Laser-Assisted Wet-Chemical Doping of Sintered Si and Ge Nanoparticle Films

Doped thin films of group-IV semiconductors can be fabricated using the adsorption of dopant species from a liquid source to a precursor nanoparticle film, followed by laser-sintering to incorporate and activate the dopants in the sintered thin film. A detailed study of the doping of germanium films with arsenic reveals diffusion of dopants into the film and their adsorption to the nanoparticle surface as kinetically governing steps, benefiting from the large internal surface area of the nanoparticle film. The resulting charge carrier concentration can be adjusted by the internal surface area via the nano­particle diameter, by controlling the dopant concentration in the liquid, and by the immersion time and temperature. It is shown that the method can be successfully transferred to silicon and silicon–germanium alloy films using group-III and -V elements, which lead to p- and n-type conductivity, respectively. Atomic dopant concentrations above 10²⁰ cm⁻³ can be realized by laser-sintering, which are electrically active to a high extent and lead to effective conductivities well above 10 S cm^–1 in the mesoporous films is investigated here. The method allows flexible printing of devices using inks for the nanoparticles and the dopant and avoids toxic substances for the doping of nanoparticles in the gas phase.