A comparison between defects created by light soaking and tritium decay in amorphous silicon

We compare two ways to create defects in a-Si:H, namely decay of bonded tritium and irradiation with visible light. Tritium decays to He$^{3}$, emitting a beta particle and an antineutrino. In tritium doped a-Si:H samples each beta decay of tritium bonded to silicon will create a defect by converting a bonded tritium to an interstitial helium, leaving behind a silicon dangling bond. We track these defects using electron spin resonance (ESR). We have kept the sample in liquid nitrogen for two years. After two years the defect density increases without saturation to a value of 7x10$^{19}$/cm$^{3}$. In the second experiment, we have kept the sample in liquid nitrogen irradiated with white light of intensity about 100mW/cm$^{2}$. After about 6 months, the spin density increased to about 9x10$^{17}$/cm$^{3}$ with no evidence of saturation. In the tritiated sample the increase in the defect density is proportional to the time, t, while in the light-soaked sample the increase is approximately proportional to t$^{1/3}$. This difference in behavior will be discussed.