Analysis of the energy structure of nitrogen δ-doped GaAs superlattices for high efficiency intermediate band solar cells

Nitrogen δ-doped GaAs superlattices were fabricated and their energy structures were investigated. Several transitions related to E
₊
band of nitrogen δ-doped regions were observed in photoreflectance (PR) spectra at energies ranging 1.5-1.7 eV for the superlattices at which no transitions were observed for uniformly doped GaAsN. The PR signal intensity of E
₊
related band transitions is significantly higher than those observed in uniformly doped GaAsN. This enhancement of E
₊
related band transitions is advantageous as an intermediate band material, and thus, nitrogen δ-doped GaAs superlattice structures are expected to be an excellent alternative for the use of intermediate band solar cells.