Epitaxial InGaN on nitridated Si(111) for photovoltaic applications

There is great potential in using InGaN as an absorber material in photovoltaic cells, particularly when combined in a heterojunction with p-type Si. However, at typical growth temperatures, Ga and In easily form a eutectic with Si, which creates voids at the interface, resulting in a surface unsuitable for epitaxial growth. In this paper we demonstrate how a simple nitridation process of a Si(111) substrate at a temperature of 800 °C results in the formation of crystalline SiN. The surface of the SiN layer is seen to be reconstructed, indicating the SiN is crystalline and well ordered. The interface between InGaN and SiN is seen to be sharp with no evidence of eutectic formation. The SiN layer is estimated to be ~3 nm thick so is unlikely to significantly affect the electrical conductivity. The series resistance of a prototypical Si(111)/SiN/InGaN sample has been found to be 1.2Ω.