Low-temperature Surface Passivation of Moderately Doped Crystalline Silicon by Atomic-layer-deposited Hafnium Oxide Films

Hafnium oxide (HfO2) films synthesized by thermal atomic layer deposition (ALD) are investigated for low-temperature surface passivation of moderately doped crystalline silicon (c-Si). At intermediate bulk injection levels, effective surface recombination velocities of 55 cm/s and 24 cm/s are achieved on 2.1 ♣cm p-type and 3.3 ♣cm n-type c-Si, respectively, demonstrating a good level of surface passivation. Fourier transform infrared spectroscopy and cross-sectional transmission electron microscopy experiments are conducted to provide insight into the surface passivation mechanism of HfO2 on c-Si. The good passivation quality is shown to be due to both chemical passivation and field-effect passivation. The latter is due to built-in positive charges in the HfO2 film, which is particularly beneficial for the passivation of n-type c-Si.