Comparison of diffusion length in a-SiGe:H,F after light or proton irradiation

Changes in the minority carrier diffusion length, in reverse-bias photocurrent and dark current of thin films of amorphous silicon germanium alloys (a-SiGe:H,F) caused by prolonged illumination with AM1 light were compared with changes caused by irradiation with 12 MeV protons. Both light soaking and proton irradiation degrade the μ tau products of electrons and holes while introducing metastable defects. The time needed to reduce the photocurrent by one order of magnitude in Schottky barrier structures containing a 2 μm thick film of a-Si:H and a-SiGe:H was 8 min and 15 min, respectively. Comparable degradation in a-Si:H and a-SiGe:H,F samples due to illumination with AM1 light is reached after several hundred hours. In a-Si:H the diffusion length decreased from 0.2 μm to near the measurement limit of 0.03 μm. While having similar effects, proton irradiation can be performed on a much shorter time scale than light soaking