Thermal stability of p-type doped amorphous silicon suboxides

We investigate the effects of thermal annealing on the optical and electrical properties of p-type doped amorphous silicon suboxide (a-SiO_x:H) samples prepared by plasma enhanced chemical vapour deposition (PECVD). Changes in the microscopic structure of the amorphous network upon thermal annealing at low temperatures (<550 K) cause a dopant activation of the p-type samples. The resulting increase of the dark conductivity becomes smaller with increasing oxygen content, but still comprises almost 2 orders of magnitude for samples with 9 at.% oxygen. Thermal annealing at higher temperatures (>550 K) leads to an effusion of hydrogen, thereby reducing the optical bandgap, E₀₄, of the samples. The dependence of E₀₄ on the hydrogen content for amorphous suboxides with different oxygen content is found to be similar to that of amorphous silicon.