Microwave-induced resonant changes in transport and recombination in hydrogenated amorphous silicon

Abstract

We report on a detailed study of spin-dependent photoconductivity (SDPC) in undoped and doped hydrogenated amorphous silicon films. The SDPC spectra contain contributions from all paramagnetic states known from electron spin resonance, light-induced electron spin resonance and optically detected magnetic resonance studies. It is shown that phosphorus states are strongly involved in both transport and recombination. In all undoped films a spectacularly broad signal (δHFWHM = 210G) is found which we assign to the recombination of exchange coupled electron-hole pairs. The influence of the Fermi level position on the various contributions of the recombination channels is examined, the Fermi level being shifted by defect creation which is accomplished by both prolonged illumination and bombardment with electrons of high energy.