Charge Trapping Properties of Ge Nanocrystals Grown via Solid-State Dewetting

In the present work, we report on the charge trapping properties of Germanium Nanocrystals (Ge NCs) self assembled on SiO₂ thin layer for promising applications in next-generation non volatile memory by the means of Deep Level Transient Spectroscopy (DLTS) and high frequency C-V method. The Ge NCs were grown via dewetting phenomenon at solid state by Ultra-High Vacuum (UHV) annealing and passivated with silicon before SiO₂ capping. The role of the surface passivation is to reduce the electrical defect density at the Ge NCs-SiO₂ interface. The presence of the Ge NCs in the oxide of the MOS capacitors strongly affects the C-V characteristics and increases the accumulation capacitance, causes a negative flat band voltage (V_FB) shift. The DLTS has been used to study the individual Ge NCs as a single point deep level defect in the oxide. DLTS reveals two main features: the first electron traps around 255 K could correspond to dangling bonds at the Si/SiO₂ interface and the second, at high-temperature (>300 K) response, could be originated from minority carrier generation in Ge NCs.