Fast photoelectrochemical etching of quarter-micrometer diffraction gratings in n-InP

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Abstract
A maskless etch process for diffraction gratings in n‐InP is described in detail which permits simple and reliable large‐area fabrication of gratings for distributed feedback (DFB) or Bragg‐reflector (DBR) lasers. With respect to processes reported earlier the exposure and etching times are reduced by an order of magnitude without sacrificing resolution, modulation depth, or surface morphology. In accordance with the recently published diffusion theory for minority‐carriers generated under holographic illumination, a high etch rate is found to be advantageous with respect to high spatial resolution. In addition, however, the results demonstrate that the chemical stability of the In‐rich (211) and (111) planes as against the (100) surface is of final importance for obtaining good first‐order DFB gratings.