Electrochemical etching of cpd. semiconductor crystals for use as phot - using strongly alkaline soln. which features alkali or alkaline earth-cyanide as complexing agent, used for photodetectors

摘要

The surface of the cpd. semiconductor wafer is etched electrochemically using the water as anode and an inert cathode. The electrolyte is a highly viscous soln. of a strong base, pref. with a pH of more than 10, pref. using a glycerine-water or ethyleneglycol-water mixt. A constant current is forced for a fixed time, pref. 0.01-10 mA/cm2 for 1-60 mins. The feature is that the electrolyte contains a complex forming cpd. pref. the cyanide of an alkali- or alkaline-earth element, pref. in a concn. of more than 0.01- mole/l. The strong base used is pref. an alkali-hydroxide. USE/ADVANTAGE - The complexing agent prevents redespn. of etched materials on the surface, resulting in a surface with a stoichiometrical compsn. The method also allows accurate calculation of the amt. of material being removed, which corresponds with 0.7mm per mAmp. sec/cm2. The resulting surface is free of oxide-charge and allows both p- and n-type surfaces to be prepared for photo-detection with an improved sensitivity.