Anomalous Behavior of Schottky Barrier-Type Surface Photovoltages in Chromium-Contaminated N-Type Silicon Wafers Exposed to Air

概要

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A study of frequency dependent AC surface photovoltages (SPV) in n-type silicon (Si) wafers contaminated with an aqueous solution containing chromium (Cr) was carried out. Immediately after rinsing (5 min exposure to air), the Cr ($\text{Cr$^{3+}$}+\text{3e$^{-}$} \rightarrow \text{Cr}$) deposited on the surfaces of the wafers had already been converted into Cr(OH)3 and/or Cr2O3. This Cr(OH)3–Si contact forms a Schottky barrier on n-type Si. This gives rise to depletion and/or an inversion layer formed at the surface, resulting in the appearance of a frequency-dependent AC SPV. With exposure to air, the AC SPV in n-type Si wafers was reduced. This happens because Cr is oxidized and the Cr(OH)3 becomes Cr2O3 through the reaction $\text{2Cr(OH)$_{3}$} \rightarrow \text{Cr$_{2}$O$_{3}$}+\text{3H$_{2}$O}$, thus reducing the Schottky barrier height. Another factor is compensation by the positive oxide charge formed when the surface goes into accumulation, resulting in a suppression of the AC SPV in n-type Si. A schematic band diagram of the Schottky barrier was developed, and the barrier height was calculated to be 0.75 eV for n-type Si.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2006-06-15