Design of high quality thermally diffused p+n and n+p InP structures with the help of electrochemical studies

The authors report on the use of electrochemical (EC) techniques for characterization and step-by-step optimization of n⁺p and p⁺n InP structures fabricated by thermal diffusion, for making high efficiency radiation resistant InP solar cells. The emitter layer and the junction proximity of the base are characterized as functions of: (a) various surface preparation procedures; (b) diffusion cap; (c) diffusion source; and (d) diffusion conditions consisting of diffusion temperature and time, amount of source material and added phosphorus, and temperature difference between the source and substrates. The EC characterization of the emitter layer provides: (a) thickness of front damaged layers; (b) density of surface and deep dislocations, and precipitates; (c) net majority carrier concentration depth profiles; and (d) surface and deep trap levels. The EC characterization was done both before and after irradiating the structure with high energy electrons and protons