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

Abstract

Thermally grown SiO2 is widely used for silicon surface passivation in solar cells and other applications due to excellent interfacial properties. SiO2 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 ${1.4}\times {10}^{{10}}$ cm $^{\boldsymbol -{2}}$ eV $^{\boldsymbol -{1}}$ on n-type and ${2.0}\times {10}^{{10}}$ cm $^{\boldsymbol -{2}}$ eV $^{\boldsymbol -{1}}$ on p-type were achieved. Fixed oxide charges in the range of 7.1– ${9.4}\times {10} ^{{11}}$ cm $^{\boldsymbol -{2}}$ and 3.9– ${6.5}\times {10} ^{{11}}$ cm $^{\boldsymbol -{2}}$ on n- and p-type, respectively, are obtained. Excellent passivation results in the effective surface recombination velocity of 0.97 cms $^{\boldsymbol -{1}}$ and 8.07 cms $^{\boldsymbol -{1}}$ at minority carrier concentration of $10^{{15}}$ cm $^{\boldsymbol -{3}}$ on n- and p-type Czochralski silicon, respectively, without the use of capping layer. SiO2 film exhibits dielectric breakdown field strength of 4.3 MVcm $^{\boldsymbol -{1}}$ and 5.6 MVcm $^{\boldsymbol -{1}}$ and leakage current density of ${2.2}\times 10 ^{\boldsymbol -{8}}$ Acm $^{\boldsymbol -{2}}$ and ${1.1}\times {10} ^{\boldsymbol -{8}}$ Acm $^{\boldsymbol -{2}}$ at 1 MVcm $^{\boldsymbol -{1}}$ on n- and p-type silicon, respectively. These values are superior to sol-gel-based SiO2 films reported previously and are comparable to or better than those reported for other methods for the growth or deposition of SiO2 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 x film.