An ESR study of bandtail states in phosphorus doped microcrystalline silicon

We report on a detailed electron spin resonance (ESR) study of the CE center in phosphorus doped μc-Si:H films. It is shown that the CE states originate from both delocalized electrons in the impurity and conduction band as well as from electrons trapped in bandtail states located at grain boundaries. The metal–insulator transition occurs, like in c-Si, at NP≈4×1018 cm−3 which suggests that the donors are homogeneously distributed within the crystalline phase. Due to the presence of bandtail states the P donor is not occupied at low doping levels and hence the hyperfine structure as a typical fingerprint of the P states in an c-Si environment are not observed.