Direct photoelectrochemical (PEC) etching of submicron diffraction gratings in n-InP and n-Ga-InAsP has been studied using laser interference holography. In this technique the semiconductor is placed in an electrolyte and electrically biased to form a depletion region at the sample surface. A 2-mole HF/0.5-mole KOH solution was used in these experiments. Etching is controlled by the laser beam intensity at the electrolyte-crystal interface and for n-type materials occurs by an oxidative decomposition reaction involving photogenerated holes. Holographic exposure of the sample results in selective photoetching since the light-to-dark etch rate ratio is > 100:1. Development of such a maskless technique for producing gratings has potential application in the fabrication of distributed feedback (DFB) lasers which are currently made by a multistep photoresist process.
© 1984 Optical Society of AmericaPDF Article