Photo-sensitive Ge nanocrystal based films controlled by substrate deposition temperature

Lowering the temperature of crystallization by deposition of thin films on a heated substrate represents the easiest way to find new means to develop and improve new working devices based on nanocrystals embedded in thin films. The improvements are strongly related with the increasing of operation speed, substantially decreasing the energy consumption and reducing unit fabrication costs of the respective semiconductor devices. This approach avoids major problems, such as those related to diffusion or difficulties in controlling of nanocrystallites size, which appear during thermal treatments at high temperatures after deposition. It is reported here the significant progress introduced by synthesis procedure to the in-situ structuring of Ge nanocrystallites in $SiO_{2}$ thin films by heating the substrate at low temperature, 400 °C during co-deposition of Ge and $SiO_{2}$ by magnetron sputtering. As a proof-of-concept, a Si/Ge-NCs:$SiO_{2}$ photo-sensitive structure was fabricated thereof and characterized. The structure shows superior performance on broad operation bandwidth from visible to near-infrared, as strong rectification properties in dark, significant current rise in the inversion mode when illuminated, high responsivity, high photo-detectivity of 10^{14} Jones, quick response and significant conversion efficiency of 850 %. This simple preparation approach brings an important contribution to the efort of structuring Ge nanocrystallites in SiO^{2} thin films at a lower temperature for the purpose of using these materials for devices in optoelectronics, solar cells and electronics on flexible substrates.