Influence of chemical annealing on electronic properties of a-(Si, Ge)

Hydrogenated amorphous Silicon-Germanium alloy [a-(Si, Ge):H]remains an important material with applications for solar cells and detectors. In this paper, we show that the properties of the materials and devices can be significantly improved by using chemical annealing, or layer-by-layer growth, where one grows a thin layer followed by controlled hydrogen ion bombardment, and then repeats the process. The properties measured include H bonding, photo-conductivity, electron and hole mobility-lifetime products and p-i-n solar cell device properties. We also measured the stability of solar cells subjected to light soaking and find significant improvements in stability for chemically annealed devices compared to devices produced using normal, continuous growth. The improvement in stability and electronic properties is ascribed to an improved hydrogen microstructure produced in the material due to chemical annealing as indicated by an examination of the infrared absorption in the films.