Preparation of Ultrathin Germanium on Insulator Films Using a Wet Etching Process

We demonstrate a wet etching method to reduce the thickness of thin germanium-on-insulator (GOI) films using a dilute solution (a NH4OH:H2O2:H2O 2:1:4000 mixture) at a low temperature (5 degrees C). The etch rate and thickness uniformity were well controlled. The root mean square roughness after wet etching was less than 0.5 nm and did not degrade compared with the original sample. Finally, back gate junctionless transistors were fabricated using the GOI wafers with 15-nm-thick Ge films, thinned by the developed method. The transistors had good I-on/I-off ratio and mobility qualities, indicating that the wet etching process effectively thinned the Ge films. (C) The Author(s) 2015. Published by ECS. All rights reserved.