Shallow n+ diffusion into InP by an open-tube diffusion technique

Abstract

Very shallow n+ layers have been obtained in InP by using gallium sulfide as a source for sulfur diffusion, and chemically vapor deposited SiO2 as a cap. Diffusions were carried out from 585 to 725 °C in an open-tube system with a nitrogen ambient. The doping profile of sulfur in InP is estimated to be of the complementary error function type with a surface concentration of 5.6×1018/cc and a diffusion constant of 1.1×10−14 cm2/s at 670 °C. Diodes made on n+-p junctions obtained by this diffusion technique show ideality factors close to unity and saturation current densities as low as 3.4×10−15 A/cm2, signifying the presence of a defect-free junction. These diffusions, with junction depths in the 400–700 Å range, are ideal for solar cell applications.