Determination of the densities of gap states in hydrogenated polycrystalline Si and Si0.8Ge0.2 films

The densities of gap states are determined using the field-effect conductance method for hydrogenated polycrystalline Si0.8Ge0.2 for the first time, and also for polycrystalline Si. The polycrystalline films were hydrogenated by high dose H+ implantation and subsequent low-temperature anneal. The density of states is found to be higher in hydrogenated Si0.8Ge0.2 than in hydrogenated Si, for the low-pressure chemical vapor deposited films used in this work. The Si0.8Ge0.2 film is slightly n-type whereas the Si film is slightly p-type. The polycrystalline Si density of states shows the characteristic hump associated with silicon dangling bonds. These dangling bond states are located 0.63 eV below the conduction band. In the case of polycrystalline Si0.8Ge0.2, the dangling bond states are more complicated.