Passivation Of P-type Black Silicon With Al₂O₃Film Deposited By Chemical Liquid Phase Deposition

Surface passivation process has been widely used in the semiconductor industry include integrated circuit and silicon solar cell. Inorganic oxide films, such as SiO2, SiNx and Al2O3et al. have become important points in the studying of semiconductor surface passivation process. Compared with other inorganic oxide, Al2O3with a large fixed negative charge density, which is very suitable to be used as the passivation material for p-type silicon solar cells. However, atom layer deposition used to passivate Al2O3on the silicon solar cells is expensive and complex. In order to seek a method aiming at operation simplification and cost reduction, we fabricated Al2O3thin film on p-type silicon by chemical liquid phase deposition (CLD). And then we researched the influence of different annealing temperatures on the electrical properties as well as the passivation effect of the film. The measurements include X-ray diffraction (XRD) and scanning electron microscope (SEM) were carried out to study the phase change, morphology and the thickness of the film. We found the high-quality Al2O3film can be obtained by CLD. The reflectance measurement shows the reflectivity of the samples increased approximately4%, which is caused by total internal reflection effect. Capacitance-voltage measurement (C-V) as well as transient surface photo-voltage (SPV) measurement suggested that the annealing temperatures can influence on the electric property and passivation effect. C-V curves shows a low density of fixed negative charge of the film for the lack of interstitial O and increasing annealing temperature even decrease its density, at the same time, the mobile positive charge density increased, which can degrade the field passivation effect of the film. SPV shows the recombination velocity of photon-generated carriers decreased that means carrier lifetime increased. A better passivation effect can be achieved by annealing between300and600℃. The exorbitant can lead to an inferior recombination velocity which implies a degenerated passivation effect.