Electronic properties of highly P and B doped thin Si layers grown by ECR–CVD

Thin Si films strongly doped with P and B are grown at 325°C by electron cyclotron resonance chemical vapor deposition (ECR–CVD) on quartz substrates and Si wafers. Films deposited on quartz are microcrystalline. By an analysis of Hall effect data it is shown that the electrical transport in these films is controlled by potential barriers at grain boundaries. Using a simple barrier-limited transport model it is found that the effective interface defect density Qit increases with the doping level Nd,a following a power law. A study of electron spin resonance shows that the in-grain mobility of electrons is much higher than the Hall mobility. At high doping levels the films grew epitaxially on Si substrates. Such films are used as emitter layers in solar cell structures and efficiencies of 14% are demonstrated.