Excitation Intensity Dependence of Light-Induced Electron Spin Resonance in Hydrogenated Amorphous Silicon Films

ABSTRACTLight-induced electron spin resonance in a-Si:H films was measured using second harmonic detection over a wide range of excitation intensities. Second harmonic detection results in an undifferentiated absorption lineshape that saturates much less easily with increasing microwave power. The ratio of the spin densities of the broad line to the narrow line is approximately 3 at a generation rate of 1019 cm−3s−1, and this ratio increases only slightly with decreasing excitation intensity. The kinetics of the LESR after the light is turned on or off show dispersive behavior. The dispersive response of the LESR is related to the dispersive transport of carriers at low temperature. A model that assumes a bimolecular recombination fits the experimental results reasonably well.