High quality thermally diffused p/sup +/-n InP structures

Abstract

Cd diffusion and Zn diffusion into n-InP:S (N/sub D/ =3.5*10/sup 16/ and 4.5*10/sup 17/ cm/sup -3/) were performed by a closed ampoule technique at diffusion temperatures from 500 to 600 degrees C by using either high-purity Cd and Zn or Cd/sub 3/P/sub 2/ and Zn/sub 3/P/sub 2/. The Czochralski LEC grown substrates with etch pit densities (EPDs) from 3*10/sup 4/ to 7*10/sup 4/ cm/sup -2/ were used. Diffusions were performed through either bare surfaces or using SiO/sub 2/ (50-100 AA thick) and phosphorus-rich anodic and chemical oxides (25-50 AA thick) as cap layers. Specular surfaces have been obtained after Cd diffusion from Cd/sub 3/P/sub 2/ through P-rich oxide cap layers with a very low surface dislocation density which goes through a minimum of 400-800 cm/sup -2/ at the diffusion temperature of 560 degrees C. AM0 250 degrees C V/sub oc/ values as high as 860 mV from solar cells made on these structures are reported.<>