UBC Theses and Dissertations
Electron paramagnetic resonance of phosphorus doped silicon in the intermediate impurity concentration range Cullis, Pieter Rutter
The EPR properties of phosphorus-doped, silicon samples were investigated through the temperature range 11°K ≤ T ≤ 35°K and the impurity concentration range 5 x 10¹⁶ donors/cm³ ≤ N[sub d] ≤ 2 x 10¹⁸ donors/cm³. Rapid passage spectra obtained are interpreted directly as undifferentiated absorption envelope spectra. Slow passage absorption derivative signals were integrated to obtain similar absorption envelope. These absorption envelope spectra were decomposed into the three major components observed--a broad centre line (BCL), two hyperfine lines, and a discrete central pair line. Each of these components is found to be characterized by a symmetric "Voigt profile" lineshape—i.e. by a convolution of a Gaussian envelope function with Lorentzian "spin packets". Spin lattice relaxation times and spin packet widths were measured for each of these components as functions of temperature and concentration. These data appear to be consistent with the proposal that the hyperfine line spins cross-relax with faster relaxing BCL spins. The extrinsic hyperfine spin-lattice relaxation times are noted to be temperature dependent according to T[sup H/ sub 1] ∝T[sup -3/2]. The "g" values of the hyperfine lines and BCL were determined at various temperatures and impurity concentrations„ Both lines are observed to exhibit effective "g" shifts as the impurity concentration is increased. These "g" shifts are shown to be inconsistent with the ferromagnetic exchange model of Morigaki and Maekawa. The relative susceptibility of the BCL as a function of impurity concentration is shown to be reasonably consistent with the conjecture that the BCL arises primarily from clusters of three or more impurities. All observed effects would indicate that the BCL is the precursor of the single EPR line observed for more heavily doped samples.
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