Magnetic Ge:Mn nanocrystals grown by MBE on insulator substrate for solar cell and photodetector applications

In this work, we successfully grew novel dilute magnetic Ge:Mn nanocrystals (Ge:Mn NCs) on SiO2 thin film for metal-oxidesemiconductor (MOS) solar cell and photodetector applications. The innovative Ge:Mn NCs have been grown via solid-state dewetting of ultra-pure thin amorphous Ge:Mn nanolayer deposited by high precision molecular beam epitaxy (MBE) on thin SiO2/Si film. The morphological and structural properties of the Ge:Mn NCs have been determined by atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HR-TEM). The results indicate the formation of homogeneous Ge:Mn NCs on SiO2 with a well-defined spherical shape and small size (∼8 nm). The incorporation of Mn element into Ge matrix has been confirmed by scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX). The magnetic properties of the Ge:Mn NCs have been determined by the superconducting quantum interference device (SQUID). The results show that the Ge:Mn NCs are ferromagnetic and having a Curie temperature above room temperature (∼310 K). The electrical transport and the photocurrent generation in the novel Ge:Mn NCs embedded in the SiO2 film of MOS structure are studied by I-V and photocurrent spectroscopies. The results show that when the Ge:Mn NCs are inserted as an active layer in a SiO2 film of MOS structure, the photocurrent of the MOS structure increase 10 times higher than the dark current.