Miscellaneous Applications of Photoelectrochemical Etching

A number of examples have been reported of using photoelectrochemical etching as a step in fabricating electronic and electro- optical devices. 

Ostermayer et al. (28) reported the photoelectrochemical fabrication of lenses onto light emitting diodes (LEDs). The spherical lenses were formed by projection of the lens pattern onto an n-InP/InGaAsP double 

Cheng and Kohl (29) demonstrated that fiducial patterns on one side of an n-lnP wafer, defined in photoresist, could be photoelectrochemically etched through to the other side of a wafer about 90 pm thick. The metallized mask served the dual purpose of the electrical contact, which was at the front surface in this case. The process was carried out by illumination with a collimated beam from a HeNe laser and an electrode polarization of 0.2 - 0.4 volt (SCE) in 2 - 4 N HCI. Best results were obtained at light intensities 260 mW/cm due to reduced effects of diffraction and light scattering within the growing hole. 

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