High quality thermally diffused p+-n InP structures

Cd diffusion and Zn diffusion into n-InP:S (N_D =3.5×10¹⁶ and 4.5×10¹⁷ cm^-3) were performed by a closed ampoule technique at diffusion temperatures from 500 to 600°C by using either high-purity Cd and Zn or Cd₃P₂ and Zn₃P₂. The Czochralski LEC grown substrates with etch pit densities (EPDs) from 3×10⁴ to 7×10⁴ cm^-2 were used. Diffusions were performed through either bare surfaces or using SiO₂ (50-100 Å thick) and phosphorus-rich anodic and chemical oxides (25-50 Å thick) as cap layers. Specular surfaces have been obtained after Cd diffusion from Cd₃P₂ through P-rich oxide cap layers with a very low surface dislocation density which goes through a minimum of 400-800 cm^-2 at the diffusion temperature of 560°C. AM0 250°C V_oc values as high as 860 mV from solar cells made on these structures are reported