CHEMICAL ETCHING OF GERMANIUM

Epitaxial germanium is an important material for the fabrication of tandem solar cells and long wavelength photodetectors. The polishing of germanium substrates, prior to germanium epitaxy, is thus an important step. A series of etching experiments have been conducted to evaluate chemical etches for this approach. It is found that the most satisfactory surfaces are obtained with a 2-3 min treatment in HNO//3:CH//3COOH:H//2O in an 18:8:5 ratio by volume.