Electrical and dielectric properties of ferromagnetic GeMn nanocrystals embedded in metal-oxide-semiconductor Schottky diodes (Al/SiO2:GeMn NCs/n-Si) grown by MBE

This study examines the electrical and dielectric characteristics of magnetic GeMn nanocrystals integrated into a metal-insulator-semiconductor (MOS) configuration for optoelectronic applications. The nanocrystals were produced by solid-state dewetting of an amorphous GeMn layer deposited by MBE on SiO2/Si. The nanocrystals exhibit a well-defined hemispheric shape, high homogeneity, and with a Curie temperature higher than that of the ambient temperature. Characterizations by transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS) revealed the crystallinity of the nanocrystals and optimal incorporation of manganese in the nanocrystals, eliminating the usual diffusion or segregation anomalies observed during growth of GeMn alloy on silicon or germanium. Electrical and dielectric tests conducted via current-voltage and impedance spectroscopies on these structures confirmed the integrity of the oxide layer surrounding the GeMn nanocrystals from defects associated with the manganese. In addition, these measurements validated the proper functioning of the MOS structure as a MOS-type Schottky diode. The in-depth analysis of dielectric parameters, such as permittivity (ε), tangent δ, and electric modulus (M) as a function of frequency and bias voltage, revealed no anomalies, thus reinforcing the high quality of the MOS structure enclosing the GeMn nanocrystals. These results mark a significant advance in the growth and integration of magnetic semiconductor nanostructures for optoelectronic applications, paving the way for promising technological developments. •Manganese-doped germanium nanocrystals (GeMn NCs), produced by MBE via a solid-state dewetting process, are successfully integrated into MOS capacitors for optoelectronic applications.•The electrical study focused on the transport mechanisms present in MOS capacitors integrating GeMn NCs, highlighting the Schottky diode metal-insulator-semiconductor.•Impedance spectroscopy was used to conduct the study on the interface state density and the impact of GeMn nanocrystals on the dielectric properties of the MOS structure containing GeMn nanocrystals. The findings unequivocally indicate the absence of any anomalies associated with manganese doping, affirming the exceptional quality of the GeMn nanocrystals.