Raman scattering controlled free-carrier and composition distribution in solar cell structures

A new contactless method using Raman scattering spectroscopy for the determination of the free-carrier density (FCD) and the composition distribution across the thickness of III-V multi-layer solar cell (SC) structures is developed and used for the optimization of an AlGaAs and GaSb SC technology. The method includes a step anodic oxidation of a SC structure and an analysis of Raman spectra (RS) from optical phonons and phonon-plasmon modes of different layers. The method provides simultaneous measurements of the element composition and the thickness (D) of the structure layers (for D>4 nm) together with the FCD(n, p=10/sup 15/-10/sup 20/ cm/sup -3/, for D>20 nm). The results of measurements of FCD and composition distributions of the LPE grown AlGaAs and Zn-diffused GaSb solar cell structures are presented and discussed.