Surface passivation of phosphorus‐diffused n⁺‐type emitters by plasma‐assisted atomic‐layer deposited Al₂O₃

In recent years Al 2 O 3 has received tremendous interest in the photovoltaic community for the application as surface passivation layer for crystalline silicon. Especially p‐type c‐Si surfaces are very effectively passivated by Al 2 O 3 , including p‐type emitters, due to the high fixed negative charge in the Al 2 O 3 film. In this Letter we show that Al 2 O 3 prepared by plasma‐assisted atomic layer deposition (ALD) can actually provide a good level of surface passivation for highly doped n‐type emitters in the range of 10–100 Ω/sq with implied‐ V oc values up to 680 mV. For n‐type emitters in the range of 100–200 Ω/sq the implied‐ V oc drops to a value of 600 mV for a 200 Ω/sq emitter, indicating a decreased level of surface passivation. For even lighter doped n‐type surfaces the passivation quality increases again to implied‐ V oc values well above 700 mV. Hence, the results presented here indicate that within a certain doping range, highly doped n‐ and p‐type surfaces can be passivated simultaneously by Al 2 O 3 . (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)