Electron spin resonance study of interacting donor clusters in phosphorus-doped silicon at 100 GHz and low temperatures

International audienceESR experiments have been performed on phosphorus-doped silicon with concentrations ranging from 1.9 x 10 17 cm-3 to 2.8 ×1018 cm-3 at 1.4-4.2 K and 100 GHz. The peak shift of the central ESR line with respect to the center of the two hyperfine lines has been investigated as a function of donor concentration, temperature, and microwave power. In general, it consists of a microwave power-dependent part and of a microwave power-independent one. The former part is interpreted in terms of the Overhauser effect ; the latter one is due to an asymmetry of the spectrum, understood on the basis of a new model proposed by one of the authors, which takes into account the clustering of nearby donors according to the exchange interaction between their electronic spins, and the hyperfine interaction with 31P nuclei