GERMANIUM IMPLANTATION INTO AMORPHOUS-SILICON FILMS

The influence of the Ge+ dose and post-implantation annealing on the d c dark-, photo conductivity and EPR of amorphous Si films have been in vestigated. Amorphous Si (a-Si) thin films have been deposited by evap oration. Doses ranged from 6 x 10(14) to 3 x 10(16) Ge cm(-2) when inc reasing the Ge concentration to ''critical'' value (0.12-0.8 at.%) in a-Si and raising the annealing temperature to 400-450 degrees C, a dec rease of density of localized stated (DLS) was observed. It follows fr om the decrease of hopping conductivity contribution in dark conductiv ity as well as from the increase of photosensitivity sigma(photo)/sigm a(dark) up to 10(3) (AM1) and from the minimum-like dose dependence of spin density. We have found that B+ and P+ implantation into a-Si fil ms predoped by 1.6 x 10(15) Ge cm(-)2 increased the dark conductivity in the 10(-9)-10(-3) Omega(-1) cm(-1) range, if samples were annealed at 400 degrees C. The Fermi level location varied from (E(v) + 0.2) to (E(c) + 0.2) eV for the impurity valence respectively. Thus, a-Si wit h a critical concentration of Ge is similar to a-Si:H in its propertie s. The present results are discussed using the model of dangling bond self-saturation during random network structural relaxation that occur s due to Si and Ge atom size differences.