Excellent Si surface passivation by low temperature SiO 2 using an ultrathin Al 2 O 3 capping film

It is demonstrated that the application of an ultrathin aluminum oxide (Al 2 O 3 ) capping film can improve the level of silicon surface passivation obtained by low‐temperature synthesized SiO 2 profoundly. For such stacks, a very high level of surface passivation was achieved after annealing, with S eff < 2 cm/s for 3.5 Ω 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 Al 2 O 3 capping layer induced a high level of chemical passivation at the Si/SiO 2 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 SiO 2 . (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)