Some Aspects Of Phosphorus Diffusion In Germanium In In0,01ga0,99as / In0,56ga0,44p / Ge Heterostructures

The results of experimental and theoretical researches of phosphorus distribution in the first cascade of a multi cascade solar cell based on nanoscale structures AIIIBV / Ge are presented. Secondary ion mass spectroscopy has been applied to obtain profiles of phosphorus and gallium in In0.01Ga0.99As / In0.56Ga0.44P / Ge heterostructure. In the germanium surface there is a thin layer of about 26 nm, in which the gallium concentration exceeds the concentration of phosphorus. Therefore a nanoscale p-n junction forms that does not have a significant impact on the solar cells performance at room temperature. Phosphorus diffusion is much slower in this area than in area with electronic conductivity. The main p-n junction is formed at a distance of 130-150 nm from the surface of the germanium. Diffusivity of gallium (D-Ga = 1,4.10(-15) cm(2)/s) is markedly higher than described in a literature. Diffusivity of P increase from D-P = 3.10-15 cm(2)/s on the boundary of the heterostructure In-0,Ga-49(0),P-51 to D-P = 5,2.10(-14) cm(2)/s in n-type Ge.