Impact of hydrogen on the boron-oxygen-related lifetime degradation and regeneration kinetics in crystalline silicon

We examine the impact of hydrogen on the boron-oxygen-related lifetime degradation and regeneration kinetics in boron-doped p-type Czochralski-grown silicon wafers. We introduce the hydrogen into the silicon bulk by rapid thermal annealing. The hydrogen source are hydrogen-rich silicon nitride (SiNx:H) layers. Aluminum oxide (Al2O3) layers of varying thickness are placed in-between the silicon wafer surfaces and the SiNx:H layers. By varying the Al2O3 thickness, which acts as an effective hydrogen diffusion barrier, the hydrogen bulk content is varied over more than one order of magnitude. The hydrogen content is determined from measured wafer resistivity changes. In order to examine the impact of hydrogen on the degradation kinetics, all samples are illuminated at a light intensity of 0.1 suns near room temperature. We observe no impact of the in-diffused hydrogen content on the degradation rate constant, confirming that hydrogen is not involved in the boron-oxygen degradation mechanism. The regeneration experiments at 160°C and 1 sun, however, show a clear dependence on the hydrogen content with a linear increase of the regeneration rate constant with increasing bulk hydrogen concentration. However, extrapolation of our measurements toward a zero in-diffused hydrogen content shows that the regeneration is still working even without any in-diffused hydrogen. Hence, our measurements demonstrate that there are two distinct regeneration processes taking place. This is in good agreement with a recently proposed defect reaction model and is also in agreement with the finding that the permanent boron-oxygen deactivation also works on non-fired solar cells, though at a lower rate. •We quantify the in-diffused hydrogen content in silicon by resistivity measurements.•We vary the hydrogen content by varying the thickness of Al2O3 interlayers.•Boron-oxygen-related lifetime degradation and regeneration experiments are performed for different in-diffused hydrogen contents.•Rdeg shows no dependence on the bulk hydrogen content.•Rreg increases with increasing bulk hydrogen content and even for a vanishing hydrogen content regeneration is observed (two regeneration processes).