Photo‐Assisted Etching of p‐Type Semiconductors

A novel technique is described with which the etching of p‐type semiconductors in solution can be affected by the use of light. The method is based on the principle that illumination of a part of the surface leads to enhanced dissolution in the non‐illuminated areas. Effective separation of photogenerated charge carriers is obtained by employing a two‐compartment cell. In this cell, the dark and illuminated surfaces can be exposed to solutions of a different composition and pH. The choice of the oxidizing agent in this system is important: its reduction should not involve free carriers in the semiconductor bands in the dark, whereas it should do so under illumination. For , in , and for , in , are shown to be suitable. Ratios of etch rates under illumination and in the dark of the order of 10 3 and higher are demonstrated.