POROUS SILICON FORMATION AND OTHER PHOTOELECTROCHEMICAL EFFECTS AT SILICON ELECTRODES ANODIZED IN HYDROFLUORIC-ACID

Illumination is an important parameter in the electrochemistry of sili con. A moderately doped (< 10(18) cm(-3)) n-type silicon electrode ano dized in the dark is passivated against dissolution in HF due to the a bsence of holes which promote dissolution. Under illumination a curren t proportional to the light intensity is observed. This dependence of the current on the illumination enabled us to realize relief structure s on the electrode surface without the use of standard photolithograpy . The photoassisted formation of macropores is another aspect of the p hotoelectrochemistry of silicon reported in this work. Many useful app lications such as a silicon based capacitor or photonic band gap mater ials in the infrared regime are based on photoelectrochemically etched macropores.