Excellent Si surface passivation by low temperature SiO2 using an ultrathin Al2O3 capping film

Abstract

It is demonstrated that the application of an ultrathin aluminum oxide (Al2O3) capping film can improve the level of silicon surface passivation obtained by low-temperature synthesized SiO2 profoundly. For such stacks, a very high level of surface passivation was achieved after annealing, with Seff < 2 cm/s for 3.5 Ω cm n-type c-Si. This can be attributed primarily to a low interface defect density (Dit < 1011 eV-1 cm-2). Consequently, the Al2O3 capping layer induced a high level of chemical passivation at the Si/SiO2 interface. Moreover, the stacks showed an exceptional stability during high-temperature firing processes and therefore provide a low temperature (≤400 °C) alternative to thermally-grown SiO2. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)Dingemans et al. demonstrate an unparalleled high level of silicon surface passivation by SiO2 synthesized at low temperatures. This result was obtained by the application of an ultrathin atomic layer deposited Al2O3 capping layer and subsequent annealing. The effective hydrogenation under influence of the Al2O3 capping layer leads to very low defect densities at the Si/SiO2 interface. These results may be beneficial for next-generation solar cells. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.