Malguth, E.; Roczen, M.; Gref, O.; Schoepke, A.; Schmidt, M.: Development of ultra-thin tunneling oxides and Si/SiO2 nanostructures for the application in silicon solar cells. Physica Status Solidi A 208 (2011), p. 612-615
10.1002/pssa.201000253
Abstract:
The synthesis of Si/SiO2 nanostructures for the application as hetero-emitter and passivation layer in high-efficiency solar cells is explored with the long-term perspective of exploiting quantum size effects for next-generation photovoltaics. Ultra-thin oxides are developed by means of oxidizing crystalline silicon using neutral oxygen atoms supplied by a RF plasma source. These oxides are characterized by an abrupt Si/SiO2 junction and good passivation of Si dangling bonds at the interface, a precondition for the implementation of Si/SiO2 nanostructures in photovoltaic devices. Another decisive issue is carrier transport across the SiO2 barrier which is demonstrated in form of a tunneling current in I–V measurements. Such tunneling oxides on Si(111) wafers are used as substrates for the subsequent deposition of Si nanodots. Nanodot synthesis is accomplished by first depositing a few nanometer thick layer of amorphous Si. During a subsequent recrystallization step at T > 600 °C, the surface tension between c-Si and SiO2 causes a dewetting and, thus, the formation of crystalline Si nanodots, the size of which can be controlled by the thickness of the initial amorphous Si layer. Finally the dots are cladded with a shell of tunneling oxide. A close-packing of spheres with dots stacked on top of each other is approximated by a repetition of this process.