Surface recombination at the Si/SiO/sub 2/ overgrowth interface

Abstract

Thin silicon solar cells must meet several requirements for high efficiency. These are minority carrier diffusion lengths exceeding the active layer thickness, enhanced absorption from light trapping, and passivation of all surfaces bounding the active region. A thin silicon solar cell will in general be supported by a foreign substrate. This approach will produce a buried interface which will not allow for characterization of surface recombination by short wavelength spectral response. New methods must be developed to measure and control surface recombination at a buried interface. A gated diode device structure is proposed for this purpose. The gate will be formed at the buried interface. Varying the gate bias is expected to control carrier populations due to field effect, and hence the recombination rate at the back surface. In this work, a thin layer of single crystal silicon is formed on the gate structure by epitaxial lateral overgrowth (ELO) using liquid phase epitaxy. The dielectric insulator is currently thermally grown SiO/sub 2/. This device structure could enable control of buried surface recombination for a wide variety of substrate materials.