An electrochemical study of p-type and n-type (100) Si in acidic fluoride solutions containing bromine is described. It is shown that the electrochemical reduction of bromine takes place via the conduction band of the semiconductor. Etch rate measurements in combination with electrochemical experiments reveal that Si etching in bromine solutions involves a chemical mechanism. The etch rates of (100) and (111) surfaces are both diffusion-controlled. It is shown that bromine can be used for open-circuit photoselective etching of both p- and n-type Si. In addition, bromine etching of porous Si samples causes a shift of the photoluminescence emission maximum to shorter wavelengths.