FORMATION OF POROUS SILICON IN WATER-ETHANOL SOLUTIONS OF HYDROGEN-FLUORIDE

The effect of ethanol on the formation of deep layers of porous silico n on single-crystal n-type silicon (KEF-20) during its electrochemical treatment in water-ethanol solutions of hydrogen fluoride is investig ated. The occurrence of ethanol in the electrolyte at a concentration of 2.5-6.0 M is found to ensure the formation of porous silicon layers (pore diameter of 0.5-1.0 mu m) that are uniform in thickness and str ucture to a depth of more than 80 mu m, to decrease the effective vale nce of Si dissolution and increase the current efficiency to 160%. Mac ropores in porous Si increase in size and side blanches stop farming i n their cavities. A conclusion is drawn that ethanol is involved in th e generation of minority carriers in Si during the formation of porous layers, and a mechanism of the process is proposed.