Optical determination of Fermi-level pinning using electroreflectance

Abstract

We have investigated the low-field electrolyte electroreflectance (EER) spectra of matte, polycrystalline, electrodeposited $n$-CdSe in the vicinity of the $E_0\mathrm{}(A,B)\mathrm{}$ transitions (direct gap at $\overrightarrow{\mathrm{k}}=0\mathrm{}$. As the applied bias voltage $V_{\mathrm{dc}}$ is varied from near flatband to depletion, the EER amplitude for electrodeposited CdSe decreases by a factor of ∼40. We interpret this decrease in EER signal as evidence of Fermi-level pinning, which we attribute to the presence of surface states.