Electrochemical pore etching in germanium

Nucleation and growth of electrochemically etched pores in Germanium (Ge) was investigated for n- and p- type Ge single crystals with {100}, {110}, and {111} orientations and doping concentrations of (10(14)-10(18))cm(-3). Various types of electrolytes, illumination conditions (front side, back side or none), and pre-treatments for optimizing nucleation were used. Several kinds of macropores could be obtained, mostly for the first time. In particular, pores could be obtained in p-type Ge samples. Pore geometries, morphologies, and growth peculiarities were found to be quite different from other semiconductors. Nucleation is generally difficult, the preferred growth direction is < 100 > or < 111 >, stop planes are of {110} type, and there is always a strong electropolishing component compromising pore geometry and stability. Porous membranes have been produced showing electrocapillarity effects. (c) 2006 Elsevier B.V. All rights reserved.