Photoluminescence of Ultraviolet Initiated Green Emission from Electrochemically Deposited Germanium Films on (100) Silicon

Abstract

Photoluminescence (PL) spectra of the germanium deposited nanostructures grown on silicon (Si) substrate showed a weak UV peaked at 353 nm (∼3.4 eV), violet-blue at 402 nm (∼3.1 eV), and a broad green band emission in the 470-500 nm (∼2.46 eV) range at room temperature when illuminated by 325 nm line laser beam. Electrochemical growth was monitored and evaluated using scanning electron microscopy (SEM), Raman spectroscopy, and PL. SEM images indicated varied current-density-dependent stoichiometry. The origin of the emissions is attributable to GeO2 defect centers, exciton confined in a quantum well, and to unbridged oxygen hole centers. These results perhaps are an indication that the blue luminescence is correlated with the formation of Ge (or GeO2) nanocrystals. The radiative recombinations of excitons confined in the nanocrystals are assessed with a possibility of contributing to the shift in the peak.