Passivation of n- and p-Type Silicon Surfaces With Spray-Coated Sol-Gel Silicon Oxide Thin Film

Thermally grown SiO<sub>2</sub> is widely used for silicon surface passivation in solar cells and other applications due to excellent interfacial properties. SiO<sub>2</sub> films with thickness in the range of 17 nm deposited by industrially viable spray-coating technique on both n- and p-type silicon are reported. Low values of interface state density of <inline-formula> <tex-math notation="LaTeX">${1.4}\times {10}^{{10}}$ </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{2}}$ </tex-math></inline-formula>eV<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{1}}$ </tex-math></inline-formula> on n-type and <inline-formula> <tex-math notation="LaTeX">${2.0}\times {10}^{{10}}$ </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{2}}$ </tex-math></inline-formula>eV<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{1}}$ </tex-math></inline-formula> on p-type were achieved. Fixed oxide charges in the range of 7.1–<inline-formula> <tex-math notation="LaTeX">${9.4}\times {10} ^{{11}}$ </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{2}}$ </tex-math></inline-formula> and 3.9–<inline-formula> <tex-math notation="LaTeX">${6.5}\times {10} ^{{11}}$ </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{2}}$ </tex-math></inline-formula> on n- and p-type, respectively, are obtained. Excellent passivation results in the effective surface recombination velocity of 0.97 cms<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{1}}$ </tex-math></inline-formula> and 8.07 cms<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{1}}$ </tex-math></inline-formula> at minority carrier concentration of <inline-formula> <tex-math notation="LaTeX">$10^{{15}}$ </tex-math></inline-formula> cm<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{3}}$ </tex-math></inline-formula> on n- and p-type Czochralski silicon, respectively, without the use of capping layer. SiO<sub>2</sub> film exhibits dielectric breakdown field strength of 4.3 MVcm<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{1}}$ </tex-math></inline-formula> and 5.6 MVcm<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{1}}$ </tex-math></inline-formula> and leakage current density of <inline-formula> <tex-math notation="LaTeX">${2.2}\times 10 ^{\boldsymbol -{8}}$ </tex-math></inline-formula> Acm<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{2}}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">${1.1}\times {10} ^{\boldsymbol -{8}}$ </tex-math></inline-formula> Acm<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{2}}$ </tex-math></inline-formula> at 1 MVcm<inline-formula> <tex-math notation="LaTeX">$^{\boldsymbol -{1}}$ </tex-math></inline-formula> on n- and p-type silicon, respectively. These values are superior to sol-gel-based SiO<sub>2</sub> films reported previously and are comparable to or better than those reported for other methods for the growth or deposition of SiO<sub>2</sub> on silicon. Amorphous nature of the film is validated by high-resolution transmission electron microscopy (TEM). The X-ray photoelectron spectroscopy (XPS) analysis shows nearly stoichiometric SiO<sub><italic>x</italic></sub> film.