Thermal quenching and relaxation in doped hydrogenated amorphous silicon deposited by plasma-enhanced chemical vapor deposition from He-diluted silane

The stability of n-type and p-type rf glow discharge amorphous silicon (a-Si:H) deposited from silane-helium mixtures has been studied. Dark dc conductivity measurements were made after quenching or slow cooling and the time dependence of isothermal relaxation at different temperatures has been investigated. The equilibration temperatures are ∼155 and ∼125°C for n- and p-type films, respectively. These values are greater than those commonly reported on conventional rf glow discharge films (130 and 90°C). In comparison with conventional films, at any given temperature the relaxation times are longer with activation energies of 1 and 1.39 eV for n- and p-type films. The improved stability of the films has been discussed in relation with their particular hydrogen-related structure.