Electron Spin Resonance of Doped Glow‐Discharge Amorphous Silicon

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Abstract
The influence of doping on the ESR spectra of glow‐discharge a‐Si:H is systematically investigated in the X‐ and Q‐band for phosphorus‐ and boron‐doped samples up to a high doping level. Whereas for undoped and moderately doped material the well‐known line with g = 2.0055 is observed, for highly boron‐doped samples the broader line at g = 2.01 predominates as does the g = 2.0043 line in the case of high phosphorus doping. The linewidth of the resonance at g = 2.01, due to holes in localized valence band tail states, is mainly determined by a g‐value spectrum. With increasing boron doping the width of this spectrum decreases and its centre of gravity shifts to smaller g‐values. The narrower line with g = 2.0043, due to electrons in localized conduction band tail states, however, broadens with increasing phosphorus doping due to hyperfine interaction with the phosphorus nuclei. From these features it is concluded that the wave function of holes in valence band tail states is much more localized than that of electrons in the conduction band tail. At the same high doping level the spin density for the hole resonance at g = 2.01 is a factor of about 102 larger than for the electron line with g = 2.0043. This difference is explained by a different correlation energy U. Besides these lines a relatively weak resonance at g = 2.0026 is found for boron‐doped samples and for phosphorus‐doped material as well. Measurements on compensated samples indicate that by doping dangling bonds are created.