Impact of size distributions of Ge islands as etching masks for anisotropic etching on formation of anti-reflection structures

Abstract

The impact of the size distributions of Ge islands on the structural and optical characteristics of anti-reflection structures was investigated. The variation of island size distribution was achieved through the variation of growth temperature in gas-source molecular beam epitaxy at 700 °C-800 °C. Ge islands were utilized as etching masks to form the anti-reflection structures. By using lower growth temperature of 700 °C and subsequent etching, larger texture without many hollows was formed in contrast to that using 800 °C. Broader size distribution of islands formed at 700 °C was found to lead to larger texture size. Smaller texture is formed by smaller islands and short etching, whereas larger texture is formed by erosion of smaller texture during long etching. A potential short-circuit current density of 36.75 mA cm-2 was obtained for the sample by the islands grown at 700 °C with reduced etching margins, comparable to that of conventional pyramid textures.