Investigation of hydrogenated amorphous silicon as passivation layer by high density plasma

• Amorphous silicon film grown by hydrogen dilution is investigated for passivation.
• Lower microstructure factor demonstrates better passivation performance.
• Post thermal annealing is an effective method to improve the effective lifetime.
• Carrier lifetime is larger than 1 ms at onset of amorphous–crystalline transition.

In this study, we use an electron cyclotron resonance chemical vapor deposition to deposit hydrogenated amorphous Silicon (a-Si:H) by different process parameters. We investigated the structure and passivation quality of a-Si:H by tuning the hydrogen dilution ratio and thermal annealing. The properties of films were measured by spectroscopic ellipsometry, optical emission spectroscopy, Fourier transform infrared spectrometer, and quasi-steady-state photoconductance methods. The best passivation quality results from films are consistent with a low microstructure parameter, abundant hydrogen content, and high photosensitivity. The maximum value of τeff at about 1182 μs at an injection level of 10− 15 cm− 3 was obtained on single-side polished p-type Cz (100) substrates after thermal annealing around 270 °C. The high passivation quality can be obtained at the onset of the amorphous–crystalline transition, while the thin film remains in the amorphous phase.