On the recombination behavior of p~+-type polysilicon on oxide junctions deposited by different methods on textured and planar surfaces

摘要

We investigate the passivation quality of hole-collecting junctions consisting of thermally or wet-chemically grown interfacial oxides, sandwiched between a monocrystalline-Si substrate and a p-type polycrystalline-silicon (Si) layer. The three different approaches for polycrystalline-Si preparation are compared: the plasma-enhanced chemical vapor deposition (PECVD) of in situ p~+-type boron-doped amorphous Si layers, the low pressure chemical vapor deposition (LPCVD) of in situ p~+-type B-doped polycrystalline Si layers, and the LPCVD of intrinsic amorphous Si, subsequently ion-implanted with boron. We observe the lowest J_(0e) values of 3.8 fA cm~(−2) on thermally grown interfacial oxide on planar surfaces for the case of intrinsic amorphous Si deposited by LPCVD and subsequently implanted with boron. Also, we obtain a similar high passivation of p~+-type poly-Si junctions on wet-chemically grown oxides as well as for all the investigated polycrystalline-Si deposition approaches. Conversely, on alkaline-textured surfaces, J_(0e) is at least 4 times higher compared to planar surfaces. This finding holds for all the junction preparation methods investigated. We show that the higher J_(0e) on textured surfaces can be attributed to a poorer passivation of the p~+ poly/c-Si stacks on (111) when compared to (100) surfaces.