Electron spin resonance of shallow defect states in amorphous silicon and germanium

The nature of shallow states in a-Si:H and a-Ge:H is discussed. Spin resonance techniques can be used to distinguish between intrinsic tail states and extrinsic dopant levels. A quantitative analysis of the spin resonance data allows one to construct models for the density of states close to the mobility edges in doped samples and to explore the role of these states for carrier trapping.