, considering the case of single Mn and Cr dopants in the CdTe lattice. Optical control of single spin of such magnetic impurities trapped in a CdTe quantum dot has already been reported. We show using the first principle based calculations that the interactions with CdTe intrinsic defects poses challenges to the growth of single Cr and Mn trapped in a CdTe nanostructure. We provide a detailed thermodynamic analysis establishing that control over the growth process to embed a single Mn in CdTe, can be achieved without significant challenge but remains elusive in the case of Cr. Interestingly, some of the defect complexes resulting from the interaction of the metal dopant and intrinsic defects present the possibility to control and manipulate the spin and oxidation state of the impurity in the complex configuration. These defect complexes opens up the possibility of tuning optical and magnetic properties of single TM dopants. Finally, we propose guidelines and defect engineering strategies to mitigate or on the contrary to select the creation of such complexes.