Excellent passivation of highly doped p-type Si surfaces by the negative-charge-dielectric Al2O3

Abstract

From lifetime measurements, including a direct experimental comparison with thermal $\mathrm{Si}{\mathrm{O}}_2$ , $a\text{-}\mathrm{Si}:\mathrm{H}$ , and as-deposited $a\text{-}\mathrm{Si}{\mathrm{N}}_x:\mathrm{H}$ , it is demonstrated that ${\mathrm{Al}}_2{\mathrm{O}}_3$ provides an excellent level of surface passivation on highly B-doped $c\text{-}\mathrm{Si}$ with doping concentrations around ${10}^{19}{\mathrm{cm}}^{-3}$ . The ${\mathrm{Al}}_2{\mathrm{O}}_3$ films, synthesized by plasma-assisted atomic layer deposition and with a high fixed negative charge density, limit the emitter saturation current density of B-diffused $p^{+}$ -emitters to $\sim 10$ and $\sim 30\mathrm{fA}∕{\mathrm{cm}}^2$ on $>100$ and $54\Omega ∕\mathrm{sq}$ sheet resistance $p^{+}$ -emitters, respectively. These results demonstrate that highly doped $p$ -type Si surfaces can be passivated as effectively as highly doped $n$ -type surfaces.