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

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 S-eff < 2 cm/s for 3.5 Omega cm n-type c-Si. This can be attributed primarily to a low interface defect density (D-it < 10(11) 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 degrees C) alternative to thermally-grown SiO2. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim