Influence of oxygen on defect densities in nanocrystalline Si

A differential capacitance vs. frequency technique for determining trap densities as a function of energy in amorphous and nanocrystalline Si devices is presented. Through differential capacitance measurements, trap states can be accurately measured and profiled within the bandgap as a function of energy. Defects for amorphous silicon were shown to be Gaussian approximately 0.7 eV below the conduction band, on the order of 1015–1016 cm− 3 depending on deposition. This agrees with both external a-Si measurements and C–V defect measurements. Defects in nano-crystalline silicon were studied as a function of oxygen present in the material. Five different depositions were carried out with varying amounts of oxygen. The defect densities of each device were then measured. A large increase in defect densities corresponding to an increase in oxygen content is observed.