Electron spin resonance of light holes in porous silicon

Abstract A new ESR spectrum labeled Si-AA20 is revealed in porous silicon after annealing at 1000 °C. The AA20 line has a Dyson type that allows to attribute the AA20 to free carrier absorption. The AA20 spectrum is isotropic with g =2.0710. The high value of the g -factor indicates that the absorption can be hole-like. Intensity of the AA20 spectrum considerably changed upon rotation of the magnetic field H in the ( 0 1 ¯ 1 ) plane, at the same time the shape and half-width of the spectrum line did not change. The intensity was maximal with H along 〈1 1 1〉 directions and decreased in 2–3 times with H along 〈0 1 1〉 and 〈0 0 1〉 directions when the intensity reached minimum. The AA20 spectrum can be explained by formation of layers in porous silicon with high concentration of free holes for compensation of negative charged traps.