Electrolytic Etching of Germanium Substrates with Hydrogen Peroxide

Abstract

Anodic electrolytic etching of germanium has been performed in hydrogen peroxide etchants with controlled external conditions. In-situ current and ex-situ etch-depths were measured and tracked with respect to etchant composition and stir rates. Gas bubbles formed during the etching process were found to cause non-uniformity in etch-current and surface quality. The effects were minimized in specific composition spaces. Quantitative analysis revealed a linear correlation of the number of electrons transferred during germanium oxidation with the number of surface atoms removed. Experimental results of 2.77 electrons/atom deviate significantly from 4 electrons/atom previously reported for silicon. The conclusion is that etching mechanisms for germanium are sufficiently different from those for silicon which invalidates the direct transfer of processing techniques between the two materials.

Communication—Controlling Etching of Germanium through Surface Charge Manipulation

“…After each intermittent CV acquisition the observed current resets to its peak value of approximately −11 mA. We have previously shown that the integrated current is directly correlated to the total mass of etched germanium 2 . Hence, the difference in the shaded areas underneath the curves in Fig.…”

“…Germanium is a promising alternative for next-generation backside imagers since recent homoepitaxial growth has yielded extraordinarily low defect densities. [1][2][3][4] The intrinsic properties of germanium enable high-speed hard X-ray detection, and absorption in the near-infrared regime where silicon is essentially transparent. 1,5 Furthermore, germanium is suited as a potential foundational material in the growing field of quantum computing.…”